Anti-oxidative analysis, and identification and quantification of anthocyanin pigments in different coloured rice

Abstract

Anthocyanin pigments in coloured rice cultivars were isolated and identified using high-performance liquid chromatography techniques. Two black rice cultivars (Asamurasaki, Okunomurasaki) contained three major anthocyanins: cyanidin-3-glucoside, peonidin-3-glucoside and malvidin. Chinakuromai (black) rice additionally contained a fourth anthocyanin, petunidin-3-glucoside. Four red rice cultivars contained only malvidin. The total anthocyanin content varied greatly among black rice cultivars (79.5–473.7mg/100g), but was lower in red rice (7.9–34.4mg/100g). Total phenolic content was similar between red (460.32–725.69mg/100g) and black (417.11–687.24mg/100g) rice. The oxygen radical absorbing capacity was ranked as follows: red (69.91–130.32μmol Trolox/g)>black (55.49–64.85μmol Trolox/g)>green (35.32μmol Trolox/g)>white (21.81μmol Trolox/g) rice. The antioxidant capacity resulted mainly from the seed capsule, not the endosperm. The anthocyanin pigments contributed little to the total antioxidant capacity of red (0.03–0.1%) and black (0.5–2.5%) rice cultivars. Hence, the antioxidant capacity is derived mainly from other phenolic compounds.