Flavone glycosides acidic hydrolysis

More nsnal vegetables were stndied by Nnntila et al. [358] who characterized onions and spinach for the phenolic composition, with and without previous hydrolysis. The authors performed the simultaneous determination of phenolic acids, flavonols, flavones glycosides, and cathechins. Fignre 19.9 reprodnces the separation obtained for the standard mixture in this study. 

Acidic hydrolysis 2-5 mg of flavone glycoside dissolved in minimum amount of MeOH and mixed with 5% aqueous hydrochloric acid (1ml) and refluxed on an electrical heater for an hour. After cooling, the mixture is extracted with ether-EtOAc for the aglycone. The aqueous residue evaporated to dryness for the sugars. The EtOAc extract after drying and evaporation yields the aglycone. 

Flavonols consist of O-glycosides, but flavone O- and C-glycosides are very common they are defined by possession of a carbon-carbon linkage between the numeric carbon of a sugar molecule and the C-6 or C-8 carbon of the flavone nucleus. In contrast to O-glycosides, sugars in C-glycosides are not separated by acid hydrolysis. 

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