ABSTRACT
Flavones (including 3-hydroxyl ‘avones, also known as ‘avonols) and ‘avanones are important phytochemicals in food products. They normally occur as O-glycosidic combinations with mono-and disaccharides, although combinations with a higher number of sugars are also frequent. C-Glycosidic combinations have also been reported in different food products (cereals, grains, Swiss chard, sweet peppers, etc.). Glucose, galactose, rhamnose, arabinose, and xylose are the main monosaccharides that conjugate with ‘avonoid aglycones. In addition, uronic acids, mainly glucuronic acid, are often found in naturally occurring ‘avonoids (strawberries, grapes, spinach, etc.). The more relevant disaccharides are sophorosides [glucosyl(1 → 2)glucosides], gentiobiosides [glucosyl(1 → 6)glucosides], rutinosides [rhamnosyl(1 → 6)glucosides], and neohesperidosides [rhamnosyl(1 → 2)glucosides], although sambubiosides, glucosyl-galactosides, etc. are also found. Acylation of the ‘avonoid glycosides with aliphatic monocarboxylic (acetic, malic) or dicarboxylic (malonic, tartaric, etc.) acids, or aromatic acids (mainly hydroxycinnamic acids, such as caffeic, p-coumaric, ferulic, and sinapic) is also frequent. In some cases, they can also be conjugated with sulfate (as in the case of palm dates). The conjugation with glucuronides and/or sulfates is particularly relevant in the metabolism occurring in vivo, as a general way of detoxi‚- cation using the Phase II enzyme system. Flavone and ‘avanone aglycones have also been found in different food products. For instance, they are present as polymethoxy‘avones in citrus fruits (sinensetin, nobiletin, tangeretin, etc.), and as different ‘avone and ‘avanone combinations in propolis (pinocembrin, pinobanksin, chrysin, and galangin), a resinous by-product collected by bees from trees.
