Protective role of luteolin in 1,2-dimethylhydrazine induced experimental colon carcinogenesis

The aim of the present study was to unravel the chemopreventive effect of luteolin on bacterial enzymes such as beta-glucuronidase and mucinase in a colon carcinogenesis model induced by 1, 2-dimethyl hydrazine (DMH). Twenty mg/kg body weight of DMH were administered subcutaneously once a week for the first 15 weeks and then discontinued. Luteolin (0.1, 0.2, or 0.3 mg/kg body weight/everyday (p.o.) was administered in a dose dependent manner at the initiation and also at the post-initiation stages of carcinogenesis to DMH treated rats. The animals were sacrificed at the end of 30 weeks. Colon cancer incidence and the activities of bacterial enzymes beta-glucuronidase (in the proximal colon, distal colon, intestines, liver and colon contents) and mucinase (colon and fecal contents) were significantly increased in DMH -treated rats compared to the control rats. On luteolin administration, colon cancer incidence, number of tumors per rat and the activities of beta-glucuronidase and mucinase, were significantly decreased both in the initiation and post-initiation stages of colon carcinogenesis dependent on the three different doses given. The increase in beta-glucuronidase activity may augment the hydrolysis of glucuronide conjugates, liberating toxins, while the increase in the mucinase activity may enhance the hydrolysis of the protective mucins in the colon. Thus our results demonstrate for the first time that luteolin, a dietary flavonoid, exerts chemopreventive and anticarcinogenic effects against DMH induced colon cancer.