Extraction of cannabinoids from plant waxes

Abstract

The invention relates to a method of extracting cannabinoids from plant waxes. The method includes contacting plant waxes with an immiscible solvent combination comprising a non-polar solvent and a polar solvent. The immiscible solvents are separated to yield a wax-rich non-polar fraction and a cannabinoid- rich polar fraction. The cannabinoid-rich polar fraction is subsequently contacted with a sufficient volume of an antisolvent, thereby causing precipitation of cannabinoids. The precipitated cannabinoids may be collected and subjected to optional further processing. The method provides an efficient and selective approach to isolating cannabinoids from wax-containing plant material.

Description

[0001] EXTRACTION OF CANNABINOIDS FROM PLANT WAXES

[0002] INTRODUCTION

[0003] This invention relates to a method of extracting cannabinoids from plant waxes. In particular, but not exclusively, the invention relates to a method of extracting cannabinoids from waste plant wax material, including Cannabis derived waste plant waxes, obtained from a prior cannabinoid extraction process.

[0004] BACKGROUND

[0005] The processing of Cannabis sativa has grown rapidly since the start of the 21stcentury with the lifting of restrictions on research and the consumption of Cannabis products, with the global market size of Cannabis derived products expected to continue the rapid recent growth. This estimated growth will require an associated increase in Cannabis processing to produce medicinal or recreational products to meet the demand of a larger market. Several processing options have been reported for the extraction and isolation of the pharmaceutical components of Cannabis, such as cannabidiol (CBD) and tetrahydrocannabinol (THC). These components, considered unique to Cannabis, are some of the more than 100 compounds collectively referred to as cannabinoids that have been identified and isolated. Many of these compounds also occur in other plants and plant species.

[0006] Generally, there are two main approaches for the extraction of cannabinoids from plant material - the supercritical carbon dioxide approach and the solvent extraction approach. The solvent extraction approach utilises a range of organic solvents, typically ethanol, but non-polar solvents such as butane and heptane are also utilised. One of the disadvantages that these approaches share is the “winterisation” step required in both. In this step, after extraction, the extract solution is cooled to between -40°C to -80°C, for example, to precipitate the waxes thereby to allow for removal thereof through filtration and other particulate removal steps. The winterisation step is not only highly energy intensive, but it also produces a wax waste product, herein referred to as plant wax waste material or waste plant wax, that contains a significant concentration of cannabinoids which can range between about 40 wt% to 50 wt% of the dried waste wax product, for example.

[0007] WO 2021 / 003088 in the name of Evonik Corporation relates broadly to the separation of cannabinoids from a plant extract. This method utilises solvents selected from ethanol, methanol, acetone, butanol, isopropyl alcohol, and water, together with two separate nanofiltration steps. The use of two separate nanofiltration steps significantly adds to the cost of the process described. In addition, the method relates to a process starting from plant material, and not from a wax portion of the plant material.

[0008] WO 2023 / 081976 in the name of Cymra Life Sciences Limited relates broadly to a method for selectively extracting two or more different products from a starting material comprising steam extracted cannabis. This two-step process uses a first extraction solvent system comprising a mixture of two or more miscible solvents that has a first dielectric constant, and a second extraction solvent system comprising a mixture of two or more miscible solvents having a different dielectric constant to that of the first extraction solvent system. This method relates to the of cannabinoids from a cleaned stream, and not from a plant wax waste stream.

[0009] WO 2024 / 036346 is a prior international PCT patent application in the name of the current applicant. This application describes a method for extracting cannabinoids from plant waxes wherein the plant wax is dissolved in a solvent, preferably a solvent or a solvent mixture having a polarity index of about 4, at an elevated temperature. The solution is then cooled to allow for the precipitation of wax out of solution, with resultant separation of the cannabinoids. Although useful in certain applications, the use of heating adds to energy cost while filtration without winterisation leads to a recovered product that has lower purity compared to the method of the invention described herein.

[0010] The present invention seeks to address some of the shortcomings of the prior art and provides an improved process, or at least an alternative process, for the extraction of cannabinoids from plant wax waste material.

[0011] SUMMARY OF THE INVENTION

[0012] According to a first aspect to the present invention there is provided a method of extracting cannabinoids from plant waxes, the method comprising: a) contacting the plant waxes with an immiscible solvent combination comprising a first solvent having a dielectric constant of about 6 or less, and a second solvent having a dielectric constant of about 30 or more, b) separating the first and second solvents in the immiscible solvent combination into a wax rich non-polar fraction and a cannabinoid rich polar fraction, and c) contacting the cannabinoid rich polar fraction with a sufficient volume of an antisolvent, thereby to precipitate the cannabinoids from the cannabinoid rich fraction for optional further processing.

[0013] In one embodiment, the immiscible solvent combination comprises a first solvent having a dielectric constant of about 3 or less, and a second solvent having a relative polarity of about 35 or more.

[0014] In a preferred embodiment, the immiscible solvent combination comprises a first solvent having a dielectric constant of about 2 or less.

[0015] In a preferred embodiment, the first solvent is selected from the group consisting of heptane, hexane, and mixtures thereof.

[0016] In a preferred embodiment, the second solvent is selected from the group consisting of acetonitrile, diethylene glycol, methanol, dimethyl sulfoxide, and mixtures thereof.

[0017] In one embodiment, the plant waxes are contacted with the first solvent prior to the addition of the second solvent.

[0018] In one embodiment, the plant waxes and the immiscible solvent combination is agitated for a period of time prior to allowing the immiscible solvent combination to separate for further processing.

[0019] The immiscible solvent combination may comprise from about 10% (v / v) to about 50% (v / v) of the second solvent, about 20% (v / v) to about 40% (v / v) of the second solvent, about 25% (v / v) to about 35% (v / v) of the second solvent, or about 30% (v / v) of the second solvent.

[0020] The plant waxes may be provided at a concentration of about 20% (wt%) to about 60% (wt%) of the first solvent, about 30% (wt%) to about 50% (wt%) of the first solvent, about 35% (wt%) to about 45% (wt%) of the first solvent, or about 40% (wt%) of the first solvent. In one embodiment, the wax rich non-polar fraction separated in step (b) is recycled to step (a) for further processing.

[0021] In a preferred embodiment, the wax rich non-polar fraction separated in step (b) is subjected to a solvent recovery step to recover the first solvent.

[0022] In a further embodiment, the recovered first solvent is recycled to step (a) for further processing.

[0023] In one embodiment, the antisolvent is water.

[0024] The antisolvent may be added in an excess relative to the cannabinoid rich polar fraction of more than about 4: 1 , more than about 6:1 , or more than about 8:1.

[0025] In one embodiment, the antisolvent is added in an excess relative to the cannabinoid rich polar fraction of more than about 8: 1 .

[0026] In a preferred embodiment, step (c) further comprises the addition a third solvent having a dielectric constant of about 6 or less.

[0027] In one embodiment, the first solvent having a dielectric constant of about 6 or less of step (a) and the third solvent having a dielectric constant of about 6 or less is the same or different.

[0028] In one embodiment, the first solvent and the third solvent are heptane.

[0029] In one embodiment, the cannabinoids in the cannabinoid rich polar fraction are dissolved in the third solvent to form a cannabinoid rich non-polar fraction and a cannabinoid depleted polar fraction. In a preferred embodiment, the cannabinoid depleted polar fraction is subjected to further processing to recover the second solvent, optionally for further use in step (a).

[0030] In a preferred embodiment, the cannabinoid rich non-polar fraction is subjected to further processing.

[0031] In one embodiment, the method is performed at substantially room temperature.

[0032] In a preferred embodiment, the plant waxes are waste material obtained from a prior cannabinoid extraction process.

[0033] In one embodiment, the plant waxes are Cannabis derived plant waxes.

[0034] According to a second aspect to the present invention there is provided a cannabinoid extract obtained by the method of the invention as described.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The invention will now be described in more detail with reference to the following non-limiting embodiments and figures in which:

[0037] Figure 1 shows one embodiment of a process diagram for the implementation of a method according to the present invention;

[0038] Figure 2 shows K-values obtained for the different cannabinoids in eight immiscible organic solvent systems;

[0039] Figure 3 shows partition coefficients and recovery of total cannabinoids from an industrial plant wax by-product using the LLX step of the method of the invention;

[0040] Figure 4 shows the concentration of cannabinoids in each phase after separation; and Figure 5 shows cannabinoid concentration for each phase after different stages of antisolvent precipitation and heptane addition.

[0041] DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0042] The present invention will now be described more fully hereinafter with reference to the accompanying figures, in which some of the non-limiting embodiments of the invention are shown.

[0043] The invention as described hereinafter should not be construed to be limited to the specific embodiments disclosed, with slight modifications and other embodiments intended to be included within the scope of the invention.

[0044] Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0045] As used herein, throughout this specification and in the claims which follow, the singular forms “a”, “an” and “the” include the plural form, unless the context clearly indicates otherwise.

[0046] The terminology and phraseology used herein is for the purpose of description and should not be regarded as limiting. The use of the terms “comprising”, “containing”, “having”, “including”, and variations thereof used herein, are meant to encompass the items listed thereafter, and equivalents thereof as well as additional items.

[0047] Unless the context clearly indicates otherwise, throughout this specification the term “cannabis" is intended to mean members of the genus including the species cannabis sativa, cannabis indica and cannabis ruderalis. The cannabis plant genus also includes hemp varieties.

[0048] As used through this specification, the term “immiscible solvent combination” should be understood to mean a combination of two or more solvents that cannot form a homogenous solution room temperature, in other words a combination of two or more solvents that separates out into two or more distinct solvent layers.

[0049] As used through this specification, the term “antisolvent precipitation” or “ASP” refers to when supersaturation of a solute in an initial solvent is forced by the addition of a second solvent, referred to as the antisolvent, in which the target compound has low solubility. As a result, the solute precipitates out of solution and can be removed through various well known solid-liquid separation techniques.

[0050] Cannabinoids have been shown to have a relatively strong physical association with the lipophilic compounds in plant waxes. Accordingly, extraction of plant waxes with solvents deemed otherwise suitable for cannabinoid dissolution and extraction does not recover the desired fraction of cannabinoids from the solid wax matrix. Therefore, an alternative method of removing these cannabinoids from plant waxes is required in order to extract commercially viable concentrations of cannabinoids from plant waxes, including plant waxes produced as a waste product from a prior extraction process. Due to the relative hydrophobicity of both the wax and cannabinoids contained in the wax material, the use of standard aqueous systems does not achieve sufficient separation between the components.

[0051] The present invention advantageously provides for such a method of extracting cannabinoids from plant waxes, in particular plant waxes produced as a waste product from a prior cannabinoid extraction process. The method comprises a first liquid-liquid extraction (“LLX”) system step wherein the LLX system comprises two immiscible organic solvents capable of separating the cannabinoid components based on differential solubilities and solvent polarity.

[0052] The method of the invention comprises contacting the plant waxes with an immiscible solvent combination comprising a first solvent having a dielectric constant of about 6 or less, and a second solvent having a dielectric constant of about 30 or more, separating the first and second solvents in the immiscible solvent combination into a wax rich non-polar fraction and a cannabinoid rich polar fraction, and contacting the cannabinoid rich polar fraction with a sufficient volume of an antisolvent, thereby to precipitate the cannabinoids from the cannabinoid rich fraction for optional further processing. In an optional further step, a third solvent having a dielectric constant of about 6 or less is added to the polar solvent and antisolvent combination, thereby extracting the cannabinoids to the third solvent for optional further processing.

[0053] Figure 1 shows an exemplary process diagram 10 for implementation of one embodiment of the invention. An immiscible solvent combination comprising a first solvent having a dielectric constant of about 6 or less, preferably about 3 or less, and a second solvent having a dielectric constant of about 30 or more, preferably about 35 or more, is provided in a first agitation vessel 20. The plant wax waste material may be dissolved in the first solvent prior to the introduction of the second solvent of the immiscible solvent combination. The first solvent may be selected from any suitable non-polar solvent having a dielectric constant of about 6 or less including solvents selected from the group consisting of heptane, hexane, and mixtures thereof. The second solvent may be selected from any suitable non-polar solvent having a dielectric constant of about 30 or more, including solvents selected from the group consisting of acetonitrile, diethylene glycol, methanol, dimethyl sulfoxide, and mixtures thereof.

[0054] The solvents used in the immiscible solvent combination, and the ratios thereof, may be selected based on the composition and characteristics of the plant wax starting material. The immiscible solvent combination may, for example, comprise from about 10% (v / v) to about 50% (v / v) of the second solvent, about 20% (v / v) to about 40% (v / v) of the second solvent, about 25% (v / v) to about 35% (v / v) of the second solvent, or about 30% (v / v) of the second solvent, based on the total volume of the solvent combination. Similarly, the concentration of the plant wax material in the solvent combination will, to some extent, be determined by the starting wax material and the other optimised method parameters. However, it is envisaged that the plant wax starting material may be provided at a concentration of about 20% (wt%) to about 60% (wt%), about 30% (wt%) to about 50% (wt%), about 35% (wt%) to about 45% (wt%), or about 40% (wt%), based on the weight of the first solvent in the solvent combination.

[0055] The immiscible solvent combination including the plant wax waste material is agitated for a set period of time, before optionally being transferred to a second settling vessel 30 wherein the mixture is allowed to reach equilibrium before being separated into a wax rich non-polar fraction (top phase) and a cannabinoid rich polar fraction (bottom phase) devoid of waxes.

[0056] In one embodiment of the invention, the wax rich non-polar fraction is optionally transferred to a solvent recovery unit 40 which is adapted to allow for the separation and recovery of the first solvent. In one embodiment, the so recovered first solvent may recycled to the first agitation vessel 20. In an alternative embodiment, the so recovered first solvent may be utilised in a further extraction step in another, separate agitation and / or settling vessel (not shown). In other words, it is envisaged that the method of the invention may include a series of agitation / settling vessels to which the first solvent may be recycled for further processing before or after the solvent recovery process. The cannabinoid depleted wax product may be recovered from the solvent recovery unit 40 for further alternative uses.

[0057] Returning now to the settling vessel 30, after phase separation the cannabinoid rich polar fraction (bottom phase) is optionally transferred to a further processing vessel 50 in which the cannabinoid rich polar fraction is contacted with an antisolvent in an antisolvent precipitation step. Cannabinoids are typically oils at room temperature and are known to have low solubility in aqueous phases. Accordingly, the inventors of the present invention have found that the addition of a suitable antisolvent forces the cannabinoids out of solution from the polar solvent, separated from the immiscible solvent combination. The antisolvent may be added in an excess relative to the cannabinoid rich polar fraction of more than about 2:1 , more than about 4:1 , more than about 6:1 , or about 8:1 or more. The selection of the appropriate antisolvent and the ratio of the antisolvent to the cannabinoid rich polar fraction will, again, depend on the other parameters of the particular method employed. In one example, the antisolvent may be water, or a solvent mixture comprising essentially of water, preferably added in a ratio of more than about 6: 1 , preferably about 8: 1 or more.

[0058] In a preferred embodiment of the invention, in addition to the introduction of an antisolvent to the cannabinoid rich polar fraction, a third solvent having a dielectric constant of about 6 or less may be introduced to the mixture contained in the processing vessel 50. This third solvent may, in some examples, be the same as the first solvent utilised in the immiscible solvent combination for the dissolution of the plant wax material. However, depending on the other parameters of the method selected and the particular starting material, it may also be different to the first solvent. The third solvent may be selected from heptane, hexane, and mixtures thereof. With the addition of the third solvent, the cannabinoids present in the cannabinoid rich polar fraction (possibly an aqueous fraction in the case of the addition of water as the antisolvent) will partition to the third solvent thereby forming a cannabinoid rich non-polar fraction and a cannabinoid depleted polar (aqueous) fraction.

[0059] After separation, the cannabinoid rich non-polar fraction may be removed for further processing including solvent evaporation and dissolution of the cannabinoid product in an alternative solvent, as required by the producer according to the particular application. The cannabinoid depleted polar (aqueous) fraction may be transferred to a solvent recovery unit 60, which may be adapted to distil and recover the polar solvent for re-use in agitation vessel 20.

[0060] Examples

[0061] Selection of Immiscible Solvent Combinations

[0062] The development and selection of an appropriate immiscible organic solvent system or solvent combination for use in the invention was a critical step for the development of the liquid-liquid extraction (“LLX”) step of the method. Broadly, the selection of the appropriate solvents was governed by the mutual miscibility of solvents, sufficient solubility in water for the polar solvent phase (i.e. a solvent having a dielectric constant of about 30 or more), and the safety of use of the potential solvents.

[0063] For the LLX part of the method it was required that the solvent system exhibits sufficiently limited miscibility as to ensure phase separation. Broadly, the LLX part of the method and the selection of appropriate solvents are based on the requirement that the wax portion of the plant wax material should sufficiently partition in the first solvent while the cannabinoids, which are known to have a strong physical association with the lipophilic compounds comprising the plant waxes, should sufficiently partition to the second solvent. In addition, after thorough mixing, the selected solvents should separate sufficiently to allow for ease of further processing and the avoidance of undesirable levels of contamination between phases. The inventors have found that these requirements are met where the immiscible solvent combination comprises a first solvent having a dielectric constant of about 6 or less, preferably about 3 or less, even more preferably about 2 or less, and a second solvent having a dielectric constant of about 30 or more, preferably about 35 or more. The third solvent, which is used in an optional further processing step after antisolvent precipitation, advantageously has a dielectric constant of about 6 or less.

[0064] Mutual solubility data for various organic solvent and water mixture systems are readily available in literature, however data for pairs of organic solvents and multicomponent systems are often not available. Several solubility estimates for organic solvent pairs have been established, such as the Godfrey’s miscibility numbers (“GMN”). These values, generated from experimental miscibility testing, serves as an additional assessment on whether an organic solvent pair would exhibit partial or no miscibility at ambient conditions (D. Green and M. Southard, “Liquid-liquid extraction and other liquid-liquid operations and equipment,” Perry’s Chemical Engineers’ Handbook, 9th ed., McGraw Hill Education, 2018). The miscibility assessment using GMNs are done by calculating the difference (A) between the two potential solvents’ miscibility numbers and applying the following rules, known as Godfrey’s rules:

[0065] 1. If A < 12, the solvents would likely by miscible below 25°C; 2. If 13 < A < 15, the solvents would be partially miscible, with an upper critical saturation temperature (“LICST") between 25°C and 50°C. Phase separation can be forced through addition of water in borderline cases.

[0066] 3. If A = 16, the solvents would be immiscible with an LICST between 25°C and 75°C.

[0067] 4. If A > 17, the solvents would be immiscible with an LICST above 75°C.

[0068] The LICST is the temperature at which solvents would become miscible due to increased solubility from the increase in temperature. Therefore, for phase separation experiments conducted at room temperature, solvent pairs having a A of > 16 would be suitable for complete phase separation. Commonly used water soluble solvents were identified and the GMN were applied to determine suitable solvents that would form a two-phase system. The identified systems were further reduced by removing solvents deemed unsafe for use in food and pharmaceutical processes. Other considerations undesirably high viscosity and the relative cost of solvents.

[0069] After applying the GMN, 19116 potential immiscible solvent systems were identified. Further refinement included the identification of water-soluble polar solvents and the removal of those solvents that were deemed unsafe or otherwise undesirable. Table 1 below details the 8 solvent systems ultimately identified for further testing and the determination of cannabinoid partition coefficients.

[0070] Table 1 : Identified immiscible solvents systems to be used for determining the partition coefficients of cannabinoids. LLX Experimental Setup - Cannabinoid Partitioning

[0071] The experimental setup used in the partitioning experiments detailed below consisted of five 100 mL glass separating funnels, sealed with polytetrafluoroethylene (PTFE) stop-cocks. The funnels were submerged in a 30 L water bath, filled with enough water to ensure that the funnels were completely submerged for the entire experimental run. The stems of the funnels were sealed with silicone plugs so that no water could enter into the system during experimentation. Poly vinyl chloride (PVC) plugs were manufactured to accommodate two stainless steel sheaths, through which the sampling needles could be fitted. A 2kW immersion heater with pump with PID control was used to control the temperature of the water bath. Water was circulated through the bath via a pump operating at 16 L / min.

[0072] Cannabinoid Partitioning in Selected Immiscible Solvent Combinations

[0073] Components were loaded into separating funnels using a 10 mL pipette and the weight was determined using an electronic scale with an error 0.001 g. Components were loaded so that the volumes of the non-polar and polar organic solvent phases were equal and approximately 100 mL, the total capacity of the separating funnel. Cannabinoids were introduced into the system at a set mass, dissolved in the appropriate non-polar solvent. After all the components were loaded the funnel was vigorously shaken and placed in the water bath, preheated to the operating temperature for the specific experiment. After loading, the submerged funnels were allowed to reach thermal equilibrium for 1 hour. After reaching thermal equilibrium, the funnels were individually removed and shaken vigorously for 15s and returned to the water bath to minimise change in temperature. This process was repeated 10 times for each funnel. At the end of the agitation session the stoppers were removed and replaced with the custom PVC plugs. A 115 mm stainless steel sampling needle, used to sample the bottom phase, was inserted and purged with air before being sealed by a gastight luer lock valve.

[0074] Sampling was done with the funnels secured in the water bath so as to not to disturb thermal equilibrium. The bottom phase sampling needle was first purged by drawing approximately 500 pL into a gas tight 4 mL glass syringe. Where dilution was required, 2 mL of the sample was drawn into another 4 mL glass syringe containing a measured amount (approximately 2 mL) of acetone. For the top phase, another 115 mm stainless steel needle was fitted onto a 4 mL glass syringe, containing ~2 mL acetone, and used to draw 2 mL of the sample into the syringe. Where dilution was not required, 4 mL of each phase was sampled into an empty syringe. Sampling of the two phases was done in quick succession, as to prevent departure from equilibrium. Samples were immediately refrigerated to prevent evaporation losses.

[0075] Samples were analysed using HPLC to determine the cannabinoid content in both the top and bottom phases. These values were then used to calculate the partition coefficients of CBDA, CBD, THCA, and A9-THC in the different organic systems. The results from HPLC testing were used to calculate the partition coefficients of the individual cannabinoids, as well as the total cannabinoid content of each organic system, following the equation below:

[0076] For each system duplicate runs were performed, and the average of the concentrations were taken.

[0077] Figure 2 shows the K-values for each of CBDA, CBD, A9-THC, and THCA in the various solvent systems. As can be seen from Figure 2, as expected, all four cannabinoids largely partitioned to the polar organic phase. Between the four cannabinoids, in all systems THCA (and to a lesser extent THC) had the highest concentration in the non-polar phase, but preferably partitioned to the polar phase like the other cannabinoids. CBDA showed the highest preference for partitioning towards the polar phase, followed by CBD.

[0078] Cannabinoid Extraction from Plant Wax Material

[0079] The experimental setup described above was also used in experiments to investigate the performance of an immiscible solvent system according to the method of the invention in the recovery of cannabinoids from plant wax waste material. The immiscible solvent combination used in these experiments was DMSO and n-heptane, although any of the other immiscible solvent systems described above, or any other immiscible solvent system having the required dielectric constants as specified could have been used. Three different loading volumes were used as to investigate the effect of concentration on recovery. The results of the partition coefficient (K) and the recovery (%) of cannabinoids is given in Figure 3.

[0080] As can be seen from Figure 3, the recovery at the different concentrations did not differ notably, and for all three points cannabinoid recovery was greater than 95%, which confirms the experimental partitioning results. The partition coefficients decreased with an increase in loading volume, indicating that the partitioning of cannabinoids to the non-polar phase was better at higher levels of cannabinoids in the system, but that this is not necessarily an essential or critical parameter in the broader method described herein.

[0081] Scale-up Experiments with Industrial Waste Material

[0082] A 25 L vessel was used for primary mixing and mass transfer. The vessel was left at ambient laboratory temperature (about 20°C) for the duration of the run. A immiscible solvent combination utilised in the scale-up experiments was a combination of n-heptane (as the non-polar solvent having a dielectric constant of about 6 or less) and dimethyl sulfoxide (as the polar solvent having a dielectric constant of about 30 or more).

[0083] In these experiments, the immiscible solvent combination consisted of 30 % (v / v) DMSO in the final solvent combination of DMSO:n-heptane, while the plant wax was provided in a concentration of about 30% (wt%) based on the weight of the n-heptane fraction in the solvent combination.

[0084] In these experiments, the minimal ratio of water to ensure antisolvent precipitation of the cannabinoids from solution was found to be about 4:1 (volume watervolume cannabinoid rich polar phase (bottom phase). Testing was done using ratios of 6:1 and 8:1 , at bench scale, to determine the effect of antisolvent addition on cannabinoid precipitation. Although precipitation occurred at an water to polar phase ratio of about 4:1 , it was observed that for the particular solvent system used in the these experiments, precipitation of the cannabinoids improved at a ratio of 6:1 and 8:1 ratio.

[0085] In a further step, additional n-heptane was added to the system after the addition of water, in a ratio of 1 :1 (volume n-heptane:volume bottom phase) to serve as a carrier for the precipitated cannabinoids. The procedure as followed was:

[0086] In a 25 L vessel 5 L of n-heptane and 2.15 L of DMSO were added to form an immiscible solvent combination. 1 kg of plant wax by-product was added to the n-heptane stream, and agitated to ensure dissolution of the wax in the n- heptane. The wax-solvent combination mixture was agitated for 5 minutes, left to rest, and agitated for another 5 minutes. After the agitation period, the two phases were allowed to separate (24 hours). Once a phase boundary was formed, the mixture was systematically separated in a smaller 2 L batches using a separating funnel. The top phase (non-polar n-heptane phase) was subjected to a solvent recovery stage, in which the mixture was added to a round flask and heated to 100°C to evaporate and recover the heptane. The recovered heptane was then added back to the vessel for another round of agitation and separation. This was repeated 2 more times. The residue from heptane recovery was collected and weighed after each recovery stage. After three rounds of heptane recycling, the phases were allowed to separate, and the top phase (non-polar n-heptane phase) was removed and the solvent recovered.

[0087] The bottom phase (cannabinoid rich polar fraction) was combined with water, in the specified ratios, in the antisolvent precipitation part of the method. Following the addition of water, heptane was added to the aqueous mixture (water, DMSO) to again form a two phase system. The mixture was then separated to provide a cannabinoid depleted aqueous fraction and a cannabinoid rich non-polar fraction (top phase), which was removed and collected for further processing. The cannabinoid depleted aqueous fraction was distilled to remove the water and recover the DMSO, which was recycled and reused for liquid-liquid extraction. The cannabinoid rich non-polar fraction was subjected to evaporation to remove all residual heptane. The evaporated product was redissolved in ethanol (any other suitable solvent may be used).

[0088] In the experiments conducted, samples were taken after each separation stage. The cannabinoid concentration of each sample was determined by HPLC to show the transfer of mass during each experimental run (Figure 4). As can be seen in Figure 4, the cannabinoid concentration of the non-polar top phase (heptane) remained more or less consistent after each addition of heptane to the DMSO phase. This indicates that during the initial mixing of by-product wax, heptane and DMSO, the majority of the cannabinoids partition to the bottom phase and low levels are then extracted by the top phase during each stage. This means that even though some cannabinoids are removed by the non-polar top phase (along with the wax), this amount is very low in comparison to the amounts that remain in the DMSO phase. Consequently, implementing additional mixing and separation stages to reduce wax content of the polar bottom phase will not significantly reduce cannabinoid recovery from the wax material.

[0089] Further experiments were conducted to investigate ratios of 6:1 and 8:1 (water to aqueous bottom phase) added at the various extraction stages (tested at 50 mL scale) to determine the most effective configuration for the particular immiscible solvent system and antisolvent (water) used. A third solvent having a dielectric constant of about 6 or less, n-heptane in this case, was added in a ratio of 1 :1 (volume heptane to volume aqueous bottom phase) to serve as carrier phase for the precipitated cannabinoids and to facilitate further improved separation from the aqueous phase. Three stages of extraction were done for each ratio of water addition, with fresh heptane added after each separation. Samples were taken of both the heptane and aqueous phase and the cannabinoid concentrations determined by HPLC. The results are shown in Figure 5.

[0090] As can be seen from Figure 5, in the particular immiscible solvent system used in these experiments, increasing the amount of the antisolvent (water) added to the system increased the recovery of cannabinoids from the bottom aqueous phase. The highest concentration of cannabinoids in a sample was for the top heptane phase after the first stage at the water addition ration of 8:1. The concentration of the top heptane phase at this ratio in the following stages decreased drastically, while the concentration of the bottom phase only decreased slightly. This means that the majority of the cannabinoids are removed during the first addition of heptane to the aqueous mixture, and that consecutive extraction stages are likely not required. Lower water addition ratios displayed similar trends, but had less effective extraction and needed additional stages of heptane addition to reduce the cannabinoid concentration of the bottom phase to the same as the higher water addition ratio experiments after the first stage.

[0091] This above description of some of the illustrative embodiments of the invention is to indicate how the method of the invention can be carried out. Those of ordinary skill in the art will know that various details or parameters may be modified thereby arriving at further embodiments, but that many of these embodiments will remain within the scope of the invention, as defined by the claims which follow. For example, it will be appreciated by those of ordinary skill in the art that the selection of the appropriate solvents for the immiscible solvent combination, the ratios thereof, wax loading concentration, antisolvent selection and ratios, and the use of multiple extraction and solvent recovery stages, to name a few, will be dependent on the nature of the feed stock which will differ depending on the primary cannabinoid feedstock and primary cannabinoid extraction method producing the plant wax by-product.

Claims

CLAIMS1. A method of extracting cannabinoids from plant waxes, the method comprising: a) contacting the plant waxes with an immiscible solvent combination comprising a first solvent having a dielectric constant of about 6 or less, and a second solvent having a dielectric constant of about 30 or more, b) separating the first and second solvents in the immiscible solvent combination into a wax rich non-polar fraction and a cannabinoid rich polar fraction, and c) contacting the cannabinoid rich polar fraction with a sufficient volume of an antisolvent, thereby to precipitate the cannabinoids from the cannabinoid rich fraction for optional further processing.

2. The method according to claim 1 , wherein the immiscible solvent combination comprises a first solvent having a dielectric constant of about 3 or less, and a second solvent having a dielectric constant of about 35 or more.

3. The method according to claim 1 or claim 2, wherein the first solvent is selected from the group consisting of heptane, hexane, and mixtures thereof.

4. The method according to any one of the preceding claims, wherein the second solvent is selected from the group consisting of acetonitrile, diethylene glycol, methanol, dimethyl sulfoxide, and mixtures thereof.

5. The method according to any one of the preceding claims, wherein the plant waxes are contacted with the first solvent prior to the addition of the second solvent.

6. The method according to any one of the preceding claims, wherein the plant waxes and the immiscible solvent combination is agitated for a period of time prior to allowing the immiscible solvent combination to separate for further processing.

7. The method according to any one of the preceding claims, wherein the immiscible solvent combination comprises from about 10% (v / v) to about 50% (v / v) of the second solvent, about 20% (v / v) to about 40% (v / v) of the second solvent, about 25% (v / v) to about 35% (v / v) of the second solvent, or about 30% (v / v) of the second solvent.

8. The method according to any one of the preceding claims, wherein the plant waxes are provided at a concentration of about 20% (wt%) to about 60% (wt%) of the first solvent, about 30% (wt%) to about 50% (wt%) of the first solvent, about 35% (wt%) to about 45% (wt%) of the first solvent, or about 40% (wt%) of the first solvent.

9. The method according to any one of the preceding claims, wherein the wax rich non-polar fraction separated in step (b) is recycled to step (a) for further processing.

10. The method according to any one of claims 1 - 9, wherein the wax rich non-polar fraction separated in step (b) is subjected to a solvent recovery step to recover the first solvent.11 . The method according to claim 10, wherein the recovered first solvent is recycled to step (a) for further processing.

12. The method according to any one of the preceding claims, wherein the antisolvent is water.

13. The method according to any one of the preceding claims, wherein the antisolvent is added in an excess relative to the cannabinoid rich polar fraction of more than about 4: 1 , more than about 6: 1 , or more than about 8:1.

14. The method according to claim 13, wherein the antisolvent is added in an excess relative to the cannabinoid rich polar fraction of more than about 8:1 .

15. The method according to any one of the preceding claims, wherein step (c) further comprises the addition a third solvent having a dielectric constant of about 6 or less.

16. The method according to claim 15, wherein the first solvent having a dielectric constant of about 6 or less of step (a) and the third solvent having a dielectric constant of about 6 or less is the same or different.

17. The method according to claim 6, wherein both the first solvent and the third solvent are heptane.

18. The method according to any one of claims 15 - 17, wherein the cannabinoids in the cannabinoid rich polar fraction are dissolved in the third solvent to form a cannabinoid rich non-polar fraction and a cannabinoid depleted polar fraction.

19. The method according to claim 18, wherein the cannabinoid depleted polar fraction is subjected to further processing to recover the second solvent, optionally for further use in step (a).

20. The method according to claim 18, wherein the cannabinoid rich nonpolar fraction is subjected to further processing.21 . The method according to any one of the preceding claims, wherein the method is performed at substantially room temperature.

22. The method according to any one of the preceding claims, wherein the plant waxes are waste material obtained from a prior cannabinoid extraction process.

23. The method according to any one of the preceding claims, wherein the plant waxes are Cannabis derived plant waxes.

24. A cannabinoid extract obtained by the method as claimed in any one of the preceding claims.

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