Preparation method and application of composite plant extract for inhibiting glutamate dehydrogenase activity

Abstract

The invention discloses a preparation method and application of a composite plant extract for inhibiting glutamate dehydrogenase activity, and belongs to the technical field of plant extract preparation. The process provided by the invention comprises the following steps: mixing and crushing licorice roots and honeysuckle buds together, adding water, adding cellulase and pectinase, carrying out ultrasonic-assisted enzymolysis to release cell contents, carrying out transglycosylation reaction by using endogenous enzymes in the cell contents, drying the obtained dissolved substance, carrying out alcohol extraction, centrifuging, and taking filtrate; and freeze-drying to obtain the composite plant extract. The extract has a good inhibition effect on the enzymatic activity of glutamate dehydrogenase, and can not only effectively reduce the odor degree of ammonia in excrement but also improve the digestive ability of pet cats after the pet cats are fed with the extract.

Description

Technical Field

[0001] The invention relates to the technical field of plant extract preparation, and in particular to a method for preparing a composite plant extract capable of inhibiting glutamate dehydrogenase activity and application of the composite plant extract in cat food. Background Art

[0002] Glutamate dehydrogenase is an enzyme widely found in animals. It is related to a variety of physiological processes, including ammonia metabolism, acid-base balance and energy metabolism. In particular, it plays a key role in the oxidative deamination reaction of glutamate. Under its catalytic action, glutamate is converted into α-ketoglutarate and ammonia. Glutamate plays a variety of beneficial roles in animals, such as regulating intracellular energy balance, stimulating central nervous system excitatory effects, and repair. However, when the activity of glutamate dehydrogenase in the intestines of animals is high, it will lead to excessive degradation of glutamate in food digestion products, reduce the body's bioavailability of glutamate, and part of the ammonia produced by degradation will be absorbed by the digestive tract, causing toxic side effects in organs such as the liver and kidneys.

[0003] Licorice is a perennial herbaceous plant of the genus Glycyrrhiza in the family Leguminosae. Its roots and rhizomes are thick, its skin is brown, and it has a sweet taste. Honeysuckle is the dried buds or flowers with just opened flowers of the plant Lonicera japonica of the family Caprifoliaceae. Both licorice and honeysuckle are Chinese medicinal materials. In addition to being well applied in human food and health products (Development of Licorice and Honeysuckle Cooling Beverage, 2016; Process Research on Honeysuckle, Chrysanthemum and Licorice Composite Health Herbal Tea Beverage, 2009), they have also attracted attention in the development of pet food or snacks, such as pet tear stain removal (a Chinese medicine composition for pet tear stain removal and its preparation method, CN202210788459.7; a freeze-dried tear stain removal pet cat staple food and its preparation method, CN202110496950.8), oral care (a lysozyme-containing oral care spray for dogs and cats and its preparation method, CN202011236480.3), and antiviral (application of Chinese medicine compositions or their fermentation products, animal feed and animal feed additives, CN202210283614.X). However, there are currently no reports on the preparation of plant extracts with the ability to inhibit the activity of glutamate dehydrogenase using licorice and honeysuckle as raw materials. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a composite plant extract capable of inhibiting the activity of glutamate dehydrogenase and application of the composite plant extract in cat food.

[0005] The first aspect of the present invention provides a composite plant extract having the function of inhibiting the activity of glutamate dehydrogenase, which is composed of the following raw materials in weight fractions:

[0006] 20-80 parts of licorice rhizomes;

[0007] 20 to 80 pieces of honeysuckle buds.

[0008] The second aspect of the present invention provides a method for preparing a composite plant extract having the function of inhibiting the activity of glutamate dehydrogenase, which is carried out according to the following steps:

[0009] (1) 20 to 80 parts by weight of liquorice rhizomes and 20 to 80 parts of honeysuckle buds are mixed, crushed twice, sieved, and then cellulase and pectinase are added;

[0010] (2) Ultrasound-assisted enzymatic hydrolysis of cellulose and pectin to release cell contents (such as flavonoids, carbohydrates, glycosidases and glycosyltransferases, etc.); keeping the mixture at 35-45°C, using endogenous enzymes in the cell contents to perform transglycosylation reaction for 2-3 hours, centrifuging, collecting the filtrate, concentrating, freeze-drying and pulverizing to obtain a powder sample;

[0011] (3) The powder sample was added to an ethanol solution at a ratio of 1:10 (g / mL) for stirring and extraction. The filtrate after centrifugation was concentrated and freeze-dried to obtain a composite plant extract.

[0012] In the above step (1), the cellulase activity is 100,000 U / g; the pectinase activity is 50,000 U / g; and the amount of the two enzymes added is 2% to 3% based on the mass ratio of the enzyme to the substrate raw material.

[0013] The licorice rhizomes in the above step (1) are preferably dried licorice rhizomes with a storage period of less than three months after natural sun drying, and can also be replaced by fresh licorice rhizomes.

[0014] The honeysuckle buds in the above step (1) are preferably dried honeysuckle buds with a storage period of less than three months after natural sun drying, and can also be replaced by fresh honeysuckle buds.

[0015] In the above step (2), the ultrasonic assisted strengthening has the following ultrasonic parameters: frequency 20-60 kHz, power 80-120 W, temperature 30-50° C., and time 30-50 min.

[0016] In the ethanol solution in step (2) above, the volume proportion of anhydrous ethanol is 30% to 60%.

[0017] The third aspect of the present invention provides the use of the composite plant extract prepared by the above method in cat food.

[0018] Furthermore, the above-mentioned composite plant extract can also be applied to other pets such as dogs, foxes, hamsters, etc.

[0019] Furthermore, the application method is to feed the composite plant extract prepared by the above method to cats by directly feeding or mixing it into cat food (or snacks).

[0020] The present invention has the following beneficial effects:

[0021] The dried liquorice rhizome product and the dried honeysuckle bud product are mixed and crushed twice. The two plants are powdered in the first crushing, but the particle sizes of the two powders are uneven and the mixing is insufficient. The second crushing plays a role of further refinement and sufficient mixing, which creates favorable conditions for the subsequent enzymatic hydrolysis process and the contact and reaction of the active substances in the two plants. In the present invention, cellulase and pectinase are used for enzymatic hydrolysis, which helps to destroy the cell wall. At the same time, ultrasonic waves are applied during the enzymatic hydrolysis process to promote the release of plant cell contents. Licorice rhizome is rich in flavonoids, and honeysuckle buds have a high content of glycosides. Their cell contents are rich in various glycosidases, glycosyltransferases, etc. The two plants can generate flavonoid glycoside active substances through the action of glycosidases during the co-crushing, enzymatic hydrolysis, and alcohol extraction of flavonoids and glycosides, thereby improving the functional activity of the composite plant extract.

[0022] The total glycoside content of the composite plant extract prepared by the method of the present invention is 7.38-8.19 mg / g, which is 7.94-10.36 times that of the mixture prepared by direct crushing without extraction (reference examples 2-4), and 3.00-3.59 times that of the mixture of extracts obtained by extracting two plants separately (reference examples 5-7); it has a good inhibitory effect on glutamate dehydrogenase, IC 50 It is 7.64-8.13 g / L, which is 71.72%-76.44% lower than the mixture prepared by direct crushing without extraction (Control Examples 2-4), and is 58.56%-67.50% lower than the mixture of extracts obtained by extracting two plants separately (Control Examples 5-7).

[0023] The results of the cat feeding test show that the composite plant extract prepared by the method of the present invention has the effect of reducing the activity of glutamate dehydrogenase in cat feces. The activity of glutamate dehydrogenase in cat feces fed with the extract is 11.25-12.72 U / mL, which is 52.63%-58.10% lower than that of the cats not fed with the extract (Control Example 1), 47.72%-55.43% lower than that of the cats fed with the mixture directly crushed without extraction (Control Examples 2-4), and 32.91%-45.15% lower than that of the cats fed with the mixture of extracts extracted from two plants (Control Examples 5-7).

[0024] The composite plant extract prepared by the method of the present invention has a good effect of alleviating the ammonia odor of cat feces. The feces odor score of cats fed with the extract is 2.4-2.8 points, the volatile basic nitrogen content is 86.82-91.55 mg / 100 g, and the ammonia content is 0.37-0.45 ppm / g. These three indicators are reduced by 36.82%-64.08% compared with the case where the extract is not fed (control example 1), reduced by 32.47%-62.63% compared with the case where the mixture prepared by directly crushing without extraction is fed (control examples 2-4), and reduced by 20.00%-54.88% compared with the case where the mixture of extracts obtained by extracting two plants separately is fed (control examples 5-7).

[0025] The composite plant extract prepared by the method of the present invention has the effect of improving the digestive ability of cats. The apparent digestibility of protein in the feed for cats supplemented with the extract is 95.86% to 97.17%, which is 17.12% to 18.72% higher than that when the extract is not supplemented (control example 1), 11.26% to 14.71% higher than that when the mixture is prepared by directly crushing without extraction (control examples 2 to 4), and 4.57% to 8.46% higher than that when the mixture is supplemented with extracts obtained by extracting two plants separately (control examples 5 to 7). DETAILED DESCRIPTION

[0026] The terms used in the present invention, unless otherwise specified, generally have the meanings commonly understood by those of ordinary skill in the art. The present invention will be further described in detail below in conjunction with specific embodiments and with reference to data. It should be understood that these embodiments are only further explanations of the present invention and cannot be construed as limiting the scope of protection of the present invention. Technical engineers in this field may make some non-essential improvements and adjustments to the present invention based on the content of the above invention.

[0027] In the following examples, various processes and methods not described in detail are conventional methods known in the art. The sources, trade names and components of the reagents used are indicated when they first appear, and the same reagents used thereafter are the same as those indicated for the first time unless otherwise specified.

[0028] The dried liquorice rhizome product and the dried honeysuckle bud product (both of which are dried products with a storage period of less than three months after natural sun drying) used in the present embodiment and the comparative example are both commercially available.

[0029] The method for determining the total glycoside content of plant extracts and mixtures in the present embodiment and reference examples is as follows:

[0030] Take 1g of the composite plant extract or mixture sample and dissolve it in 10mL of ethanol solution (50%), dilute it to a reasonable multiple and then determine the total glycoside content. The specific determination is carried out according to the method of Qin Honglin (Extraction and Activity Study of Total Glycosides of Ligustrum Lucidum in Ligustrum Lucidum, 2007).

[0031] The half inhibitory concentration (IC 50 ) Determination method:

[0032] Prepare glutamate dehydrogenase enzyme solution, and at the same time, centrifuge the aqueous solution of the extract and retain the supernatant. Mix the supernatant and glutamate dehydrogenase enzyme solution in equal volumes and let stand at 37°C for 10 minutes. Determine the glutamate dehydrogenase enzyme activity of the mixed solution according to the kit instructions. The control group used distilled water instead of supernatant for enzyme activity determination, and other operations remained consistent. The enzyme activity inhibition rate was calculated according to the formula: enzyme activity inhibition rate (%) = [(enzyme activity of the control group - enzyme activity of the assay group) / enzyme activity of the control group] × 100%. Use the extract concentration as the horizontal axis and the enzyme activity inhibition rate as the vertical axis to draw a curve and calculate its IC 50 .

[0033] Method for determining the activity of glutamate dehydrogenase in cat feces in this embodiment and control example:

[0034] Fresh cat feces samples were collected and mixed with physiological saline at a mass ratio of 1:1, and then the tissue was broken and centrifuged (10000r / min, 10min) to collect the supernatant. The glutamate dehydrogenase activity of the sample solution was determined according to the instructions of the kit.

[0035] The manual evaluation method of feces odor degree in this embodiment and reference example is as follows:

[0036] 30g of fresh cat feces was placed in a 50mL stoppered test tube, and the tester conducted a sensory evaluation of the odor of the cat feces at a distance of 10cm from the tube mouth. The higher the odor, the higher the score, with a faint odor of 1 point, a perceptible odor of 2 points, a tolerable odor of 3 points, a strong odor that is difficult to tolerate of 4 points, and an extremely strong odor that is unbearable of 5 points.

[0037] Method for determining the volatile basic nitrogen content of cat feces in this embodiment and the reference examples:

[0038] Weigh 5g of fresh feces sample from cats into a conical flask, add 10mL trichloroacetic acid solution (150g / L) and 40mL distilled water, and stir and extract for 30min. Take 30mL of the extract and centrifuge it (3500r / min, 10min), then take 10mL of the supernatant into the digestive tube, add 10mL of sodium hydroxide solution (40g / L) and immediately distill it on the machine. Refer to "GB / T 32141-2015 Determination of Volatile Basic Nitrogen in Feed" to determine the volatile basic nitrogen content of the supernatant.

[0039] Method for determining ammonia content in cat feces in this embodiment and reference examples:

[0040] Weigh 10g of fresh cat feces sample and put it into a ziplock bag. Insert the portable gas detector probe into the bag and ensure that the insertion length and angle are consistent. Record the reading after it stabilizes.

[0041] Each plant extract or plant mixture prepared in the control example and the embodiment was directly mixed into the cat's daily diet at 0.05% for supplementary feeding. The feces of the fed pet cats had a serious ammonia odor (odor score exceeded 4 points). 30 British shorthair cats, orange cats, ragdoll cats and Chinese rural cats were randomly divided into 10 groups, each group containing 3 cats of each of the above 4 types. After 3 days of supplementary feeding, the feces were taken for fecal glutamate dehydrogenase enzyme activity determination, odor degree evaluation, volatile basic nitrogen content, ammonia content and protein apparent digestibility determination.

[0042] The method for determining the apparent digestibility of protein in the present embodiment and the control example is as follows:

[0043] Six healthy cats were selected. After 10 days of adaptive feeding of cat food, when the cats did not have abnormal conditions such as vomiting and diarrhea for 3 consecutive days, the feces of the cats for 5 days were collected by the full feces collection method, weighed, weighed and crushed after drying, and weighed for testing. The protein content in the cat food and feces was determined by the Kjeldahl method, and the apparent digestibility of the protein in the cat food was calculated. Protein apparent digestibility (%) = (1-(protein content in feces × feces mass / protein content in cat food × cat food intake mass)) × 100.

[0044] Comparative Example 1

[0045] Cats with severe fecal ammonia odor were fed a normal cat diet without adding extracts. After the feeding test, the fecal glutamate dehydrogenase activity was 26.85U / mL, the odor score was 4.7 points, the volatile basic nitrogen content was 144.91mg / 100g, and the ammonia content was 1.03ppm / g. The apparent digestibility of protein in cat food was 81.85%.

[0046] Comparative Example 2

[0047] The dried liquorice rhizome product is ground and passed through a 40-mesh sieve, and then ground again and passed through an 80-mesh sieve to obtain liquorice rhizome powder.

[0048] The results of physical and chemical tests showed that the total glycoside content of the liquorice rhizome powder was 0.79 mg / g, and the IC 50 It is 30.84g / L.

[0049] Animal test results show that after the feeding test, the fecal glutamate dehydrogenase activity of cats was 25.24U / mL, the odor score was 4.5 points, the volatile basic nitrogen content was 138.62mg / 100g, and the ammonia content was 0.94ppm / g. The apparent digestibility of cats for protein in cat food was 84.71%.

[0050] Comparative Example 3

[0051] The dried honeysuckle bud product was crushed and passed through a 40-mesh sieve, and then crushed again and passed through an 80-mesh sieve to obtain honeysuckle bud powder.

[0052] The results of physical and chemical tests showed that the total glycoside content of the honeysuckle bud powder was 0.93 mg / g, and the IC 50 It is 32.43g / L.

[0053] Animal test results show that after the feeding test, the fecal glutamate dehydrogenase activity of cats was 24.33U / mL, the odor score was 4.4 points, the volatile basic nitrogen content was 140.24mg / 100g, and the ammonia content was 0.99ppm / g. The apparent digestibility of cats for protein in cat food was 86.16%.

[0054] Comparative Example 4

[0055] The dried licorice rhizome product and the dried honeysuckle bud product were crushed separately and passed through a 40-mesh sieve, and then crushed again and passed through an 80-mesh sieve. The two sieved products were mixed in a mass ratio of 1:1 to obtain a licorice-honeysuckle mixed powder.

[0056] The results of physical and chemical tests showed that the total glycoside content of the licorice-honeysuckle mixed powder was 0.86 mg / g, and the IC 50 It is 28.75g / L.

[0057] Animal test results show that after the feeding test, the fecal glutamate dehydrogenase activity of cats was 24.66U / mL, the odor score was 4.5 points, the volatile basic nitrogen content was 135.57mg / 100g, and the ammonia content was 0.95ppm / g. The apparent digestibility of cats for protein in cat food was 85.44%.

[0058] Comparative Example 5

[0059] Take the dried product of licorice root and stem, grind it and pass it through a 40-mesh sieve, and grind it again and pass it through an 80-mesh sieve. Take 100g of the sieved powder, add 2g of cellulase (enzyme activity 100,000 U / g) and 2g of pectinase (enzyme activity 50,000 U / g), then add 2.5L of distilled water, mix well and adjust the pH to 7.0, and perform ultrasonic (frequency 20kHz, power 120W, temperature 30°C) assisted enzymolysis for 30min, keep warm at 35°C, and use the endogenous enzyme in the cell content to perform transglycosylation reaction for 3h. After cooling, filter and retain the filtrate, concentrate under reduced pressure and freeze-dry to obtain a powder sample, then add ethanol solution (30%) at 1g / 10mL, extract at 50°C for 30min, cool and centrifuge to retain the supernatant, concentrate under reduced pressure at 60°C, and freeze-dry again to obtain a licorice extract.

[0060] The results of physical and chemical tests showed that the total glycoside content of the licorice extract was 2.46 mg / g, and the IC 50 It is 22.79g / L.

[0061] Animal test results show that after the feeding test, the fecal glutamate dehydrogenase activity of cats was 20.51U / mL, the odor score was 3.7 points, the volatile basic nitrogen content was 125.24mg / 100g, and the ammonia content was 0.81ppm / g. The apparent digestibility of cats for protein in cat food was 90.22%.

[0062] Comparative Example 6

[0063] Take the dried product of honeysuckle buds, grind it, pass it through a 40-mesh sieve, and grind it again through an 80-mesh sieve. Take 100g of the sieved powder, add 2g of cellulase (enzyme activity 100,000 U / g) and 2g of pectinase (enzyme activity 50,000 U / g), then add 2.5L of distilled water, mix well and adjust the pH to 7.0, and use ultrasound (frequency 20kHz, power 120W, temperature 30°C) to assist enzymolysis for 30min. Keep warm at 35°C, use the endogenous enzyme in the cell content to carry out transglycosylation reaction for 3h, filter and retain the filtrate after cooling, obtain a powder sample after reduced pressure concentration and freeze drying, then add ethanol solution (30%) at 1g / 10mL, extract at 50°C for 30min, cool and centrifuge to retain the supernatant, concentrate under reduced pressure at 60°C, and freeze dry again to obtain the honeysuckle extract.

[0064] The results of physical and chemical tests showed that the total glycoside content of the honeysuckle extract was 2.28 mg / g, and the IC 50 It is 23.51g / L.

[0065] Animal test results show that after the feeding test, the fecal glutamate dehydrogenase activity of cats was 18.96U / mL, the odor score was 3.5 points, the volatile basic nitrogen content was 123.42mg / 100g, and the ammonia content was 0.82ppm / g. The apparent digestibility of cats for protein in cat food was 91.67%.

[0066] Comparative Example 7

[0067] Take the dried products of licorice rhizomes and honeysuckle buds, grind them respectively, pass through a 40-mesh sieve, grind them again and pass through an 80-mesh sieve, and extract them respectively. Take 100g of the sieved powder, add 2g of cellulase (enzyme activity 100,000 U / g) and 2g of pectinase (enzyme activity 50,000 U / g), add 2.5L of distilled water, mix well and adjust the pH to 7.0, and use ultrasound (frequency 20kHz, power 120W, temperature 30°C) to assist enzymolysis for 30min. Keep warm at 35°C, use the endogenous enzyme in the cell content to carry out transglycosylation reaction for 3h, filter and retain the filtrate after cooling, obtain a powder sample after reduced pressure concentration and freeze drying, then add ethanol solution (30%) at 1g / 10mL, extract at 50°C for 30min, cool and centrifuge to retain the supernatant, concentrate under reduced pressure at 60°C, and freeze dry again to obtain licorice extract and honeysuckle extract respectively. The two extracts were mixed in a mass ratio of 1:1 to prepare a licorice extract-honeysuckle extract mixture.

[0068] The results of physical and chemical tests showed that the total glycoside content of the liquorice extract-honeysuckle extract mixture was 2.35 mg / g, and the IC 50 It is 19.62g / L.

[0069] Animal test results show that after the feeding test, the fecal glutamate dehydrogenase activity of cats was 19.38U / mL, the odor score was 3.7 points, the volatile basic nitrogen content was 118.59mg / 100g, and the ammonia content was 0.77ppm / g. The apparent digestibility of cats for protein in cat food was 89.59%.

[0070] Example 1

[0071] 200g of dried licorice rhizome and 800g of dried honeysuckle bud are mixed by weight, crushed together, passed through a 40-mesh sieve, and then crushed again through an 80-mesh sieve. 100g of the sieved powder is taken, 2g of cellulase (enzyme activity 100,000 U / g) and 2g of pectinase (enzyme activity 50,000 U / g) are added, and then 2.5L of distilled water is added, and the pH is adjusted to 7.0 after mixing evenly, and ultrasonic (frequency 20kHz, power 120W, temperature 30°C) is used to assist enzymolysis for 30min. The mixture is kept warm at 35°C, and the endogenous enzyme in the cell content is used for transglycosylation reaction for 3h. After cooling, the filtrate is filtered and retained, and a powder sample is obtained after reduced pressure concentration and freeze drying. Then, an ethanol solution (30%) is added at 1g / 10mL, and the mixture is extracted at 50°C for 30min. After cooling, the supernatant is retained by centrifugation, and after reduced pressure concentration at 60°C, the supernatant is retained and freeze dried again to obtain a composite plant extract.

[0072] The results of physical and chemical tests showed that the total glycoside content of this composite plant extract reached 7.38 mg / g, and the IC 50 Only 8.13g / L.

[0073] Animal test results show that after the feeding test, the activity of glutamate dehydrogenase in cat feces dropped to 12.72U / mL, the odor score dropped to 2.8 points, the volatile basic nitrogen content dropped to 91.55mg / 100g, and the ammonia content dropped to 0.41ppm / g. The apparent digestibility of cats for protein in cat food is 96.46%.

[0074] Example 2

[0075] 800g of dried liquorice rhizome and 200g of dried honeysuckle bud are mixed by weight, crushed together, passed through a 40-mesh sieve, and then crushed again through an 80-mesh sieve. 100g of the sieved powder is taken, 3g of cellulase (enzyme activity 100,000 U / g) and 3g of pectinase (enzyme activity 50,000 U / g) are added, and then 2.5L of distilled water is added, and the pH is adjusted to 7.0 after mixing evenly, and ultrasonic (frequency 60kHz, power 80W, temperature 50°C) is used to assist enzymatic hydrolysis for 50min. The mixture is kept warm at 45°C, and the endogenous enzyme in the cell content is used for transglycosylation reaction for 2h. After cooling, the filtrate is filtered and retained, and a powder sample is obtained after reduced pressure concentration and freeze drying. Then, an ethanol solution (60%) is added at 1g / 10mL, and the mixture is extracted at 50°C for 30min. After cooling, the supernatant is retained by centrifugation, and after reduced pressure concentration at 60°C, the supernatant is retained and freeze dried again to obtain a composite plant extract.

[0076] The results of physical and chemical tests showed that the total glycoside content of this composite plant extract reached 8.19 mg / g, and the IC 50 Only 7.91g / L.

[0077] Animal test results show that after the feeding test, the activity of glutamate dehydrogenase in cat feces dropped to 11.25U / mL, the odor score dropped to 2.4 points, the volatile basic nitrogen content dropped to 86.82mg / 100g, and the ammonia content dropped to 0.45ppm / g. The apparent digestibility of cats for protein in cat food is 97.17%.

[0078] Example 3

[0079] 500g of dried licorice rhizome and 500g of dried honeysuckle bud are mixed by weight, crushed together, passed through a 40-mesh sieve, and then crushed again through an 80-mesh sieve. 100g of the sieved powder is taken, 2.5g of cellulase (enzyme activity 100,000 U / g) and 2.5g of pectinase (enzyme activity 50,000 U / g) are added, and then 2.5L of distilled water is added, and the pH is adjusted to 7.0 after mixing evenly, and ultrasonic (frequency 40kHz, power 100W, temperature 40°C) is used to assist enzymatic hydrolysis for 40min. The mixture is kept warm at 30°C, and the endogenous enzyme in the cell content is used for transglycosylation reaction for 2.5h. After cooling, the filtrate is filtered and retained, and a powder sample is obtained after reduced pressure concentration and freeze drying, and then an ethanol solution (60%) is added at 1g / 10mL, and the mixture is extracted at 50°C for 30min. After cooling, the supernatant is retained by centrifugation, and after reduced pressure concentration at 60°C, the supernatant is retained and freeze dried again to obtain a composite plant extract.

[0080] The results of physical and chemical tests showed that the total glycoside content of this composite plant extract reached 7.96 mg / g, and the IC 50 Only 7.64g / L.

[0081] Animal test results show that after the feeding test, the activity of glutamate dehydrogenase in cat feces dropped to 11.37U / mL, the odor score dropped to 2.4 points, the volatile basic nitrogen content dropped to 88.75mg / 100g, and the ammonia content dropped to 0.37ppm / g. The apparent digestibility of cats for protein in cat food is 95.86%.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite plant extract for inhibiting the enzymatic activity of glutamate dehydrogenase, characterized in that The invention is composed of the following components in weight fractions: 20 to 80 parts of liquorice rhizomes and 20 to 80 parts of honeysuckle flower buds.

2. The method for preparing the composite plant extract for inhibiting glutamate dehydrogenase activity according to claim 1, characterized in that Follow these steps: (1) 20 to 80 parts by weight of liquorice rhizomes and 20 to 80 parts of honeysuckle buds are mixed, crushed twice, sieved, and then cellulase and pectinase are added; (2) Ultrasound-assisted enhanced enzymatic hydrolysis of cellulose and pectin to release cell contents; keeping warm at 35-45°C, using endogenous enzymes in the cell contents to perform transglycosylation reaction for 2-3 hours, centrifuging, collecting the filtrate, concentrating, freeze-drying, and pulverizing to obtain a powder sample; (3) The powder sample was added to an ethanol solution at a ratio of 1:10 (g / mL) for stirring and extraction. The filtrate after centrifugation was concentrated and freeze-dried to obtain a composite plant extract.

3. The method for preparing the composite plant extract for inhibiting glutamate dehydrogenase activity according to claim 2, characterized in that In step (1), the cellulase activity is 100,000 U / g; the pectinase activity is 50,000 U / g; and the amount of the two enzymes added is 2% to 3% based on the mass ratio of the enzyme to the substrate raw material.

4. The method for preparing the composite plant extract for inhibiting glutamate dehydrogenase activity according to claim 2, characterized in that The licorice rhizome in step (1) is a dried licorice rhizome product that has been naturally dried and has a storage period of less than three months, or a fresh licorice rhizome.

5. The method for preparing the composite plant extract for inhibiting glutamate dehydrogenase activity according to claim 2, characterized in that The honeysuckle buds in step (1) are dried honeysuckle buds that have been naturally dried and have a storage period of less than three months, or fresh honeysuckle buds.

6. The method for preparing the composite plant extract for inhibiting glutamate dehydrogenase activity according to claim 2, characterized in that In step (2), ultrasound-assisted enhanced enzymatic hydrolysis of cellulose and pectin to release cell contents, the ultrasound parameters are frequency 20-60 kHz, power 80-120 W, temperature 30-50° C., and time 30-50 min.

7. The method for preparing the composite plant extract for inhibiting glutamate dehydrogenase activity according to claim 2, characterized in that In the ethanol solution in step (2), the volume proportion of anhydrous ethanol is 30% to 60%.

8. Use of the composite plant extract for inhibiting glutamate dehydrogenase activity according to claim 1 in cat food.