Flower colors and their anthocyanins in Platycodon grandiflorus (Jacq.) A. DC. (Campanulaceae)

Abstract

The flower colors and anthocyanin composition of three strains (consisting of 18 cultivars) of Platycodon grandiflorus (Jacq.) A. DC. were surveyed to assess the relationship between these two parameters. Eleven anthocyanins, four flavones, chlorogenic acid, and 1-O-(trans-caffeoyl)-β-glucopyranoside were isolated from the flowers of these cultivars, and their structures were identified using chemical and spectroscopic methods. Among them, three undescribed anthocyanins, i.e., cyanidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside]-7-O-[6-O-(4-O-(6-O-(4-O-(β-glucopyranosyl)-trans-caffeoyl)-β-glucopyranosyl)-trans-caffeoyl)-β-glucopyranoisde] (for convenience, we termed this undescribed anthocyanin as purproplatyconin), pelargonidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside]-7-O-[6-O-(4-O-(6-O-(4-O-(β-glucopyranosyl)-trans-caffeoyl)-β-glucopyranosyl)-trans-caffeoyl)-β-glucopyranoside] (for convenience, we termed this undescribed anthocyanin as rubroplatyconin), and pelargonidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside]-7-O-[6-O-(4-O-(β-glucopyranosyl)-trans-caffeoyl)-β-glucopyranoside], were discovered in the corollas of the ‘Astra Pink’ and ‘Omotenashi Pink’ cultivars. Moreover, pelargonidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside]-7-O-(β-glucopyranoside), pelargonidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside], cyanidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside], and delphinidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside] were also discovered in these cultivars for the first time in P. grandiflorus. The structures, conditions, and concentrations of these anthocyanins, as well as their intramolecular co-pigmentation effects were considered to be responsible for the flower color variation observed in P. grandiflorus cultivars.