In vitro absorption and metabolism of nobiletin, a chemopreventive polymethoxyflavonoid in citrus fruits

The polymethoxyflavonoid (PMF), nobiletin (NOB), specifically occurs in citrus fruits, and is currently believed to be a promising anti-inflammatory and anti-tumor promoting agent. In the present study, we investigated the in vitro absorption and metabolism of NOB and compared them with those of the polyhydroxyflavonoid (PHF), luteolin (LT). NOB preferentially accumulated in a differentiated Caco-2 cell monolayer, which is a model for small intestinal epithelial cells, while LT did not. Treatment of NOB with a rat liver S-9 mixture led to the formation of 3'-demethyl-NOB, while that of LT did not. We thus suggest that PMFs including NOB have properties distinct from those of general flavonoids for absorption and metabolism in vitro.