Prevention of N-nitrosodiethylamine-induced lung tumorigenesis by ellagic acid and quercetin in mice

The polyphenolic antioxidants. consumed as an integral part of vegetables. fruits and beverages, are suggested as possessing anticarcinogenic properti es. In the present study we have looked into the anticarcinogenic potential of plant polyphenols ellagic acid (EA) and quercetin against N-nitrosodith ylamine-induced lung tumorigenesis in mice. Ellagic acid was able to signif icantly reduce tumour incidence to 20% from the control value of 71.2%. Sim ilarly. tumour burden was also decreased. although not significantly, from 3.15 to 2.5. Quercetin (QR) caused the tumour incidence to decrease from 76 .4% to 44.4% when fed until the third dose of carcinogen. Both of the polyp henols suppressed the tumour incidence mainly by acting at the initiation p hase of the carcinogenesis, since continuing the feeding of polyphenols unt il the termination of the experiment did not cause any apparent change in t umour incidence or tumour burden. Besides this, ellagic acid was found to b e a better chemopreventor than quercetin. In order to starch for their mech anism of action. the effect of feeding of these compounds on reduced glutat hione (GSH). an important endogenous antioxidant, and on lipid peroxidation was investigated. Both ellagic acid and QR caused a significant increase i n GSH and decrease in NADPH- and ascorbate-dependent lipid peroxidation. El lagic acid was found to be more effective in decreasing thr lipid peroxidat ion and increasing the GSH. This may be one of the reasons for its observed better anticarcinogenic property as compared to quercetin. (C) 1999 Publis hed by Elsevier Science Ltd. All rights reserved.