Cranberries are abundant food sources of the anthocyanidins (such as
cyanidin and peonidin), flavonols (such as
quercetin). Cranberry juice is traditionally consumed for the prevention of urinary tract infections but in-vitro studies have recently shown that cranberry phytochemicals have also anti-cancer activity, but their effectiveness in humans has not been well established and may be limited by poor absorption and rapid elimination.
In 2007 Catherine Neto made a review of in-vitro studies about the anticancer properties of cranberry phytochemicals. These studies demonstrated the anticancer effects of cranberry phytochemicals in cultured cancer cells of breast, colon, lung and prostate. The observed effects were attributed to different phytochemicals: flavonols, proanthocyanidin oligomers and triterpenoids. The possible mechanisms of these phytochemicals are direct antioxidant activity, induction of apoptosis of cancer cells, reduction of ornithine decarboxylase activity and inhibition of matrix metalloproteinases expression.
The team looked at studies involving the use of whole cranberry fruit and extracts, but also individual phytochemicals. Water soluble extracts effectively inhibited proliferation of several human cancer lines. Quercetin is the most abundant flavonols in cranberry and is likely responsible for much of the anticancer effect. This phytochemical is capable of inducing apoptosis, probably through activation of the mitochondrial apoptosis pathway. Cyanidin and peonidin are the major anthocyanins in cranberry and may inhibit tumorgenesis through their strong antioxidant activities. Inhibition of ornithine decarboxylase activity has been linked to the proanthocyanidin fraction of whole cranberry fruit. Overexpression of ornithine decarboxylase plays a role in the transformation, invasion and angiogenesis. The cranberry triterpenoids, such as ursolic acid, are found in the cranberry skin and have been show to inhibit the growth of several leukaemia cell lines and human lung cancer carcinoma. The inhibition of COX enzyme activity by cranberry phytochemicals may also reduce the risk cancer development.
The authors concluded that evidence suggest that cranberry phytochemicals are likely to have mitigating effect on certain types of tumors, but that the in-vivo anticancer effect of cranberry phytochemicals need still to be thoroughly researched. Future studies should also take into account that different cranberry phytochemicals may produce synergistic biological effects.
Source: Neto CC. Cranberry and its phytochemicals: a review of in vitro anticancer studies
. J Nutr. 2007 Jan;137(1 Suppl):186S-193S