Extraction of guayule resin

Abstract

To provide methods for extracting various components from Parthenium argentatum resin.SOLUTION: A method starts with a non-polar resin solution that is manipulated by the addition of a polar solvent and water to precipitate a low molecular weight isoprene rubber to form a separable aqueous polar liquid fraction and a non-polar liquid fraction. Here, the aqueous polar liquid fraction is rich in argentatin and the non-polar liquid fraction is rich in guayulin. In other variations, an aqueous polar solvent is added to the non-polar resin solution to directly create a two-phase system. The extraction method can be fully automated by using a continuous countercurrent liquid / liquid extractor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates generally to the separation of natural products, and more particularly, to methods for extracting components found in guayule resin. [Background technology]

[0002] Guayule resin is a product produced from the processing of guayule (Parthenium argentatum) shrub for natural polyisoprene rubber. Guayule resin may be obtained in acetone during the process of deresinizing guayule rubber, or the resin may be extracted directly from the ground shrub material using acetone in a Soxhlet extraction. Rather than isolating and extensively purifying guayule resin, this low-cost sticky gum may be minimally processed to produce wood preservatives or adhesives. Some of the natural products that contain guayule resin could be commercially interesting if cost-effective techniques were available to separate guayule resin from the complex resin mixture.

[0003] Guayule resin contains many isoprene-based compounds, including terpenes, sesquiterpenes, terpenoids, sesquiterpenoids and triterpenes. Of commercial interest are, for example, guayulin A and guayulin B, both of which are sesquiterpene esters that have found applications in fragrances and insect pheromone production, and argentatins A, B, C and D, respectively, which are tetracyclic triterpenes with potential antioxidant and antitumor activity. In particular, argentatins can be converted into various compounds that are promising pharmaceutical active substances. See, for example, G. Flores-Rosete et al., "Anti-inflammatory and Cytotoxic Cycloartanes from Guayule (Parthenium argentatum)," Natural Products Communications, 2008, 3(3), 413-422. This paper details the chemical structures of each of the naturally occurring argentatins found in guayule.

[0004] Complicating the separation of these potentially valuable isoprene compounds is that a complex mixture of unrelated materials is also present in the resin along with the isoprene materials, including fatty acid triglycerides, waxes, low molecular weight (MW) isoprene rubber, carotenoids, and residual lignocellulosic materials.

[0005] Therefore, what remains needed are efficient and cost-effective methods for extracting these potentially high-value natural products from guayule resin. Summary of the Invention

[0006] It has now been discovered that by starting with a non-polar guayule resin solution, such as a solution containing guayule resin dissolved in toluene or other non-polar solvent or mixture of solvents, a series of solvent operations results in the straightforward separation of solid and liquid fractions, each enriched in a particular resin component or group of resin components.

[0007] According to various embodiments of the present disclosure, methods are described for extracting guayule resin that include changing the solvent polarity, filtration and phase separation to obtain resin fractions enriched in specific resin components or groups of resin components.

[0008] In various embodiments, the extraction process begins with a non-polar guayule resin solution to provide lignocellulosic material, low MW isoprene rubber, argentatin and guayulin.

[0009] In various embodiments, the extraction methods herein are suitable for automation in a continuous countercurrent extractor-centrifuge. [Brief description of the drawings]

[0010] Subject matter is particularly pointed out and distinctly claimed in the concluding portion of this specification, however, a more complete understanding can best be obtained by reference to the detailed description and claims when considered in conjunction with the following drawings. [Figure 1] A process is presented for guayule resin extraction starting from a resin solution in a non-polar solvent, resulting in the isolation of lignocellulosic solids, coagulated low MW isoprene solids, argentatin and guayulin. [Diagram 2] A process is presented for guayule resin extraction starting from a resin solution in a non-polar solvent, resulting in the isolation of lignocellulosic solids, argentatin and guayulin. [Diagram 3] 1 shows a continuous operation for recovering the guayule resin component. [Figure 4A] 1 shows a schematic flow chart of the guayule resin extraction and solvent recovery operation illustrated in Example 2. [Figure 4B] 1 shows a schematic flow chart of the guayule resin extraction and solvent recovery operation illustrated in Example 2. [Figure 4C] 1 shows a schematic flow chart of the guayule resin extraction and solvent recovery operation illustrated in Example 2. [Figure 4D] 1 shows a schematic flow chart of the guayule resin extraction and solvent recovery operation illustrated in Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The detailed description of the exemplary embodiments refers to the accompanying drawings which illustrate, by way of example, exemplary embodiments and their best modes. Although these exemplary embodiments have been described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that logical, chemical, and mechanical changes may be made without departing from the spirit and scope of the invention. Thus, the detailed description is presented for purposes of illustration only and not limitation. For example, unless otherwise stated, the steps recited in any of the method or process descriptions may be performed in any order and are not necessarily limited to the order presented. Furthermore, any reference to the singular includes embodiments in the plural and any reference to two or more components or steps may include embodiments or steps in the singular. Additionally, any reference to attached, fixed, connected, etc. may include permanent, removable, temporary, partial, complete, and / or any other possible attachment options. Additionally, any reference to no contact (or similar phrases) may also include reduced or minimal contact.

[0012] According to various embodiments of the present disclosure, a method for extracting guayule resin is described. The method involves a change in solvent polarity and phase separation utilized to obtain a resin fraction enriched in a particular resin component or group of resin components. The method is easily adaptable to automation in a continuous countercurrent extractor-centrifuge.

[0013] Definitions and Interpretations: As used herein, the plural "s" when used in conjunction with a hydrocarbon, e.g., pentane or hexane, infers a mixture of isomers of the hydrocarbon, recognizing that some technical grade low boiling point hydrocarbons are mixtures of isomers. Thus, for example, the term "pentane" refers to a mixture of hydrocarbons including n-pentane, iso-pentane, and neo-pentane, and the term "hexane" generally refers to a mixture of hydrocarbons including n-hexane, iso-hexane, 3-methylpentane, 2,3-dimethylbutane, and neo-hexane. When used, a singular reference to a hydrocarbon, such as cyclohexane, refers to a technical grade solvent that is at least 95.5% or more cyclohexane, or a reagent grade solvent that is 99% or more cyclohexane, rather than a mixture of isomers.

[0014] As used herein, the term "aromatic hydrocarbon" has its ordinary meaning in chemistry and relates primarily to low boiling liquid solvents such as benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, mesitylene, 2-ethyltoluene, 3-ethyltoluene, and 4-ethyltoluene.

[0015] As used herein, the term "petroleum ether" has its ordinary meaning in chemistry and refers to a mixture of low-boiling aliphatic hydrocarbons.

[0016] The term "polar" as used herein with respect to a solvent has its ordinary meaning in chemistry to indicate a solvent having a partial charge or dipole moment. In addition to water, classic examples of polar solvents include alcohols and ketones.

[0017] The term "non-polar" as used herein with respect to a solvent has its ordinary meaning in chemistry to indicate a solvent that has no partial charges or dipole moments. Classical examples of non-polar solvents in chemistry include hydrocarbons such as pentane, hexane, cyclohexane, and aromatic solvents such as benzene and toluene.

[0018] General embodiment 1. Extraction method 100 In a first process embodiment, a combination of a non-polar solvent, a polar solvent, and water is used to separate the guayule resin into a commercially usable product stream that further includes lignocellulosic materials, low MW isoprene rubber, various argentatins, and various guayulins.

[0019] 1, step 110 of extraction method 100 involves dissolving guayule resin in a non-polar solvent to obtain a non-polar resin solution and a first precipitate. Prior to dissolution in the non-polar solvent, the resin may start out substantially free of any solvent and may include a product recovered from the de-resinization of isoprene rubber obtained from guayule shrubs.

[0020] In various embodiments, the ratio of guayule resin to non-polar solvent depends on the nature of the non-polar solvent and its ability to selectively dissolve some resin components and not others.

[0021] In various embodiments, the w / w ratio of guayule resin to non-polar solvent in preparing the non-polar resin solution is from about 1:1 resin to non-polar solvent to about 1:2 resin to non-polar solvent. That is, by weight, 100 parts guayule resin is dissolved in about 100 to 200 parts non-polar solvent. The dissolving step may further include external heating to accelerate the process, such as heating from above ambient temperature to below the boiling point of the non-polar solvent. In various embodiments, the external heating to form the non-polar resin solution may be from just above ambient temperature up to about 100° C. and below the boiling point of the non-polar solvent. In a more specific example, when the non-polar solvent used in the dissolving step includes toluene (BP=111° C. at atmospheric pressure), the toluene may be heated to about 50° C. to accelerate the dissolution of the guayule resin in the toluene to form the non-polar resin solution.

[0022] In various embodiments, the non-polar solvent is selected from the group consisting of C3-C7 aliphatic hydrocarbons, aromatic hydrocarbons, and mixtures thereof. In various embodiments, the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof. In various embodiments, the non-polar solvent is selected from the group consisting of toluene, cyclohexane, or mixtures thereof. In various examples, the non-polar solvent comprises toluene. In various embodiments, the non-polar solvent comprises cyclohexane. Although various embodiments and examples are described with the use of one non-polar solvent, e.g., toluene, the scope of the method according to the present disclosure includes the use of "at least one non-polar solvent," and improvements to the process herein, including automation, may require a mixture of non-polar solvents for the formation of the initial non-polar resin solution.

[0023] The non-polar resin solution obtained in step 110 of the extraction method 100 results in a first precipitate that can be removed by any combination of decantation, gravity filtration, vacuum filtration, centrifugation or other methods, for example, centrifugation performed in batches or in a suitably configured continuous extraction-centrifuge. Centrifugation facilitates the separation of colloidal material that may otherwise clog the filter paper or filtration medium. The first precipitate thus obtained as a solid mass, or a mixed batch of solids, can be rinsed with a suitable solvent to remove residual resin components. These filtrates from further washing of the first precipitate can be mixed with the precipitate-free non-polar resin solution for use in the next step of the method.

[0024] In various embodiments, the first precipitate from the non-polar resin solution comprises lignocellulosic material in the form of solid particles. The lignocellulosic material thus obtained constitutes a first potential commercial product stream.

[0025] The non-polar resin solution resulting from step 110 (to which an aliquot of solvent from washing the first precipitate is optionally added) comprises a low viscosity fluid carrying all of the other remaining components of the resin in the non-polar solvent.

[0026] Continuing to refer to Figure 1, step 120 of extraction method 100 involves mixing a polar solvent with a non-polar resin solution to produce a mixed polar resin solution. The w / w ratio of non-polar resin solution to polar solvent is about 1:0.5 to about 1:2. That is, the polar solvent is added at about 50 to 200 parts by weight per 100 parts by weight of the non-polar resin solution.

[0027] In various embodiments, the polar solvent is selected from the group consisting of low molecular weight alcohols, acetone, and mixtures thereof. In various embodiments, the polar solvent is selected from the group consisting of methanol, ethanol, isopropanol, acetone, and mixtures thereof. In various embodiments, the polar solvent is methanol.

[0028] Step 120 of the extraction method 100 produces a second precipitate in coagulated solid form that contains low molecular weight (MW) isoprene rubber. The rubber coagulant may be removed by any combination of decantation, gravity filtration, vacuum filtration, and centrifugation, for example, in batches or in a continuous extractor-centrifuge. Centrifugation facilitates separation of colloidal material that may otherwise clog the filter paper or filtration media. The rubber may be rinsed with additional aliquots of polar solvent to remove residual resin components, and these washes may be combined into the resulting mixed polarity resin solution. The low MW isoprene rubber constitutes a second possible commercial product stream.

[0029] With continued reference to Figure 1, step 130 of extraction method 100 involves adding water to the mixed polarity resin solution to form a two-phase system including an aqueous polar phase and a non-polar phase. Depending on the w / w ratio of water to the mixed polarity resin solution, the aqueous polar solvent phase can be either the top or bottom layer in this two-phase system, as shown in Figure 1. Step 130 further involves separation of the aqueous polar liquid fraction from the non-polar liquid fraction in this two-phase system.

[0030] In various embodiments, the w / w ratio of water to the mixed polar resin solution is expressed as the w / w ratio of water to the polar solvent used in step 120 above. In various embodiments, the w / w ratio of water to polar solvent is about 1:20 to about 1:2. Stated another way, the amount of water added is about 5 parts water / 100 parts polar solvent to about 50 parts water / 100 parts polar solvent. In various embodiments, it is preferred to use a w / w ratio of about 1:20 to about 1:5 (5-20 parts water / 100 parts polar solvent), whereby the top layer is an aqueous polar liquid fraction comprising the polar solvent and water with the polar resin component, and the bottom layer is a non-polar liquid fraction.

[0031] In step 130, any remaining isoprene rubber not previously precipitated in step 110 is found in a non-polar liquid fraction layer that also contains the non-polar solvent used in step 110. Optionally, the separated aqueous polar liquid fraction can be extracted with additional aliquots of a non-polar solvent, such as a C3-C7 hydrocarbon, like pentane or hexane, which can be discarded. These extractions can reduce the color of the aqueous polar liquid fraction.

[0032] Continuing to refer to FIG. 1, steps 140 and 150 each comprise a desolventization process. Desolventization involves evaporating volatile materials to leave a solid residue, and may include any combination of heat (or ambient temperature) and vacuum. In various embodiments, desolventization steps 140 and 150 involve the removal of all volatile materials in a vacuum. Indeed, these two desolventization steps may be performed in either order, or there is the option of discarding one of the layers if the material in a particular layer is undesirable for any reason.

[0033] In step 140, the aqueous polar liquid fraction is desolventized to recover a first mixture of solids rich in argentatin having a melting point of about 50° C. These solids are substantially free of low MW isoprene rubber. The mixture of argentatins constitutes a third possible commercial product stream. Individual argentatins in this mixture of argentatins may be isolated and purified by chromatographic methods.

[0034] In step 150, the non-polar liquid fraction can be desolventized to obtain a second solids mixture enriched in guayuline. The mixture of guayulines constitutes a fourth possible commercial product stream. The individual guayulines present in this guayuline mixture can be isolated and purified by chromatographic methods.

[0035] Optionally, the non-polar liquid fraction can be extracted one or more times with aliquots of an aqueous polar solvent, such as a mixture of water and the polar solvent used in step 120, to recover more argentatin-rich solids.

[0036] Countercurrent liquid / liquid extraction The above steps 120 and 130 can be fully automated by using a continuous liquid / liquid countercurrent extractor. In various embodiments, the continuous liquid / liquid countercurrent extraction method is accomplished by using a suitable extractor-centrifuge. The method 100 can include an automated process by passing a non-polar resin solution stream countercurrently to an aqueous polar solvent stream in such a manner that the aqueous product stream removes argentatin from the non-polar resin solution, leaving a guayulin-rich non-polar resin solution stream. In the automated process, the low MW isoprene rubber particles can be precipitated during continuous mixing of the countercurrent flows and continuously centrifuged in the extractor-centrifuge into a collector screen.

[0037] In automated process variations, the countercurrent liquid / liquid extraction may be continuous or semi-continuous. In a semi-continuous version, a series of mixing / settling tanks may be used for the step of settling the low MW isoprene rubber particles.

[0038] In various embodiments of the automated countercurrent process, the polar solvent stream comprises a composition that changes compositionally over time. For example, the polar solvent countercurrent stream may start as an anhydrous polar solvent, such as the polar solvent (e.g., methanol) selected for step 120 in method 100. Starting the automated process in this manner, the precipitated low MW rubber particles may be continuously centrifuged before changing the composition of the polar solvent stream. As the process continues, and perhaps signaled by the cessation of rubber particle precipitation, water may be fed into the countercurrent polar solvent stream so that the stream becomes more aqueous over time. Meanwhile, the countercurrent streams become more enriched in the more soluble compounds in each stream. That is, as in the single step 130 in method 100, the aqueous polar stream becomes more enriched in argentatin, while the non-polar solvent stream becomes more enriched in guayulin.

[0039] In other embodiments, a certain aqueous polar solvent composition is used as a countercurrent flow to the non-polar resin solution stream. This composition can be a combination of water and polar solvent from method 100, and in some cases can be the same w / w ratio of water / polar solvent used in the illustrated method. Thus, for example, the countercurrent polar stream can include a mixture of water / polar solvent of 1:20 to about 1:2 by weight. In certain embodiments, the countercurrent polar stream can include a water / polar solvent w / w ratio of 1:20 to about 1:5. In various embodiments, the two countercurrent flow streams include a non-polar resin solution stream and an aqueous methanol stream.

[0040] An exemplary extractor-centrifuge for use herein is a Podbielniak extractor centrifuge. This type of extractor provides centrifugal force to improve separation efficiency of both liquid / liquid and solid-liquid phases. Podbielniak extractor centrifuges are available from Siebtechnik Tema, Inc., Cincinnati, Ohio, USA.

[0041] 2. Extraction method 200 In the second method, a combination of non-polar and aqueous polar solvents is used to separate a commercially available product stream containing lignocellulosic material, low MW isoprene rubber, various argentatins, and various guayulines. In various embodiments, extraction method 200 is a more streamlined and simpler version of extraction method 100 detailed above, in which the low MW isoprene rubber ends up in a liquid phase rather than as agglomerated particles that can be centrifuged.

[0042] 2, step 210 of extraction method 200 is identical to step 110 of extraction method 100 (FIG. 1) and involves dissolving guayule resin in a non-polar solvent, such as toluene and / or cyclohexane, to obtain a non-polar resin solution and a precipitate containing lignocellulosic particles. For the sake of brevity, details can be found above and will not be repeated here.

[0043] 2, step 220 of extraction method 200 involves extracting the non-polar resin solution with an aqueous polar solvent mixture to extract the polar components of the resin. Extraction method 200 differs from extraction method 100 at this stage in that an aqueous polar solvent, rather than an anhydrous polar solvent, is mixed with the non-polar resin solution. As a result, the low MW isoprene rubber does not precipitate out of solution, but instead results in a final two-phase system.

[0044] In various embodiments, step 220 involves mixing an aqueous polar solvent with the non-polar resin solution in a specific w / w ratio to promote a two-phase system that can separate into liquid fractions. In various embodiments, the aqueous polar solvent mixture includes about 5-25 parts water and 100 parts polar solvent by weight. Multiple extractions may be performed to recover as much of the polar components as possible without extracting undesirable amounts of low molecular weight rubbers. Alternatively, the combined aqueous polar solvent extract may be washed with a non-polar solvent to remove any rubbers and most of the terpenes and sesquiterpenes.

[0045] In step 230, the combined aqueous polar liquid fraction may be desolventized to recover a solids fraction that is rich in argentatin, low in guayulin content, and free of any gums.

[0046] After multiple extractions with the aqueous polar solvent mixture, a rubber-rich solution in the non-polar solvent remains. The rubber solution may be purified by the addition of a polar solvent to remove residual non-rubber resin components. This results in a concentrated low MW rubber product that is largely free of impurities.

[0047] The non-polar liquid fraction is desolventized in step 240. This liquid fraction containing natural rubber can be desolventized into rubber chunks or can be used directly for other processes such as isoprene latex production.

[0048] Countercurrent liquid / liquid extraction According to the automation of the method 100, the above step 220 can be fully automated by using a continuous liquid / liquid countercurrent extractor. The method 200 can include an automated process by passing the non-polar resin solution stream countercurrently to the aqueous polar solvent stream in such a manner that the aqueous product stream removes argentatin from the non-polar resin solution, leaving a non-polar resin solution stream rich in guayulin, except for the initial resin dissolution step 210 and the two desolvation steps 230 and 240. In the automation of the extraction of the method 200, there is no precipitated rubber, since the rubber remains in the non-polar liquid fraction. Thus, to automate the method 200, an extractor-centrifuge is not necessarily required, since there are no solid particles to be separated, but the centrifugation capacity also helps the separation of the liquid phase.

[0049] In various embodiments, a certain aqueous polar solvent composition is used as a countercurrent flow to the non-polar resin solution stream. This composition can be a combination of water and polar solvent from method 200, and in some cases can be the same w / w ratio of water / polar solvent used in the method illustrated in FIG. 2. Thus, for example, the countercurrent polar stream can include a mixture of water / polar solvent of 1:20 to about 1:2 by weight. In certain embodiments, the countercurrent polar stream can include a water / polar solvent w / w ratio of 1:20 to about 1:5. In various embodiments, the two countercurrent flow streams include a non-polar resin solution stream and an aqueous methanol stream.

[0050] As the automated continuous liquid / liquid countercurrent extractor operates, the aqueous polar solvent stream becomes enriched in argentatin, while the non-polar resin solution stream becomes enriched in low MW isoprene rubber.

[0051] Figure 3 shows one embodiment of a continuous operation that may be used to recover the resin component in guayule resin. In various aspects, the representative continuous operation shown in Figure 3 represents an automation of the method 200 shown in Figure 2 (with the addition of a pentane wash, in accordance with the hexane used in Example 2 below). It is important to note that the process shown in Figure 3 is only one example, and the relative amounts of materials (shown as "parts") may be altered, and in some cases, the production amount (also shown as "parts") may vary from this example.

[0052] The automated process of Figure 3 begins with a resin solution 310 that includes a non-polar solvent, such as toluene, and guayule resin. Methanol and water are mixed at 320 to form an aqueous polar solvent system, which is mixed with the non-polar system in the resin column at 330. The second point 335 is where the two-phase system is separated, with the upper right portion of the flow chart showing the process including the non-polar phase and the lower right portion of the flow chart showing the process including the aqueous polar phase. As illustrated, the non-polar phase provides terpenes and sesquiterpenes, while the aqueous polar phase, in addition to providing argentatin, may also provide the monoterpene elemol and the monoterpenoid β-eudesmol. EXAMPLES

[0053] Example 1: 1. A non-polar resin solution of guayule resin dissolved in a non-polar solvent was prepared by adding about 100 mL of toluene to about 55.8 grams of resin previously obtained from guayule processing. The starting resin was solid at room temperature and had a softening point of about 50° C. The non-polar resin solution was gravity or suction filtered through a Buchner funnel to remove precipitated lignocellulosic material. About 5 mL of the resulting filtrate was added to 35 mL of methanol to coagulate the isoprene rubber in solution. The coagulated rubber was collected, dried, the methanol was recovered, and vacuum dried to yield 0.448 g of isoprene rubber and 1.123 g of resin. The solids filtered from the 55.8 grams of resin in toluene solution were dried and weighed to yield 1.95 g of solids, or 3.5% of the original resin weight.

[0054] 2. 20 mL of the toluene filtrate from step 1 was measured into each of four (4) centrifuge tubes. 25 mL of methanol was added to each tube. The tubes were agitated by hand and then centrifuged at 8,000 rpm for 20 minutes. The dark liquid layer from each tube was decanted and collected in a new centrifuge tube and processed in step 3 below. The rubber remaining in the tube was rinsed with a first rinse of 20 mL acetone, then a second rinse of 20 mL acetone. The acetone aliquots were mixed and desolventized to give a total of 1.98 g of solids. The rubber was collected by redissolving in hexane and collecting the solution in a pre-weighed pan and desolventizing in a vacuum oven. The rinsed and desolventized rubber weighed 4.64 g or 14% of the treated resin.

[0055] 3. The decanted solution from step 2 was treated by adding 2.5 mL of water to each tube (approximately 12.5 parts based on added methanol of 25 mL or 19.8 g of methanol per centrifuge tube). The four tubes were centrifuged at 8,000 rpm for 20 minutes. A dark layer of approximately 7-10 mL volume resulted in each tube. The dark layers were mixed and desolventized in a vacuum oven. The weight of the resulting solids was 10.05 g or 30.3% of the resin.

[0056] 4. The combined lighter layers from step 3 above were further treated by adding 2.5 mL of water (approximately 12.5 parts water based on the methanol added). The tubes were agitated and centrifuged to give another 7-10 mL volume of dark layer in each tube. The dark layers were combined and dried in a vacuum oven to give 9.94 g of solids.

[0057] 5. The lighter layers remaining from step 4 were mixed and further processed by adding 5 mL of water and 5 mL of hexane to each tube. The tubes were vortexed and centrifuged to produce a two-phase system with the non-polar phase as the top layer. This layer was collected and desolventized in a vacuum oven to yield 3.36 g of solids.

[0058] 6. The remaining polar layer from step 5 was mixed and desolvated to give approximately 2.12 g of solids.

[0059] Table 1 below summarizes the resin fractions obtained in Example 1, steps 1-6.

[0060] [Table 1]

[0061] Example 2: The steps used in Example 2 are also generally described as flow charts in Figures 4A, 4B, 4C and 4D. Sample numbers and step numbers correlate between the steps written below and the illustrated flow charts. The illustrated method proceeds over four figures. In the flow charts, trapezoid symbols indicate liquid-liquid separations (e.g., phase separations performed in a separatory funnel). Other separations include the use of a rotary evaporator (rotovap) to remove solvent from the solution ("desolvation") to obtain recovered solvent and residual solids. Example 2, described below and shown in Figures 4A-4D, illustrates the recovery and reuse of the solvent for further extractions. A sample of 1.486 grams of pourable resin (resin with some residual solvent present from the previous guayule process) was diluted with 300 grams of toluene. 2. Simple hand mixing was sufficient to dissolve the resin and form a non-polar resin solution. 3. Two 45 mL aliquots of the non-polar resin solution were transferred to two centrifuge tubes which were spun to remove solids. 48.7 g of resin was obtained. 4. Each of the two supernatant solutions was mixed with 200 mL of methanol and 40 mL of water in a separatory funnel. 5. The solids from the centrifuge tube were rinsed twice with hexane and the solids were collected as sample #20. 6. The separatory funnel was allowed to stand for several days to allow the phases to separate. 47.5 mL of the non-polar phase was separated. 7.100 mL of hexane was added to the polar phase and allowed to settle. 8. The aqueous methanol phase was collected for concentration. Tare weight of flask = 174.69 g, methanol / water = 395.99 g, or approximately 220.3 g of solution for concentration. 9. The solids / solvent were concentrated / recovered using a rotary evaporator. 10. Weight after concentration was 185.72g. Material was transferred to sample vial sample #2 and a collected sample of aqueous methanol was collected as sample #1 for GC / FID. 196 mL of aqueous methanol was collected and transferred back to the separator after removing hexane. 11. Hexane was collected into a rotary evaporator with flask tare weight = 203.47g, hexane was 298.18g. After concentration = 209.86g, which was transferred to a vial as sample #4. 12. A sample of the recovered hexane - sample #3, and a solution of the residual hexane extract, sample #4, were collected for GC / FID. 13. Four (4) additional 45 mL aliquots of the raw resin solution after centrifugation were then added to the recovered methanol / water in the separatory funnel. Essentially no solids were present. (97.94 g resin). 14. The non-polar fraction was poured into a centrifuge tube and 170 mL of the 180 mL was collected. Hexane was then added to the separatory funnel. 15. The collected polar fraction was transferred to a rotary evaporator, tare weight of flask = 175.04 g, 195.56 g after rotary evaporator concentration. 140 mL of methanol / water was collected (sample #5). 20.5 g of polar solids was collected (sample #6). 16. The hexane layer was passed through a rotary evaporator: flash weight 204.06 g. There appeared to be about 8 g of extractables (not tested by GC). 17.60 mL of hexane + 20 mL of water was recovered. The hexane was treated as sample #7 and the water was extracted with toluene (toluene sample #8). (Note: the aqueous phase is from the polar concentration and is collected as solids on the condenser). 18. Methanol was added and the methanol / water was collected from 140 mL to 240 mL and returned to the separatory funnel. 19. The five non-polar tubes from step 14 were re-extracted with the methanol / water from step 18. 80 mL of non-polar solution was recovered (from the 170 mL added). 20.120 mL of hexane was added to the methanol / water. After rotary evaporation of 21.202.3 g, the polar solution was transferred to flask 174.78 g along with solution 449 (sample #10). Approximately 4 g remaining in the flask was dissolved in 22 mL of acetone and stored. 250 mL of solvent containing 22.2 mL of low density fluid (hexane or toluene) was collected and the low density fluid was sampled in sample #9. 23. The methanol / water phase was transferred to a flask, tare = 174.79 g, 375.13 g fluid, 179.80 g dried. Dry polar solids 5.03 g (Sample #12). 24.184 mL of solvent was recovered. 25. The hexane layer was collected from the separatory funnel and transferred to a flask, tare = 203.48 g, 307.91 g fluid, 218.92 g dried. The black liquid was collected as Sample #11. 15.4 g non-polar solids were collected (Sample #13). 26. Polar methanol / water from step 24 + non-polar phase from step 19. Collect 60 mL of non-polar phase. Added 140 mL of fresh hexane. 27. Methanol / water was collected into a separatory funnel, flask tare = 174.77 g, 339.58 g solvent, 179.19 g was dried (dried sample #14). Collected Methanol Sample #15. 28. The hexane was collected into a separatory funnel and transferred to a flask, tare = 203.51, total 317.50 g, concentrated to 211.53 g, dried sample #16-black liquid. 29. The remaining non-polar solution (60 mL) was separated into a centrifuge tube and extracted with 2x volume of methanol, then rinsed again with 1x volume of methanol. 30. Methanol was added to a separatory funnel and 30 mL of water was added. The black bottom layer was transferred to a rotary evaporator, tare = 203.5 g, total 209.55 g, concentrated to 207.3 g (sample #17). 31. The methanol layer was collected and concentrated on a rotary evaporator, tare = 174.8 g, total 338.7 g, 177.4 g was dried (sample #18), approximately 20 mL of water was removed as liquid from the sample before drying was complete. Water was collected as sample #19. 32. The solvent methanol was recovered (sample #20). 33. The rubber was collected by dissolving the rubber residue in hexane, then rinsing the tube with more hexane and collecting all of the rubber into a pan with a tare weight of 12.94 g, 45.04 g was air dried and 38.91 g was vacuum oven dried (Sample #21). 34. Liquid was collected from the cold trap after the vacuum oven (sample #22).

[0062] Table 2 shows differential scanning calorimetry (DSC) data for the numbered samples identified in Example 2 and also shown in the flow charts of Figures 4A-4D. Sample numbers (1-21) appear in the left-most column as hyphenated suffixes to the larger experiment number 20190812. The DSC instrument used was a TA Instruments Q2000 DSC, run from -120°C to 200°C at a rate of approximately 10°C / min.

[0063] [Table 2]

[0064] In Table 2, Tg refers to the glass transition temperature, which indicates, for example, if polyisoprene is present in the sample (e.g., a Tg of -50°C would indicate such). The absence of a measurable glass transition temperature indicates that the isoprene rubber has been removed.

[0065] In Table 2, Tm is the melting temperature and J / g indicates Joules / gram of sample. Tm correlates with high melting point components such as triglycerides around 50° C. or triterpenes (e.g., argentatin) at >70° C.

[0066] In Table 2, the Tm data entries for sample IDs 20190812-5 and 20190812-12 are marked with an asterisk to indicate that these samples exhibit high concentrations of argentatin.

[0067] Table 3 shows the fraction weights of the samples numbered in Example 2 and shown in the flow charts of Figures 4A-4D. The sample numbers are in the left-most column as hyphenated suffixes to the larger experiment number 20190812. Data was obtained on an instrument capable of gas chromatography with flame ionization detection (GC / FID).

[0068] [Table 3]

[0069] In Table 3, the abbreviations "Rub.Area", "Peak2", "Peak3", "Peak4", "Peak5", and "Peak6" represent low molecular weight (low MW) column GPC data (area under the peaks converted to weight percent). "Rubber Area" refers to low MW isoprene rubber, "Peak2" and "Peak3" are expected to be triacylglycerides, "Peak5" is argentatin, and "Peak6" is guayurin. The numbers listed in the top row of Table 2 are the typical MW measured for these peaks.

[0070] As shown in Table 3, most samples were high in argentatin. Samples 20190812-11, -16 and -17, especially sample -21, showed significant isoprene rubber content. Samples 20190812-11 and -17 showed higher triglyceride content.

[0071] Thus, it has been demonstrated that the controlled polarity extraction method of guayule resin can be used to isolate isoprene rubber, argentatin and guayulin from the resin.

[0072] Additional Aspects In various embodiments, a method for extracting Parthenium argentatum resin components from Parthenium argentatum resin includes: (a) dissolving Parsenium argentatum resin in at least one non-polar solvent to obtain a non-polar resin solution and a first precipitate; (b) separating the first precipitate from the non-polar resin solution; (c) adding a polar solvent to the non-polar resin solution to obtain a mixed polarity resin solution and a second precipitate; (d) separating the second precipitate from the mixed polarity resin solution to obtain a mixed solvent filtrate; (e) adding water to the mixed solvent filtrate to obtain a two-phase system comprising an aqueous polar liquid fraction and a non-polar liquid fraction; (f) separating the aqueous polar liquid fraction from the non-polar liquid fraction; (g) recovering a first solids mixture by desolventizing the polar liquid fraction; (h) recovering a second solids mixture by desolventizing the non-polar liquid fraction.

[0073] In various embodiments, the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof, hi various embodiments, the non-polar solvent comprises toluene and the polar solvent comprises methanol.

[0074] In various embodiments of the above process, step (g) and / or step (h) may be optional, such as if these product streams are not commercially available or are undesirable for any reason.

[0075] In various embodiments of the above method, the process is fully automated by use of a continuous countercurrent liquid / liquid extractor, where the non-polar resin solution flows as a non-polar solution stream countercurrent to a polar solution stream comprising a mixture of water and a polar solvent, and the non-polar solution stream is increasingly enriched in guayulin and the polar solution stream is increasingly enriched in argentatin, and the second precipitate is continuously removed by centrifugation.

[0076] In various embodiments, a method for extracting Parthenium argentatum resin components from Parthenium argentatum resin includes: (a) dissolving Parsenium argentatum resin in at least one non-polar solvent to obtain a non-polar resin solution and a precipitate; (b) separating the precipitate from the non-polar resin solution; (c) adding an aqueous polar solvent to the non-polar resin solution to obtain a two-phase system comprising an aqueous polar liquid fraction and a non-polar liquid fraction; (d) separating the aqueous polar liquid fraction from the non-polar liquid fraction; (e) recovering a first solids mixture by desolventizing the polar liquid fraction; (f) recovering a second solids mixture by desolventizing the non-polar liquid fraction.

[0077] In various embodiments, the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof, hi various embodiments, the non-polar solvent comprises toluene and the polar solvent comprises methanol.

[0078] In various embodiments, step (e) and / or step (f) may be optional, such as if these product streams are not commercially available or are undesirable for any reason.

[0079] In various embodiments, the extraction process is fully automated through the use of a continuous countercurrent liquid / liquid extractor, where the non-polar resin solution flows as a countercurrent non-polar solution stream to a polar solution stream comprising a mixture of water and a polar solvent, the non-polar solution stream becoming increasingly enriched in low MW isoprene rubber and the polar solution stream becoming increasingly enriched in argentatin.

[0080] In various embodiments, a method for separating lignocellulosic material from Parthenium argentatum resin includes: (a) dissolving Parsenium argentatum resin in at least one non-polar solvent to form a non-polar resin solution further comprising precipitated lignocellulosic material; (b) separating the precipitated lignocellulosic material from the non-polar resin solution; (c) optionally washing the precipitated lignocellulosic material with an aliquot of a non-polar solvent.

[0081] In various embodiments, the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof.

[0082] In various embodiments, a method for separating low MW isoprene rubber from Parthenium argentatum resin includes: (a) dissolving Parsenium argentatum resin in a non-polar solvent to form a non-polar resin solution further comprising a first precipitate; (b) separating the first precipitate from the non-polar resin solution; (c) adding a polar solvent to the non-polar resin solution to precipitate the low MW natural polyisoprene rubber in the form of agglomerated particles; (d) recovering the precipitated low MW natural polyisoprene rubber from the non-polar resin solution.

[0083] In various embodiments, the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof, hi various embodiments, the non-polar solvent comprises toluene and the polar solvent comprises methanol.

[0084] In various embodiments, the method for isolating a mixture of triterpenes from Parthenium argentatum resin comprises: (a) dissolving Parsenium argentatum resin in at least one non-polar solvent to form a non-polar resin solution further comprising a first precipitate; (b) separating the first precipitate from the non-polar resin solution; (c) adding a polar solvent to the non-polar resin solution to form a mixed polarity resin solution further comprising a second precipitate; (d) separating the second precipitate from the mixed polarity resin solution; (e) adding water to the mixed polarity resin solution to form separable aqueous polar and non-polar liquid fractions; (f) separating the aqueous polar liquid fraction from the non-polar liquid fraction; (g) recovering the mixture of triterpenes by desolvating the aqueous polar liquid fraction.

[0085] In various embodiments, the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof, hi various embodiments, the non-polar solvent comprises toluene and the polar solvent comprises methanol.

[0086] In various embodiments, a method for isolating a mixture comprising terpenes and sesquiterpenes from Parthenium argentatum resin includes: (a) dissolving Parsenium argentatum resin in at least one non-polar solvent to form a non-polar resin solution further comprising a first precipitate; (b) separating the first precipitate from the non-polar resin solution; (c) adding a polar solvent to the non-polar resin solution to provide a mixed polarity resin solution further comprising a second precipitate; (d) separating the second precipitate from the mixed polarity resin solution; (e) adding water to the mixed polarity resin solution to form separable aqueous polar and non-polar liquid fractions; (f) separating the non-polar liquid fraction from the aqueous polar liquid fraction; (g) recovering the mixture comprising terpenes and sesquiterpenes by evaporating the non-polar liquid fraction.

[0087] In various embodiments, the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof, hi various embodiments, the non-polar solvent comprises toluene and the polar solvent comprises methanol.

[0088] In the detailed description, references to "various embodiments," "one embodiment," "embodiment," "exemplary embodiment," and the like indicate that the described embodiment may include a particular feature, structure, or characteristic, but not all embodiments necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Moreover, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is believed to be within the knowledge of one of ordinary skill in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described. After reading the description, it will be apparent to one of ordinary skill in the art(s) how to implement the present disclosure in alternative embodiments.

[0089] The steps described in any of the method or process descriptions may be performed in any order and are not necessarily limited to the order presented. Additionally, any reference to the singular may include plural embodiments, and any reference to two or more components or steps may include singular embodiments or steps. Additionally, any reference to attached, fixed, connected, coupled, etc. may include permanent (e.g., integral), removable, temporary, partial, complete, and / or any other possible attachment options. Any of the components may be coupled to one another via friction, snaps, sleeves, brackets, clips, or other means now known or hereafter developed in the art. Additionally, any reference to no contact (or similar phrases) may also include reduced or minimal contact.

[0090] Benefits, other advantages, and solutions to problems have been described herein with respect to certain embodiments. However, the benefits, advantages, solutions to problems, and any elements that may cause or make any benefit, advantage, or solution more pronounced should not be construed as critical, necessary, or essential features or elements of the disclosure. Thus, the scope of the disclosure is not limited by anything other than the appended claims, and references to elements in the singular do not mean "one and only one" unless expressly stated as such, but rather "one or more." Furthermore, when phrases similar to "at least one of A, B, and C" or "at least one of A, B, or C" are used in the claims or specification, the phrases are intended to be interpreted to mean that only A may be present in an embodiment, that only B may be present in an embodiment, that only C may be present in an embodiment, or that any combination of elements A, B, and C may be present in a single embodiment. For example, A and B, A and C, B and C, or A and B and C.

[0091] All structural, chemical, and functional equivalents to the elements of the various embodiments described above known to those skilled in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims of the present invention. Moreover, it is not necessary for an apparatus or an apparatus component, or a method of using an apparatus, to address each and every problem sought to be solved by the present disclosure in order to be encompassed by the claims of the present invention. Moreover, no element, component, or method step in the present disclosure is intended to be dedicated to the public, regardless of whether that element, component, or method step is expressly recited in the claims. No element of a claim invokes 35 U.S.C. 112(f) unless that element is expressly recited using the phrase "means for." As used herein, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a chemical, chemical composition, process, method, article, or apparatus that includes a list of elements does not include only those elements, but may include other elements not expressly listed or that are inherent to such chemical, chemical composition, process, method, article, or apparatus.

Claims

1. 1. A method for extracting a Parthenium argentatum resin component from Parthenium argentatum resin, the method comprising: (a) dissolving the Parsenium argentatum resin in a non-polar solvent to obtain a non-polar resin solution and a first precipitate; (b) separating the first precipitate from the non-polar resin solution; (c) adding a polar solvent to the non-polar resin solution to obtain a mixed polarity resin solution and a second precipitate; (d) separating the second precipitate from the mixed polarity resin solution to obtain a mixed solvent filtrate; (e) adding water to the mixed solvent filtrate to obtain a two-phase system comprising an aqueous polar liquid fraction and a non-polar liquid fraction; (f) separating the aqueous polar liquid fraction and the non-polar liquid fraction; (g) recovering a first solids mixture by desolventizing the polar liquid fraction; (h) recovering a second solids mixture by desolventizing the non-polar liquid fraction.

2. 2. The method of claim 1, wherein the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof.

3. 2. The method of claim 1, wherein the non-polar solvent is at least one of toluene and cyclohexane.

4. The method according to any one of claims 1 to 3, wherein the polar solvent is selected from the group consisting of methanol, ethanol, isopropanol, acetone, and mixtures thereof.

5. The method of any one of claims 1 to 4, wherein the polar solvent comprises methanol.

6. 6. The method of any one of claims 1 to 5, wherein the first precipitate comprises lignocellulosic material and the second precipitate comprises coagulated low molecular weight isoprene rubber particles.

7. The method of any one of claims 1 to 6, wherein the first solids mixture comprises argentatin.

8. The method of any one of claims 1 to 7, wherein the second solids mixture comprises guayuline.

9. 9. The method of any one of claims 1 to 8, wherein the step of dissolving the Parsenium argentatum resin in a non-polar solvent comprises mixing a w / w ratio of Parsenium argentatum resin to non-polar solvent of about 1:1 to about 1:

2.

10. 10. The method according to any one of claims 1 to 9, wherein the step of dissolving the Parsenium argentatum resin in a non-polar solvent further comprises heating to a temperature below the boiling point of the non-polar solvent to accelerate dissolution.

11. 11. The method of any one of claims 1 to 10, wherein the step of adding the polar solvent to the non-polar resin solution comprises mixing the polar solvent and the non-polar resin solution in a w / w ratio of about 0.5:1 to about 2:

1.

12. 12. The method of any one of claims 1 to 11, further comprising a continuous countercurrent extraction process, wherein the non-polar resin solution flows as a non-polar solution stream countercurrent to a polar solution stream comprising a mixture of water and the polar solvent, the non-polar solution stream being increasingly enriched in guayulin and the polar solution stream being increasingly enriched in argentatin, and the second precipitate being continuously removed by centrifugation.

13. 1. A method for extracting a Parthenium argentatum resin component from Parthenium argentatum resin, the method comprising: (a) dissolving the Parsenium argentatum resin in a non-polar solvent to obtain a non-polar resin solution and a precipitate; (b) separating the precipitate from the non-polar resin solution; (c) adding water or an aqueous polar solvent to the non-polar resin solution to obtain a two-phase system comprising an aqueous polar liquid fraction and a non-polar liquid fraction; (d) separating the aqueous polar liquid fraction and the non-polar liquid fraction; (e) recovering a first solids mixture by desolventizing the polar liquid fraction; (f) recovering a second solids mixture by desolventizing the non-polar liquid fraction.

14. 14. The method of claim 13, wherein the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof.

15. The method of any one of claims 13 to 14, wherein the non-polar solvent comprises at least one of toluene and cyclohexane.

16. 16. The method of any one of claims 13 to 15, wherein the aqueous polar solvent comprises a mixture of water and a polar solvent selected from the group consisting of methanol, ethanol, isopropanol, acetone, and mixtures thereof.

17. A method according to any one of claims 13 to 16, wherein the precipitate comprises lignocellulosic material in the form of solid particles.

18. 18. The method of any one of claims 13 to 17, wherein the first solids mixture comprises argentatin.

19. The method of any one of claims 13 to 18, wherein the second mixture of solids comprises low MW isoprene rubber.

20. 20. The method of any one of claims 13-19, further comprising a continuous countercurrent extraction process, wherein the non-polar resin solution flows as a non-polar solution stream countercurrent to a polar solution stream comprising a mixture of water and the polar solvent, the non-polar solution stream being increasingly enriched in low MW isoprene rubber and the polar solution stream being increasingly enriched in argentatin.

21. 1. A method for separating lignocellulosic material from Parthenium argentatum resin, the method comprising: (a) dissolving the Parsenium argentatum resin in at least one non-polar solvent to form a non-polar resin solution further comprising precipitated lignocellulosic material; (b) separating the precipitated lignocellulosic material from the non-polar resin solution; (c) optionally washing the precipitated lignocellulosic material with an aliquot of the non-polar solvent.

22. 22. The method of claim 21, wherein the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof.

23. 1. A method for separating low molecular weight isoprene rubber from Parthenium argentatum resin, the method comprising: (a) dissolving the Parsenium argentatum resin in a non-polar solvent to form a non-polar resin solution further comprising a first precipitate; (b) separating the first precipitate from the non-polar resin solution; (c) adding a polar solvent to the non-polar resin solution to precipitate low MW natural polyisoprene rubber in the form of agglomerated particles; (d) recovering the precipitated low MW natural polyisoprene rubber from the non-polar resin solution.

24. 24. The method of claim 23, wherein the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof.

25. 25. The method of any one of claims 23 to 24, wherein the polar solvent is selected from the group consisting of methanol, ethanol, isopropanol, acetone, and mixtures thereof.

26. 1. A method for isolating a mixture of triterpenes from Parthenium argentatum resin, the method comprising: (a) dissolving the Parsenium argentatum resin in a non-polar solvent to form a non-polar resin solution further comprising a first precipitate; (b) separating the first precipitate from the non-polar resin solution; (c) adding a polar solvent to the non-polar resin solution to form a mixed polarity resin solution further comprising a second precipitate; (d) separating the second precipitate from the mixed polarity resin solution; (e) adding water to the mixed polarity resin solution to form separable aqueous polar and non-polar liquid fractions; (f) separating the aqueous polar liquid fraction from the non-polar liquid fraction; (g) recovering said mixture of triterpenes by desolvating said aqueous polar liquid fraction.

27. 27. The method of claim 26, wherein the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof.

28. 28. The method of any one of claims 26 to 27, wherein the polar solvent is selected from the group consisting of methanol, ethanol, isopropanol, acetone, and mixtures thereof.

29. 1. A method for isolating a mixture of terpenes and sesquiterpenes from Parthenium argentatum resin, the method comprising: (a) dissolving the Parsenium argentatum resin in a non-polar solvent to form a non-polar resin solution further comprising a first precipitate; (b) separating the first precipitate from the non-polar resin solution; (c) adding a polar solvent to the non-polar resin solution to provide a mixed polarity resin solution further comprising a second precipitate; (d) separating the second precipitate from the mixed polarity resin solution; (e) adding water to the mixed polarity resin solution to form separable aqueous polar and non-polar liquid fractions; (f) separating the non-polar liquid fraction from the aqueous polar liquid fraction; (g) recovering the mixture comprising terpenes and sesquiterpenes by evaporating the non-polar liquid fraction.

30. 30. The method of claim 29, wherein the non-polar solvent is selected from the group consisting of hexane, pentane, petroleum ether, toluene, cyclohexane, and mixtures thereof.

31. 31. The method of any one of claims 29 to 30, wherein the polar solvent is selected from the group consisting of methanol, ethanol, isopropanol, acetone, and mixtures thereof.

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