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

Background: 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
Methods: 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.
Results: 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.
Conclusions: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.