Dietary administration of citrus nobiletin inhibits azoxymethane-induced colonic aberrant crypt foci in rats.

The modifying effects of dietary feeding of a polymethoxyflavonoid nobiletin isolated from Citrus unshiu on the development of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) were investigated in male F344 rats. We also assessed the effects of nobiletin on cell proliferation activity of ACF using a monoclonal antibody MIB-5. Rats were given subcutaneous injections of AOM (15 mg/kg body weight) once a week for 3 weeks to induce ACF. They also received the experimental diet containing 0.01% or 0.05% nobiletin for 5 weeks, starting one week before the first dosing of AOM. AOM exposure produced 139 +/- 35 ACF/rat at the end of the study (week 5). Dietary administration of nobiletin caused significant reduction in the frequency of ACF: 70 +/- 15 (50% reduction, p<0.001) at a dose of 0.01% and 63 +/- 10 (55% reduction, p<0.001) at a dose of 0.05%. Nobiletin feeding significantly lowered MIB-5-index in ACF. Also, dietary administration of nobiletin significantly reduced prostaglandin E2 content in the colonic mucosa. These findings might suggest possible chemopreventive ability of nobiletin, through suppression of cell proliferating activity of ACF, in the development of ACF.