A surfactant with antioxidant function and its preparation method and application

Abstract

The present invention discloses a surfactant with an antioxidant function, which is a compound of formula I or a quaternary ammonium salt of the compound of formula I, wherein the compound of formula I is: The biosurfactant has mild synthesis conditions and simple operation, has a quenching effect on a variety of free radicals, and can increase the solubility of some insoluble drugs in water, and is expected to be applied to skin care products or as a solubilizer for drugs.

Description

Technical Field

[0001] The present invention belongs to the field of medicine or cosmetics, and specifically relates to a novel biosafe and efficient sophorolipid-based surfactant with antioxidant function, and a preparation method and application thereof. Background Art

[0002] Exploring the anti-aging mechanism of the human body and developing anti-aging products have become hot topics in the world today. At present, the theories with a high degree of consensus in the academic community include "free radical aging theory", "telomere theory" and "cell damage theory". In particular, the "free radical aging theory" has long been highly concerned by scientific researchers. The theory was first proposed by Harman in 1954. He believed that free radicals and related oxidants produced by the environment and internal metabolism would damage cell components, thereby affecting cell structure and body function. In 1968, McCord and others first discovered superoxide dismutase, which popularized the recognition of free radicals as by-products of oxidative metabolism. The mitochondrial free radical aging theory proposes that oxidative damage caused by mitochondrial free radicals is the main driving force of the aging process. The oxidative stress theory proposed in 1991 expanded aging research from biochemistry and cell biology to nutritional science, environmental medicine and molecular micro-based redox medicine.

[0003] Scientific research on the aging of the human body caused by free radicals has been recognized by most people. Although the mechanisms and forms of aging are diverse, they are generally manifested as various age-related stress reactions, inflammatory reactions, certain chronic diseases and cancers. Free radicals refer to free radicals containing unpaired electrons, ions, atoms, atomic groups or molecules. According to their atomic composition, they are mainly divided into the following categories: oxygen-centered free radicals (O2ˉ·, ·OH, RCOO·, RO·), nitrogen-centered free radicals (NO·), sulfur-centered free radicals (HS·, LS·), carbon-centered free radicals (R·), and the most studied of them are oxygen free radicals. Under normal circumstances, the production and removal of free radicals in the human body are in a dynamic equilibrium state. They are indispensable substances for the human body and play an important role in aerobic respiration electron transfer, cell signal transduction and gene regulation, inducing cell proliferation, maintaining homeostasis of the internal environment, and resisting bacteria, viruses, and cancer. However, when the body is damaged, pathologically affected, or affected by external environmental factors, the balance of free radicals in the body is broken, and free radicals will trigger a series of free radical chain reactions, causing oxidative damage to proteins, enzymes, lipids, and nucleic acids in the body. Many documents have reported the damage that free radicals can cause to the human body. For example, in vascular reconstruction therapy, nitrogen free radicals and oxygen free radicals can cause cerebral ischemia-reperfusion injury; hydroxyl free radicals can react with bases through addition and cause DNA damage; excessive production of free radicals can lead to an increased risk of different types of cancer; some literature shows that it is also related to the pathogenesis of Alzheimer's disease and other neurodegenerative diseases.

[0004] Surfactants can reduce surface tension and play roles in cleaning, foaming, emulsification, wetting, dispersion, and solubilization. The amount used in skin cleansing products is as high as 10~15%. High frequency, high concentration or improper contact with surfactants will destroy the structure of the skin surface, prompting surfactants to penetrate into the living cell layer, enhance the oxidative stress of cells, induce cells to secrete free radicals, and induce the release of inflammatory factors, ultimately leading to skin inflammation. At the same time, the hydrophobic chain of surfactants will destroy the three-dimensional structure of keratin and insert into the phospholipid bilayer of the cell membrane of keratinocytes, destroying the cell membrane structure, increasing the permeability of the cell membrane, and causing skin irritation and dryness. For example, the most commonly used sodium dodecyl sulfate (SDS) causes skin erythema, itching and other symptoms by destroying the stratum corneum barrier; lauric acid sulfate solution can also cause stratum corneum swelling. Surfactants such as K12, which are often used as emulsifiers in skin care products and skin topical preparations, may also induce inflammatory reactions. In order to be mild to the skin, non-ionic surfactants such as Span and Tween are often used to complete the emulsification of functional components, while mild surfactants with antioxidant functions are rare. In order to ensure skin safety and reduce the adverse reactions of surfactants, finding surfactants with skin protection function and mildness has become the research focus.

[0005] In recent years, the role of free radicals in skin aging has attracted more and more attention, and the widely used synthetic antioxidants such as BHA (butylated hydroxyanisole), BHT (butylated hydroxytoluene), PG (propyl gallate) are increasingly rejected by people due to their potential toxicity and carcinogenicity. Therefore, it has become an inevitable trend to find natural, efficient and low-toxic antioxidants. Replacing synthetic antioxidants with antioxidants extracted from natural plants will be a research hotspot in the future skin care and medical and health care industries. Some natural product extracts such as baicalin, vitamin E, resveratrol, caffeic acid, etc. that have been discovered and reported have high scavenging rates for various free radicals, and their antioxidant function has been reported in many reports, but their low water solubility and poor stability are their main disadvantages. How to improve their solubility has become a difficulty in the innovation of skin care product formulas.

[0006] Therefore, the development of excellent free radical scavenging products is of great significance in preventing aging, resisting and delaying aging, and reducing chronic diseases. Summary of the invention

[0007] In view of the above problems of the prior art, the present invention provides a surfactant with antioxidant function, a preparation method and application thereof. The surfactant is a new type of biosurfactant obtained by modifying sophorolipids, which can not only significantly improve the scavenging efficiency of free radicals, but also improve the solubility of baicalin and the like in water, and is an ideal antioxidant product component.

[0008] To achieve the above object, the present invention adopts the following technical solution:

[0009] A surfactant with antioxidant function, which is a compound of formula I or a quaternary ammonium salt of a compound of formula I, wherein the compound of formula I is:

[0010] ;

[0011] Among them, R1, R2, and R3 are alkyl groups.

[0012] Preferably, the quaternary ammonium salt of the compound of formula I has a structure shown in formula II:

[0013] ;

[0014] Among them, R1, R2, R3, and R4 are alkyl groups, and X is a halogen.

[0015] Preferably, R1, R2, and R3 are each independently selected from a C1-C4 alkyl group.

[0016] Preferably, R4 is selected from C1~C4 alkyl.

[0017] Preferably, X is chlorine, bromine or iodine.

[0018] The present invention also provides a method for preparing the compound of formula I, comprising the following steps:

[0019] After activating the carboxylic acid group in the acid-type sophorolipid in the first solvent, an alcoholamine compound is added and reacted at 20-40° C. to obtain the compound of formula I.

[0020] Preferably, the activation comprises the following steps:

[0021] The acid-type sophorolipid is added to the first solvent, and N,N-dicyclohexylcarbodiimide and 4-dimethylaminopyridine are added under stirring at 0-5°C.

[0022] Preferably, the first solvent is one or more of tetrahydrofuran, dioxane, N,N-dimethylformamide, dimethyl sulfoxide or acetonitrile.

[0023] The present invention also provides a method for preparing the compound of formula II, comprising the following steps:

[0024] The compound of formula I and halogenated hydrocarbon are reacted in a second solvent at 80-90° C. to obtain a compound of formula II.

[0025] Preferably, the second solvent is one or more of tetrahydrofuran, methanol, ethanol, acetone, dioxane, N,N-dimethylformamide, dimethyl sulfoxide or acetonitrile.

[0026] Preferably, the acid-type sophorolipid is prepared by the following steps:

[0027] (1) Add 3-5 equivalents of alkali and 3-7 times the mass of water to the aqueous solution of mixed sophorolipids, dissolve and react at 90-100°C for 2-3 hours;

[0028] (2) Slowly add acid to the solution obtained in step (1) to make the pH value be 3-4, then add dichloromethane, let stand to separate the layers, and obtain a three-layer solution. Take the middle layer to obtain the product.

[0029] Preferably, the base added in step (1) is 3.5 equivalents, and 5 times the mass of water is added.

[0030] Preferably, the reaction time in step (1) is 2 hours.

[0031] Preferably, the acid in step (2) is sulfuric acid or hydrochloric acid.

[0032] Preferably, the volumes of dichloromethane and the reaction solution added in step (2) are equal.

[0033] Preferably, step (2) further comprises the step of washing and concentrating the obtained intermediate layer to dryness. The washing step comprises washing once with an equal volume of dichloromethane to the intermediate layer and then washing three times with an equal volume of water.

[0034] Preferably, the mixed sophorolipid is obtained by fermentation and purification of a yeast strain. Most preferably, the yeast is Candida albicans.

[0035] Preferably, the alcoholamine compound is N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-dipropylethanolamine, N,N-dibutylethanolamine, N,N-dimethylpropanolamine, N,N-diethylpropanolamine, N,N-dipropylpropanolamine, N,N-dibutylpropanolamine, N,N-dimethylbutanolamine, N,N-diethylbutanolamine, N,N-dipropylbutanolamine or N,N-dibutylbutanolamine.

[0036] Preferably, the halogenated hydrocarbon is methyl iodide, 1-ethyl chloride, 1-ethyl bromide, 1-propane bromide or 1-butane bromide.

[0037] The present invention also provides application of the surfactant with antioxidant function.

[0038] The application is to prepare anti-aging cosmetics or to increase the concentration of poorly soluble plant extracts.

[0039] The ability of the surfactant with antioxidant function to scavenge free radicals is improved by 4 to 7 times compared with that of unmodified acid-type sophorolipids.

[0040] The surfactant with antioxidant function of the present invention improves the solubility of baicalin in water by 3 to 4 times compared with acid-type sophorolipids.

[0041] The technical solution of the present invention has the beneficial effects of:

[0042] The surfactant with antioxidant function prepared by the present invention is a surfactant of modified acidic sophorolipid, which not only has better antioxidant performance, but also can enhance the solubility of some poorly soluble drugs in water because it has a lower critical micelle concentration (CMC).

[0043] Therefore, the surfactant with antioxidant function prepared by the present invention can provide lone pair electrons to react with free radicals because of the introduction of tertiary amine structure and can become quaternary ammonium salt, thereby greatly enhancing the free radical scavenging rate. The CMC value of the modified biosurfactant is reduced, the surface activity is enhanced, and composite micelles can be formed, thereby increasing the solubility of some poorly soluble and insoluble drugs in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is the acid-type sophorolipid SL-COOH prepared in Example 1 1 HNMR spectrum.

[0045] Figure 2 is the surfactant SL-DMEA prepared in Example 1 1 HNMR spectrum.

[0046] Figure 3 The quaternary ammonium salt biosurfactant SL-DMEA-1 prepared in Example 2 1 HNMR spectrum.

[0047] Figure 4 It is the FT-IR graph of the acid-type sophorolipid SL-COOH, the biosurfactant SL-DMEA, and the quaternary ammonium salt biosurfactant SL-DMEA-1 prepared in Example 1 and Example 2.

[0048] Figure 5 It is a line graph showing the surface tension of the aqueous solution tested in Example 6 as a function of concentration.

[0049] Figure 6 It is a line graph showing the change in surface tension of the aqueous solution tested in Example 12 as a function of concentration.

[0050] Figure 7 It is a line graph of the DPPH radical scavenging rate of the biosurfactants tested in Example 6.

[0051] Figure 8 It is a line graph of the DPPH radical scavenging rate of the biosurfactants tested in Example 12.

[0052] Fig. 9 It is a line graph of the hydroxyl radical scavenging rate of the biosurfactants tested in Example 6.

[0053] Fig.10 is a line graph of the hydroxyl radical scavenging rate of the biosurfactants tested in Example 12.

[0054] Fig.11 is a line graph of the superoxide anion scavenging rates of the biosurfactants tested in Example 6.

[0055] Fig.12 is a line graph of the superoxide anion scavenging rates of the biosurfactants tested in Example 12.

[0056] Fig.13 This is a comparison chart of the solubilization effects of the biosurfactants prepared in Examples 1-5 and the control group on baicalin in Example 13.

[0057] Fig.14 This is a comparison chart of the solubilization effects of the biosurfactants prepared in Examples 7-11 and the control group on baicalin in Example 13. DETAILED DESCRIPTION

[0058] Test method:

[0059] (1) Surface tension test method:

[0060] The surface tension was determined by the platinum plate method. 4 ml of each solution of different concentrations was prepared. The automatic surface tension meter was calibrated with pure water before the experiment (the surface tension of pure water is 72 mN / m). The platinum plate was cleaned with purified water before each measurement, and then burned on an alcohol lamp until it turned red. The surface tensions of solutions of different concentrations were obtained and the surface tension curves were drawn. The minimum surface tension and critical micelle concentration of the three prepared biosurfactants were calculated based on the surface tension curves.

[0061] (2) DPPH (1,1-diphenyl-2-trinitrophenylhydrazine) free radical scavenging rate determination method:

[0062] Take 1.5 ml of DPPH (130 μmol / L) ethanol solution and 2.5 ml of the antioxidant solution or ultrapure water to be tested, shake well and incubate at room temperature for 30 minutes, and measure the absorbance with a UV-visible spectrophotometer (wavelength 517 nm, 1 cm pathlength cuvette). Calculate the result according to the formula: Scavenging rate % = [1-(As-Ab) / Ac] × 100%, where As is the absorbance of the DPPH solution after adding the antioxidant, Ab is the absorbance of the mixed solution of the antioxidant and ethanol (2.5 ml), and Ac is the absorbance of the mixed solution of DPPH and ultrapure water (1.5 ml).

[0063] (3) Hydroxyl radical scavenging rate test method:

[0064] Hydroxyl radicals are generated by Fenton reaction: H2O2 + Fe 2+ → OH + H2O + Fe 3+ . Hydroxyl radicals can destroy C=C in crystal violet and reduce the absorbance of crystal violet at 580nm. Therefore, the scavenging ability of antioxidants on hydroxyl radicals can be measured by the change in the absorbance of crystal violet at 580nm. Mix 1ml FeSO4 (2mmol / L), 0.5ml crystal violet solution (0.25mmol / L) with antioxidant or ultrapure water at room temperature, then add H2O2 (1mmol / L) and incubate at room temperature for 10min. Then measure the absorbance at 580nm using a UV-visible spectrophotometer. Scavenging rate % = [1-(As-Ab) / Ac] × 100%, where As is the absorbance of the crystal violet solution after adding antioxidants, Ab is the absorbance of the blank antioxidant, and Ac is the absorbance of the blank crystal violet solution without adding antioxidants.

[0065] (4) Superoxide anion clearance test method:

[0066] The superoxide anion scavenging activity was determined by the inhibition rate of pyrogallol auto-oxidation: pyrogallol solution (10 mmol / L) was mixed with antioxidants, and then Tris-HCl buffer with pH = 8 was added. After the mixed solution was incubated at room temperature for 30 minutes, the pH value of the solution was adjusted to 3 to stop the reaction. The absorbance at 420 nm was measured using a UV-visible spectrophotometer. The results were calculated according to the following formula: scavenging rate % = [1-(As-Ab) / Ac] × 100%, where As is the absorbance of the pyrogallol solution after adding antioxidants, Ab is the absorbance of the blank antioxidant, and Ac is the absorbance of the pyrogallol auto-oxidation control solution.

[0067] Example 1

[0068] (1) Preparation of acid-type sophorolipid (SL-COOH):

[0069] Weigh the mixed fermented sophorolipid solution (50g) into a 500ml three-necked flask, add 200ml purified water, stir evenly, then slowly add the prepared sodium hydroxide solution (3.5 equivalent NaOH, 50ml purified water), stir, the system gradually dissolves and heats to 90~100℃. React for 2.5h. After the reaction is completed, cool to room temperature, and then adjust the pH of the solution to 3~4 with acid. After adjustment, the solution becomes turbid. Transfer the solution to a 1L reaction bottle, add 250ml dichloromethane, stir for 10min, stand for 30min, and the solution is divided into three layers. Remove the upper aqueous phase and the lower organic phase, wash the intermediate product phase 100ml with 100ml dichloromethane once, and then wash it three times with 100ml purified water to wash away inorganic salts, fermentation residual sugars, oleic acid and other substances in the material. The acid-type sophorolipid obtained in the middle was evaporated on a rotary evaporator to remove dichloromethane and water, set at 50°C and vacuum -0.1Mpa. The 28.3g yellow-brown solid obtained is the acid-type sophorolipid. Its chemical structure is as follows Figure 1 shown.

[0070] (2) Weigh 11.0 g of acid-type sophorolipid (SL-COOH) solid and add it to the reaction bottle, add 40 ml of tetrahydrofuran, stir and dissolve at room temperature, add 4.0 g of N,N-dicyclohexylcarbodiimide while stirring at 0-5 °C, then add 0.1 g of 4-dimethylaminopyridine, stir and dissolve, and finally add 4.5 g of N,N-dimethylethanolamine, raise the temperature to 20-40 °C and stir for 12 h. After the reaction is completed, purify it with silica gel and elute with methanol: dichloromethane = 10:1. The obtained 9.6 g of light yellow solid is the biosurfactant SL-DMEA, and its chemical structure is as follows Figure 2 shown.

[0071] Example 2

[0072] Preparation of iodomethane-SL-DMEA biosurfactant (SL-DMEA-1):

[0073] Weigh 3.5 g of the SL-DMEA solid obtained in Example 1 and add it to a 100 ml reactor, then add 20 ml of tetrahydrofuran, then add 0.5 g of iodomethane, seal the reactor, heat to 85°C, and react for 8 hours. After the reaction is completed, evaporate the reaction solution on a rotary evaporator, then add 5 ml of ethanol to the residue to dissolve it, then add 20 ml of methyl tert-butyl ether during stirring, and stir and crystallize for 5 hours. Then filter with suction, and dry the obtained filter cake under vacuum at 45°C. The obtained 3.1 g of light yellow solid is a quaternary ammonium salt biosurfactant, recorded as SL-DMEA-1, and its chemical structure is as follows: Figure 3 shown.

[0074] Example 3

[0075] Preparation of 1-chloroethane-SL-DMEA biosurfactant SL-DMEA-2:.

[0076] Weigh 4.0 g of the biosurfactant SL-DMEA solid obtained in Example 1 and add it to a 100 ml reactor, then add 20 ml of tetrahydrofuran, then add 1.1 g of 1-chloroethane, seal the reactor, heat to 85°C, and react for 8 hours. After the reaction is completed, evaporate the reaction solution on a rotary evaporator, then add 5 ml of ethanol to the residue to dissolve it, then add 20 ml of methyl tert-butyl ether during stirring, and stir and crystallize for 5 hours. Then filter with suction, and the obtained filter cake is vacuum dried at 45°C. The obtained 3.4 g of light yellow solid is a quaternary ammonium salt biosurfactant, recorded as SL-DMEA-2.

[0077] Example 4

[0078] Preparation of 1-bromoethane-SL-DMEA biosurfactant SL-DMEA-3:

[0079] Weigh 4.0 g of the biosurfactant SL-DMEA solid obtained in Example 1 and add it to a 100 ml reactor, then add 20 ml of tetrahydrofuran, then add 0.7 g of 1-bromoethane, seal the reactor, heat to 85°C, and react for 8 hours. After the reaction is completed, evaporate the reaction solution on a rotary evaporator, then add 5 ml of ethanol to the residue to dissolve it, then add 20 ml of methyl tert-butyl ether during stirring, and stir and crystallize for 5 hours. Then filter with suction, and the obtained filter cake is vacuum dried at 45°C. The obtained 3.3 g of light yellow solid is a quaternary ammonium salt biosurfactant, recorded as SL-DMEA-3.

[0080] Example 5

[0081] Preparation of 1-bromopropane-SL-DMEA biosurfactant SL-DMEA-4:.

[0082] Weigh 3.6 g of the biosurfactant SL-DMEA solid obtained in Example 1 and add it to a 100 ml reactor, then add 20 ml of tetrahydrofuran, then add 0.7 g of 1-bromopropane, seal the reactor, heat to 85 ° C, and react for 8 hours. After the reaction is completed, evaporate the reaction solution on a rotary evaporator, then add 5 ml of ethanol to the residue to dissolve it, then add 20 ml of methyl tert-butyl ether during stirring, and stir and crystallize for 5 hours. Then filter with suction, and the obtained filter cake is vacuum dried at 45 ° C. The obtained 3.2 g of light yellow solid is a quaternary ammonium salt biosurfactant, namely SL-DMEA-4.

[0083] Example 6

[0084] SL-COOH, SL-DMEA, SL-DMEA-1, SL-DMEA-2, SL-DMEA-3 and SL-DMEA-4 prepared in Examples 1-5 were tested using the aforementioned method.

[0085] (1) Prepare aqueous solutions of the above different samples, measure the surface tension of each solution using the platinum plate method, and draw surface tension curves. The results are as follows: Figure 5 shown.

[0086] from Figure 5 It can be seen that compared with the acid-type sophorolipid SL-COOH, the biosurfactant of the present invention not only has a lower minimum surface tension, but also has a faster rate of surface tension decrease, and has better surface activity. This shows that the biosurfactant of the present invention has a lower CMC value, can form micelles at low concentrations, and improves the emulsification efficiency.

[0087] (2) Aqueous solutions of the above different samples were prepared, and aqueous solutions of N,N-dimethyldodecylamine (DTDA) and cetyltrimethylammonium bromide (CTAB) were prepared as comparisons. The scavenging rates of each sample on DPPH free radicals, hydroxyl free radicals, and superoxide anions were measured. The results are as follows: Figure 7 , 9 , as shown in 11.

[0088] It can be seen from the figure that compared with tertiary amine surfactants and quaternary ammonium salt surfactants, the biosurfactant prepared by the present invention has a higher scavenging rate for DPPH, hydroxyl radicals and superoxide anions.

[0089] Example 7

[0090] (1) The acid-type sophorolipid SL-COOH was prepared by the method of (1) in Example 1.

[0091] (2) Weigh 10.0 g of acid-type sophorolipid SL-COOH solid and add it to the reaction bottle, add 40 ml of tetrahydrofuran, stir and dissolve at room temperature, add 3.8 g of N,N-dicyclohexylcarbodiimide and then add 0.1 g of 4-dimethylaminopyridine and stir and dissolve, and finally add 4.4 g of N,N-dimethylpropanolamine and stir at 20-40 °C for 12 h. After the reaction, purify it with silica gel and elute with methanol: dichloromethane = 10:1. The obtained 8.5 g of light yellow solid is the biosurfactant SL-DMPA.

[0092] Example 8

[0093] Preparation of iodomethane-SL-DMPA biosurfactant SL-DMPA-1:

[0094] Weigh 4.1 g of the biosurfactant SL-DMPA solid obtained in Example 7 and add it to a 100 ml reactor, then add 20 ml of tetrahydrofuran, then add 0.6 g of iodomethane, seal the reactor, heat to 85°C, and react for 8 hours. After the reaction is completed, evaporate the reaction solution on a rotary evaporator, then add 5 ml of ethanol to the residue to dissolve it, then add 20 ml of methyl tert-butyl ether during stirring, and stir and crystallize for 5 hours. Then filter with suction, and the obtained filter cake is vacuum dried at 45°C. The obtained 3.6 g of light yellow solid is a quaternary ammonium salt biosurfactant, recorded as SL-DMPA-1.

[0095] Example 9

[0096] Preparation of 1-chloroethane-SL-DMPA biosurfactant SL-DMPA-2:

[0097] 5.1 g of the biosurfactant SL-DMPA solid obtained in Example 7 was weighed and added to a 100 ml reactor, followed by 20 ml of tetrahydrofuran and 0.6 g of 1-chloroethane. The reactor was sealed and heated to 85°C for 8 h. After the reaction was completed, the reaction solution was evaporated to dryness on a rotary evaporator, and then 5 ml of ethanol was added to the residue to dissolve it. Then 20 ml of methyl tert-butyl ether was added during stirring and stirred for crystallization for 5 h. Then the filter cake was vacuum dried at 45°C to obtain 3.8 g of a light yellow solid, which was a quaternary ammonium salt biosurfactant, and was recorded as SL-DMPA-2.

[0098] Example 10

[0099] Preparation of 1-bromoethane-SL-DMPA biosurfactant SL-DMPA-3:

[0100] 5.0 g of the biosurfactant SL-DMPA solid obtained in Example 7 was weighed and added to a 100 ml reactor, followed by 20 ml of tetrahydrofuran and 0.7 g of 1-bromoethane. The reactor was sealed and heated to 85°C for 8 h. After the reaction was completed, the reaction solution was evaporated to dryness on a rotary evaporator, and then 5 ml of ethanol was added to the residue to dissolve it. Then 20 ml of methyl tert-butyl ether was added during stirring and stirred for crystallization for 5 h. Then the filter cake was vacuum dried at 45°C to obtain 4.1 g of a light yellow solid, which was a quaternary ammonium salt biosurfactant, and was recorded as SL-DMPA-3.

[0101] Embodiment 11

[0102] Preparation of 1-bromopropane-SL-DMPA biosurfactant SL-DMPA-4:

[0103] Weigh 4.8 g of the biosurfactant SL-DMPA solid obtained in Example 7 and add it to a 100 ml reactor, then add 20 ml of tetrahydrofuran, then add 0.6 g of 1-bromopropane, seal the reactor, heat to 85 ° C, and react for 8 hours. After the reaction is completed, evaporate the reaction solution on a rotary evaporator, then add 5 ml of ethanol to the residue to dissolve it, then add 20 ml of methyl tert-butyl ether during stirring, and stir and crystallize for 5 hours. Then filter with suction, and the obtained filter cake is vacuum dried at 45 ° C. The obtained 4.5 g of light yellow solid is a quaternary ammonium salt biosurfactant, recorded as SL-DMPA-4.

[0104] Example 12

[0105] SL-COOH, SL-DMPA, SL-DMPA-1, SL-DMPA-2, SL-DMPA-3, and SL-DMPA-4 prepared in Examples 7-11 were tested using the aforementioned method.

[0106] (1) Prepare aqueous solutions of the above different samples, measure the surface tension of each solution using the platinum plate method, and draw surface tension curves. The results are as follows: Figure 6 shown.

[0107] from Figure 6 It can be seen that compared with the acid-type sophorolipid SL-COOH, the biosurfactant of the present invention also has a faster efficiency in reducing surface tension and a lower CMC value. The biosurfactant of the present invention is easier to form micelles, their molecules are more closely arranged and distributed on the interface, and the formed micelles are more stable, so they have better surface activity.

[0108] (2) Aqueous solutions of the above different samples were prepared, and aqueous solutions of N,N-dimethyldodecylamine (DTDA) and cetyltrimethylammonium bromide (CTAB) were prepared as comparisons. The scavenging rates of each sample on DPPH free radicals, hydroxyl free radicals, and superoxide anions were measured. The results are as follows: Figure 8 , 10 , as shown in 12.

[0109] It can be seen from the figure that the biosurfactant prepared by the present invention has a higher scavenging rate for DPPH, hydroxyl radicals and superoxide anions.

[0110] Example 13

[0111] Solubilization experiment of baicalin by biosurfactant:

[0112] The biosurfactants prepared in Examples 1-5 and 7-11 were prepared into aqueous solutions with a concentration of 2 mmol / L, and 10 ml of each solution was taken. 100 mg of baicalin solid was added to each 10 ml surfactant solution, and ultrasonic treatment was performed for 30 min. Then, each solution was filtered and the absorbance of the filtrate was measured at 317 nm by an ultraviolet spectrophotometer. The concentration of baicalin in each filtrate was obtained by using the standard curve of baicalin concentration. The measurement results are shown in FIG. Fig.13 , 14 shown.

[0113] from Fig.13 , 14 It can be seen that the biosurfactant prepared by the present invention can significantly increase the solubility of poorly soluble baicalin.

Claims

1. A surfactant having an antioxidant function, characterized in that: The surfactant is a compound of formula I or a quaternary ammonium salt of a compound of formula I, wherein the compound of formula I is: ； Wherein, R1, R2, and R3 are each independently selected from a C1~C4 alkyl group.

2. The surfactant according to claim 1, characterized in that The quaternary ammonium salt of the compound of formula I has the structure shown in formula II: ； Wherein, R1, R2, R3, and R4 are each independently selected from C1-C4 alkyl groups, and X is a halogen.

3. The surfactant according to claim 2, characterized in that X is chlorine, bromine or iodine.

4. The method for preparing the surfactant according to claim 1, characterized in that: The steps include: After activating the carboxylic acid group in the acid-type sophorolipid in the first solvent, an alcoholamine compound is added and reacted at 20-40° C. to obtain the compound of formula I.

5. The preparation method according to claim 4, characterized in that: The activation comprises the following steps: The acid-type sophorolipid is added to the first solvent, and N,N-dicyclohexylcarbodiimide and 4-dimethylaminopyridine are added under stirring at 0-5°C.

6. The preparation method according to claim 5, characterized in that: The first solvent is one or more of tetrahydrofuran, dioxane, N,N-dimethylformamide, dimethyl sulfoxide or acetonitrile.

7. The preparation method according to claim 4, characterized in that: The acid-type sophorolipid is prepared by the following steps: (1) Add 3-5 equivalents of alkali and 3-7 times the mass of water to the aqueous solution of mixed sophorolipids, dissolve and react at 90-100°C for 2-3 hours; (2) Slowly add acid to the solution obtained in step (1) to make the pH value be 3-4, then add dichloromethane, let stand to separate the layers, and obtain a three-layer solution. Take the middle layer to obtain the product.

8. The preparation method according to claim 7, characterized in that: The reaction time in step (1) is 2 hours.

9. The preparation method according to claim 7, characterized in that: The added base in step (1) is 3.5 equivalents, and the added water is 5 times the mass.

10. The preparation method according to claim 7, characterized in that: The acid in step (2) is sulfuric acid or hydrochloric acid.

11. The preparation method according to claim 7, characterized in that: The mixed sophorolipid is obtained by fermentation and purification of yeast strains.

12. The preparation method according to claim 11, characterized in that: The yeast is Candida albicans.

13. The preparation method according to claim 4, characterized in that: The alcoholamine compound is N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-dipropylethanolamine, N,N-dibutylethanolamine, N,N-dimethylpropanolamine, N,N-diethylpropanolamine, N,N-dipropylpropanolamine, N,N-dibutylpropanolamine, N,N-dimethylbutanolamine, N,N-diethylbutanolamine, N,N-dipropylbutanolamine or N,N-dibutylbutanolamine.

14. Use of the surfactant with antioxidant function as claimed in claim 1.

15. The use according to claim 14, characterized in that: The application is to prepare anti-aging cosmetics or to increase the solubility of baicalin.

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