Changes in total phenolic and monomeric anthocyanin composition and antioxidant activity of three varieties of sorrel (Hibiscus sabdariffa) during maturity

Three varieties of sorrel (Hibiscus sabdariffa) were analyzed for total phenolic, monomeric anthocyanins and antioxidant activity at five stages of maturity. The varieties designated traditional red (TRED), early bearing red (ERED) and white (WHTE) were sampled at the pre-flowering stage, as well as 3 days, 7 days, 21 days and 35 days after flowering. The total phenolic composition ranged from 5 to 24 mg/g and, while found in all varieties, was highest for TRED and ERED. Anthocyanins were only observed in the red varieties and ranged from 0.5 to 3.5 mg/g. The levels of both total phenolics and monomeric anthocyanins fluctuated, initially declining then increasing with maturation. The three sorrel varieties exhibited antioxidant activity, inhibiting lipid peroxidation between 69 and 79%. Increasing maturity at harvest tended to increase antioxidant activity for all varieties. A linear relationship existed between antioxidant activity and stage of maturity (r = 0.59). This research has implications for the sorrel industry as the antioxidant phytonutrients of sorrel could add value to sorrel currently produced and consumed.