Identification of antioxidant components and fatty acid profiles of the leaves and fruits from Averrhoa carambola

The antioxidant compounds of leaves and fruits from Averrhoa carambola were extracted with acetone:water (7:3, v/v) and distilled water. The acetone:water extracts (AWE) were separated into five different subfractions, three obtained by liquid–liquid extraction using n-hexane (HF), ethyl acetate (EAF) and water (WF), and the other two obtained by further fractionation of the WF on a Sephadex LH-20 column (WS1 and WS2). The antioxidant activities, total phenolics and total flavonoids of these extracts and fractions were investigated. Results showed that all the extracts and fractions possessed potent antioxidant activities, as measured by DPPH, ABTS and FRAP methods, with the strongest for WS2 fractions accompanied with the highest total phenolics and total flavonoids. Reversed-phase HPLC, normal-phase HPLC, MALDI-TOF-MS and ¹³C NMR analyses identified that the main antioxidant components present in WS2 fractions were essentially of procyanidin-type proanthocyanidins, consisting mainly of epicatechin units linked by B-type interflavan bonds. In addition, GC–MS analysis revealed that the most abundant fatty acids were α-linolenic acid (62.04 ± 1.65%) for leaves and oleic acid (55.44 ± 1.37%) for fruits. The amount of total unsaturated fatty acids in leaves and fruits comprised more than 77% of total fatty acid.