Flavonoids in the flowers of Primula ×polyantha Mill. and Primula primulina (Spreng.) H. Hara (Primulaceae)

Abstract

Two undescribed anthocyanins and two undescribed flavonols were isolated from the flowers of Primula ×polyantha Mill., along with five known anthocyanins and four known flavonols. The two undescribed anthocyanins and the two undescribed flavonols were determined to be hirsutidin 3-O-β-galactopyranoside-5-O-β-glucopyranoside, 7-O-methyl-petunidin 3-O-β-galactopyranoside-5-O-β-glucopyranoside, quercetin 3-O-β-[(6""-acetylglucopyranosyl)-(1 → 2)-β-glucopyranosyl-(1 → 6)-β-glucopyranoside], and kaempferol 3-O-β-[(6""-acetylglucopyranosyl)-(1 → 2)-β-glucopyranosyl-(1 → 6)-β-glucopyranoside] using chemical and spectroscopic methods. They were also found in the flowers of the Himalayan wild species, Primula primulina (Spreng.) H. Hara except for quercetin 3-O-β-[(6""-acetylglucopyranosyl)-(1 → 2)-β-glucopyranosyl-(1 → 6)-β-glucopyranoside]. The flower color variations of P. ×polyantha cultivars, reflected by the hue values (b*/a*) of the colors, were due to the glycosidic patterns in the anthocyanins and their concentrations in the petals. Moreover, in the P. ×polyantha cultivars with violet-blue flowers, both the intermolecular copigmentation occurs between hirsutidin 3-O-β-galactopyranoside-5-O-β-glucopyranoside and another flavonol, quercetin 3-O-β-glucopyranosyl-(1 → 2)-β-glucopyranosyl-(1 → 6)-β-glucopyranoside. Moreover, the flower color variation was affected by the pH value.

Keywords: 7-O-Methyl-anthocyanin; Cyanidin; Flavonols; Flower color; Hirsutidin; Intermolecular copigmentation; Peonidin.