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.