A hydrophobically modified vitamin B6 and its preparation method and application

Abstract

The present invention discloses a hydrophobically modified vitamin B6, a preparation method thereof, and an application thereof, belonging to the field of cosmetic technology. Nervonic acid is selected as a hydrophobic modifier for water-soluble vitamin B6, and pyridoxine neuramide is synthesized. This allows the water-soluble vitamin B6 to carry natural nervonic acid through the stratum corneum of the skin, thereby increasing the transdermal absorption of vitamin B6. The present invention selects nervonic acid as a hydrophobic modifier for water-soluble vitamin B6, and synthesizes pyridoxine neuramide. This allows the water-soluble vitamin B6 to carry natural nervonic acid through the stratum corneum of the skin, thereby increasing the transdermal absorption of vitamin B6. The pyridoxine neuramide prepared by the present invention simultaneously exerts the physiological activities of vitamin B6 and nervonic acid on the skin, has a good skin barrier repair effect, reduces transepidermal water loss of the skin, improves moisturizing efficiency, and also has certain anti-inflammatory and antioxidant effects. It is a skin conditioning agent that is easy to use and has excellent effects.

Description

Technical Field

[0001] The present invention belongs to the technical field of cosmetics, and in particular relates to a hydrophobically modified vitamin B6 and a preparation method and application thereof. Background Art

[0002] Vitamin B6, a water-soluble vitamin in the B complex, is extremely unstable under light and alkaline conditions and is intolerant to high temperatures. Commonly used vitamin B6 products in the cosmetics market include pyridoxine hydrochloride and pyridoxine derivative esters. Vitamin B6 and its derivatives can regulate sebaceous gland activity, promote protein and amino acid metabolism, and alleviate the body's oxidative stress response, effectively maintaining hair follicle and scalp health, regulating skin oil secretion, and repairing and strengthening the skin barrier. They are highly effective skin and hair conditioners in cosmetics. However, vitamin B6's water solubility limits its transdermal absorption efficiency, and exposure to light and alkaline environments increases its instability in cosmetic systems. Therefore, suitable methods are needed to modify its hydrophobicity. Currently, there are only a few hydrophobic derivatives of vitamin B6, including vitamin B6 palmitate and vitamin B6 octanoate. The carbon chain length of the hydrophobic group in these two derivatives is relatively short, resulting in poor fat solubility and skin permeability.

[0003] Nervonic acid (NA) is an ultra-long-chain n-9 monounsaturated fatty acid, chemically known as cis-15-tetracosenoic acid. It is a core natural component of brain nerve fibers and cells, and an essential nutrient for brain development and maintenance. It has biological functions such as repairing nerve ending activity and enhancing immunity. Current studies indicate that Acer truncatum seed oil, a plant oil rich in NA, can effectively balance skin permeability and promote skin barrier repair, significantly improving skin elasticity and smoothness. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a hydrophobically modified vitamin B6, a preparation method thereof, and an application thereof. The hydrophobic group of the modified VB6 is tetracosenoic acid, which has better skin affinity, increased transdermal absorption, and has a good skin barrier repair effect, reduces transepidermal water loss, improves moisturizing efficiency, and also has certain anti-inflammatory and antioxidant effects.

[0005] Technical solution: To achieve the above purpose, the present invention adopts the following technical solution:

[0006] A hydrophobically modified vitamin B6 is pyridoxine neurate, and the structural formula is:

[0007] Where R = C 23 H 45 .

[0008] A method for preparing hydrophobically modified vitamin B6 comprises the following steps:

[0009] (1) Acylation of nervonic acid: dissolve nervonic acid in solvent benzene, install a reflux device and a gas absorption device, fill the reaction system with nitrogen for protection, and then slowly add thionyl chloride to the reaction system. After the addition is completed, heat it to 80-85°C and continue stirring to react for 2.5 hours. After stopping the reaction, maintain a nitrogen atmosphere, continue to keep warm, and remove excess thionyl chloride and solvent benzene by vacuum distillation to obtain nervonic acid chloride;

[0010] (2) Synthesis of pyridoxine ceramide: A certain amount of pyridoxine was dissolved in 5% sodium hydroxide solution, and then dichloromethane was added. The dichloromethane solution of ceramide chloride and 1 mol / L sodium hydroxide solution were added to two dropping funnels respectively, and the mixture was slowly added dropwise to the reaction system at room temperature. The pH of the sodium hydroxide solution was maintained at 8.5-9.5. The addition was completed within 1 hour. The mixture was then reacted at 20-25°C for 20 hours. After the reaction was completed, an appropriate amount of dichloromethane was added and stirred thoroughly. The reaction solution was transferred to a separating funnel and allowed to stand for stratification. The lower layer solution was removed and washed with 1% hydrochloric acid and deionized water, and then dried over anhydrous sodium sulfate. Finally, the dichloromethane was removed by distillation under reduced pressure. The crude product was washed with ethanol and dried under vacuum to obtain a crude product. The pure pyridoxine ceramide was recrystallized from 95% ethanol.

[0011] In the above steps, the molar ratio of reactants in step (1) is nervonic acid: thionyl chloride = 2:3, and the molar ratio of reactants in step (2) is pyridoxine: nervonic acid chloride = 1: (1-2); thionyl chloride is added dropwise to the reaction system over a period of 30 minutes;

[0012] The hydrophobically modified vitamin B6 is used in skin care products, which contain the following components by weight: 2-5% emulsifier, 5-10% emollient, 2-6% moisturizer, 0.05% chelating agent, 0.1-1% pyridoxine neurate, 0.1-0.5% preservative, and deionized water to make up the balance.

[0013] The skin care product containing hydrophobically modified vitamin B6 comprises the following preparation steps:

[0014] S1: Mix disodium EDTA, glycerin, methylparaben and a certain amount of water in appropriate proportions, heat to 80°C, stir evenly and dissolve completely;

[0015] S2: Mix the emulsifier, emollient and propylparaben in proportion, heat to 80°C and melt completely;

[0016] S3: Pour S2 into S1, stir for 3 minutes, and homogenize for 5 minutes until emulsification is complete;

[0017] S4: After the material is cooled to 40°C, pyridoxine neurate and the remaining amount of deionized water are added.

[0018] In the above steps, the emulsifier is one or more of cetearyl olivate, sorbitan olivate, glyceryl stearate, and PEG-100 stearate; the emollient is one or more of cetearyl alcohol and caprylic / capric triglyceride; the humectant is glycerin; the chelating agent is disodium EDTA; and the preservatives are methylparaben and propylparaben.

[0019] Beneficial effects: The present invention provides a hydrophobically modified vitamin B6 and its preparation method and application, which have the following beneficial effects compared with the prior art:

[0020] 1) The hydrophobically modified vitamin B6 pyridoxine neurate prepared by the present invention uses neuraminic acid as a hydrophobic modifier for water-soluble vitamin B6 to synthesize pyridoxine neurate, which enables water-soluble vitamin B6 to carry natural neuraminic acid through the stratum corneum of the skin, thereby increasing the transdermal absorption of vitamin B6;

[0021] 2) The hydrophobically modified vitamin B6 pyridoxine neurate prepared by the present invention has a simple synthesis process, utilizing a conventional acyl chloride method, avoiding high-temperature reactions during the reaction process, and employing a low-boiling-point solvent for easy removal. The synthesized pyridoxine neurate has good biodegradability.

[0022] 3) The hydrophobically modified vitamin B6 pyridoxine neurate prepared by the present invention simultaneously exerts the physiological activities of vitamin B6 and neuric acid on the skin, has a good skin barrier repair effect, reduces the transepidermal water loss of the skin, and improves the moisturizing efficiency. It also has certain anti-inflammatory and antioxidant effects. It is a skin conditioner that is easy to use and has excellent effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Attachment Figure 1 Figure 2 shows the results of measuring the moisturizing properties of skin care products made from hydrophobically modified vitamin B6 obtained in various embodiments of the present invention;

[0024] Attachment Figure 2 The TEWL value change rate of the skin care products made from the hydrophobically modified vitamin B6 obtained in each embodiment of the present invention;

[0025] Attachment Figure 3 This is the synthetic route of the hydrophobically modified vitamin B6 in the examples of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the accompanying drawings.

[0027] The main experimental materials and sources used:

[0028] Experimental raw materials Name and specifications factory nervonic acid Nervonic acid 95%, GC Aladdin benzene AR99.5% Sinopharm Shanghai trial Thionyl chloride AR99.0% Sinopharm Shanghai trial Pyridoxine Vitamin B6, 99% Aladdin Sodium hydroxide AR96% Sinopharm Shanghai trial dichloromethane AR99.5% Sinopharm Shanghai trial Anhydrous sodium sulfate AR99.0% Sinopharm Shanghai trial Anhydrous ethanol CP99.5% Sinopharm Shanghai trial EDTA2Na 99.0％ Nanjing Fancheng Olivem1000 Cetearyl Olivate, Sorbitan Olivate Hallstar TEGOCare165 Glyceryl Stearate, PEG-100 Stearate Evonik GTCC Caprylic / capric triglyceride Nanjing Fancheng Cetearyl Alcohol Cetearyl Alcohol Emery glycerin glycerin Evyap Methylparaben Methylparaben Nanjing Fancheng Paraben Propylparaben Nanjing Fancheng VB6 dipalmitate <![CDATA[Pyridoxine dipalmitate [1] > -- Deionized water Deionized water Nanjing Fancheng

[0029] The main experimental instruments used:

[0030] Vacuum drying oven, constant temperature water bath, rotary evaporator, constant temperature incubator, high shear average emulsifier, blender, pH meter, WRS-2 microcomputer melting point instrument, etc.

[0031] Example 1

[0032] The method for preparing the hydrophobically modified vitamin B6 pyridoxine neurate of this embodiment comprises the following steps:

[0033] (1) Acylation of nervonic acid: Dissolve nervonic acid (0.2 mol) in solvent benzene (25 ml), install a reflux device and a gas absorption device, and fill the reaction system with nitrogen protection. Then slowly add thionyl chloride (0.3 mol in total) to the reaction system. After the addition is completed, heat it to 80-85°C and continue stirring to react for 2.5 hours. After stopping the reaction, maintain a nitrogen atmosphere, continue to keep it at 80-85°C, and remove excess thionyl chloride and solvent benzene by vacuum distillation to obtain nervonic acid chloride.

[0034] (2) Synthesis of pyridoxine ceramide: 0.04 mol of pyridoxine was dissolved in 5% sodium hydroxide solution (50 ml), and then 100 ml of dichloromethane was added. 15 ml of dichloromethane solution containing 0.04 mol of ceramide chloride and 10 ml of 1 mol / L sodium hydroxide solution were added to two dropping funnels respectively. The mixture was slowly added dropwise to the reaction system at room temperature. The pH of the sodium hydroxide solution was maintained at 8.5-9.5. The addition was completed within 1 hour. The mixture was then reacted at 20-25°C for 20 hours. After the reaction was completed, an appropriate amount of dichloromethane was added and stirred thoroughly. The reaction solution was transferred to a separating funnel and allowed to stand for separation. The lower layer solution was removed and washed with 1% hydrochloric acid and deionized water, and then dried over anhydrous sodium sulfate. Finally, the dichloromethane was removed by distillation under reduced pressure. The crude product was washed with anhydrous ethanol and dried under vacuum to obtain a pure product. The crude product was recrystallized from 95% ethanol.

[0035] The yield of pyridoxine neurate was 53.3%. The hydrophobic modification rate of pyridoxine neurate was characterized by measuring the change in nitrogen content of pyridoxine before and after modification. Due to analytical errors and a small amount of impurities in the sample, the nitrogen content of pyridoxine was 5.3%, and the nitrogen content of the obtained pyridoxine neurate was 1.9%, indicating that pyridoxine neurate was successfully prepared. Its melting point was measured to be 109-119°C.

[0036] Example 2

[0037] In this example, the method for preparing the hydrophobically modified vitamin B6 pyridoxine neurate was modified to 0.02 mol of pyridoxine, and the remaining steps were the same as in Example 1. The yield of pyridoxine neurate in this example was 54.2%, the nitrogen content of the obtained pyridoxine neurate was 1.6%, and the melting point was measured to be 109-118°C.

[0038] Example 3

[0039] In this example, the method for preparing hydrophobically modified vitamin B6 pyridoxine ceramide was modified to 0.02 mol of pyridoxine and 0.03 mol of ceramide chloride. The remaining steps were the same as in Example 1. The yield of pyridoxine ceramide in this example was 58.1%. The nitrogen content of the resulting pyridoxine ceramide was 2.1%, and its melting point was measured to be 109-119°C.

[0040] The hydrophobically modified vitamin B6 pyridoxine neurate prepared in Examples 1-3 of the present invention was applied to the basic formula of skin care products to examine its conditioning performance on the skin.

[0041] A skin care product containing pyridoxine neurate prepared in the above example comprises the following components by weight: 2-5% emulsifier, 5-10% emollient, 2-6% humectant, 0.05% chelating agent, 0.1-1% pyridoxine neurate, and 0.1-0.5% preservative, with deionized water making up the balance. The emulsifiers are cetearyl olivate, sorbitan olivate, glyceryl stearate, and PEG-100 stearate; the emollients are cetearyl alcohol and caprylic / capric triglyceride; the humectant is glycerin; the chelating agent is disodium EDTA; and the preservatives are methylparaben and propylparaben.

[0042] The steps for preparing the skin care product containing pyridoxine neurate are as follows:

[0043] S1: Mix disodium EDTA, glycerin, methylparaben and a certain amount of water in appropriate proportions, heat to 80°C, stir evenly and dissolve completely;

[0044] S2: Mix the emulsifier, emollient and propylparaben in proportion, heat to 80°C and melt completely;

[0045] S3: Pour S2 into S1, stir for 3 minutes, and homogenize for 5 minutes until emulsification is complete;

[0046] S4: After the material is cooled to 40°C, pyridoxine neurate and the remaining amount of deionized water are added.

[0047] The specific ingredients and their mass percentages are shown in Table 1 below. The blank example does not contain the pyridoxine neurate prepared in the present invention and any other skin conditioning components. The comparative example replaces the pyridoxine neurate prepared in the present invention with pyridoxine dipalmitate available on the market. The applied example adds the pyridoxine neurate prepared in Example 3.

[0048] Table 1 Percentage of each raw material content in blank example, application example and comparative example

[0049] Element Blank example Application Example 1 Application Example 2 Application Example 3 Comparative Example 1 Comparative Example 2 Olivem1000 3 3 3 3 3 3 TEGOCare165 1 1 1 1 1 1 GTCC 5 5 5 5 5 5 Cetearyl Alcohol 1.5 1.5 1.5 1.5 1.5 1.5 Propylparaben 0.1 0.1 0.1 0.1 0.1 0.1 EDTA2Na 0.05 0.05 0.05 0.05 0.05 0.05 glycerin 5 5 5 5 5 5 Methylparaben 0.15 0.15 0.15 0.15 0.15 0.15 Pyridoxine neurate 0 0.1 0.5 1 0 0 VB6 dipalmitate 0 0 0 0 1 0 Vitamin B6 0 0 0 0 0 1 Deionized water To100 To100 To100 To100 To100 To100

[0050] Test 1: Stability evaluation of skin care products containing pyridoxine neurate

[0051] Refer to the methods in T / SHFCA002-2021 "Guidelines for Cosmetic Stability Testing" to evaluate the stability of skin care products containing pyridoxine neurate.

[0052] 1. Test items and operation steps

[0053] 1.1 Influencing factors test

[0054] 1.1.1 High temperature stability

[0055] Place the sample in a sealed clean container, then place it in a constant temperature incubator pre-adjusted to (45℃±2℃) for 30 days. Take samples on the 5th, 10th, 20th and 30th day. After the test, return to room temperature and observe the odor, color, and the presence of precipitation and stratification.

[0056] 1.1.2 Temperature stability

[0057] Place the sample in a sealed clean container, then place it in a constant temperature incubator pre-adjusted to (45℃±2℃), take it out after 24 hours, move it into a refrigerator pre-adjusted to (-5℃±2℃) and store it for 24 hours, then take it out, move it into a constant temperature incubator (40℃±2℃) and store it for 24 hours, then take it out again and place it into a refrigerator (-5℃±2℃) and store it for 24 hours. Repeat this cycle 5-7 times. After the test, return it to room temperature and observe the odor, color, and whether there is precipitation and stratification.

[0058] 1.2 Accelerated stability test

[0059] Place the sample in a constant temperature and humidity chamber at 40°C ± 2°C and 75% ± 5% relative humidity for 6 months. Test at at least four time points (e.g., 1, 2, 3, and 6 minutes). Return to room temperature and compare with 0 minutes to observe odor, color, and the presence of sedimentation and stratification.

[0060] 1.3 Long-term stability test

[0061] The samples were placed in a constant temperature and humidity chamber at 25°C ± 2°C and a relative humidity of 60% ± 10% for 24 months. Samples were taken at 3, 6, 9, 12, 18, and 24 minutes, returned to room temperature, and compared with the temperature at 0 minutes to observe odor, color, and the presence of sedimentation.

[0062] 2. Test results

[0063] The results of the stability evaluation test of skin care products containing pyridoxine neurate are shown in Table 2.

[0064] Table 2 Stability evaluation test results of skin care products containing pyridoxine neurate

[0065]

[0066] The above results show that Application Examples 1-3, the blank example, and Comparative Example 1 all showed no abnormalities in any stability evaluation test, demonstrating excellent stability. This indicates that the vitamin B6 ester added to the formulation does not affect the stability of the system. However, the poor stability of Comparative Example 2 suggests that the unhydrophobically modified vitamin B6 oxidizes and degrades, thereby affecting the stability of the system.

[0067] Experiment 2: Evaluation of the moisturizing properties of skin care products containing pyridoxine neurate

[0068] The moisturizing properties of skin care products containing pyridoxine neurate were evaluated with reference to the method in QB / T4256-2011 “Guidelines for Evaluation of Moisturizing Efficacy of Cosmetics”.

[0069] 1. Materials and Reagents

[0070] Latex finger cots, syringes, analytical balances, and skin moisture testers.

[0071] 2. Operation method

[0072] 2.1 Preparation before testing

[0073] Select 20 eligible volunteers. The test area should be marked on the inside of each forearm of each arm, with a minimum area of ​​3 cm x 3 cm. Multiple areas can be marked on the same arm, with at least 1 cm between each test area. Clean the test area before testing. Before the actual test, sit quietly in a standard room for at least 20 minutes, refraining from drinking water or other beverages. Keep your forearm exposed and relaxed in the test position.

[0074] 2.2 Determination steps

[0075] The product application area and the blank control area should be randomly distributed in the calibration area of ​​the left and right arms to ensure that the positions of all products and blank areas are statistically balanced. 2Apply the sample evenly in the test area using a latex fingertip and record the actual amount of sample applied.

[0076] After adjusting the instrument according to the skin moisture meter's instructions, measure the product area and the control area, performing at least three replicate measurements on each area. First, measure the initial value for each test area (before sample application). Then, measure the skin moisture content of the test and control areas 1 hour, 3 hours, and 6 hours later. Testing of the same subject must be performed using the same instrument and by the same person. Clean the measuring probe between measurements.

[0077] 3. Test results

[0078] The moisturizing performance test results of the skin care products of each embodiment are shown in Figure 1 ,Depend on Figure 1 The results show that the samples all contain a certain amount of moisturizing agents such as glycerol, GTCC, etc., so the skin water content will increase to a certain extent. Compared with the blank group (no sample was applied), Application Examples 1-3 and Comparative Example 1 have good moisturizing properties. The water content of the stratum corneum of the skin is significantly increased after 3h and 6h, and the increase in the water content of the stratum corneum of the skin after treatment with Application Example 3 (containing 1% pyridoxine ceramide) is the largest, indicating that the pyridoxine ceramide prepared by the present invention has higher moisturizing efficiency, and the moisturizing effect increases with the increase of the added amount.

[0079] Experiment 3: Evaluation of the barrier repair performance of skin care products containing pyridoxine neurate

[0080] The barrier repair function of skin care products is evaluated using the lactic acid sting test and the transepidermal water loss (TEWL) value measurement.

[0081] 1. Materials and Reagents

[0082] Tewameter transepidermal water loss meter, 10% lactic acid aqueous solution, lint-free tissue

[0083] 2. Test operation

[0084] 2.1 Preparation before the experiment

[0085] Twenty-five female subjects aged 18 to 45 who tested positive for the lactic acid sting test were selected. After cleansing their faces morning and evening, subjects applied an appropriate amount of the sample to their entire face in circular motions until absorbed, twice daily for 28 days. Clinical testing and evaluation were performed on days 0, 14, and 28.

[0086] 2.2 Determination steps

[0087] Lactic acid sting test scoring: The subject cleansed their face and dried it with a lint-free paper. After sitting quietly for 30 minutes in an environment with a constant temperature of (21±1)°C and a constant humidity of 50%±5%, 50μL of a 10% lactic acid aqueous solution was applied to the cheek on either side of the nasolabial groove. The subject rated the degree of itching, stinging, and burning pain at the test site after 30 seconds, 2.5 minutes, and 5 minutes. The score was based on a 4-point scale (0: no sensation, 1: mild, 2: moderate, 3: severe). A cumulative stinging sensation of 3 or more after 30 seconds, 2.5 minutes, and 5 minutes was considered positive for lactic acid sting.

[0088] TEWL value determination: Tewameter instrument was used to measure the transepidermal water loss rate (TEWL) value of the volunteers' skin.

[0089] 3. Experimental Results

[0090] Table 3 shows the lactic acid sting test scores for each sample. Lactic acid sting scores were measured on days 0, 14, and 28 for volunteers using different samples. Application Examples 1-3 and Comparative Example 1 showed significant improvements, with Application Example 3 (containing 1% pyridoxine ceramide) showing the greatest improvement. This indicates that skincare products containing 1% pyridoxine ceramide have a stronger barrier-repairing effect, and that this effect is positively correlated with the amount of pyridoxine ceramide added. The blank sample showed almost no skin barrier-repairing effect.

[0091] Table 3 Lactic acid sting test results

[0092]

[0093] The change rate of the transepidermal water loss rate TEWL value of each sample is as follows Figure 2 As shown. The mean TEWL values ​​of volunteers using different samples were measured on day 0, 14 and 28 respectively, and the change rates of 14 and 28 days compared with day 0 were calculated. Figure 2 As can be seen, Application Examples 1-3 and the comparative example were able to reduce the TEWL value of the test area, with Application Example 3 (containing 1% pyridoxine ceramide) showing the greatest rate of change. This indicates that skincare products containing 1% pyridoxine ceramide have a stronger barrier-repairing function, and that this function is positively correlated with the amount of pyridoxine ceramide added. The TEWL value of the blank sample remained virtually unchanged over 28 days.

[0094] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A hydrophobically modified vitamin B6, characterized in that It is pyridoxine neurate, with the structural formula: , where R=-(CH2) 13 - CH=CH-(CH2)7- CH 3。 2. A method for preparing the hydrophobically modified vitamin B6 according to claim 1, characterized in that: The following steps are involved: (1) Acylation of nervonic acid: Dissolve nervonic acid in a solvent, protect with nitrogen, and slowly add thionyl chloride to the nervonic acid solution. After the addition is complete, heat the solution to 80-85°C and continue stirring to react. After stopping the reaction, maintain a nitrogen atmosphere, continue to keep the temperature, and remove excess thionyl chloride and solvent by vacuum distillation to obtain nervonic acid chloride. (2) Synthesis of pyridoxine ceramide: Pyridoxine was dissolved in sodium hydroxide solution, and then dichloromethane was added. At room temperature, dichloromethane solution of ceramide chloride and sodium hydroxide solution were slowly added dropwise. After the addition was completed, the mixture was reacted at 20-25°C. After the reaction was completed, pyridoxine ceramide was purified to obtain pyridoxine ceramide.

3. The method for preparing hydrophobically modified vitamin B6 according to claim 2, wherein The molar ratio of nervonic acid to thionyl chloride in step (1) is 2:

3.

4. The method for preparing the hydrophobically modified vitamin B6 according to claim 2 or 3, wherein: The reaction time in step (1) is 2.5 h.

5. The method for preparing hydrophobically modified vitamin B6 according to claim 2, wherein In step (2), the molar ratio of pyridoxine to ceramide chloride is 1:(1~2).

6. The method for preparing the hydrophobically modified vitamin B6 according to claim 2 or 5, wherein: The reaction time of step (2) is 20 h.

7. The method for preparing the hydrophobically modified vitamin B6 according to claim 2 or 5, wherein: In step (2), sodium hydroxide solution is added dropwise to maintain the pH at 8.5-9.

5.

8. The method for preparing the hydrophobically modified vitamin B6 according to claim 2 or 5, wherein: The purification process after the reaction in step (2) is as follows: after the reaction is completed, an appropriate amount of dichloromethane is added and stirred thoroughly, the reaction solution is transferred to a separatory funnel and allowed to stand for stratification, the lower layer solution is taken and washed with 1% hydrochloric acid and deionized water, and then dried with anhydrous sodium sulfate, and finally the dichloromethane is removed by vacuum distillation, and the crude product is washed with ethanol and vacuum dried to obtain a crude product, which is recrystallized with 95% ethanol to obtain pure pyridoxine neuramide.

9. The use of the hydrophobically modified vitamin B6 according to claim 1, characterized in that: The hydrophobically modified vitamin B6 is used in a skin care product, which contains the following components in weight percentage: 2-5% emulsifier, 5-10% emollient, 2-6% moisturizer, 0.05% chelating agent, 0.1-1% pyridoxine neurate, 0.1-0.5% preservative, and deionized water makes up the balance.

10. The use of the hydrophobically modified vitamin B6 according to claim 9, characterized in that: The preparation of the skin care product comprises the following steps: S1: Mix disodium EDTA, glycerin, methylparaben and a certain amount of water in appropriate proportions, heat to 80°C, stir evenly and dissolve completely; S2: Mix the emulsifier, emollient and propylparaben in proportion, heat to 80°C and melt completely; S3: Pour S2 into S1, stir for 3 minutes, and homogenize for 5 minutes until emulsification is complete; S4: After the material is cooled to 40°C, pyridoxine neurate and the remaining amount of deionized water are added.

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