Litchi extract as well as preparation method and application thereof

Abstract

The invention belongs to the field of deep processing of agricultural products, and discloses a preparation method and application of a litchi extract, the preparation method of the litchi extract comprises the following steps: S1, precooling litchis to a low temperature, and then soaking the litchis in a salt solution to obtain the litchis subjected to low temperature-salt water treatment; s2, performing ultraviolet stress treatment on the litchis subjected to low-temperature-saline water treatment, the ultraviolet wavelength is 254-310 nm, the irradiation intensity is 2-10 W / m, and the litchis subjected to enrichment treatment are obtained; and S3, crushing, extracting, filtering and concentrating the litchi subjected to enrichment treatment to obtain the litchi extract. According to the preparation method disclosed by the invention, a precooling-salt solution-ultraviolet triple stress mechanism is adopted and matched with each other, the content of GABA in the obtained litchi extract is up to 1.93 mg / g, the content of phenolic substances is up to 22.19 GAEmg / g, and the litchi extract has the technical effects of controlling oil and whitening skin when being applied to daily chemical products.

Description

Technical Field

[0001] The present invention relates to the field of deep processing of agricultural products, and more specifically, to a litchi extract and a preparation method and application thereof. Background Art

[0002] Lychee (Litchi chinensis Sonn.) is a tropical fruit widely distributed in southern my country and Southeast Asia. It is loved by consumers for its unique flavor and rich nutritional value. Lychee fruit is rich in a variety of active ingredients that are beneficial to the human body, such as vitamins, phenolic compounds, flavonoids, etc., and has antioxidant and immune-boosting effects.

[0003] In recent years, as people pay more attention to health, some specific functional ingredients in litchi, such as γ-aminobutyric acid (GABA) and phenolic substances, have gradually become research hotspots. Among them: GABA is a naturally occurring four-carbon, non-protein functional amino acid. It is an important neuroinhibitor in the mammalian nervous system and has functions such as lowering blood pressure, regulating hormone secretion, enhancing brain vitality, whitening, calming and soothing, anti-oxidation and improving sleep; phenolic substances are an important antioxidant ingredient that can scavenge free radicals, reduce oxidative stress, and protect biological macromolecules or cells from potential damage. It has the effects of slowing down skin aging, anti-inflammatory and acne removal, moisturizing and oil control, as well as lowering blood sugar and blood pressure, and preventing chronic diseases.

[0004] Prior art CN104432354B discloses a method for preparing lychee juice rich in γ-aminobutyric acid and lychee juice thereof. The method for extracting GABA from lychees is to subject lychees to low-temperature stress, i.e., to simple enrichment and extraction after soaking in cold water. The mass content of GABA in the obtained lychee extract is only 0.1%, which limits the further application of the lychee extract. Summary of the invention

[0005] The invention provides a method for preparing a litchi extract. The content of GABA in the litchi extract obtained by the preparation method is higher than that in the prior art.

[0006] Another object of the present invention is to provide a litchi extract.

[0007] Another object of the present invention is to provide use of the litchi extract in preparing cosmetics.

[0008] In order to solve the above technical problems, the technical solution provided by the present invention is: A method for preparing a litchi extract comprises the following steps: S1. After precooling the litchi, soak it in a salt solution to obtain a low-temperature-salt-water-treated litchi; S2. The lychees treated with low temperature and salt water were subjected to ultraviolet stress treatment, wherein the ultraviolet wavelength was 254 to 310 nm and the irradiation intensity was 2 to 10 W / m² to obtain enriched lychees; S3. crushing, extracting, filtering and concentrating the enriched litchi to obtain litchi extract.

[0009] The preparation method of the present invention adopts the triple stress technology of low temperature, salt water and ultraviolet rays. First, the double stress of low temperature and salt water in S1 mainly reduces the oxygen concentration of cells inside the litchi by appropriate low temperature and salt water concentration, induces hypoxia stress to change ion homeostasis, activates the stress response of the plant, thereby enhancing the stress resistance of the litchi and accumulating secondary metabolites, regulating the synthesis pathway of GABA and phenolic substances; on the basis of low temperature and salt water stress in S1, the third stress - ultraviolet stress - is carried out in step S2, which can enhance the ROS level and related gene expression inside the plant and promote the synthesis of metabolites.

[0010] The triple stress of low temperature, salt water and ultraviolet light has a synergistic effect on increasing the GABA content in litchi extract: (1) the ion imbalance caused by salt stress will enhance the effects of low temperature and ultraviolet stress, further increasing the level of ROS in litchi; (2) the synergistic effect of low temperature, salt water stress and ultraviolet stress can activate specific signal pathways in litchi, such as the MAPK (mitogen-activated protein kinase) pathway and anti-stress transcription factors (such as DREB, CBF, etc.). These signal pathways jointly activate and enhance the stress response of litchi, making it respond more quickly in adversity. The three different stress modes interact with each other to form a positive cycle and produce a synergistic effect, stimulating the secondary metabolism of litchi fruit, enhancing the synthesis of secondary metabolites of litchi, and accelerating the synthesis and accumulation of GABA and phenolic substances.

[0011] In summary, the litchi extract prepared by the method for preparing the litchi extract provided by the present invention has a high content of GABA and phenolic substances, wherein the GABA content is as high as 1.93 mg / g, and the phenolic substance content is as high as 22.19 GAE mg / g, which is superior to the prior art.

[0012] According to the preparation method provided by the present invention, the contents of GABA and phenolic substances in the litchi extract are higher than those in the prior art. GABA has the effect of inhibiting the synthesis of some tyrosinase, and phenolic substances such as chlorogenic acid, catechin, vanillic acid, ferulic acid, quercetin, resveratrol, etc. can inhibit the activity of synthesized tyrosinase, and inhibiting the expression of tyrosinase has the effect of whitening the skin. GABA and phenolic substances complement each other in the whitening mechanism and have a synergistic effect on whitening the skin. When there are low contents of GABA and phenolic substances in the litchi extract, only GABA or phenolic substances alone in the litchi extract, and one of the contents of GABA or phenolic substances in the litchi extract is too low, the synergistic effect of GABA and phenolic substances in the litchi extract on skin whitening cannot be achieved.

[0013] Preferably, the litchi precooling method in S1 is to place the litchi at a temperature of 2-10° C. for 2-6 hours.

[0014] Preferably, the solute in the salt solution in S1 is selected from one of sodium chloride, calcium chloride and potassium chloride, and the concentration of the salt solution is 1% to 3%; the soaking time is 2 to 6 hours; Preferably, the wavelength of the ultraviolet light in S2 is 265-295 nm.

[0015] Preferably, the ultraviolet irradiation intensity in S2 is 4~8W / m².

[0016] Preferably, the ultraviolet irradiation time in S2 is 10 to 60 minutes.

[0017] Preferably, the extraction method in S3 is to first extract the flesh of the enriched lychees, add ethanol and then crush them, and then heat and extract them.

[0018] Preferably, the amount of ethanol added in S3 is 1:(5-20) by mass of litchi to ethanol, and the ethanol concentration is 40%-60%.

[0019] Preferably, the heating temperature in S3 is 40° C. to 80° C., and the extraction time is 1 to 5 hours.

[0020] The present invention also provides application of the litchi extract in preparing whitening and oil-controlling daily chemical products.

[0021] The whitening and oil-controlling daily chemical product of the present invention is selected from toner, essence, cream, shower gel and shampoo. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the HPLC detection spectrum of GABA content in the litchi extract obtained in Example 1.

[0023] Figure 2This is the detection spectrum of the phenolic substance content in the litchi extract obtained in Example 1. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with specific implementation methods.

[0025] Example 1 A method for preparing a litchi extract comprises the following steps: S1. First, the freshly picked lychees were precooled at 4 ° C for 4 h, and then soaked in a 2% mass concentration of sodium chloride solution for 4 h, the sodium chloride solution temperature was 6 ° C, and finally the soaked lychees were washed and drained to obtain lychees treated with low temperature-salt water; S2. The litchi subjected to low temperature-salt water stress was placed in an ultraviolet device for ultraviolet stress treatment, with an ultraviolet wavelength of 275nm, an irradiation intensity of 5W / m², an irradiation time of 30min, and was turned over every 5 minutes to obtain enriched litchi; S3. After the enrichment treatment, the flesh of the lychee is taken out and 50% ethanol is added to break the wall, and the mixture is heated at 60°C for extraction for 3 hours, filtered and concentrated to obtain a lychee extract; the mass ratio of lychee to ethanol is 1:10.

[0026] Example 2 This embodiment is the second embodiment of the present invention. The difference from the embodiment 1 is that the precooling temperature in S1 is 2° C. and the precooling time is 2 hours.

[0027] Example 3 This embodiment is the third embodiment of the present invention. The difference from the embodiment 1 is that the precooling temperature in S1 is 10° C. and the precooling time is 6 hours.

[0028] Example 4 This embodiment is the fourth embodiment of the present invention. The difference from the embodiment 1 is that the concentration of the sodium chloride solution in S1 is 1%, the solution temperature is 4° C., and the soaking time is 2 h.

[0029] Example 5 This embodiment is the fifth embodiment of the present invention. The difference from the first embodiment is that the concentration of the sodium chloride solution in S1 is 3%, the solution temperature is 10° C., and the soaking time is 6 hours.

[0030] Example 6 This embodiment is the sixth embodiment of the present invention. The difference from the first embodiment is that the wavelength of the ultraviolet rays in S2 is 265 nm.

[0031] Example 7 This embodiment is the seventh embodiment of the present invention. The difference from the first embodiment is that the wavelength of the ultraviolet rays in S2 is 295 nm.

[0032] Example 8 This embodiment is the eighth embodiment of the present invention. Different from the embodiment 1, the ultraviolet irradiation intensity in S2 is 4 W / m².

[0033] Example 9 This embodiment is the ninth embodiment of the present invention. Different from the first embodiment, the ultraviolet irradiation intensity in S2 is 8W / m².

[0034] Example 10 This embodiment is the tenth embodiment of the present invention. The difference from the first embodiment is that the wavelength of the ultraviolet rays in S2 is 254 nm, the irradiation intensity is 2 W / m², and the irradiation time is 10 min.

[0035] Embodiment 11 This embodiment is the eleventh embodiment of the present invention. The difference from the first embodiment is that the wavelength of the ultraviolet rays in S2 is 310 nm, the irradiation intensity is 10 W / m², and the irradiation time is 60 min.

[0036] Example 12 This embodiment is the twelfth embodiment of the present invention. Different from the first embodiment, in the S3, the flesh of the enriched lychee is taken out and 40% ethanol is added for wall breaking treatment, the extraction is heated at 40°C for 1 hour, filtered and concentrated to obtain the lychee extract; the lychee:ethanol mass ratio is 1:5.

[0037] Embodiment 13 This embodiment is the thirteenth embodiment of the present invention. Different from the first embodiment, in the S3, the flesh of the enriched lychee is taken out and 60% ethanol is added for wall breaking treatment, and the extraction is heated at 80°C for 5h, filtered and concentrated to obtain the lychee extract; the mass ratio of lychee to ethanol is 1:20.

[0038] Comparative Example 1 This comparative example is the first comparative example of the present invention. Different from Example 1, this comparative example only adopts low temperature stress to prepare litchi extract. The specific preparation method is as follows: The picked lychees were placed in a 4°C environment for precooling for 6 hours, the pulp was taken out, 50% ethanol was added for wall breaking, the pulp was heated at 60°C for extraction for 3 hours, filtered and concentrated to obtain lychee extract; the mass ratio of lychee to ethanol was 1:10.

[0039] Comparative Example 2 This comparative example is the second comparative example of the present invention. Different from Example 1, this comparative example only adopts low temperature-salt water stress to prepare litchi extract, and there is no ultraviolet stress treatment of S2 in the preparation method.

[0040] Comparative Example 3 This comparative example is the third comparative example of the present invention. Different from Example 1, this comparative example only adopts low temperature-ultraviolet stress to prepare litchi extract, and the pre-cooled litchi is not soaked in sodium chloride solution in preparation method S1.

[0041] Comparative Example 4 This comparative example is the fourth comparative example of the present invention. The difference from Example 1 is that the concentration of the sodium chloride solution in S1 is 0.5%, the solution temperature is 3° C., and the immersion time is 1 h.

[0042] Comparative Example 5 This comparative example is the fifth comparative example of the present invention. It is different from Example 1 in that the concentration of the sodium chloride solution in S1 is 4%, the solution temperature is 12° C., and the soaking time is 7 h.

[0043] Comparative Example 6 This comparative example is the sixth comparative example of the present invention. Different from Example 1, the wavelength of the ultraviolet light in S2 is 365nm, the irradiation intensity is 13W / m², and the irradiation time is 70min.

[0044] Comparative Example 7 This comparative example is the seventh comparative example of the present invention. Different from Example 1, this comparative example only adopts salt water-ultraviolet stress to prepare litchi extract, and there is no pre-cooling stress treatment of S1 in the preparation method.

[0045] The relevant process parameters for preparing litchi extracts in Examples 1 to 13 and Comparative Examples 1 to 6 are shown in Table 1 Performance testing: Detection of γ-aminobutyric acid content: The litchi extract obtained in Example 1 was mixed with the derivatization reagent in a volume ratio of 1:1 and reacted for 2 minutes, then passed through a membrane for detection. The derivatization reagent was prepared as follows: 150 mg of o-phthalaldehyde was weighed, dissolved in mL of methanol, and then 27 mL of 0.4 mol / L sodium tetraborate buffer, 0.5 mL of β-mercaptoethanol and 30 mg of ascorbic acid were added. HPLC detection method: mobile phase A (methanol), mobile phase B (0.1% formic acid). Gradient elution program: 0-15 min, 35%-28% (B); 15-16 min, 28%-35% (B); 16-20 min, 35% (B). The flow rate was 0.7 mL / min, the column temperature was 30°C, the injection volume was 10 µL, and the detection wavelength was 332 nm. The HPLC spectra of γ-aminobutyric acid in the litchi extracts obtained in the other embodiments and comparative examples are similar. Figure 1 The contents of γ-aminobutyric acid in the litchi extracts obtained in specific examples 1 to 13 and comparative examples 1 to 7 are shown in Table 2.

[0046] Table 1 Specific preparation method parameters of Examples 1 to 13 and Comparative Examples 1 to 7

[0047] Total phenol content detection: Take 1 mL of the litchi extract obtained in Example 1, add 2 mL of Folin phenol solution and 2 mL of 10% (W / V) Na2CO3 solution, react at room temperature in the dark for 1 hour, and measure the absorbance at 700 nm. The standard curve is drawn with gallic acid (GAE) as the standard solution to calculate the content of phenolic substances, and the unit is expressed in GAE mg / g, which refers to the total phenols in gallic acid equivalents contained in each gram of litchi. The specific HPLC test method for phenolic substances is as follows: The litchi extract obtained in Example 1 is filtered through a 0.22 μm filter membrane and then subjected to HPLC analysis. HPLC detection method: Mobile phase A is 0.4% (v / v) acetic acid, mobile phase B is acetonitrile, elution gradient: 0-40 min, 5%-25% (B); 40-45 min, 25%-35% (B); 45-50 min, 35%-50% (B). The column temperature was 30°C, the flow rate was 1.0 mL / min, the injection volume was 20 µL, and the detection wavelength was 280 nm. The HPLC spectra of phenolic substances in the litchi extracts obtained in the other embodiments and comparative examples are similar. Figure 2 The total phenol content in the litchi extracts obtained in specific Examples 1 to 13 and Comparative Examples 1 to 7 is shown in Table 2.

[0048] The GABA content detection spectrum of litchi extract obtained in Example 1 is shown in Figure 1 , the phenolic substance content detection spectrum is shown in Figure 2 . Figure 1 Peak 1 is litchi GABA, Figure 2 Peak 1 is gallic acid, peak 2 is chlorogenic acid, peak 3 is catechin, peak 4 is vanillic acid, peak 5 is epicatechin, peak 6 is tetramethylcatechol, peak 7 is coumaric acid, peak 8 is ferulic acid, peak 9 is resveratrol, and peak 10 is quercetin. Figure 1 and Figure 2 It can be seen that the litchi extract obtained in Example 1 is rich in GABA and phenolic substances.

[0049] The specific contents of GABA and phenolic substances in the litchi extracts obtained in the examples and comparative examples are shown in Table 2. The content of GABA in the litchi extract obtained in the examples is up to 1.93 mg / g, and the content of phenolic substances is up to 22.19 mgGAE / g, which are better than the contents of GABA and phenolic substances in the litchi extract obtained in the comparative example.

[0050] It can be seen from Examples 1, 2 and 3 that if the precooling temperature is too high or too low, or if the precooling time is too long or too short, the contents of GABA and phenolic substances in the litchi extract will be reduced. It can be seen from Example 1 and Comparative Example 7 that when no precooling process is performed, the GABA content in the litchi extract changes from 1.93 mg / g to 1.25 mg / g, and the phenolic substance content changes from 22.19 mgGAE / g to 14.62 mgGAE / g, and the contents of both are significantly reduced.

[0051] It can be seen from Example 1 and Examples 4 and 5 that the selection of salt stress solution concentration, soaking temperature and soaking time will affect the contents of GABA and phenolic substances in the litchi extract; it can be seen from Example 1 and Comparative Examples 4 to 5 that when the salt stress solution concentration is too high or too low, the soaking temperature is too high or too low, and the soaking time is too long or too short, the GABA content in the obtained litchi extract changes from 1.93 mg / g to 1.21 mg / g, and the phenolic substance content changes from 22.19 mgGAE / g to 11.63 mgGAE / g, and the contents of both are reduced; it can be seen from Example 1 and Comparative Example 3 that when the salt stress process is not performed, the GABA content in the litchi extract changes from 1.93 mg / g to 1.03 mg / g, and the phenolic substance content changes from 22.19 mgGAE / g to 10.36 mgGAE / g, and the contents of both are significantly reduced.

[0052] It can be seen from Examples 1 and 6 to 11 that the selection of UV stress wavelength and irradiation intensity will affect the contents of GABA and phenolic substances in the litchi extract; it can be seen from Example 1 and Comparative Example 6 that when the UV wavelength is too long and the irradiation intensity is too high, the GABA content in the obtained litchi extract changes from 1.93 mg / g to 1.04 mg / g, and the phenolic substance content changes from 22.19 mgGAE / g to 11.85 mgGAE / g, and the contents of both are reduced; it can be seen from Example 1 and Comparative Example 2 that when the UV stress process is not performed, the GABA content in the litchi extract changes from 1.93 mg / g to 0.85 mg / g, and the phenolic substance content changes from 22.19 mgGAE / g to 10.22 mgGAE / g, and the contents of both are significantly reduced.

[0053] Whitening activity effect test: Tyrosinase is a key enzyme that produces melanin through melanocytes. Inhibiting the catalytic activity of tyrosinase is the most prominent and effective target for whether melanin is produced or not. Therefore, tyrosinase inhibition test is one of the commonly used whitening efficacy evaluation methods. Tyrosinase can catalyze dopa to form dopaquinone, and dopaquinone spontaneously undergoes a series of reactions to finally form melanin. In a phosphoric acid solution with a pH of 6.8, tyrosinase can catalyze the conversion of dopa into dopaquinone, and the absorbance value can be measured at 475nm in a spectrophotometer. The specific test method is: dilute the litchi extract obtained in Example 1 to 1% crude drug amount, and obtain a sample solution. The reaction is carried out in a 96-well plate, and PBS buffer (pH = 6.8), sample solution and 50U / mL tyrosinase solution are added in sequence and mixed thoroughly. Place in a constant temperature incubator, incubate at 37°C for 10 min, add a substrate 0.75mmol / L levodopa solution, and incubate at 37°C for 20min. Finally, acetonitrile is added to terminate the reaction, and the same volume of PBS is used as a negative blank control. The absorbance at 475 nm was detected by an enzyme-labeled instrument.

[0054] The tyrosinase inhibition effects of the litchi extracts obtained in the examples and comparative examples are shown in Table 2. The tyrosinase inhibition rate of the litchi extract obtained in the examples is as high as 72.61%, which is better than the tyrosinase inhibition rate of the litchi extract obtained in the comparative example.

[0055] It can be seen from Examples 1, 2 and 3 that if the precooling temperature is too high or too low, or if the precooling time is too long or too short, the tyrosinase inhibition rate of the litchi extract will be reduced. It can be seen from Example 1 and Comparative Example 7 that when the precooling process is not performed, the tyrosinase inhibition rate in the litchi extract changes from 72.61% to 50.26%, and the inhibition effect is significantly reduced.

[0056] It can be seen from Example 1 and Examples 4 and 5 that the selection of salt stress solution concentration, soaking temperature and soaking time will affect the inhibition rate of tyrosinase by litchi extract; it can be seen from Example 1 and Comparative Examples 4 to 5 that when the salt stress solution concentration is too high or too low, the soaking temperature is too high or too low, and the soaking time is too long or too short, the inhibition rate of tyrosinase by the obtained litchi extract varies from 72.61% to 49.56%; it can be seen from Example 1 and Comparative Example 3 that when the salt stress process is not performed, the inhibition rate of tyrosinase by litchi extract varies from 72.61% to 45.46%, and the inhibition effect is significantly reduced.

[0057] It can be seen from Example 1 and Examples 6 to 11 that the selection of UV stress wavelength and irradiation intensity will affect the tyrosinase inhibition rate of litchi extract; it can be seen from Example 1 and Comparative Example 6 that when the UV wavelength is too long and the irradiation intensity is too high, the tyrosinase inhibition rate of the obtained litchi extract changes from 72.61% to 48.15%; it can be seen from Example 1 and Comparative Example 2 that when the UV stress process is not performed, the tyrosinase inhibition rate of litchi extract changes from 72.61% to 43.52%, and the inhibitory effect is significantly reduced.

[0058] Oil control effect test: 5α-reductase is a key metabolic enzyme in the skin, which can irreversibly convert testosterone into dihydrotestosterone (DHT), which can induce excessive secretion of oil by sebaceous glands. Therefore, the inhibition rate of 5α-reductase activity can be tested to determine whether the test object has the ability to relieve excessive secretion of oil by sebaceous glands, so as to evaluate the oil control effect of cosmetics. The specific test method is: dilute the litchi extract obtained in Example 1 to 1% crude drug amount, that is, obtain a sample solution. Add 2mL of reaction buffer, 50μL of 5α-reductase solution, and 100μL of the sample solution to be tested to the cuvette, incubate at 37°C for 10min, then add 200μL of reduced coenzyme II (NADPH) solution and 50μL of substrate testosterone (T) solution in sequence, and then immediately use a UV spectrophotometer to measure the absorbance value A0 at 340nm, and incubate at 37°C for 30min and measure the absorbance value A30 again at 340nm, calculate the change value △A of absorbance, and repeat twice. A blank group (phosphate buffer + 5α-reductase + NADPH + T), a positive control group (phosphate buffer + 5α-reductase + finasteride + NADPH + T), and a sample group (phosphate buffer + 5α-reductase + test sample + NADPH + T) were set up; then the inhibition rate of the samples on 5α-reductase was determined respectively.

[0059] The inhibitory effects of the litchi extracts obtained in the examples and comparative examples on 5α-reductase are shown in Table 2. The inhibition rate of the litchi extract obtained in the examples on 5α-reductase is as high as 78.53%, which is better than the inhibition rate of the litchi extract obtained in the comparative example on tyrosinase.

[0060] It can be seen from Examples 1, 2 and 3 that if the precooling temperature is too high or too low, or if the precooling time is too long or too short, the tyrosinase inhibition rate of the litchi extract will be reduced. It can be seen from Example 1 and Comparative Example 7 that when the precooling process is not performed, the tyrosinase inhibition rate in the litchi extract changes from 78.53% to 54.85%, and the inhibition effect is significantly reduced.

[0061] It can be seen from Examples 1 and 4 and 5 that the concentration of the salt stress solution, the soaking temperature, and the soaking time The choice of the salt stress process will affect the tyrosinase inhibition rate of litchi extract; from Example 1 and Comparative Examples 4-5, it can be seen that when the salt stress solution concentration is too high or too low, the soaking temperature is too high or too low, and the soaking time is too long or too short, the tyrosinase inhibition rate of the obtained litchi extract changes from 78.53% to 43.86%; from Example 1 and Comparative Example 3, it can be seen that when the salt stress process is not performed, the tyrosinase inhibition rate of litchi extract changes from 78.53% to 42.52%, and the inhibition effect is significantly reduced.

[0062] Table 2 Performance test of litchi extracts obtained in Examples 1 to 13 and Comparative Examples 1 to 7

[0063] It can be seen from Example 1 and Examples 6 to 11 that the selection of UV stress wavelength and irradiation intensity will affect the tyrosinase inhibition rate of litchi extract; it can be seen from Example 1 and Comparative Example 6 that when the UV wavelength is too long and the irradiation intensity is too high, the tyrosinase inhibition rate of the obtained litchi extract changes from 78.53% to 42.97%; it can be seen from Example 1 and Comparative Example 2 that when the UV stress process is not performed, the tyrosinase inhibition rate of litchi extract changes from 78.53% to 40.11%, and the inhibitory effect is significantly reduced.

[0064] In summary, in the preparation method of litchi extract in the present application, the triple stress mechanism of pre-cooling-salt solution-ultraviolet should be coordinated with each other, and appropriate parameters should be selected to increase the content of GABA and phenolic substances in the obtained litchi extract, which has the technical effects of oil control and skin whitening.

[0065] The above is only an implementation method of the invention, and does not limit the scope of patent protection. Those skilled in the art can make non-substantial changes or substitutions based on the invention, which still fall within the scope of patent protection.

Claims

1. A method for preparing a litchi extract, characterized in that: The following steps are involved: S1. The lychees are pre-cooled to a low temperature and then immersed in a salt solution to obtain lychees treated with low temperature-salt water; S2. The lychees treated with low temperature and salt water were subjected to ultraviolet stress treatment, wherein the ultraviolet wavelength was 254 to 310 nm and the irradiation intensity was 2 to 10 W / m² to obtain enriched lychees; S3. crushing, extracting, filtering and concentrating the enriched litchi to obtain litchi extract.

2. The method for preparing the litchi extract according to claim 1, characterized in that: In S1, the litchi precooling method is to place the litchi at a temperature of 2-10°C for 2-6 hours.

3. The method for preparing the litchi extract according to claim 1, characterized in that: In S1, the solute in the salt solution is selected from one of sodium chloride, calcium chloride and potassium chloride, and the concentration of the salt solution is 1% to 3%; the soaking time is 2 to 6 hours.

4. The method for preparing the litchi extract according to claim 1, characterized in that: In S2, the wavelength of ultraviolet light is 265~295nm.

5. The method for preparing the litchi extract according to claim 1, characterized in that: In S2, the UV radiation intensity is 4~8W / m².

6. The method for preparing the litchi extract according to claim 1, characterized in that: In S2, the ultraviolet irradiation time is 10 to 60 minutes.

7. The method for preparing the litchi extract according to claim 1, characterized in that: In S3, the extraction method is to first extract the flesh of the enriched lychee, add ethanol and then crush it, and then heat and extract it.

8. The method for preparing the litchi extract according to claim 7, characterized in that: In S3, the amount of ethanol added is 1:(5~20) of litchi:ethanol mass, and the ethanol concentration is 40%~60%.

9. The method for preparing the litchi extract according to claim 7, characterized in that: In S3, the heating temperature is 40°C to 80°C, and the extraction time is 1 to 5 hours.

10. Use of the litchi extract prepared by the preparation method according to any one of claims 1 to 9 in whitening and oil-controlling daily chemicals.

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