Kiwifruit flower extract solid beverage with uric acid reducing effect as well as preparation method and application of kiwi fruit flower extract solid beverage

Abstract

The invention provides a kiwi flower extract solid beverage with a uric acid reducing effect as well as a preparation method and application thereof, and belongs to the technical field of functional foods. Fresh yellow heart kiwi fruit flowers are sequentially subjected to drying, smashing, microwave enzyme deactivation and vacuum freeze drying operation to obtain kiwi fruit flower powder, then the kiwi fruit flower powder is subjected to gradient targeted extraction, firstly, subcritical water extraction is adopted, the flavone yield is increased, macromolecular impurities are removed through ceramic membrane filtration, an extracting solution A and filter residues are obtained, and the yellow heart kiwi fruit flower powder is obtained. The preparation method comprises the following steps: mixing filter residues with ethanol, then carrying out ultrasonic extraction to improve the extraction rate of polyphenol in the extract, carrying out suction filtration and concentration to obtain an extracting solution B, finally carrying out steady-state processing, mixing the extracting solution A and the extracting solution B, and carrying out freezing granulation to obtain the kiwi flower extract solid beverage with the effect of reducing uric acid and high content of flavonoid and high-phenol effective substances. The solid beverage of the kiwi flower extract has an excellent improvement effect on hyperuricemia.

Description

Technical Field

[0001] The invention relates to the technical field of kiwi flower extracts, and in particular to a solid beverage of yellow-heart kiwi flower extracts with uric acid-lowering efficacy, and a preparation method and application thereof. Background Art

[0002] With the improvement of living standards, people's dietary structure has also become diversified. The proportion of high-sugar, high-salt, and high-fat food intake has increased, which can easily lead to the occurrence of metabolic diseases such as hyperlipidemia, hyperglycemia, and hyperuricemia (HUA), which poses a new threat to people's health. HUA is a chronic metabolic disease caused by purine metabolism disorders in the body, which manifests as an abnormal increase in uric acid levels in the blood. According to the White Paper on the Trend of Hyperuricemia and Gout in China in recent years, the overall prevalence of HUA in my country has increased year by year to 13.3%, and the overall incidence of gout is 1.1%. Nearly 60% of the population are young people aged 18 to 35, and HUA has become the second largest metabolic disease after diabetes.

[0003] People are paying more and more attention to health and wellness. The series of medicine and food products are natural, safe, nutritious, and effective, meeting the needs of modern consumers for healthy food. In the future, with the further improvement of health awareness, the market size of the medicine and food industry is expected to continue to grow. At the same time, under the strategic background of the "Healthy China 2030" Outline, more and more traditional Chinese medicine institutions have joined the medicine and food industry, and the industry's scientific and technological innovation capabilities have been continuously enhanced. With the dual support of national strategies and policies, as well as the vast market space and excellent growth potential on the demand side, the development of medicine and food brands and industries has become the general trend of the current and future food industry.

[0004] In my country, kiwifruit has a long history. The Book of Songs, written more than 2,000 years ago, recorded: "There is a Changchu in the marsh, and its branches are adorned with angelica." According to scholars, "Changchu" refers to the current kiwifruit. As the "king of fruits", the efficacy and value of kiwifruit have always been recognized by people. Many medical books have recorded it, such as "Supplement to Materia Medica" and "Compendium of Materia Medica". Chinese medicine believes that kiwifruit has the functions of regulating qi, clearing away heat and promoting urination, promoting fluid and moistening dryness, and relieving fever and relieving restlessness. The 1977 edition of the Chinese Pharmacopoeia has officially included it. In the theory of traditional Chinese medicine, the "four properties and five flavors" of Chinese medicine can also be applied to food, so many plants have the characteristics of medicine and food. A large number of medical studies have also proved that kiwifruit has the function of being both medicine and food.

[0005] Kiwi flowers are often discarded as a by-product of the fruit ripening process. Studies have shown that kiwi flowers are rich in nutritional value, with polysaccharides, proteins, and soluble sugars all higher than leaves. Studies have shown that flavonoids from natural plants can scavenge free radicals by forming complexes with trace elements such as copper, thereby exerting an antioxidant effect. Studies have pointed out that by inhibiting the activity of xanthine oxidase (XOD), the production of uric acid is inhibited, uric acid excretion is promoted, and hyperuricemia is prevented and treated. The specific mechanism is that flavonoids inhibit the release of inflammatory transmitters from neutrophils, inhibit the secretion of inflammatory cytokines induced by urate crystals and their gene expression, or increase uric acid excretion by regulating the expression of uric acid transporters, thereby exerting a pharmacological effect of lowering uric acid. However, the development value of the potential nutritional effects of kiwi flowers has not yet been discovered and reported. Summary of the invention

[0006] The present invention aims to provide a solid beverage of yellow heart kiwi flower extract with uric acid lowering effect, and its preparation method and application. The solid beverage of yellow heart kiwi flower extract prepared by the method provided by the present invention has a high content of flavonoid compounds and polyphenol compounds with uric acid lowering effective substances, so that it has an excellent uric acid lowering effect.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a solid beverage of yellow heart kiwifruit flower extract having uric acid lowering effect, comprising the following steps:

[0009] The fresh kiwifruit flowers are sequentially dried, crushed, microwaved to inactivate enzymes and vacuum freeze-dried to obtain kiwifruit flower powder;

[0010] Subcritical water extraction and ceramic membrane filtration are performed on the kiwi flower powder to obtain an extract A and a filter residue;

[0011] After mixing the filter residue and ethanol, ultrasonic extraction and concentration are performed in sequence to obtain extract B;

[0012] The extract A and the extract B are mixed in a certain ratio, and frozen and granulated to obtain a solid drink of kiwi flower extract.

[0013] Preferably, the fresh kiwifruit flowers are in full bloom.

[0014] Preferably, the drying temperature is 100-120° C., and the drying time is 4-8 h; the frequency of the microwave enzyme inactivation is 2000-3000 MHz, the power of the microwave enzyme inactivation is 700-900 W, and the microwave enzyme inactivation time is 80-100 s.

[0015] Preferably, the temperature of the subcritical water extraction is 35 to 55° C., the pressure of the subcritical water extraction is 35 to 50 MPa, and the time of the subcritical water extraction is 1 to 2 hours.

[0016] Preferably, the filter membrane used for the ceramic membrane filtration is an ultrafiltration membrane of 30 to 70 kDa.

[0017] Preferably, the ratio of the mass of the filter residue to the volume of ethanol is 1 g:(19-22) mL, and the volume concentration of the ethanol is 40%.

[0018] Preferably, the temperature of the ultrasonic extraction is 40-60° C., the time of the ultrasonic extraction is 40-65 min, the power of the ultrasonic extraction is 260-400 W, and the frequency of the ultrasonic extraction is 40-60 kHz.

[0019] Preferably, the mixing volume ratio of the extract A and the extract B is (2-4):1; the temperature of the freeze granulation is -55°C to -40°C, the time of the freeze granulation is 2 to 8 hours, and the vacuum degree of the freeze granulation is 0.06 to 0.16 mbar.

[0020] The present invention also provides a solid beverage of kiwi flower extract prepared by the preparation method described in the above technical scheme.

[0021] The present invention also provides a solid beverage of kiwi flower extract obtained by the preparation method described in the above technical scheme, or the use of the solid beverage of kiwi flower extract described in the above technical scheme in a kiwi flower compound beverage for improving hyperuricemia.

[0022] The invention provides a preparation method of a solid beverage of kiwi flower extract with uric acid lowering effect. The method comprises the following steps: firstly subjecting fresh yellow-heart kiwi flower to raw material pretreatment, including sequentially drying, crushing, microwave enzyme inactivation and vacuum freeze drying to obtain kiwi flower powder, and then subjecting the kiwi flower powder to gradient targeted extraction. Firstly, the kiwi flower powder is subjected to subcritical water extraction to improve the flavonoid yield (by 40%), and then subjected to ceramic membrane filtration to remove macromolecular impurities to obtain an extract A and a filter residue. The filter residue is mixed with ethanol and then subjected to ultrasonic extraction to improve the polyphenol extraction rate in the extract (>85%). The extract B is obtained by nanofiltration concentration, and finally subjected to stabilization processing. The extract A and the extract B are mixed in a certain proportion, and subjected to freezing granulation to obtain a kiwi flower powder solid beverage with a high content of effective substances of flavonoids and polyphenol compounds with uric acid lowering effect. The solid beverage of the kiwi flower extract has an excellent improvement effect on hyperuricemia. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1The concentrations of uric acid, creatinine and urea nitrogen in the serum of mice in the NC group, PO group, HKF group, MKF group and LKF group in the present invention are statistically shown, wherein: Figure 1 a, b, c and d represent significant differences, Figure 1 1) Uric acid, Figure 1 2) is creatinine, Figure 1 3) is urea nitrogen;

[0024] Figure 2 is a statistical graph of XOD concentration in the liver of mice in the NC group, PO group, HKF group, MKF group and LKF group in the present invention, wherein: Figure 2 a, b, c and d represent significant differences;

[0025] Figure 3 The figure is the result of renal histological analysis of mice in the NC group, PO group, HKF group, MKF group and LKF group in the present invention, wherein Figure 3 From A to E in the middle are NC group, PO group, HKF group, MKF group, and LKF group (HE, ×200);

[0026] Figure 4 The expression results of uric acid transporter in renal tissue of mice in NC group, PO group, HKF group, MKF group and LKF group in the present invention are shown in FIG. Figure 4 a, b, c and d represent significant differences, Figure 4 1) is URAT1, Figure 4 2) is GLUT9, Figure 4 Middle 3) is ABCG2;

[0027] Figure 5 The results of the mRNA expression of Keap1-Nrf2 pathway genes in the kidney tissue of mice in the NC group, PO group, HKF group, MKF group and LKF group in the present invention are shown in FIG. Figure 5 a, b, c and d represent significant differences, Figure 5 1) is Keap1, Figure 5 Middle 2) is Nrf2, Figure 5 3) is HO-1, Figure 5 4) is NQO-1, Figure 5 (5) is GR. DETAILED DESCRIPTION

[0028] The present invention provides a preparation method or application of a solid beverage of kiwi flower extract having the effect of lowering uric acid, comprising the following steps:

[0029] The fresh kiwifruit flowers are sequentially dried, crushed, microwaved to inactivate enzymes and vacuum freeze-dried to obtain kiwifruit flower powder;

[0030] Subcritical water extraction and ceramic membrane filtration are performed on the kiwi flower powder to obtain an extract A and a filter residue;

[0031] After mixing the filter residue and ethanol, ultrasonic extraction and concentration are performed in sequence to obtain extract B;

[0032] The extract A and the extract B are mixed and frozen and granulated to obtain a solid drink of kiwi flower extract.

[0033] In the present invention, unless otherwise specified, the raw materials used are conventional commercially available products in the art.

[0034] In the present invention, the fresh kiwifruit flowers are preferably in full bloom. In the present invention, the fresh kiwifruit flowers are preferably picked from yellow-heart kiwifruit varieties. The present invention uses fresh kiwifruit flowers in full bloom of yellow-heart kiwifruit as raw materials to increase the content of flavonoids and polyphenol compounds with uric acid lowering properties in the prepared solid beverage of kiwifruit flower extract.

[0035] In the present invention, the drying temperature is preferably 100-120° C., more preferably 100-105° C., and the drying time is preferably 4-8 h, more preferably 6 h.

[0036] In the present invention, the pulverization preferably further comprises sieving the pulverized kiwifruit flowers through 10-20 meshes. The present invention controls the particle size of the kiwifruit flower powder within the above range to facilitate the dissolution of the effective components of flavonoids and polyphenols that lower uric acid during subsequent extraction.

[0037] In the present invention, the frequency of the microwave enzyme inactivation is preferably 2000-3000MHz, more preferably 2200-2800MHz. The power of the microwave enzyme inactivation is preferably 700-900W, more preferably 750-850W, and the time of the microwave enzyme inactivation is preferably 80-100s, more preferably 85-95s. The present invention uses microwave enzyme inactivation to achieve rapid and uniform inhibition of enzyme activity while retaining the nutritional components and color of the material; the enzyme protein structure is directly destroyed by the non-thermal effect of high-frequency electromagnetic waves to avoid the deterioration of material texture caused by traditional thermal inactivation; it has the synergistic advantages of low energy consumption, high efficiency, strong penetration and no chemical residues.

[0038] In the present invention, the temperature of the vacuum freeze drying is -60 to -45°C, and the vacuum degree of the vacuum freeze drying is 0.02 to 0.09 mbar. The present invention uses vacuum freeze drying to retain the active ingredients, color and porous structure of the material to the greatest extent, avoids the degradation of heat-sensitive substances through low-temperature sublimation dehydration, inhibits microbial activity and prolongs the shelf life of the product; combines the synergistic effect of low temperature and high vacuum to reduce the mechanical damage of ice crystals to the cell structure, and ensures the rapid rehydration and quality stability of the dried material.

[0039] In the present invention, the temperature of the subcritical water extraction is preferably 35-55°C, more preferably 40-50°C; the pressure of the subcritical water extraction is preferably 35-50MPa, more preferably 35-45MPa; the time of the subcritical water extraction is preferably 1-2h, more preferably 1.5h. The present invention uses subcritical water extraction to increase the content of effective ingredients of flavonoids in the solid beverage of kiwi flower extract.

[0040] In the present invention, the filter membrane used for the ceramic membrane filtration is preferably an ultrafiltration membrane of 30-70 kDa. The present invention removes macromolecular impurities by filtration through the ceramic membrane.

[0041] In the present invention, the ratio of the mass of the filter residue to the volume of ethanol is preferably 1 g:(19-22), more preferably 1 g:20 mL; the volume concentration of the ethanol is preferably 40%. The present invention controls the ratio of the mass of the filter residue to the volume of ethanol within the above range to increase the content of the effective components of polyphenol compounds in the solid beverage of kiwi flower extract.

[0042] In the present invention, the temperature of the ultrasonic extraction is preferably 40-60°C, more preferably 50°C, the time of the ultrasonic extraction is preferably 40-65min, more preferably 55min, the power of the ultrasonic extraction is preferably 260-400W, more preferably 360W; the frequency of the ultrasonic extraction is preferably 40-60kHz, more preferably 45-55kHz. The present invention uses ethanol as an extractant, cooperates with ultrasonic extraction, promotes the dissolution of effective components of polyphenol compounds, and obtains a solid beverage of kiwi flower extract with excellent uric acid lowering effect.

[0043] In the present invention, the concentration is preferably nanofiltration concentration; the molecular weight cutoff of the filter membrane used for the nanofiltration concentration is preferably 120 to 300 Da, more preferably 160 to 260 Da. The present invention uses nanofiltration concentration to efficiently intercept the target active substance and remove small molecule impurities, achieve gentle concentration under low temperature and low pressure conditions, and avoid denaturation of heat-sensitive components; at the same time, selectively separate inorganic salts and organic small molecules, improve product purity and reduce subsequent processing energy consumption.

[0044] In the present invention, the mixed volume ratio of the extract A and the extract B is preferably (2-4):1, more preferably 3:1. The present invention controls the mixed volume ratio of the extract A and the extract B within the above range to coordinately regulate the polarity and permeability of the solvent, balance the dissolution efficiency and selective extraction of the target component, and inhibit the dissolution of the ineffective component and reduce the solvent residue; by optimizing the mass transfer kinetics of the two-phase interface, the extraction rate and product purity are improved.

[0045] In the present invention, the temperature of the freeze granulation is preferably -55°C to -40°C, more preferably -50°C to -42°C. The time of the freeze granulation is preferably 2 to 8 hours, more preferably 3 to 5 hours, and the vacuum degree of the freeze granulation is preferably 0.06 to 0.16 mbar, more preferably 0.08 to 0.12 mbar. The present invention uses freeze granulation to quickly solidify the material under low-temperature vacuum conditions, avoid inactivation of heat-sensitive components, and form a uniform porous particle structure, thereby improving product stability, dissolution rate and process controllability, and reducing subsequent drying energy consumption.

[0046] The present invention also provides a solid beverage of kiwi flower extract prepared by the preparation method described in the above technical scheme.

[0047] The present invention also provides a solid beverage of kiwi flower extract prepared by the preparation method described in the above technical scheme, or the use of the solid beverage of kiwi flower extract described in the above technical scheme in a kiwi flower compound beverage that can improve hyperuricemia.

[0048] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Example 1

[0050] A preparation method or application of a solid beverage containing kiwi flower extract having the effect of lowering uric acid, comprising the following steps:

[0051] 20 g of fresh kiwifruit flowers of yellow-heart kiwifruit in full bloom were dried at 105°C for 6 h, crushed, sieved through 20 meshes, microwaved for 90 s at a frequency of 200 and a power of 100,000,000, and then vacuum-freeze-dried at -55°C and 0.05 mbar for 5 h to obtain kiwifruit flower powder;

[0052] The kiwi flower powder was subjected to subcritical water extraction at 45° C. and 35 MPa for 1.5 h, and ceramic membrane filtration was performed using a 50 kDa ultrafiltration membrane to remove macromolecular impurities, thereby obtaining an extract A and a filter residue;

[0053] After mixing the filter residue and ethanol, ultrasonic extraction is performed at 360W and 50°C for 55 minutes, and then the extract obtained by ultrasonic extraction is concentrated under reduced pressure until no liquid is evaporated, to obtain extract B;

[0054] The extract A and the extract B are mixed in a volume ratio of 3:1, and vacuum dried at -45°C and 0.1 mbar, i.e., freeze granulated for 5 hours to obtain a solid drink of kiwi flower extract;

[0055] The ratio of the mass of the kiwifruit flower to the volume of ethanol is 1 g:20 mL, and the volume concentration of the ethanol is 40%.

[0056] Comparative Example 1

[0057] A solid beverage of kiwi flower extract was prepared according to the method of Example 1, except that the subcritical water extraction was replaced by water extraction at normal pressure and 100°C.

[0058] Comparative Example 2

[0059] A solid beverage of kiwi flower extract was prepared according to the method of Example 1, except that the filtrate residue was mixed with water and then subjected to ultrasonic extraction.

[0060] Comparative Example 3

[0061] A solid beverage of kiwi flower extract was prepared according to the method of Example 1, except that fresh kiwi flowers of yellow-heart kiwi fruit in the late flowering period were used.

[0062] Comparative Example 4

[0063] A solid beverage of kiwi flower extract was prepared according to the method of Example 1, except that fresh kiwi flowers of Actinidia chinensis in full bloom were used.

[0064] Comparative Example 5

[0065] A solid beverage of kiwi flower extract was prepared according to the method of Example 1, except that fresh kiwi flowers of Xuxiang kiwi fruit in full bloom were used.

[0066] The mass percentage (wt %) of total flavonoids in the solid beverages of kiwi flower extract prepared in Example 1 and Comparative Examples 1 to 5 was measured by spectrophotometry. The results are shown in Table 1.

[0067] Specific detection process: The solid beverage of kiwi flower extract prepared in the embodiment and the comparative example is diluted with 50% ethanol by volume at a ratio of 1:10 to obtain the test solution;

[0068] Accurately pipette 1 mL of the test solution into a 10 mL test tube, perform the color reaction according to the steps, and add 5% NaNO 2 0.3 mL of solution was shaken and allowed to stand for 6 min; 10% Al(NO) was added again. 30.3 mL of the solution was shaken and allowed to stand for 6 min, 4 mL of 4% NaOH solution was added successively, the volume was adjusted to the mark with 70% ethanol and allowed to stand for 15 min, and the absorbance at 510 nm was measured. The mass concentration of total flavonoids in the test solution sample was calculated according to the rutin standard curve and the following formula 1, and the results are shown in Table 1.

[0069]

[0070] In Formula 1, X is the total flavonoid content in the solid drink of kiwi flower extract (%); c is the total flavonoid concentration of the test sample calculated by the standard curve (g / L); V is the volume of the extract (mL); D is the dilution factor; and m is the mass of the sample (g).

[0071] The colorimetric method was used to detect the mass percentage (wt %) of total polyphenol compounds in the solid beverages of kiwi flower extract prepared in Example 1 and Comparative Examples 1 to 5. The results are shown in Table 1.

[0072] Specific detection process: refer to "T / AHFIA005-2018 Determination of total polyphenol content in plant extracts and their products", take 1mL of filtrate in a 10mL colorimetric tube, add 2.5mL of Folin phenol reagent, shake well, then add 2.5mL of 15% sodium carbonate solution, add water to the scale, shake well. Place in a 40℃ water bath for 60min, let stand and cool, and measure the absorbance at a wavelength of 778nm. According to C 1 V 1 =C 2 V 2 Calculate the polyphenol content.

[0073] Table 1 Concentrations of total flavonoids and total polyphenols in solid beverages of kiwi flower extract prepared in Example 1 and Comparative Examples 1 to 5

[0074]

[0075] As can be seen from Table 1, the solid beverage of yellow-heart kiwi flower extract prepared in Example 1 of the present application has the highest concentrations of total flavonoids and polyphenols.

[0076] Animal experiments

[0077] Fifty male C57BL / 6J mice were housed in a standard animal room with a temperature of (23±2)°C, 12h light-dark alternation, and a relative humidity of (50±20)%. Before the experimental treatment, the mice were given normal sterile feed and purified water for 7 days for adaptive feeding.

[0078] After the mice were adapted to feeding, they were randomly divided into 5 groups, with 10 mice in each group as biological replicates, and divided into normal group (NC), model group (PO), high-dose group (HKF) of solid drink of kiwi flower extract, medium-dose group (MKF) of solid drink of kiwi flower extract, and low-dose group (LKF) of solid drink of kiwi flower extract. This study chose to continuously give PO for 21 days to establish a chronic HUA model. The mouse HUA model was established with a dose of 250 mg / kg of potassium oxonato (Potassium Oxonato, PO). During the modeling process, except for the normal group, each group of mice was gavaged with PO drugs on a regular basis every morning. One hour after the PO treatment, the solid drink of kiwi flower extract prepared in Example 1 was gavaged. The normal control group and the model group mice were gavaged with an equal volume of normal saline. The specific treatment conditions of each group are shown in Table 2. Gavage dose: 0.1 mL / 10 g, potassium oxonato solution preparation: 250 mg / 10 mL normal saline.

[0079] Table 2 Statistics of treatment conditions in each group of animal experiments

[0080]

[0081] The body weight and food intake of mice in each group were recorded before the scheduled administration every morning. One hour after the last treatment on the 21st day (the uric acid level of mice administered PO increased significantly within 2 hours and then gradually decreased), the mice in each group were anesthetized and blood was collected from the orbital vein to collect whole blood samples. After the whole blood sample was placed on a sterile workbench at room temperature for about 1 hour, it was centrifuged at 3500g for 10 minutes, and the upper serum was aspirated and stored in a -65℃ freezer. After the mice were killed by spine severance, the required tissues and organs were taken, washed with 4℃ physiological saline, and placed in 10mL centrifuge tubes. All tissues and samples were stored in a -65℃ freezer for subsequent testing.

[0082] Uric acid (UA) can be used to assess whether purine metabolism is abnormal. Increased creatinine (Cr) levels indicate renal impairment. Increased urea nitrogen (BUN) levels can be used to assess renal impairment. Cr and BUN are important indicators of renal injury, and accumulation in the kidneys can lead to renal injury. XOD (i.e., xanthine oxidase) is widely present in the liver and intestinal tissues of mammals, catalyzing the oxidation of hypoxanthine to xanthine and ultimately generating uric acid. XOD levels can be used to assess the degree of oxidative stress damage. These indicators are tested below.

[0083] (1) The UA, Cr, and BUN levels in the serum of the mice in the above-mentioned groups were determined by colorimetry, and the concentrations of UA, Cr, and BUN in the serum of the mice in the NC group, PO group, HKF group, MKF group, and LKF group were statistically shown in the following figure. Figure 1 shown.

[0084] Depend on Figure 1 It can be seen that compared with the NC group, the content of the PO group increased significantly (P<0.05), indicating that the modeling is effective. Compared with the PO group, the serum UA, Cr, and BUN of the HKF, MKF, and LKF groups decreased to varying degrees, and each group was significantly different from the PO group (P<0.05). The HKF group was significantly different from the PO and NC groups (P<0.05), indicating that the solid drink of kiwi flower extract prepared in Example 1 can effectively reduce the uric acid level of hyperuricemia mice.

[0085] (2) XOD (i.e., xanthine oxidase) is a key enzyme in the uric acid synthesis pathway in the body. Inhibiting its activity can reduce the uric acid level in the body. In order to further study the role of solid beverages containing kiwi flower extract in uric acid synthesis, the level of XOD in the liver of each group of mice was detected by colorimetry. The concentration of XOD in the liver of mice in the NC group, PO group, HKF group, MKF group, and LKF group was statistically shown in the figure below. Figure 2 As shown. Figure 2 It can be seen that compared with the NC group, the XOD enzyme activity in the liver of mice treated with PO was significantly enhanced (P < 0.05). Compared with the PO group, the HKF group, MKF group and LKF group all significantly reduced the activity of XOD, and the HKF group had the best effect. The results show that the solid drink of kiwi flower extract prepared in Example 1 can reduce the production of uric acid by inhibiting the key enzymes of uric acid synthesis in the liver, thereby alleviating hyperuricemia.

[0086] (3) HE staining was used to detect the renal pathological changes of mice in each group. The results of renal histological analysis of mice in the NC group, PO group, HKF group, MKF group, and LKF group were shown in the figure. Figure 3 As shown, Figure 3 From A to E, they are NC group, PO group, HKF group, MKF group, and LKF group (HE, ×200). Figure 3 It can be seen that pathological changes such as inflammatory cell infiltration and epithelial cell shedding were observed in the renal interstitium of the PO group. The renal tissue cells of the NC group were neatly arranged, the renal tubular structure was clear, and the cell morphology was normal. Compared with the PO group, the solid beverage of kiwi flower extract at a high dose treated group improved renal tubular dilatation to a certain extent, indicating that the solid beverage of natural plant-derived kiwi flower extract prepared in Example 1 can reduce the damage of renal tubular epithelial cells.

[0087] (4) Western blotting was used to detect the expression of uric acid transporter in the kidney of each group of mice. The expression results of uric acid transporter in the kidney tissue of mice in the NC group, PO group, HKF group, MKF group and LKF group were as shown in the figure. Figure 4 As shown. Figure 4It can be seen that after PO induction, the expression of URAT1 and GLUT9 proteins in the kidneys of mice increased significantly (P < 0.05), and the expression level of ABCG2 in the kidneys decreased significantly (P < 0.05). Three doses of kiwi flower extract intervention: The results showed that the expression level of URAT1 in the kidneys was inhibited, and the expression level of ABCG2 was increased; at the same time, the HKF group showed a better intervention effect in reversing the increase in the expression of URAT1, GLUT9, and ABCG2 (P < 0.05). It shows that the increase in the dose of the solid drink of kiwi flower extract prepared in Example 1 has a positive effect on the improvement of hyperuricemia mice.

[0088] (5) RT-qPCR was used to detect the mRNA expression of Keap1-Nrf2 pathway genes in the kidney tissues of mice in the NC group, PO group, HKF group, MKF group, and LKF group. Figure 5 As shown. Figure 5 It can be seen that compared with the NC group, the mRNA transcription level of Keap1 gene in the PO group was significantly increased (P < 0.05), and the mRNA transcription levels of Nrf2, HO-1, NQO-1, GR and other genes were significantly decreased (P < 0.05), indicating that the oxidative stress response destroyed the balance of Nrf2 and its downstream redox system, while the mRNA transcription levels of the corresponding genes in mice treated with kiwi flower flavonoids extract were restored; compared with the PO group, the mRNA transcription level of Keap1 gene in the HKF group was significantly decreased (P < 0.05), and the mRNA transcription levels of Keap1 gene in the MKF and LKF groups were significantly decreased (P < 0.05). The mRNA transcription level of ap1 gene decreased; the mRNA transcription levels of Nrf2, GR, HO-1, NQO-1 and other genes increased significantly (P < 0.05), and the mRNA expression levels of Nrf2, GR, HO-1, NQO-1 and other genes in the kidney tissue of mice in the MKF and LKF groups increased. This shows that the solid drink of kiwi flower extract prepared in Example 1 has a certain dose-effect relationship in improving hyperuricemia mice, and can regulate renal oxidative stress by regulating the Keap1-Nrf2 pathway signal level, thereby improving the metabolic level of hyperuricemia mice.

[0089] In summary, the solid beverage of yellow-heart kiwi flower extract prepared in Example 1 can effectively reduce the uric acid level of hyperuricemia mice, and can also reduce the production of uric acid by inhibiting the key enzymes of uric acid synthesis in the liver, thereby alleviating hyperuricemia and reducing the damage of renal tubular epithelial cells. And the increase in the dose of the solid beverage of kiwi flower extract prepared in Example 1 has a positive effect on the improvement of hyperuricemia mice. The solid beverage of kiwi flower extract prepared in Example 1 has a certain dose-effect relationship in the improvement of hyperuricemia mice, and can regulate the oxidative stress of the kidneys by regulating the signal level of the Keap1-Nrf2 pathway, thereby improving the metabolic level of hyperuricemia mice.

[0090] 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 principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a solid beverage containing kiwi flower extract having the effect of lowering uric acid, characterized in that: The following steps are involved: The fresh kiwifruit flowers are sequentially dried, crushed, microwaved to inactivate enzymes and vacuum freeze-dried to obtain kiwifruit flower powder; Subcritical water extraction and ceramic membrane filtration are performed on the kiwi flower powder to obtain an extract A and a filter residue; After the filter residue and ethanol are mixed, ultrasonic extraction (solid-liquid ratio is 1 g: (19-22) mL, ethanol concentration is 40%) and concentration are performed in sequence to obtain extract B; The extract A and the extract B are mixed and frozen and granulated to obtain a solid drink of kiwi flower extract.

2. The preparation method according to claim 1, characterized in that: The fresh kiwifruit flowers are in full bloom.

3. The preparation method according to claim 1, characterized in that: The drying temperature is 100-120° C., and the drying time is 4-8 hours. The frequency of the microwave enzyme inactivation is 2000-3000 MHz, the power of the microwave enzyme inactivation is 700-900 W, and the microwave enzyme inactivation time is 80-100 seconds.

4. The preparation method according to claim 1, characterized in that: The temperature of the subcritical water extraction is 45-55° C., the pressure of the subcritical water extraction is 35-45 MPa, and the time of the subcritical water extraction is 1-2 hours.

5. The preparation method according to claim 1, characterized in that: The filter membrane used in the ceramic membrane filtration is an ultrafiltration membrane of 30-70 kDa.

6. The preparation method according to claim 1, characterized in that: The ratio of the mass of the filter residue to the volume of ethanol is 1 g: (19-22) mL, and the volume concentration of the ethanol is 40%.

7. The preparation method according to claim 1, characterized in that: The temperature of the ultrasonic extraction is 40-60° C., the time of the ultrasonic extraction is 40-65 min, the power of the ultrasonic extraction is 260-400 W, and the frequency of the ultrasonic extraction is 40-60 kHz.

8. The preparation method according to claim 1, characterized in that: The mixing volume ratio of the extract A and the extract B is (2-4):1; the temperature of the freeze granulation is -55°C to -40°C, the time of the freeze granulation is 2 to 8 hours, and the vacuum degree of the freeze granulation is 0.06 to 0.16 mbar.

9. A solid beverage of kiwi flower extract prepared by the preparation method according to any one of claims 1 to 8.

10. Use of a solid beverage of kiwi flower extract prepared by the preparation method according to any one of claims 1 to 8 or a solid beverage of kiwi flower extract according to claim 9 in a kiwi flower compound beverage for improving hyperuricemia.

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