Berries and berry extracts possess properties that make them important in the prevention of cancer. The high antioxidant levels of these extracts play a role, but components of the berries can have other effects on cell replication and survival. We chose to test the hypothesis that (i) although the antioxidant capacity of raspberry extracts is important for inhibiting the proliferation of tumor cells, other characteristics of the berry extracts are responsible for a major part of their antiproliferative activity, and that (ii) the relative importance of the antioxidant effect can depend on the cell type being studied. The aim of this study was to assess the relative roles of low pH and high antioxidant levels in the killing of 3 cell types by an aqueous extract from Meeker red raspberries. Stomach, colon, and breast cancer cells were treated with berry extract and with HCl and ascorbic acid solutions of the same pH. A dilution of 7.5% ascorbic acid solution, of the same pH and slightly higher antioxidant concentration than the berry extract, killed less than 10% of the stomach and colon cancer cells. In contrast, the berry extract at this same dilution killed more than 90% of these cells. Antioxidants played a more significant role in the killing of breast cancer cells, however. For these cells, approximately 50% of the killing could be attributed to antioxidant effects. We conclude that the antioxidant effect plays a minor role in the killing of 2 gastrointestinal cell types, but its role in inactivating a breast cancer cell line is much more significant. No evidence of apoptosis was observed, and caspase activation did not contribute to cell killing by the extract.
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