Purple Rice Extract Supplemented Diet Reduces DMHInduced Aberrant Crypt Foci in the Rat Colon by Inhibition of Bacterial β-Glucuronidase

Abstract

<b>Background:</b> Purple rice has become a natural product of interest which is widely used for health promotion.This study investigated the preventive effect of purple rice extract (PRE) mixed diet on DMH initiation of coloncarcinogenesis. Materials and <br/><b>Methods</b>: Rats were fed with PRE mixed diet one week before injection of DMH(40 mg/kg of body weight once a week for 2 weeks). They were killed 12 hrs after a second DMH injection tomeasure the level of O6-methylguanine and xenobiotic metabolizing enzyme activities. <br/><b>Results</b>: In rats thatreceived PRE, guanine methylation was reduced in the colonic mucosa, but not in the liver, whereas PRE did notaffect xenobiotic conjugation, with reference to glutathione-S-transferase or UDP-glucuronyl transferase. After5 weeks, rats that received PRE with DMH injection had fewer ACF in the colon than those treated with DMHalone. Interestingly, a PRE mixed diet inhibited the activity of bacterial β-glucuronidase in rat feces, a criticalenzyme for free methylazoxymethanol (MAM) release in the rat colon. These results indicated that purple riceextract inhibited β-glucuronidase activity in the colonic lumen, causing a reduction of MAM-induced colonicmucosa DNA methylation, leaded to decelerated formation of aberrant crypt foci in the rat colon. <br/><b>Conclusions</b>:The supplemented purple rice extract might thus prevent colon carcinogenesis by the alteration of the colonicenvironment, and thus could be further developed for neutraceutical products for colon cancer prevention.