Effects of Citrus Limonoids on Glutathione S-Transferase Activity in Mice

Abstract

Citrus limonoids were studied as inducers of the detoxifying enzyme system glutathione S-transferase in mice. Among eight limonoids studied, nomilin was shown to be the most potent inducer in the liver and in the small intestinal mucosa. In the forestomach, the inducing activity was low but the enzyme activity was significantly elevated when compared with that of the control. In the lung and colon no appreciable enzyme activity was induced by nomilin. Three other limonoids, obacunone, isoobacunoic acid, and ichangin, were shown to be enzyme inducers in the liver and some other tissues studied. Limonin, on the other hand, showed only marginal activity as an enzyme inducer in the small intestinal mucosa and was inactive in all other tissues studied. Limonol showed small inducing activity in the forestomach while deoxylimonin was not active in any of the tissues examined. Since anticarcinogens such as nomilin and kahweol are potent inducers of detoxifying enzymes, citrus limonoids such as obacunone, isoobacunoic acid, and others may be effective inhibitors of chemically induced carcinogenesis. © 1989, American Chemical Society. All rights reserved.