The effects of freeze-dried black raspberries on colon cancer in the F344 rat

Epidemiological studies indicate that fruit and vegetable consumption reduces the risk of colon cancer in humans. Isolated food components, a number of which are found in black raspberries, have shown cancer preventive activity in animal and in vitro studies. This dissertation examines the effects of whole black raspberries (BRB) on experimentally-induced colon cancer in three separate studies. The berries used in these studies were freeze-dried in order to concentrate and stabilize the potentially cancer preventive compounds contained in them.; The first study compared the antioxidant activity of freeze-dried BRB to other freeze-dried and drum-dried berries using the oxidative stability instrument. Alpha-tocopherol was used as a reference. The results of this study indicated that the antioxidant activity of all berries tested was similar and that the antioxidant activity of alpha-tocopherol was significantly (P < 0.05) higher than all berries tested.; The second study examined the effects of freeze-dried BRB on 2-amino-1-methyl-6-phenylimidazo-[4,5-b] pyridine (PhIP)-induced DNA adduct formation in F344 rats. For 2 weeks prior to carcinogen administration and throughout the remainder of the study, rats were fed 0, 5 or 10% BRB. PhIP was administered in the diet at 0.04% (w/w) for 2 weeks. Rats were sacrificed 1 or 8 days after PhIP administration. Colonic DNA was isolated and analyzed for PhIP adducts by 32P post-labelling. No significant differences in DNA adduct levels were observed among treatment groups. The third study examined the effects of freeze-dried BRB on azoxymethane (AOM)-induced aberrant crypt foci, adenomas, adenocarcinomas and urinary 8-hydroxy-2 ′-deoxyguanosine (8-aOHdG) in F344 rats. AOM was injected (15 mg/kg body weight) i.p. once per week for 2 weeks. AOM-treated rats began consuming diets containing 0, 2.5, 5, or 10% (w/w) BRB after the final carcinogen dose. Vehicle controls received 5% BRB or diet only. Rats were sacrificed after 9 and 33 weeks of BRB feeding for ACF enumeration and tumor analysis. The number of aberrant crypt foci, adenomas, adenocarcinomas and urinary 8-OHdG levels were significantly (P < 0.05) reduced in all BRB treated groups. These results indicate that BRB inhibit several measures of AOM-induced colon carcinogenesis and modulate a marker of oxidative stress in the F344 rat.