Standardization of the conditions for extraction of polyphenols from pomegranate peel

Pomegranate (Punica granatum) peel possess higher antioxidant activity than the edible portion. Efforts were made to extract dry peel powder at room temperature (28-30 °C) using combination of water and ethanol (EtOH, a green combination) and standardize the factors that may affect the extraction efficiency. The storage stability of the extract has been studied for >100 days at room temperature (28-30 °C), 4, 0 and -80 °C. The extract quality was monitored by measuring the radical scavenging activity (RSA) by diphenyl picrylhydrazyl (DPPH) method, total polyphenol content and by estimating the contents of punicalagins and ellagic acid, the two major ellagitannins present in the peel. The standardized conditions for extraction were found to be; Water and EtOH in 1:1 (v/v) ratio, duration of 24-48 h, ratio of 1:10 for solid to solvent and particle size in the range of 100-400 μ. Consecutive extraction of the peel powder did neither improve the yield nor polyphenol content, hence single extraction was adopted. The extract stored at room temperature for 110 days resulted in 13.2 % loss of polyphenol content followed by 8.9, 2.8, 27.5 and 14.1 % loss in Punicalgin A, B, Ellagic acid and RSA content, respectively.