What is glycyrrhetinic acid?
Licorice is a common medicinal and edible food. Licorice extract is widely used in candies and canned foods as a natural sweetener. Licorice's sweet taste comes from glycyrrhizic acid and glycyrrhetinic acid. The former is a type of triterpenoid saponin, accounting for about 4% to 5% of the dry weight of licorice root, and its sweetness is 50 times that of sucrose. Glycyrrhetinic acid is formed by hydrolyzing the sugar acid chain of glycyrrhizic acid and is 250 times sweeter than sucrose.Glycyrrhetinic acid also has antiviral effects and can inhibit the infection of cancer-causing viruses such as hepatitis virus, Epstein-Barr virus and HIV.
Pharmacological effects of glycyrrhetinic acid.
Anti-inflammatory and anti-immune effects
Glycyrrhetinic acid has anti-inflammatory effects like phenylbutazone or hydrocortisone. Glycyrrhetinic acid has inhibitory effects on cotton ball granuloma, formaldehyde foot swelling, and subcutaneous granulomatous inflammation in rats. Its anti-inflammatory potency is about 1/10 of cortisone or hydrocortisone. Glycyrrhetinic acid can inhibit experimental arthritis in rats caused by carrageenan, and can inhibit allergic reactions in guinea pigs caused by horse serum or egg albumen to varying degrees. Its anti-inflammatory and anti-allergic responses may be related to inhibition of capillary permeability, antihistamines, or reduced cell responsiveness to stimuli.
Glycyrrhetinic acid has an inhibitory effect on a variety of acute inflammations. Its anti-inflammatory effect does not depend on the pituitary-adrenocortical system, but is related to inhibiting the production of PgE2 in inflammatory tissues and antagonizing the inflammatory mediators histamine and serotonin. Sodium glycyrrhetinate can inhibit the production of malondialdehyde, a degradation product of Pg endoperoxide, in the inflamed feet of mice with protein-induced inflammation. This effect can be antagonized by exogenous arachidonic acid. Sodium glycyrrhetinate also enhances the body's non-specific cellular immune function. 18-β glycyrrhetinic acid has immunomodulatory effects on acute serum sickness in rabbits. Fifty rabbits were randomly divided into experimental groups and control groups, and bovine serum albumin (BSA) was used as the antigen to create a transient acute serum sickness model in rabbits. 18-β glycyrrhetinic acid was dissolved in olive oil (150 mg/ml), and the animals in the experimental group were injected intramuscularly with 200 mg/kg of 18-β glycyrrhetinic acid on days 3, 5, 7, and 9 after BSA injection. The control group received intramuscular injection of olive oil. Results Anti-BSA-1gg antibodies in the serum of animals in the control group and experimental group were detected on the 6th day after BSA immunization, reaching the peak on the 12th day, and the experimental group was significantly higher than the control group. The specific BSA-anti-BSA complexes in the circulation of animals in both groups were increased compared with those before immunization, and there was a significant difference, but there was no statistical difference between the two groups. The complement value in the blood was significantly higher in the experimental group than in the control group. 18-βglycyrrhetinic acid had no effect on the formation of CIC.
Effect on digestive system
Glycyrrhetinic acid can reduce blood bilirubin and increase urinary bilirubin excretion in rabbits and rats with common bile duct ligation. This effect is stronger than glucuronolactone or methionine. It has good anti-ulcer effect on pylorus ligated rats. Its therapeutic index is high.
Antitussive and expectorant effect
The choline salt of glycyrrhetinic acid has a significant antitussive effect on coughs caused by chemical stimulation (inhalation of ammonia) and electrical stimulation of the superior laryngeal nerve in cats. Therefore, it is believed that its antitussive effect is related to the central nervous system.
Antidiuretic effect
Glycyrrhetinic acid and its salts have significant antidiuretic effects. It can enhance the reabsorption of sodium and chloride by the renal tubules and exhibit antidiuretic effect; its mode of action is different from that of deoxycorticosterone, which may be due to its direct effect on the renal tubules.
Effects on inner ear auditory function
Studies using auditory electrophysiology methods have shown that after intramuscular injection of 100 mg/kg glycyrrhetinic acid into guinea pigs, the action potential response threshold of the guinea pig's auditory nerve decreases, indicating that glycyrrhetinic acid has the effect of improving the auditory function of the inner ear of guinea pigs.
Inhibition of acetylcholinesterase
When glycyrrhetinic acid is used at a concentration of 4×10\-2mg/ml. It has a significant inhibitory effect on acetylcholinesterase, which is enhanced with the increase of drug concentration within this dose range. The drug concentration at 50% inhibition rate is 21.8±1.1mg/L. The inhibitory effect of glycyrrhetinic acid on acetylcholinesterase is a mixed competitive-non-competitive type, and has similar inhibitory effects to neostigmine.
Scavenging effect on oxygen free radicals
β-glycyrrhetinic acid 0.3mmol/L has a significant scavenging effect on oxygen free radicals released by human polymorphonuclear leukocytes (PMN), but has no effect on the oxygen consumption of PMN. 18-β Glycyrrhetinic acid has an obvious scavenging effect on O-2 and -OH produced in aqueous solution systems. 30mol/L has a significant inhibitory effect on the chemiluminescence produced by PMN. The results confirmed that 18-β glycyrrhetinic acid can directly capture oxygen free radicals.
Preparation method of glycyrrhetinic acid
It is obtained by hydrolyzing glycyrrhizic acid extracted from the rhizome of the leguminous plant Glycyrrhizauralen-sisfisch and making ammonium salt. The roots and rhizomes of licorice mainly contain glycyrrhizin, which is the potassium and calcium salt of glycyrrhizic acid (Glycyrrhiz-icacid) and is the sweet component of licorice. It is about 50 times sweeter than sucrose. Add water to the crushed licorice, heat it, continuously extract it under countercurrent, separate and remove impurities from the grass residue, and obtain an aqueous solution. Evaporate, concentrate, and add sulfuric acid pH 2-3 with stirring. Leave to settle and remove the supernatant. The precipitate is washed with water to remove the sulfate radicals, heated and concentrated, and boiled to make glycyrrhizic acid paste. Crush the glycyrrhizic acid paste and extract it 2-3 times with 95% ethanol for 3 hours each time to obtain an ethanol solution. After filtration, ammonia was stirred until the pH was 7-7.5. Filter again to obtain the crude triammonium glycyrrhizinate salt, which is refined with glacial acetic acid to obtain beige monoammonium glycyrrhizinate salt. Add glycyrrhizic acid monoammonium salt to 5% sulfuric acid aqueous solution, stir and heat to nearly boiling, reflux and hydrolyze for 15 hours, filter and wash with water to obtain crude glycyrrhetinic acid. After recrystallization and decolorization, base oxalic acid with a content of more than 92% is obtained. Based on licorice, the total yield is about 0.5%.
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