The O-methylated flavonoids or methoxyflavonoids are flavonoids with methylations on hydroxyl groups (methoxy bonds).
O-methylation has an effect on the solubility of flavonoids.
O-methylated flavonoids formation implies the presence of specific O-methyltransferase (OMT) enzymes which accept a variety of substrates.
[1] Those enzymes mediate the O-methylation on a specific hydroxyl group, like on 4' (example in Catharanthus roseus[2]) or 3' (example in rice[3]) positions.
Calamondin orange (Citrus mitis) exhibits all of those activities.