Antioxidant activity and phenolic profile of green walnut (Juglans regia L.) husks
2010
Atfa, T.
Walnut (Juglans regia L.) green husks were extracted with various solvents (water, ethanol, acetone and ethylacetate) and the respective extracts were evaluated for their total phenol content (TPC) and antioxidant activity using DPPHo, luminol induced chemiluminescence and FRAP assays. Lipid oxidation studies were additionally carried out using the Rancimat apparatus (110 deg C, 20L/h) and purified sunflower oil as oxidizing substrate.TPC was found to vary from 1.4 to 18.2 mg GAE (gallic acid equivalents) per mg of extract. Great differences in activity were observed among extracts as the antiradical activity (AAR) values using DPPHo were in the range 0.09-5.47 mg FAE (ferulic acid equivalents) per mg of extract; the IC50 values were determined using the luminol chemiluminescence assay in the range 0.001-0.25 micrograms of extract/ml and the FRAP values in the range 1.0-26.0. Under accelerated oxidation of purified and non purified sunflower oil, a rather poor activity (protection factor (PF) = 1.02-1.36) was evidenced. Among tested extracts, the one obtained with acetone had high TPC and radical scavenging activity. The phenols present in the extracts was found to contribute significantly to their radical scavenging activity as evidenced by the high correlation between the TPC and AAR (square r= 0.888) and TPC and IC50(square r= 0.925) values. Acid and alkaline hydrolyses also applied to walnut husks provided extracts with poor activity.
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