ABSTRACT
Flavonoids are a huge group of plant secondary metabolites that are widely and ubiquitously distributed throughout the plant kingdom. Chemically, flavonoids consist of C3-C6-C3 units and are classified into several subgroups according to, for example, their oxidation status, number of aromatic rings, carbon skeleton, and presence or absence of positive charge. A common chemical characteristic of flavonoids is the presence of phenolic and hydroxyl groups. Polymethylated flavonoids (PMFs) have particular chemical characteristics-specifically, hydroxyl groups that are mostly methylated, and an oxidation status of the A-ring that is distinct from that of common flavonoids, since the 6-or 8-position is oxidized in addition to the 5-and 7-positions, where common flavonoids have hydroxyl group(s) (Fig. 1). The above-mentioned hydrophobic characteristics provide PMFs with notable biological activities and metabolic properties, as described herein.
