Antioxidative Capacities of Phytochemicals in Selected Fruit Peels

Abstract

Fruit by-products in the form of peels are generally considered as wastes but they may contain significant amounts of antioxidants which can serve as basis for the alternative uses. The peels of a total of 36 kinds of fruits were subjected to rapid screening for their antioxidative capacities using a revised version of the thiocyanate method. From the results of the rapid screening, the 10 best performing kinds of fruits were selected for further assay of their peels using different extraction solvents (methanol or diethyl ether) and different peel conditions (fresh or dry). The antioxidative capacities are expressed in terms of the Oxidation Protection Efficiency (OPE). The extracts with methanol showed superior OPEs, in general, compared to those with ether indicating the dominant chemical nature of the antioxidants. Drying, on the other hand, generally led to decreases in the OPEs. Topping the list with their very high OPEs are: Garcinia mangostana (mangosteen), Nephelium lappaceum (rambutan), Diospyros blancoi (mabolo), Mangifera indica (mango), and Ananas comosus (pineapple). Their OPEs ranged from almost 100% down to 80%.