Abstract
As a result of the comparison between solubilization tests using aqueous solution of borax and reduction coloration using magnesium and hydrochloric acid in flavones and flavonols, it was found that in order to effect the former reaction it would be necessary for the presence of hydroxyl groups in a certain position of flavones and flavonols while the latter reaction necessitated the presence of a certain number of hydroxyls or methoxyls. In this respect, the mechanism of these two reactions was found to be fundamentally different. Results of the reduction coloration by magnesium or zinc and hydrochloric acid carried out on various flavonoids are shown in Table I. Tables II to VII show individual results on these flavonoids. As shown in Table VIII, there is a distinct difference between flavonols and flavonol-3-glucosides, although coloration by magnesium and hydrochloric acid is the same in both cases. Flavonols do not color with zinc and hydrochloric acid but flavonol-3-glucosides color red by it. The same is true, as shown in Table IX, of those compounds in which methyl group is attached to the hydroxyl in 3-position, instead of the sugar residue. These observations offer useful means for the distinction between flavonol-3-glycosides and flavonols.
