Phenolic compounds in berries of black, red, green, and white currants (Ribes sp.)

Multiple health benefits associated with phenolic compounds have raised the interest in the contents of these plant metabolites in foods. Several phenolic compounds were quantified from berries of Ribes nigrum (black and green currants) and Ribes x pallidum (red and white currants), by using sequential extraction with ethyl acetate and methanol and an optimized reversed-phase HPLC method with diode array detection. The highest contents of anthocyanins (3,011 mg/kg fresh weight, expressed as the aglycon) and flavonol glycosides (100 mg/kg) were found in black currant. The lack of anthocyanins in the colorless (green, white) berries was associated with increased levels of phenolic acids, especially p-coumaric acid (80 mg/kg in green currant vs. 45 mg/kg in black currant) and 4-hydroxybenzoic acid (18 mg/kg in white currant vs. 3 mg/kg in red currant). Previously, proanthocyanidins have not been quantified from berries. This study showed that the contents of extractable (22-41 mg/kg) and nonextractable proanthocyanidins (32-108 mg/kg) are comparable to those of other phenolics, with the exception of anthocyanins in black currant. Our results suggest that anthocyanins dominate in black and red currants, whereas proanthocyanidins and phenolic acids are the predominant phenolic compounds in green and white currants.