Inhibition of cellular transformation by berry extracts

Recent studies have examined and demonstrated the potential cancer chemopre ventive activity of freeze-dried berries including strawberries and black r aspberries. Although ellagic acid, an abundant component in these berries, has been shown to inhibit carcinogenesis both in vivo and in vitro, several studies have reported that other compounds in the berries may also contrib ute to the observed inhibitory effect. In the present study, freeze-dried s trawberries (Fragara ananassa, FA) or black raspberries (Rubus ursinus, RU) were extracted, partitioned and chromatographed into several fractions (FA -F001, FA-F003, FA-F004, FA-F005, FA-DM, FA-ME from strawberries and RU-F00 1, RU-F003, RU-F004, RU-F005, RU-DM, RU-ME from black raspberries). These e xtracts, along with ellagic acid, were analyzed for anti-transformation act ivity in the Syrian hamster embryo (SHE) cell transformation model. None of the extracts nor ellagic acid by themselves produced an increase in morpho logical transformation. For assessment of chemopreventive activity, SHE cel ls were treated with each agent and benzo[a]pyrene (B[a]P) for 7 days. Ella gic acid, FA-ME and RU-ME fractions produced a dose-dependent decrease in t ransformation compared with B[a]P treatment only, while other fractions fai led to induce a significant decrease. Ellagic acid, FA-ME and RU-ME were fu rther examined using a 24 h co-treatment with B[a]P or a 6 day treatment fo llowing 24 h with B[a]P. Ellagic acid showed inhibitory ability in both pro tocols. FA-ME and RU-ME significantly reduced B[a]P-induced transformation only when co-treated with B[a]P for 24 h. These results suggest that a meth anol extract from strawberries and black raspberries may display chemopreve ntive activity. The possible mechanism by which these methanol fractions (F A-ME, RU-ME) inhibited cell transformation appear to involve interference o f uptake, activation, detoxification of B[a]P and/or intervention of DNA bi nding and DNA repair.