Herbal Research

Gan Cao

RADIX GLYCYRRHIZAE (LICORICE)

Gan Cao is the dried root of Glycyrrhiza uralensis Fisch., Glycyrrhiza inflata Bat, or Glycyrrhiza glabra L. (Leguminosac). The root is collected in the spring and autumn, removed from fibrous roots and dried in the sun. The herb is mainly produced in the north, northwest and northeast of China.

CHEMISTRY

The herb contains triterpenes (Table 21-2) and flavones (Table 2 1-3). Between 5 and 11% of the herb by weight consists of glycyrrhizin, which is the calcium or potassium salt of glycyrrhizic acid, and other triterpenoid compounds1-3.
FM 100, an antiulcerative extract of liquorice is the flavonoid fraction free of glycyrrhetic acid. Ferulic acid, sinapic acid and an immunosuppressant fraction called LX (a heat-stable glycoprotein) were also isolated from the herb4.

PHARMACOLOGY

Corticoid Effects
Glucocorticoid-like effect

Intraperitoneal administration of a low dose (600 pg/kg) of glycyrrhizin to rats caused atrophy of the thymus gland and increased the weight of the adrenal gland, suggesting the presence of corticotropin-like action. In patients with mild Addison's disease requiring daily intramuscular injection of 12.5 mg of cortisone, concurrent daily intramuscular dose of glycyrrhizin starting from the 3rd day after the determination of urinary corticosterone, increased urinary free 17-hydroxycorticosterone and decreased the conjugated 17-hydroxycorticosterone, but it did not change the total amount excreted. Except for the tendency of the total 17-hydroxycorticosterone to decrease slightly, similar results were obtained in healthy individuals given intramuscular doses of glycyrrhizin at 80 mg in the morning and evening. These facts suggest that glycyrrhizin can prolong the action of cortisone 4.

Table 1 Triterpenes from Glycyrrlziza root.

Compounds

Glycyrrhiza species

Liquiritic acid Glabrolide Isoglabrolide Deoxoglabrolide Glabric acid Deoxoglycyrrhetic acid 18a-Glycyrrhetic acid lSa-Hydroxy glycyrrhetic acid Glycyrrhetol 21a-Hydroxy isoglabrolide 23-Hydroxyglycyrrhetic acid 24-Hydroxy- 11-deoxy glycyrrhetic acid 24-Hydroxy liquiritic acid Liquiridiolic acid 28-Hydroxyglycyrrhetic acid Methyl 3b,24-dihydroxyolean- 11,13(18)-dien-30-oate 24-Hydroxy glabrolide Uralsaponins A and B Uralenolide Licorice-saponins A3, B2, C2, D3, E2, F3, C2, H2, J2 and K2 Araboglycyrthizin Apioglycyrrhizin 24-hydroxy glycyrrhetic acid Deoxoglycyrrhetic acids I and II 3b-Hydroxyolean- 11,13(1 8)-dien-30-oic acid

G. glabra G. glabra, G. uralensis G. glabra G. glabra G. glabra G. glabra G. glabra C. glabra, C. uralensis C. glabra G. glabra U glabra, C. uralensis G. glabra C. glabra G. glabra U glabra C. uralensis C. uralensis G. uralensis U uralensis C. uralensis C. inflata C. inflata U uralensis G. uralensis G. uralensis

Table 2 Flavones and phenols from GIvcyrrhiza root.

Compounds

Clycyrrhiza species

Liquiritin Liquiritigenin Isoliquiritin Isoliquiritigenin Neoliquiritin Neoisoliquiritin Rhamnoliquiritin Rhamnoisoliquiritin Licurazide Liquiritoside Liquiritoginine Licoricidin Licochalcones A and B Glycyrrhisoflavone Glycoricone Genistein Glycycoumarin Licopyranocoumarin Licocoumarone Berniarin Umbelliferone Licofuranone Pterocarpan Licuroside Saponaretin Vitexin Pinocembrin Prunetin Licoricone Glabranin Formononetin Glabralide Glabranine Glabrone Glabrene Glabridin Glabrol 7-Acetoxy-2-methylisoflavone 7-Methoxy-2-methylisoflavone 7-Hydroxy-2-methylisoflavone Licochalcone A Licochalcone B 4-Hydroxychalcone Liqcoumarin Glycyrol Isoglycyrol Isolicoflavonol Liconeolignan 4'-O-b-D-Apio-n-furanosyl-( 1t2)-b-D-glucopyranosyl liquintigenin Ononin Neolicuroside Licoflavanone Glycyrrhisoflavone Glycyrrhisoflavanone Licocoumarone (E)- 1-[2,4-Dihydroxy-3-(3-methyl-2-butenyl)phenyl]-3-[4-hydroxy-3- (3-methyl-2-butenyl)phenyl]-2-propen- 1-one (E)- 1 -[2,4-Dihydroxy-3-(3-methyl-2-butenyl)phenyl]-3-[2,2-dimethyl-8- hydroxy-2H-nenzopyran-6-yl)-2-propen-1-one

G. uralensis, G. glabra G. uralensis, G. glabra C. glabra C. uralensis, U glabra C. uralensis, G. glabra G. uralensis, C. glabra U uralensis C. uralensis G. uralensis U uralensis G. uralensis C. uralensis C. uralensis G. uralensis G. uralensis G. uralensis C. uralensis G. uralensis G. uralensis C. uralensis G.urolensis G.uralensis G.uralensis 0.uralensis, 0. glabra G.glabra G.glabra 0.glabra 0.glabra G.uralensis Uglabra G.glabra 0.glabra G.glabra 0.glabra G.glabra G.glabra G.glabra 0.glabra G.glabra Uglabra G.glabra, G. inflow G.glabra G.glabra G.glabra G.uralensis G.uralensis G.uralensis Uuralensis Uuralensis 0.uralensis 0.glabra Uglabra Glycyrrbiza sp. Glycyrrbiza sp. Glycyrrhiza sp. G.inflara G.inflata

Glycyrrhetic acid inhibited 5b-reduction of cortisol, aldosterone and testosterone by rat liver preparations in vitro. Since 5b-reductase is involved in cortisol and aldosterone metabolism, glycyrrhetic acid may delay clearance of corticosteroids and prolong their biological effects in the body5.

Mineralocorticoid-like Effect

The extract of the herb, glycyrrhizin or glycyrrhetic acid exhibited deoxycorticosterone-like action, reducing urinary volume and sodium excretion and increasing potassium excretion. In bilaterally adrenalectomized rats, however, the herb could not maintain the electrolyte balance, nor could it prolong their lives. A so-called pseudo-aldosteronism with manifestation of edema and hypertension could develop in association with its clinical use4.
Glycyrrhetic acid showed mineralocorticoid-like effects. The direct mineralocorticoid effect of the herb is probably due to the affinity of glycyrrhetic acid for kidney aldosterone receptors. The relative low affinity of glycyrrhetic acid for mineralocorticoid receptors is in good agreement with the high doses of the herb required for the development of hypertension6'7.

Antiinflammatory Effect

The antiinflammatory effect of the herb resembles that of butazone or hydrocortisone. The active constituents are glycyrrhizin and glycyrrhetic acid. Cotton pledget-induced granulation, formaldehyde-induced paw swelling and subcutaneous granulomatous inflammation in rats were all inhibited by glycyrrhetic acid. Its antiinflammatory activity is about 1/10 that of cortisone or hydrocortisone. In artificial arthritis induced by carrageenin in rats the antiinflammatory activities of glycyrrhizin and glycyrrhetic acid were 14% and 3% that of hydrocortisone4.

Immunosuppressive and Antiallergic Effects

Intravenous administration of 2 mg/rat of LX inhibited the immune reaction of macrophages in rats. LX was reported to be a glycoprotein which, through its action on the phagocytosisrelated enzyme of the macrophages, reduced antigen information, thereby producing an immunosuppressive effect4. In addition, it prolonged the survival time of transplanted tissues and inhibited the production of antibodies. It has been suggested that the mechanism of action involves blocking the transfer of the immune signal from phagocytes5.
Glycyrrhizin showed an antiallergic effect9. It inhibited the passive cutaneous anaphylaxis response in rats and concentration-dependently suppressed the contraction of rabbit ileum and guinea pig trachea induced by histamine, acetyleholine or slow-reaction substances of anaphylaxis10 Ammonium glycyrrhizate inhibited PGE2 and PGF2~ formation by mouse lung and kidney both in vivo and in vitro11.

Antiulcerative Effect

Subcutaneous or intraduodenal injection of 250 mg/kg of the extract of the herb produced a marked inhibition on ulcers in rats due to ligation of the pylorus. In cincophen-induced peptic ulcer in dogs, oral dose of 6-8 g of the powdered herb resulted in eschar formation in 60% of the animals. In cases of acetic acid-induced chronic ulcer in rats, oral glycyrrhizin afforded a cure rate of 47.7%.
FM 100, the total flavones free of glycyrrhizin, given intraperitoneally at 100 mg/kg to rats with ligated pylorus could completely inhibit ulcer formation. It also significantly inhibited gastric secretion induced by oral dose of acetylcholine or intramuscular injection of histamine. Experiments on rat gastric fistulae showed that while intraperitoneal administration of 200 mg/kg of FM 100 decreased gastric secretion, it did not diminish histidine decarboxylase activity and blood gastrin level. Direct injection of FM 100 into the gastric mucosa promoted the healing of ulcers caused by subserosal injection of acetic acid. It is therefore believed that the inhibitory effect of the agent on gastric acid secretion is due to a direct action on the gastric mucosal cells but not due to the suppression of gastrin or deactivation of histidine decarboxylase.
The herb also has spasmolytic activity. Intragastric administration of the 10% extract of the herb to rabbits at the dose of 4 ml/kg gradually weakened gastric motility and almost completely arrested it 30 mm after medication. FM 100 at 2 x 10-4 M exerted spasmolytic action in the isolated intestinal tract of guinea pigs. Isoliquiritigenin at 10-4 M also inhibited the isolated intestinal tract. Both FM 100 and isoliquiritigenin could also relieve intestinal spasm elicited by acetylcholine, barium chloride and histamine. This antispasmodic action also attributes to the effectiveness of the herb in ulcer treatment4.

Antitussive and Expectorant Effects

Subcutaneous administration of 1 mg/kg of glycyrrhetic cholate inhibited 80% of cough incidence elicited by ammonia aspiration in guinea pigs. The effect was not different from that of subcutaneous dose of 1 mg/kg of codeine. A marked antitussive action was also observed in cough of cats due to electrostimulation of the superior laryngeal nerve. The same dose of hydrocortisone also exhibited an antitussive effect but with a different dose-response curve, and it was ineffective in cough of rats due to stimulation of the superior laryngeal nerve. It is therefore concluded that the antitussive mechanism of the herb has no relation to the relief of inflammation but is due to its action in the CNS4. Glycyrrhizin has saponin-type actions of assisting expectoration'2.

Antihepatotoxic Effects

Oral administration of the extract of the herb showed heptaprotective effects against carbon tetrachloride (CCl4-induced cytotoxicity in rats. It markedly abated hepatic degeneration and necrosis, promoted the recovery of hepatocelular glycogen and ribonucleic acid and also lowered serum glutamic pyruvic transaminase4. Glycyrrhizin and glycyrrhetic acid are able to prevent the development of experimental cirrhosis. In rats intoxicated with CC14, the elevation of serum glutamic oxalacetic transaminase and the accumulation of triglyceride in the liver were decreased. Histopathological studies revealed that liver lesions in rats induced by tetrachloride were less severe in lycyrrhizin- and glycyrrhetic acid-treated animals than in the controls'3. Glycyrrhizin significantly increased the leukocyte count and the clearance rate of charcoal particles'4. Both glycyrrhizin and glycyrrhetic acid were active in antiheptotoxicity. Comparison of antihepatotoxic activities between glycyrrhizin and glycyrrhetic acid both in vitro and in vivo found that 1 8b- or 18a-glycyrrhetic acid was a more potent antihepatotoxic agent than corresponding glycyrrhizin, and the potency of action was perhaps related to the absorbability into hepatocytes. Glycyrrhizin and glycyrrhetic acid could further inhibit the proliferation of liver fibre in rats and thus reduce the incidence of cirrhosis, but they did not promote collagen degradation or re-absorption15.

Antiviral Activity

Glycyrrhizin at 8 mM completely inhibited the growth and cytopathic effects of vaccinia, herpes simplex type 1, Newcastle disease and vesicular stomatitis viruses in cultures of human aneuploid HEP-2 cells. The mechanism of action of glycyrrhizin is probably based on the interaction with sensitive virus proteins at the virionic stage and during a later phase when these proteins are synthesized in host cells16. Glycyrrhizin was also antiviral against varicella zoster virus in human embryonic fibroblast cells in vitro and the antiviral activity was ascribed to inhibition of penetration, uncoating or release of virus particle17. Furthermore, glycyrrhizin completely inhibited HIV-induced plaque formation in MT-4 cells at 0.5 mg/ ml. The ID50 was 0.125 mg/ml. It also completely inhibited human HIV-induced cytoplasmic effect and virus-specific antigen expression in MT-4 cells18. Glycyrrhizin sulfate was more active than glycyrrhizin against HIV19. The activation of macrophage in vivo system and stimulation of nitric oxide production may participate in antiviral activity of glycyrrhizin20.

Other Effects

Antitumor activities have been reported for glycyrrhizin, glycyrrhetic acid and liquiritin. Glycyrrhizin and glycyrrhetic acid were antipyretic. FM 100 showed significant analgesic action. Glycyrrhizin and glycyrrhetic acid had antidiuretic action4.

FUNCTIONS AND APPLICATIONS

Traditional Description

Gan Cao has a sweat taste and a neutral property, acting on the heart, lung, spleen and stomach channels. It has the functions of:

(i) invigorating the function of the spleen and replenishing Qi, used in weakness of the spleen and stomach marked by lassitude and weakness, palpitation, and shortness of breath;
(ii) eliminating phlegm and arresting cough, used in cough with much phlegm;
(iii) relieving spasmodic pain, used in spasmodic pain in the epigastrium, abdomen and limbs.

In addition, the herb has the function of reducing the toxic or drastic action of other herbs, and also harmonizes the properties of other herbs.

Applications4

Addison's disease

Four cases had been treated with the extract of the herb at the dose of 15 ml daily. The objective improvements included increase of serum sodium, elevation of blood pressure and decrease of skin pigmentation. To advanced and severe cases the herb was not very effective.

Gastric and duodenal ulcer

The herb extract was used in 100 cases of early peptic ulcer (of which 86 were unresponsive to conventional treatment) at the dose of 15 ml four times daily for 6 weeks. It produced good effects in 90% of the cases. Among the 58 cases by X-ray examination, ulcer craters disappeared in 22 cases and improved in 28 cases.

Infectious hepatitis

The 100% decoction of the herb 15-20 ml thrice daily for 10-20 days had been used to treat 13 cases of infectious hepatitis. The icterus index was nonnalized in a mean of 12.9 days; the urinary bile pigments became negative in 9.9 days and marked reduction of hepatomegaly was observed in 9.2 days. Pain over the liver area disappeared in 7.8 days.

DOSAGE

3-9g.

SIDE EFFECTS AND TOXICITY

Continuous and over-dosaged application of the herb can result in sodium retention and water accumulation, leading to edema and hypertension in 20% of the patients. This herb also has a tendency to lower the basal metabolic rate and decrease thyroid function.
The MLD of glycyrrhizin in mice by subcutaneous admlnistration was 1 g/kg. The LD50 of glycyrrhetic acid mice by intraperitoneal administration was 308 mg/kg4. The LD50 values of a crude extract of the herb containing about 50% glycyrrhizin were 1.4-1.7 g/kg by intraperitoneal and 14-18 g/kg by oral administration in rats and mice. Rats given an oral daily dose of 2.5 g/kg for 3 months exhibited decreased body weight gain, blood cell count and thymus weight. Atrophic cortex and sporadic lymphofollicle formation were noted in the medulla of the thymus. All changes disappeared after discontinuation of medication1.

REFERENCES

1. Tang, W., Eisenbrand, G. (1992) Chinese Drugs of Plant Origin - Chemistry, pharmacology, and use in traditional and modern medicine, pp. 567-588. Berlin, Heidelberg: Springer-Verlag.
2. Zhou, RH. (1993) Resource Science of Chinese Medicinal Materials, pp. 293-303. Beijing: China Medical & Pharmaceutical Sciences Press.
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4. Wang, Y.S. (1983) Pharmacology and Applications of Chinese Materia Medica, pp. 264-277. Beijing: People's Health Publisher.
5. Tamura, Y., Nishikawa, T., Yamada, K., Yamamoto, M., Kumagai, A. (1979) Effects of glycyrrhetinic acid and its derivatives on A4-Sa- and 513-reductase in rat liver. Arzneimirtelforschung, 29, 647-649.
6. Corval, P., Ulmann, A., Michaud, A., Menard, J. (1975) Mineralcorticoid-like effect of glycyrrhetinic acid. Research of Steroids, 6, 65-75.
7. Tamaya, T., Sato, S., Okada, H.H. (1986) Possible mechanism of steroid action of the plant herb extracts glycyrrhizin, glycyrhetinic acid and paenoniflorin: inhibition by plant herb axtract of steroid protein binding in the rabbit. American Journal of Obstetrics and Gynecology, 155, 1134-1139.
8. Huang, K.C. (1993) The Pharmacology of Chinese Herbs, pp. 275-278. Boca Raton: CRC Press.
9. Inoue, H., Mori,T., Shibata, S., Saito, H. (1987) Pharmacological activities of glycyrrhetinic acid derivatives; analgesic and anti-type IV allergic effects. Chemical and Pharmaceutical Bulletin, 35, 3888-3893.
10. Zhang, H.Q., Liu, F., Sun, B., Li, G.H. (1986) Antiallergic action of glycyrrhizin. Acta Pharmacologica Sinica, 7, 175-177.
11. Ren, J., Cheng, J.X., Wang, Z.G. (1988) The effect of ammonium glycyrrhizininate on the biosynthesis of prostaglandins E2 and F2~ Kexue Tongbao, 33, 1561-1564.
12. Weiss, R.F. (1988) Herbal Medicine, p. 215. Gothenburg: AB Arcanum.
13. Zhao, M.Q., Han, D.W., Ma, X.H., Zhao, Y.C., Yin, L., Li, C.M. (1983) Preventive and therapeutic effects of glycyrrhizin, glycyrrhetic acid and sikosides on experimental cirrhosis in rats. Acta Pharmaceutica Sin ica, 18, 325-331.
14. Zhang, H.Q., Liu, F., Zeng, H.Q., Li, G.H. (1984) Some pharmacologic effects of glycyrrhizin in mice. Acta Pharmaceutica Sinica, 19, 926-927.
15. Nose, M., Ito, M., kamimura, K., Shimizo, M., Ogihara, Y. (1994) A comparison of the antihepatotoxic activity between glycyrrhizin and glycyrrhetinic acid. Planta Medico, 60, 136-139.
16. Pompei, R., Flore, 0., Marecialis, M.A., Pani, A., Loddo, B. (1979) Glycyrrhizic acid inhibits virus growth and inactivates virus particles. Nature, 281, 689-690.
17. Baba, M., Shigeta, S. (1987) Antiviral activity of glycyrrhizin against varicella-zoster virus in vitro. Antiviral Research, 7, 99-107.
18. Ito, M., Nakashima, H., Baba, M., Pauwels, R., DeClercq, E., Shigeta, S., et al. (1987) Inhibitory effect of glycyrrhizin on the in vitro infectivity and cytopathic activity of the human immunodeficiency virus [HIV (HTLV-IILfLAV)]. Antiviral Research, 7, 127-137.
19. Nakashima, H., Matsui, T., Yoshda, 0., Isowa, Y., Kido, Y., Motoki, Y., et al. (1987) A new anti-human imunodeficiency virus substance, glycyrrhizin sulfate: endowmwns of glycyrrhizin with reverse transcriptaseinhibitory activity by chemical modification. Japanese Journal of Cancer Research, 78, 767-771.
20. Kondo, Y., Takano, F. (1994) Nitric oxide production in mouse peritoneal macrophages enhanced with glycyrrhizin. Biological and Pharmaceutical Bulletin, 17, 759-761.
21. Huang, K.C. (1993) The Pharmacology of Chinese Herbs, pp. 275-278. Boca Raton: CRC Press.