Preparation method of lignin-flavone co-separation product and application of lignin-flavone co-separation product in sunscreen cream

Abstract

The invention relates to the technical field of functionalized lignin preparation, and discloses a preparation method of a lignin-flavone co-separation product and application of the lignin-flavone co-separation product in sunscreen cream. The method comprises the following steps: adding L-cysteine or a derivative thereof into an acidic material / dioxane solution to serve as a reaction solution, mixing and heating a plant raw material and the reaction solution, and separating after the reaction is completed to obtain a lignin-flavone co-separation product. The content of total flavonoids in the lignin-flavone co-separation product disclosed by the invention is obviously increased and can reach 26.47 mg / g. When the obtained lignin-flavone co-separation product is applied to a sunscreen product, the SPF value is greater than 32, the PFA value is greater than 10, and the light stability is good.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of functionalized lignin, and more particularly, to a method for preparing a lignin-flavonoid co-separation product and its application in sunscreen. Background Art

[0002] Lignin in plants can effectively absorb ultraviolet rays in sunlight due to the presence of benzene rings and a large number of carbonyl groups, double bonds and other structures, and a large number of phenolic hydroxyl groups can timely capture free radicals generated by ultraviolet light, reducing the oxidative damage caused by ultraviolet radiation. Therefore, it has good anti-ultraviolet and antioxidant properties. Existing studies have shown that after mixing alkali lignin with blank cream and commercial sunscreen, the corresponding sun protection factor (SPF) has been improved, and excellent synergistic effects have been shown between lignin and commercial sunscreen. However, the lack of a large conjugated system in lignin molecules requires improvement in its protection in the UVA region (320-400 nm). In order to improve the UVA protection ability of lignin, people have carried out nanosizing and chemical modification on lignin. These include adding the extracted lignin into tetrahydrofuran (THF) to convert it into submicron particles, and its protection effect in the UVA region is better than that of commercially available sunscreen with SPF15. In addition, some researchers have introduced a spiropyran structure (SP) into lignin, enhancing the absorbance of lignin in the UVA and UVB regions. However, most of the current preparation of lignin nanoparticles and modification grafting involve the use of different solvents such as tetrahydrofuran (THF), dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF), etc., which pose potential health risks and the operation process is complex. Therefore, it is crucial to develop a simple and safe method to improve the UVA protection ability of lignin for its application in sunscreen.

[0003] Flavonoids are natural phenolic compounds commonly found in many higher plants. The ultraviolet absorption spectra of some flavonoid compounds peak between 320 and 385 nm, which covers an important part of the UVA spectrum. Due to their unique long conjugated structure, they exhibit good ultraviolet absorption ability in the UVA region and can be used as a photoprotectant. Researchers obtained flavonoid-rich extracts from plants, and the prepared emulsions showed good UVA protection performance. As a member of the flavonoid family, tricin is widely distributed in the leaves and stems of Gramineae plants. It has been confirmed to be a lignin monomer and is linked to other lignin monomers through β-O-4 bonds. Some studies have shown that compared with softwood lignin and hardwood lignin without tricin, wheat straw lignin containing tricin exhibits a higher SPF value. Therefore, increasing the content of tricin in lignin can improve the protection ability of lignin in the UVA region. In addition, some Gramineae plant raw materials contain flavonoid substances other than tricin, most of which are combined with glycogen to form glycosides or exist in the form of carbon glycosides. However, the process of separating flavonoids alone from raw materials is complex and time-consuming.

[0004] In the prior art 202211247795.7, an aqueous solution of L-cysteine hydrochloride and an organic acid is used as a pretreatment solution, and the lignocellulosic raw material is mixed with the pretreatment solution for pretreatment. The β-O-4 structure is retained in the obtained L-cysteine lignin, improving the anti-ultraviolet radiation performance of commercial sunscreen. However, this method has a complex process, the raw materials need to be dewaxed first, and the obtained product has a low flavonoid content and limited sunscreen performance. Summary of the Invention

[0005] The present invention aims to overcome the above-mentioned defects of the prior art, such as the need for prior dewaxing treatment, the lignin separated without flavonoids, the complex and time-consuming process, insufficient sunscreen performance, and poor environmental friendliness, and provides a preparation method for a lignin-flavonoid co-separation product;

[0006] Another object of the present invention is to provide a lignin-flavonoid co-separation product;

[0007] Another object of the present invention is to provide an application of a lignin-flavonoid co-separation product.

[0008] To solve the above technical problems, the technical solution of the present invention is as follows:

[0009] A preparation method for a lignin-flavonoid co-separation product, comprising the following steps: adding L-cysteine or its derivative to an acidic substance / organic solvent as a reaction solution, mixing the plant raw material with the reaction solution and heating, and separating to obtain the lignin-flavonoid co-separation product after the reaction is completed; the organic solvent includes butanol compounds or dioxane.

[0010] Preferably, the acidic substance includes hydrochloric acid for providing an acidic environment.

[0011] Preferably, the molar concentration of the acidic substance is 2 mol / L.

[0012] Preferably, the L-cysteine derivative includes L-cysteine salt and L-cysteine hydrate.

[0013] Preferably, in the acidic substance / organic solvent solution, the volume ratio of the acidic substance to the organic solvent is 9:1.

[0014] Preferably, the plant raw material is not subjected to dewaxing treatment.

[0015] Furthermore, the plant raw material is a gramineous plant.

[0016] Preferably, the gramineous plant raw material includes banana leaves, bamboo leaves, wheat straw, and rice straw.

[0017] Furthermore, the mass ratio of the added L-cysteine hydrochloride to the plant raw material is 0.2 - 1, and the mass ratio of the acidic substance / organic solvent to the plant raw material is 8 - 20.

[0018] Preferably, the mass ratio of the added L-cysteine hydrochloride to the plant raw material is 0.46, and the mass ratio of the acidic substance / organic solvent to the plant raw material is 17.52.

[0019] Furthermore, the heating temperature is 80 - 130 °C, and the heating time is 0.5 - 3 h.

[0020] Preferably, the heating temperature is 120 °C, and the heating time is 1.5 h.

[0021] A lignin-flavonoid co-separation product is prepared by the preparation method of the lignin-flavonoid co-separation product.

[0022] Furthermore, the total flavonoid content of the lignin-flavonoid co-separation product is greater than 10 mg / g.

[0023] Preferably, the total flavonoid content of the lignin-flavonoid co-separation product is 10 - 50 mg / g.

[0024] An application of a lignin-flavonoid co-separation product is for preparing an anti-UV sunscreen product.

[0025] A sunscreen product includes the lignin-flavonoid co-separation product.

[0026] Furthermore, the content of the lignin-flavonoid co-separation product in the sunscreen product is 1 - 20 wt%.

[0027] Application of a lignin separation reagent for preparing a co-separation product of lignin and flavonoids; the lignin separation reagent comprises L-cysteine or its derivative added with an acidic substance / organic solvent; the organic solvent comprises a butanol compound or dioxane.

[0028] Through an innovative method, the present invention realizes the co-separation of lignin and flavonoids, breaking through the limitations of traditional lignin extraction technology in sunscreen applications. Existing technologies generally rely on dewaxing pretreatment to remove non-polar impurities on the plant surface, but this process causes the loss of flavonoid substances, resulting in the weak ultraviolet absorption ability of the finally separated lignin in the UVA region and making it difficult to form an efficient sunscreen barrier. The present invention proposes a co-separation strategy without dewaxing. By using an acidic substance / organic solvent and L-cysteine as a reaction system, a flavonoid-containing lignin is prepared from gramineous plant raw materials, and the free flavonoids in the extract, the non-free flavonoids in the lignin, and the lignin are co-separated, improving the content of total flavonoids in the separated lignin sample. The reducing property of L-cysteine not only helps to maintain the β-O-4 bond structure of lignin, but also can avoid the oxidative degradation of flavonoids during the separation process, thereby effectively increasing the flavonoid content of the final product.

[0029] In terms of ultraviolet protection performance, the phenylpropane structure of lignin provides a certain ultraviolet shielding ability, but its absorption band is mainly concentrated in the UVB region. Due to the electron transition characteristics of the conjugated system of flavonoid molecules, they can significantly enhance the UVA absorption. The co-separation product of lignin and flavonoids prepared by the present invention has excellent antioxidant properties and has a synergistic effect with titanium dioxide, zinc oxide, etc. in sunscreen products, improving the protection ability in the UVA and UVB regions and making up for the deficiencies of using lignin alone as a sunscreen ingredient. Compared with traditional alkali lignin, the sunscreen performance of the present invention is significantly improved, and it can be directly applied to sunscreen formulations without relying on chemical modification, having more excellent industrial potential.

[0030] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0031] 1. Improve the flavonoid retention rate: The present invention directly uses gramineous plant raw materials without complex dewaxing pretreatment, effectively avoiding the loss of flavonoids, increasing the flavonoid content of the final product, and enhancing the antioxidant and ultraviolet absorption abilities.

[0032] 2. Improvement of sun protection performance: Different from traditional lignin separation methods that only obtain lignin, the present invention can simultaneously enrich lignin and flavonoids. After being compounded with a low-fold sunscreen containing a physical sunscreen agent, the sun protection performance is significantly improved, with more excellent ultraviolet absorption ability in the UVA and UVB regions, SPF value > 32, PFA value > 10, and good light stability. Compared with traditional methods, the method of the present invention increases SPF by 24.7% - 69.4% and PFA by 13.2% - 31.5%, which is suitable for the development of highly efficient natural sunscreen agents.

[0033] 3. Simplify operation and improve efficiency: This method uses an L-cysteine or its derivative / acetic substance / organic solvent system, and the co-separation of lignin-flavonoids can be completed within 1.5 hours, and the separation yield of lignin can reach 47.7%. Compared with traditional methods, it reduces the reaction steps and time, and improves the industrial production efficiency.

[0034] 4. Environmentally friendly process: Avoid using organic solvents such as dichloromethane and acetone for dewaxing and extraction, greatly reducing environmental pollution and making the production process more green and sustainable. Using gramineous plant raw materials also broadens the high-value utilization ways of biomass resources. Description of the Drawings

[0035] Figure 1 It is the 2D-HSQC NMR spectrum of lignin-flavonoids obtained from the separation of banana leaves in Example 1;

[0036] Figure 2 It is the 2D-HSQC NMR spectrum of lignin-flavonoids obtained from the separation of bamboo leaves in Example 2;

[0037] Figure 3 It is the 2D-HSQC NMR spectrum of lignin obtained from the separation of banana leaves in Comparative Example 1;

[0038] Figure 4 It is the 2D-HSQC NMR spectrum of lignin obtained from the separation of bamboo leaves in Comparative Example 2;

[0039] Figure 5 It is the ultraviolet absorption curve of the samples obtained in Examples 1 and 2 and Comparative Examples 1 and 2. Detailed Embodiments

[0040] The following further illustrates the present invention in conjunction with the drawings of the specification and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0041] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0042] Example 1

[0043] 1. Preparation of lignin-flavonoid co-separation product

[0044] Mix dioxane and 2M HCl solution in a volume ratio of 9:1 for later use. Weigh 5.0 g of banana leaf raw material into a round-bottom flask, add the prepared 1,4-dioxane / hydrochloric acid solution thereto, and then add 2.3 g of L-cysteine hydrochloride. The solid-liquid ratio is 1:12 (g / mL). Stir and react in a sand bath at 120 °C for 1.5 h. After the reaction, cool to room temperature, filter and collect the filtrate, and adjust the pH value to about 3.0 with saturated NaHCO 3 solution. Then concentrate the solution under reduced pressure at 45 °C, drop the concentrated solution into 500 mL of deionized ice water, let it stand in a 4 °C refrigerator for 12 h, and obtain the lignin-flavonoid co-separation product NML by centrifugal freeze-drying.

[0045] 2. Application to sunscreen

[0046] Grind and sieve NML, weigh 0.02 g of the obtained lignin-flavonoid and mix it with 1.9 g of commercial SPF 15 sunscreen, and stir well at 200 rpm for 24 h under light-shielded conditions.

[0047] Example 2

[0048] 1. Preparation of lignin-flavonoid co-separation product

[0049] Mix dioxane and 2M HCl solution in a volume ratio of 9:1 for later use. Weigh 5.0 g of bamboo leaf raw material into a round-bottom flask, add the prepared 1,4-dioxane / hydrochloric acid solution thereto, and then add 2.3 g of L-cysteine hydrochloride. The solid-liquid ratio is 1:12 (g / mL). Stir and react in a sand bath at 120 °C for 1.5 h. After the reaction, cool to room temperature, filter and collect the filtrate, and adjust the pH value to about 3.0 with saturated NaHCO 3 solution. Then concentrate the solution under reduced pressure at 45 °C, drop the concentrated solution into 500 mL of deionized ice water, let it stand in a 4 °C refrigerator for 12 h, and obtain the lignin-flavonoid co-separation product NBL by centrifugal freeze-drying.

[0050] 2. Application to sunscreen

[0051] Grind and sieve NBL, weigh 0.1 g of the obtained lignin-flavonoid and mix it with 1.9 g of commercial SPF 15 sunscreen, and stir well at 200 rpm for 24 h under light-shielded conditions.

[0052] Example 3

[0053] 1. Preparation of lignin-flavonoid co-separation product

[0054] Mix dioxane and 2M HCl solution in a volume ratio of 9:1 for later use. Weigh 5.0 g of wheat straw raw materials into a round-bottom flask, add the prepared 1,4-dioxane / hydrochloric acid solution thereto, and then add 2.3 g of L-cysteine hydrochloride. The solid-liquid ratio is 1:12 (g / mL). Stir and react in a sand bath at 120 °C for 1.5 h. After the reaction is completed, cool to room temperature, filter to collect the filtrate, and adjust the pH value to about 3.0 with saturated NaHCO 3 solution. Then concentrate the solution under reduced pressure at 45 °C, drop the concentrated solution into 500 mL of deionized ice water, let it stand in a 4 °C refrigerator for 12 h, and obtain the lignin-flavonoid co-separation product NWL by centrifugal freeze-drying.

[0055] 2. Application in sunscreen

[0056] Grind and sieve NWL, weigh 0.1 g of the obtained lignin-flavonoid and mix it with 1.9 g of commercial SPF 15 sunscreen, and stir well at 200 rpm for 24 h under light-proof conditions.

[0057] Comparative Example 1

[0058] 1. Preparation of lignin sample

[0059] Mix dioxane and 2M HCl solution in a volume ratio of 9:1 for later use. Weigh 5.0 g of dewaxed banana leaf raw materials into a round-bottom flask, add the prepared 1,4-dioxane / hydrochloric acid solution thereto, and then add 2.3 g of L-cysteine hydrochloride. The solid-liquid ratio is 1:12 (g / mL). Stir and react in a sand bath at 120 °C for 1.5 h. After the reaction is completed, cool to room temperature, filter to collect the filtrate, and adjust the pH value to about 3.0 with saturated NaHCO 3 solution. Then concentrate the solution under reduced pressure at 45 °C, drop the concentrated solution into 500 mL of deionized ice water, let it stand in a 4 °C refrigerator for 12 h, and obtain the lignin ML by centrifugal freeze-drying.

[0060] 2. Application in sunscreen

[0061] Grind and sieve ML, weigh 0.02 g of the obtained lignin sample and mix it with 1.9 g of commercial SPF 15 sunscreen, and stir well at 200 rpm for 24 h under light-proof conditions.

[0062] Comparative Example 2

[0063] 1. Preparation of lignin sample

[0064] Mix dioxane and 2M HCl solution in a volume ratio of 9:1 for later use. Weigh 5.0 g of dewaxed bamboo leaves raw materials into a round-bottom flask, add the above-prepared 1,4-dioxane / hydrochloric acid solution thereto, and then add 2.3 g of L-cysteine hydrochloride. The solid-liquid ratio is 1:12 (g / mL). Stir and react in a sand bath at 120 °C for 1.5 h. After the reaction is completed, cool to room temperature, filter to collect the filtrate, and adjust the pH value to about 3.0 with saturated NaHCO 3 solution. Then concentrate the solution under reduced pressure at 45 °C, drop the concentrated solution into 500 mL of deionized ice water, let it stand in a 4 °C refrigerator for 12 h, and obtain lignin BL by centrifugal freeze-drying.

[0065] 2. Application to sunscreen

[0066] Grind and sieve BL, weigh 0.1 g of the obtained lignin sample and mix it with 1.9 g of commercial SPF 15 sunscreen, and stir well at 200 rpm for 24 h under dark conditions.

[0067] Comparative Example 3

[0068] 1. Preparation of lignin sample

[0069] Mix dioxane and 2M HCl solution in a volume ratio of 9:1 for later use. Weigh 5.0 g of dewaxed wheat straw raw materials into a round-bottom flask, add the above-prepared 1,4-dioxane / hydrochloric acid solution thereto, and then add 2.3 g of L-cysteine hydrochloride. The solid-liquid ratio is 1:12 (g / mL). Stir and react in a sand bath at 120 °C for 1.5 h. After the reaction is completed, cool to room temperature, filter to collect the filtrate, and adjust the pH value to about 3.0 with saturated NaHCO 3 solution. Then concentrate the solution under reduced pressure at 45 °C, drop the concentrated solution into 500 mL of deionized ice water, let it stand in a 4 °C refrigerator for 12 h, and obtain lignin WL by centrifugal freeze-drying.

[0070] 2. Application to sunscreen

[0071] Grind and sieve WL, weigh 0.1 g of the obtained lignin sample and mix it with 1.9 g of commercial SPF 15 sunscreen, and stir well at 200 rpm for 24 h under dark conditions.

[0072] Comparative Example 4

[0073] 1. Preparation of lignin sample

[0074] Weigh 5.0 g of dewaxed banana leaves separately into a round-bottom flask, add 50 mL of 1 M NaOH solution, and stir at 120 °C for 2 h. After the reaction is completed, filter to collect the filtrate, and adjust the pH to about 3.0 with 1 M HCl solution. Place the solution in a 4 °C refrigerator for 12 h to precipitate lignin, and obtain crude alkali lignin through centrifugation and freeze-drying. Add the crude lignin to 1,4-dioxane / water solution (96:4, v / v) with a solid-liquid ratio of 1:40, stir at room temperature for 24 h, and repeat twice. Distill the liquid part under reduced pressure. After evaporation to dryness, add 5 mL of acetone / water solution (9:1, v / v), back-titrate to 500 mL of deionized water, place it in the refrigerator to stand, centrifuge to remove the supernatant, and freeze-dry to obtain purified banana leaf alkali lignin MAL.

[0075] 2. Application to sunscreen

[0076] Grind and sieve MAL, weigh 0.1 g of the obtained lignin sample and mix it with 1.9 g of commercial SPF 15 sunscreen, and stir thoroughly at 200 rpm for 24 h under light-shielded conditions.

[0077] Control Example 5

[0078] 1. Preparation of lignin sample

[0079] Weigh 5.0 g of dewaxed bamboo leaves separately into a round-bottom flask, add 50 mL of 1 M NaOH solution, and stir at 120 °C for 2 h. After the reaction is completed, filter to collect the filtrate, and adjust the pH to about 3.0 with 1 M HCl solution. Place the solution in a 4 °C refrigerator for 12 h to precipitate lignin, and obtain crude alkali lignin through centrifugation and freeze-drying. Add the crude lignin to 1,4-dioxane / water solution (96:4, v / v) with a solid-liquid ratio of 1:40, stir at room temperature for 24 h, and repeat twice. Distill the liquid part under reduced pressure. After evaporation to dryness, add 5 mL of acetone / water solution (9:1, v / v), back-titrate to 500 mL of deionized water, place it in the refrigerator to stand, centrifuge to remove the supernatant, and freeze-dry to obtain purified bamboo leaf alkali lignin BAL.

[0080] 2. Application to sunscreen

[0081] Grind and sieve BAL, weigh 0.1 g of the obtained lignin sample and mix it with 1.9 g of commercial SPF 15 sunscreen, and stir thoroughly at 200 rpm for 24 h under light-shielded conditions.

[0082] Result analysis

[0083] Figure 1 and Figure 2, a strong aromatic signal can be observed, indicating that the flavonoids in the product are well retained, the ether bonds of lignin are not damaged, and flavonoid glycosides may be contained. The main flavonoid in the co-separation product of banana leaves is quercetin; the main flavonoids in the co-separation product of bamboo leaves are isoorientin and vicenin-2; the main flavonoid in the co-separation product of wheat straw is vicenin-2. Figures 3 to 4 The signals in the aromatic ring region are significantly reduced, especially the disappearance or weakening of some flavonoid-related peaks, indicating that the dewaxing treatment leads to flavonoid loss, leaving only the lignin structure.

[0084] Table 1

[0085]

[0086] According to the results in Table 1, Examples 1-3 significantly increased the total flavonoid content of the product. In Comparative Examples 1-3 using dewaxed raw materials, more flavonoids were lost, and the dewaxing treatment affected the co-separation of flavonoids. Using non-dewaxed bamboo leaves can better retain flavonoids (26.47 mg / g), improving the antioxidant and sunscreen properties of the final product. Comparative Examples 4-5 used traditional methods to separate and extract lignin, and the co-separation of lignin and flavonoids could not be achieved. In addition, in the lignin-flavonoid co-separation product prepared by the present invention, the separation yield of lignin can reach 47.7%.

[0087] In terms of sunscreen performance, Examples 1-3 using non-dewaxed raw materials had an SPF increase range of 24.7% - 39.1% and a PFA increase range of 13.2% - 25.4% compared with Comparative Examples 1-3 using dewaxed raw materials; compared with Comparative Examples 4-5 using the traditional alkali lignin preparation method, the SPF increase range reached 47.6% - 69.4%, and the PFA increase range reached 20.9% - 31.5%. The above results show that dewaxing reduces the flavonoid content, resulting in a decline in sunscreen performance, especially a significant decrease in the SPF value. Traditional alkali lignin cannot co-separate flavonoids, resulting in the worst sunscreen effect.

[0088] Obviously, the above examples of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a lignin-flavonoid co-separation product, characterized in that: The following steps are involved: L-cysteine ​​or its derivatives are added to an acidic substance / organic solvent as a reaction solution, the plant raw material and the reaction solution are mixed and heated, and after the reaction is completed, a lignin-flavonoid co-separation product is obtained by separation; the organic solvent includes butanol compounds or dioxane.

2. The method for preparing the lignin-flavonoid co-separation product according to claim 1, characterized in that: The plant raw materials are grass plants.

3. The method for preparing the lignin-flavonoid co-separation product according to claim 1, characterized in that: The mass ratio of the added L-cysteine ​​hydrochloride to the plant raw material is 0.2-1, and the mass ratio of the acidic substance / organic solvent to the plant raw material is 8-20.

4. The method for preparing the lignin-flavonoid co-separation product according to claim 1, characterized in that: The heating temperature is 80-130°C and the heating time is 0.5-3h.

5. A lignin-flavonoid co-separation product, characterized in that: The lignin-flavonoid co-separation product is prepared by the preparation method of any one of claims 1 to 4.

6. The lignin-flavonoid co-separation product according to claim 5, characterized in that: The total flavonoid content of the lignin-flavonoid co-separation product is greater than 10 mg / g.

7. An application of the lignin-flavonoid co-separation product according to any one of claims 5 to 6, characterized in that: Used to prepare anti-ultraviolet sunscreen products.

8. A sunscreen product, characterized in that: The invention comprises the lignin-flavonoid co-separation product as described in any one of claims 5 to 6.

9. The sunscreen product according to claim 8, characterized in that: The content of the lignin-flavonoid co-separation product in the sunscreen daily chemical product is 1-20wt%.

10. An application of a lignin separation reagent, characterized in that: Used for preparing lignin-flavonoid co-separation products; the lignin separation reagent comprises L-cysteine ​​or its derivatives added with acidic substances / organic solvents; the organic solvent comprises butanol compounds or dioxane.

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