Changes in anthocyanins in the grains of purple waxy hull-less barley during seed maturation and after harvest

Abstract

Purple waxy hull-less barley cv. Daishimochi accumulates purple pigments in the stem, awn, lemma, palea, and pericarp during seed maturation. Four major anthocyanin constituents from the grains of cv. Daishimochi were isolated and identified as cyanidin 3-O-(3,6-di-O-malonyl-beta-D-glucopyranoside) (55%), cyanidin 3-O-(6-O-malonyl-beta-D-glucopyranoside) (21%), cyanidin 3-O-(3-O-malonyl-beta-D-glucopyranoside) (12%), and cyanidin 3-O-beta- d-glucopyranoside (4%) by mass spectrometry and one- and two-dimensional NMR spectroscopy. These anthocyanins were observed after 28 days after flowering (DAF); they were most abundant at 35 DAF when the dry weight of grains was maximum. This accumulation time was later than that of proanthocyanidins, which are the most abundant polyphenol constituents in barley grains. These anthocyanins, especially cyanidin 3-O-(3,6-di-O-malonyl-beta- d-glucopyranoside), decreased at 42 DAF and during drying preparation after harvest. Most anthocyanins are localized in the outer parts of grains and distributed into bran by the pearling process. Whole grain flour and bran of cv. Daishimochi are good sources of malonylated cyanidin derivatives.