Separation and Identification of Phenolic Acids from Red Grape Seeds by HPLC

Abstract

Red grape seed extract (GSE) was examined for its phenolic acids content. Grape seed powder was defatted twice with hexane for 1h and the defatted residues were kept in methanol for 2h with gentle agitation then centrifuged at 5000rpm for 10 minutes, and the precipitates were extracted using 2M NaOH for 4h with gentle agitation, acidified with HCl to pH 2.2 and centrifuged at 5000 rpm for 10 minutes. The pooled supernatants were extracted with a mixture of diethyl ether and ethyl acetate (1:1 v/v) twice. The organic layer (upper layer) was extracted using a separating funnel. The pooled extracts were collected, the solvent was evaporated, and the extracted residues were dissolved in methanol: water (4:1 v/v) and subjected to analysis by high-performance liquid chromatography (HPLC). Ferulic and coumaric acids were abundant among other phenolic acids detected in GSE, as their concentrations reached 103.16±6.18 and 93.66±3.42 mg/100g dry weight (DW) respectively. Caffeic, gallic, hydroxybenzoic, and vanillic acids were also identified and quantified in GSE but were at relatively low concentrations of 0.05±0.01; 2.37±0.07; 1.19±0.03; and 1.96±0.04 mg/100g DW respectively. Moreover, chlorogenic and syringic acids were also identified in GSE however; they were not quantified. The results of the present study indicated that red grape seeds contain considerable concentrations of ferulic and coumaric acids. These findings support the postulation that grape seeds have a potential for application in the pharmaceuticals and functional food industry.