Screening for Bioactive Compound Rich Pomegranate Peel Extracts and Their Antimicrobial Activities : Extraction methods for increased antibacterial and antifungal properties

Abstract

In this work, seven different extracts from pomegranate (Punica granatum L., cv. Hicaz nar) peel were prepared by using different solvents (ethanol, methanol, either alone or in combination with acid, acetone and water). The phenolics (punicalagins and ellagic acid), organic acids (citric acid and malic acid) and sugars of pomegranate peel extracts (PPEs) were determined. The highest amounts of punicalagins and ellagic acid were detected by ethanol-acid extract as 13.86% and 17.19% w/v respectively, whereas the lowest levels were obtained with acetone and water extracts. Moreover, the methanol-acid (3.19% malic acid) and ethanol-acid (1.13% citric acid) extracts contained the highest levels of organic acids. The antimicrobial activities of extracts were investigated by agar well diffusion method. Methanol-acid and ethanol-acid extracts exhibited the highest antimicrobial effects on all tested microorganisms, giving inhibition zones ranging in size from 17 mm to 36 mm. Although similar antimicrobial activities were observed by ethanol, methanol and acetone extracts (up to 24 mm), the lowest antimicrobial activities were attained by water extract (0‐15 mm). All extracts were generally more effective against Gram-positive bacteria: Enterococcus faecalis, Bacillus subtilis, Bacillus cereus than Gram-negative ones: Escherichia coli and Enterobacter aerogenes (Klebsiella aerogenes). It was shown that extracts from pomegranate peels represent a good source of bioactive compounds.