Phenolic acids, anthocyanins, proanthocyanidins, antioxidant activity, minerals and their correlations in non-pigmented, red, and black rice

•Soluble-free, soluble-conjugated and insoluble-bound phenolic fractions were quantified in rice.•Soluble conjugated phenolics and anthocyanins were negatively correlated with color parameters.•Some soluble conjugated and insoluble bound phenolic acids had positive correlations with TPC and antioxidant activity.•The correlation ships among the seven mineral contents were exhibited.•Principal component analysis divided the rice samples into non-pigmented, red and black rice groups.

Soluble-free, soluble-conjugated, insoluble-bound phenolics and antioxidant activity, flavonoid (TFC), proanthocyanidins (TPAC), anthocyanins and minerals of fifteen whole rice grains with different colors were investigated. Soluble-free protocatechuic and vanillic acids were only quantified in black rice, which had the most quantities. Non-pigmented rice had no detectable conjugated protocatechuic and 2,5-dihydroxybenzoic acids both of which were found in black and red rice, respectively. The main bound phenolic acids were ferulic and p-coumaric, as well as 2,5-dihydroxybenzoic in red rice and protocatechuic and vanillic acids in black rice. Soluble-conjugated phenolics, TFC, and anthocyanins were negatively correlated with L∗, b∗, C and H° values. TPAC was positively correlated with a∗ (P < 0.01). Protocatechuic, vanillic, syringic and ferulic acids were associated with TPC and antioxidant activity in the soluble-conjugated fraction while protocatechuic and ferulic acid were correlated with those in the insoluble-bound fraction. Principal component analysis divided samples into non-pigmented, red and black rice groups.