Biological Activity, Metabolism and Separation of Polymethoxyflavonoids from Citrus Peels

Polymethoxyflavonoids (PMFs) almost exclusively exist in citrus plants. In recent years, there has been increasing and particular interests in the exploration of the health benefits associated with PMFs. PMFs are reported to exhibit a broad spectrum of biological activities, such as anti-inflammatory, anti-carcinogenic, anti-tumor, anti-viral, anti-thrombogenic and anti-atherogenic properties. Metabolic studies, especially the identification of in vivo biotransformation products of PMFs, have revealed that the major metabolites are desmethylated or hydroxylated PMFs. Biological screening of some of these metabolites has revealed that they may possess more potent bioactivities such as anti-inflammatory and anti-cancer properties. Elucidation and biological activity study of PMF metabolites may lead to further exploration and understanding of PMFs’ health benefits and the mechanism along with the beneficial properties in human beings. The increased demand of PMFs for efficacy and clinical trial studies has resulted in a demanding supply for pure PMFs in large quantities. Consequently, separation and characterization of PMFs have attracted increasing attention and new techniques have evolved dramatically in recent studies. However, the development of an efficient large-scale separation method(s) as well as robust and reliable analysis method(s) for PMFs and their metabolites are needed and eventually will be developed in the near future because of the significance and urgency. This review describes the occurrence, bioactivity, bioavailability, metabolism and chemistry of PMFs from citrus genus, especially the peels of citrus fruits. _____________________________________________________________________________________________________________