Pigments of cotton flowers. Part IV. Constitution of Herbacitrin and Herbacetin- new glucoside and aglucone (flavonol)

Abstract

Herbacitrin, the new flavonol glucoside obtained from Gossypium herbaceum (Uppam) has the formula C₂₁H₂₀O₁₂. Though isomeric with Quercimeritrin it differs from it in many properties. On hydrolysis it gives glucose and Herbacetin having the formula C₁₅H₁₀O₇ which differs from Quercetin in its reactions. In their colour reactions with alkaline buffer solutions and with p-benzoquinone Herbacitrin exhibits a very close resemblance to Gossypitrin and Herbacetin to Gossypetin. From these and other considerations Herbacetin has been given the constitution 3:5:7:8:4'-pentahydroxy-flavone and Herbacitrin is represented as its 7-glucoside. This has been confirmed by the oxidation of Herbacitrin to p-hydroxy-benzoic acid. The flavonol has now been synthesised in the Dyson Perrins Laboratories in Oxford and found to be identical with the natural specimen.