1951 年 71 巻 9 号 p. 882-885
It was assumed from the results of methylation that the specific solubilization of rutin in an aqueous solution containing sodium hydroxide and boric acid in 1:1-2 molar ratio was due to the formation of two kinds of boric acid complex salts, which exist as soluble salts in equilibrium, by the bonding of boric acids with the phenolic hydroxyls at 3′ and 4′ positions, and with the hydroxyl at 5-position and the carbonyl of the pyrone ring. The same explanation was assumed to be applicable in the case of quercetin. The dying ability of flavonols by the oxides of heavy metals are also due to the formation of complex salts but the complex salts are insoluble in this case whereas boric acid complexes of rutin become water soluble by the complex formation.