Histidine decarboxylase inhibition by O-methyl-3(+)catechin and gastric acid secretion in the cat

Gastric H+, K(+)-ATPase inhibition by catechins

Five catechins, (+)-catechin, (-)-epicatechin, (-)-epicatechin gallate, (-)-epigallocatechin and (-)-epigallocatechin gallate, inhibited gastric H+, K(+)-ATPase activity with IC50 values ranging from 1.7 x 10(-4) to 6.9 x 10(-8) M, with (-)-epigallocatechin gallate as the most potent inhibitor. The intensity of inhibitor activity paralleled the number of phenolic hydroxy groups in the molecule. The inhibition of the enzyme by (-)-epicatechin was competitive with respect to ATP and noncompetitive with respect to K+. These findings suggest that the anti-secretory and anti-ulcerogenic effects of catechins previously reported, are due to their inhibitory activity on gastric H+, K(+)-ATPase.

Histidine decarboxylase inhibition: a novel approach towards the development of an effective and safe gastric anti-ulcer drug

The involvement of histamine in mediating gastric function under normal and pathological conditions has been largely established. The relationship between gastric acid production and peptic ulcer diathesis is also well known. Recently, endogenous histamine formation and its release from mast cells has been implicated in the pathogenesis of human and experimental gastric ulcers produced by restraint and pyloric ligation. It has also been implicated in the gastric mucosal damage produced by drugs like aspirin, phenylbutazone and reserpine. These observations suggest that histidine decarboxylase inhibitors may be useful in the prevention of such lesions. Our studies on the evaluation of some histidine decarboxylase inhibitors show that these compounds have a promising potential for developing an effective and safe anti-ulcer drug. This mini-review incorporates the results of our studies which have been adequately supported by other studies as well.

The gastric antisecretory activity of 3-methoxy-5,7,3'4'-tetrahydroxyflavan (ME)--a specific histidine decarboxylase inhibitor in rats

3-Methoxy-5,7,3'4'-tetrahydroxyflavan (ME), a specific histidine decarboxylase inhibitor, has been shown to significantly reduce the gastric acid secretion and gastric tissue histamine levels in 6 h pylorus ligated rats. It has been found to be as effective as cimetidine in reducing the gastric acid secretion. However, cimetidine does not affect the gastric tissues histamine levels in the normal or pylorus ligated rats. These observations clearly establish that the two drugs reduce the gastric acid secretion by different mechanisms and suggest that their combination may show a potentiated gastric anti-ulcer activity.