ANTIMUTAGENIC AND ANTICARCINOGENIC POTENTIALS OF SOME THAI VEGETABLES

Fifteen kinds of commonly consumed Thai vegetables were sequentially e xtracted with hexane, chloroform and methanol, and then tested for ant imutagenic activities against direct-acting (AF-2 and NaN3) and indire ct-acting (AFB(1) and B(a)P) mutagens using Ames' Salmonella mutagenic ity test with Salmonella typhimurium TA100 as tester strain. It was fo und that only the methanol extract of neem leaves contain weak antimut agen inhibiting the mutagenicities of both direct-acting mutagens. Int erestingly, all vegetables studied were found to contain chemical comp ounds, mainly nonpolar ones, capable of inhibiting the mutagenicity of AFB(1), while only some vegetables contain chemical compounds capable of inhibiting the mutagenicity of B(a)P, which is also an indirect-ac ting mutagen. Studies on anticarcinogenic potentials demonstrated that Thai bitter gourd fruits, but not sweet basil leaves, at the concentr ation of 6.25% and 12.5% in the diet, partially inhibited DMBA-induced mammary gland carcinogenesis in female Sprague-Dawley rats when fed t o the animals 2 weeks prior to DMBA. Results in the present study ther efore demonstrated that most Thai vegetables contain antimutagens inhi biting the mutagenicity of some indirect-acting mutagen, particularly AFB(1). The mechanism of their antimutagenicity may probably be the in hibition of the activity of metabolic-activating enzymes in rat liver homogenates. Very interestingly, our results clearly reveal that Thai bitter gourd fruits, which possess Phase II enzymes inducing property, as well as the ability to reduce Phase I enzyme activities in rat liv er, contain some anticarcinogens or chemopreventive agents. However, s weet basil leaves that possess both Phase I and Phase II enzyme-induci ng properties may not contain any anticarcinogen, at least against DMB A-induced mammary gland carcinogenesis. (C) 1998 Elsevier Science B.V. All rights reserved.