Ge Gen

Ge Gen - Pueraria lobata
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Pin Yin
Ge Gen

Latin
Radix Puerariae lobatae.

Introduction

Radix Puerariae is offcially listed in the Chinese Pharmacopoeia as the dried root of Pueraria lobata (Willd.) Ohwi or Pueraria thomsonii Benth. (Fam. Leguminosae). The root of Pueraria labota is often cut fresh into thick slices or pieces and dried.

Western medical

This herb has muscle relaxant, antipyretic, antidysenteric and diuretic actions. It is indicated in the treatment of hypertension and traditionally used in the treatment of febrile diseases, headache, stiff neck, fidgets, thirst, acute diarrhoea and dysentery, and unerupted measles. Pueria promotes the production of body onload="highlight();" fluids.

Eastern medical

Pattern: Release Exterior Conditions.
Properties: Sweet, acrid, cool.
Channels Entered: Spleen, Stomach.

Chemical constituents

The major active principles in the root of P. Lobata are isoflavone derivatives, puerarin, daidzein, daidzin, and daidzein-7,4'-diglucoside. Daizein and daidzin are well-known compounds isolated from soybean (Phaseolus vulgaris) and some other plants. Daidzin and daidzein-7,4'-diglucoside are O-glucosides of daidzein and puerarin is a C-glucoside of daidzein. A series of studies on the determination of isoflavones in Pueraria roots with HPLC, TLC, or polarography were reported. Formononetin, 3'-hydroxypuerarin, 6"-0-Dxylosylpuerarin, 3'methoxypuerarin, puerarin 4'-O-D-glucoside, and 8-C-apiosyl-(1-6)-glucosides of daidzein and genistein were further isoflavones and isoflavone glycosides isolated from the root of P. Lobata . A coumestan derivative named puerarol was also isolated from the root of P. Lobata.
The isolation of two new aromatic glycosides named pueroside A and pueroside B from the root of P. Lobata was also reported. Besides the glycosides, a number of sapogenins with an oleanane skeleton were isolated from the root of P. Lobata . In addition, 6,7-dimethoxycoumarin, 5-methylhydantoin, ,B-sitosterol, and its glucoside were isolated from P. Lobata. Two cholinergic substances, choline chloride and acetylcholine chloride, were detected.
Studies with cell cultures revealed that the biosynthetic pathway of isoflavones from malonyl CoA and p-coumaroyl CoA in P. Lobata is catalyzed by chalcone synthase, chalcone-flavanone isomerase, and isoflavone synthase. Kinetic experiments indicated that liquiritigenin, the precursor of daidzein, is a much more favorable substrate for the isoflavone synthase in P. Lobata than naringenin, the corresponding precursor of genistein.
A new triterpene saponin was isolated from the flowers of P. Lobata , and a related saponin was isolated from both flowers and leaves of this plant. Furthermore, a glucosyltryptophan derivative was also isolated from the flower of P. Lobata.

Pharmacological actions

Miscellaneous Actions

Studies on the pharmacological activities of different fractions obtained by extracting the root of P. Lobata with different solvents revealed a coexistence of substances having a mutually reverse pharmacological effect in the root. Some fractions showed a decrease in body onload="highlight();" temperature in mice, while others showed an increase; some fractions exerted a relaxant effect on the isolated quinea pig ileum like that of papaverine, whereas some fractions possessed a contractive effect.

Hypotensive Effect

The total isoflavones from the ethanolic extract of roots of P. Lobata had a hypotensive effect on anesthetized dogs and unanesthetized hypertensive dogs. In dogs, the intraarterial or intravenous injection of total isoflavones of P. Lobata roots or puerarin dilated coronary arteries to a greater extent than other arteries examined. Heart rate, blood pressure, and total peripheral resistance decreased while cardiac output remained unchanged.

Hypertension Reducing Effect

After intravenous injection of total isoflavones, oxygen, lactate, and pyruvate content of the blood of the coronary sinus increased and the myocardial consumption of these substances decreased. These effects may be beneficial in the treatment of human coronary artery disease. The effects of the isoflavones may be due to a direct relaxation of coronary vessels. Daidzein, daidzin, and puerarin have been reported to relieve headaches and other symptoms associated with hypertension.

In dogs, intravenous administration of puerarin decreased the size of acute myocardial infarction. Puerarin was administered 5 min after acute coronary ligation. Beneficial effects of puerarin were demonstrated by epicardial electrocardiogram, plasma creatine kinase, and radiocardiogram. A clinical study in patients with hypertension or angina pectoris showed that puerarin applied intravenously at a dose of 100 200 mg decreased blood catecholamine levels, blood pressure, and heart rate.

Cardiac Arrhythmia Effect

In anesthetized rats, arrhythmia induced by aconitine and BaCI2 was antagonized by puerarin administered intravenously or orally or by daidzein administered orally. Furthermore, ventricular fibrillation induced by CaCI2 in rats and by chloroform in mice was prevented by daidzein or the alcoholic extract of P. Iobata given orally. Puerarin also antagonized the cardiac arrhythmia induced by chloroform in rabbits. The intravenous LD50 value of puerarin in mice was 738 mg/kg. Blocking of isoprenaline-induced tachycardia in cats and a decrease in normal heart rate and blood pressure in anesthetized cats by intravenous administration of puerarin was mediated by its B-adrenergic receptor-blocking activity. Puerarin showed a hypoglycemic effect in alloxan-induced diabetic mice, and also decreased serum cholesterol levels. Daidzein exerted a very high antihemolytic activity on peroxidative hemolysis in sheep erythrocytes, whereas only little activity was found in rat erythrocytes. No antihemolytic effect at all was noted in rabbit erythrocytes.

Herbal Action

Absorption, distribution, and elimination of 14C-labeled daidzein were studied in rats. Radioactivity appeared in the blood 30 min after oral administration of daidzein and reached its peak within 6-8 hours, therefore decreasing steadily. About 65% of the radioactivity was absorbed from the gastrointestinal tract within 24 h.

After intravenous injection of daidzein, the distribution phase and the elimination phase in the blood had half-lives of 13 and 42 min. respectively. Radioactivity was highest in the kidney and liver, moderate in plasma, lung, and heart, and low in skeletal muscle, spleen, testis, and brain. After intravenous injection of daidzein, about 70% of the radioactivity was excreted in urine within 24 h, while only 17 % was recovered from the feces. After oral administration, the amounts excreted in the urine and feces were about equal. Radioactivity recovered from the gastrointestinal tract, urine, and bile was mainly attributable to metabolites of daidzein, indicating that daidzein was metabolized rapidly.

The metabolism of puerarin was also studied in rats, using polyamide thinlayer chromatography and UV spectrophotometry. The blood level of puerarin following intravenous administration in rats decreased in two phases with halflives of 3 and 18 min. respectively. Puerarin was widely distributed in the body onload="highlight();" and eliminated rapidly. The highest level of puerarin was found in the kidney, moderate levels in plasma, liver, and spleen, and lowest in the brain. Absorption of puerarin from the gastrointestinal tract was rapid but incomplete. About 40% of the dose could still be recovered from the gastrointestinal content and feces 24 h after administration. About 1.8% and 36% was excreted in urine and feces within 24 h, respectively, after oral administration. After intravenous administration, about 37% was found in urine and 7% in feces. Puerarin was stable in the gastrointestinal tract, but appears to be metabolized in the blood, liver, lung, and kidney.

References

Except those noted, all references come from Weng Weiliang, et al., Clinical Chinese materia medica, Henan Science & Technology Press, 1998