Anthocyanins from flowers of Hippeastrum cultivars

Abstract

The anthocyanins, cyanidin 3-O-(6″-O-α-rhamnopyranosyl-β-glucopyranoside) (1) and pelargonidin 3-O-(6″-O-α-rhamnopyranosyl-β-glucopyranoside) (2), were isolated from the ornamental flowers of a Ugandan Hippeastrum cultivar by a combination of chromatographic techniques, and their structures were elucidated mainly by the use of homo- and heteronuclear nuclear magnetic resonance spectroscopy and electrospray mass spectrometry. The same anthocyanins were found in six different Hippeastrum cultivars purchased in Norway. However, the absolute amount of the anthocyanins (0.08–1.79 mg/g, fresh weight) and the relative proportions of the individual anthocyanins varied from cultivar to cultivar (13.2–96.5% of 1). The colours of the fresh petals of the three cultivars ‘Red Lion’, ‘Royal Velvet’ and ‘Liberty’ were described by the CIELab coordinates L* (lightness), C* (chroma) and hab (hue angles). All the cultivars showed hue angles corresponding to scarlet nuances (hab = 22–35°), with the highest value in ‘Red Lion’. The most reddish petals (in ‘Royal Velvet’) contained the highest relative proportion of 1. Thus, the in vivo colours of these cultivars seem to be correlated with the relative proportions of individual anthocyanin in the petals.