Antioxidant activities of roselle (Hibiscus sabdariffa) calyces and fruit extracts

Antioxidant rich fractions were extracted from roselle (Hibiscus sabdariffa) calyces and fruits using ethyl acetate, acetone and methanol. The extracts were screened for antioxidant property using alpha, alpha-diphenyl-beta-picryl hydrazyl (DPPH) and beta-carotene-linoleate model systems. The ethyl acetate (EtOAc), acetone, methanol (MeOH) extracts of calyces and butylated hydroxyanisole (BHA) showed 89.4, 82.97, 91.4 and 91.1% antioxidant activity (AA) with DPPH and 82.6, 76.9, 85.4 and 91.4% using beta-carotene-linoleate model systems, respectively at 500 ppm. The methanolic extract of the calyces showed highest reducing power. However, the fruit extracts showed comparatively lower activities as compared to calyces extracts. Owing to higher AA of the extracts of calyces, these were selected to study their effect on lipid peroxidation. At 500 ppm, the ethyl acetate, acetone and methanol extracts of calyces showed 29.2, 34.1 and 48.6% inhibition of lipid peroxidation in rat liver homogenates using thiobarbituric acid (TBA) method. The studies can be further extended to exploit their possible application for the preservation of food products as well as health supplement and nutraceuticals.