Anthocyanins and Flavonols from the Flowers of Ranunculus Cultivars (Ranunculaceae) and Their Color Expression

Abstract

Isolation, purification and identification of anthocyanins and flavonols were carried out on flowers of Ranunculus cultivars. Three anthocyanins and 11 flavonols were characterized by chemical and spectroscopic techniques. The anthocyanins were identified as cyanidin 3-O-sambubioside, cyanidin 3-O-(6''-malonylsambubioside) and delphinidin 3-O-(6''-malonylsambubioside). The flavonols were identified as 3-O-glucosides and 3-O-sophorosides of kaempferol and quercetin, and their acylated compounds with malonic acid. Flower colors were divided into six groups, Red-Purple, White, Yellow-Orange, Orange, Red, and Violet groups using the Royal Horticultural Society Colour Chart. The absorption maxima of buffer solutions containing anthocyanins and flavonols isolated in this study were measured to understand the effect of intermolecular copigmentation between these compounds on flower color. The results showed that by addition of 3-O-(6''-malonylglucoside) of kaempferol or quercetin, the absorption maximum of cyanidin 3-O-(6''-malonylsambubioside) or delphinidin 3-O-(6''-malonylsambubioside) shifted bathochromically and exhibited a closer absorption maximum to fresh flower petals than anthocyanin alone. This indicates that the intermolecular copigment effect between anthocyanins and flavonols is responsible for the flower color expression in Ranunculus cultivars.