Effect of Anthocyanin, Flavonol Co-Pigmentation and pH on the Color of the Berries of Ampelopsis brevipedunculata

Abstract

Summary Four anthocyanins and two flavonol glycosides were identified using chromatographic and spectrophotometric techniques in the epicarp of the berries of Ampelopsis brevipedunculata . The anthocyanins were malvidin 3- O -rhamnoside-5- O -glucoside, petunidin 3- O -rhamnoside-5- O -glucoside, delphinidin 3- O -rhamnoside-5- O -glucoside and malvidin 3- O -glucoside-5- O -glucoside, in the ratio of approximately 5.6:1:2:1.5. Quercetin 3- O -rhamnoside (quercitrin) and myricetin 3- O -rhamnoside (myricitrin) were the major flavonols present, and their ratio was approximately 1:0.8. The color of berries changed from green via reddish-purple to bluish-purple to blue as maturation proceeded, and then finally the the color faded. Concurrently with the color changes, the pH of the berries increased from 4.8 (green) to 6.5 (blue). The bluish-purple berries had the highest content of anthocyanin (0.26 mg · g −1 fr.wt.). At the same stage, the quercitrin and myricitrin contents were 0.62 and 0.55 mg · g −1 fr.wt. respectively, and the pH of berries was 5.8. A visible absorption spectrum of the intact epicarp of the bluish-purple berries was simulated with a solution of anthocyanin and flavonols at the same molarity and pH as those of the berries. When the pH (5.8) of the solution, which gave a fairly stable bluish-purple color, was increased to 6.5, the color changed to blue. This indicated that the change of berry color from reddish-purple to blue was related to the pH of the tissue and that the berry color was due to the occurrence of anthocyanin flavonol co-pigmentation.