Phenolic profile and antioxidant activity of Pistacia vera var. Sarakhs hull and kernel extracts: the influence of different solvents

Abstract

Iran is among the main exporters of pistachio (Pistacia vera L.). Thus, evaluation of phytochemical properties of this product is of crucial importance. In this study, effects of three types of solvents namely, polar protic solvents (i.e. ultrapure water, methanol and ethanol), polar aprotic solvents (i.e. acetone and ethyl acetate) and a non-polar solvent (i.e. hexane), on total phenolic compounds, total flavonoids, and total proanthocyanidins extractability as well as antioxidant activity (as evaluated by 2,2-diphenyl-1-picrylhydrazyl and ferric reducing antioxidant power assay) of P. vera var. Sarakhs hull and kernel, were investigated. High extraction yields were observed following utilization of less polar solvents (43.14 and 34.19% for hull and kernel, respectively). There were significant differences among solvents in terms of the amount of antioxidant compounds extracted. Ethanolic hull and kernel extract showed the maximum amounts of total phenols (113.21 and 169.53 mg of gallic acid equivalent per g of dried plant, respectively), total flavonoids (87.03 and 139.47 mg of quercetin equivalent per g of dried plant, respectively) and total proanthocyanidins (110.60 and 150.32 mg of catechin equivalents per g of dried plant, respectively) followed by methanol > ultrapure water > ethyl acetate > hexane. Assessment of antioxidant activity showed that the ethanol extract of hull and kernel had the least IC50 (3.04 and 6.8 µg/ml, respectively) and the greatest value when assessed by FRAP (8.80 and 5.59 mmol/g, respectively). The results suggested that P. vera var. Sarakhs hull and kernel extract can be regarded as a promising alternative for synthetic antioxidants.