Effect of Siamese cassia leaves on the activities of chemical carcinogen metabolizing enzymes and on mammary gland carcinogenesis in the rat

Abstract

Male Wistar rats were fed AIN-76 semipurified diet or diet containing 5% ground lyophilized Siamese cassia leaves for 2 weeks before sacrifice. Hepatic S9 fractions were prepared and assayed for the level of cytochrome P450 ( P450), the activities of monooxygenase, i.e., aniline hydroxylase (ANH), aminopyrine- N-demethylase (AMD) as well as the capacity to metabolically activate the mutagenicities of aflatoxin B 1 (AFB 1) and benzo( a)pyrene (B( a)P). In addition, the activities of detoxificating enzymes such as glutathione- S-transferase (GST) and UDP-glucuronyltransferase (UGT) were also measured. It was found that feeding of Siamese cassia leaves significantly reduced the activities of hepatic ANH and AMD as well as the capacity to activate the mutagenicity of AFB 1 towards Salmonella typhimurium TA100, being 31, 73 and 41% of control group, respectively. It also slightly decreased, but not significantly, the capacity to activate the mutagenicity of B( a)P towards S. typhimurium YG1029. On the other hand, however, the activities of both GST and UGT were markedly increased in those animals, being 250 and 220% of control animals. The anticarcinogenic potential of Siamese cassia leaves was also investigated in female Sprague Dawley rats treated with 9,10-dimethyl-1,2-benzanthracene (DMBA). The animals were fed control diet or diet containing ground lyophilized Siamese cassia leaves 2 weeks prior to and 1 week after intragastrically administration of DMBA, and then they were placed on a pellet diet for additional 25 weeks. Interestingly, it was found that feeding of diet containing 2.5 and 4% Siamese cassia leaves resulted in a significant decrease in the multiplicity of mammary gland tumors as well as a slight delay of the onset of tumor development. The incidence of tumors in the group fed 4% Siamese cassia leaves, but not in the 2.5% group, was lowered, although not significantly, than that of control group. The results in the present study therefore demonstrated that Siamese cassia leaves possess phase II enzyme inducing property as well as the ability to reduce some phase I enzyme activities in rat liver. This Thai vegetable also exhibit cancer chemopreventive potential, at least against DMBA-induced mammary gland carcinogenesis which may be partly due to phase II inducing capacity as well as phase I inhibitory activity.