Intercontinental variability in the polyphenolic profile and total antioxidant capacity of pomegranate peel

Pomegranate (Punica granatum Linn.) is one of the natural products with high antioxidant properties. Previous studies suggested that pomegranate peel (PGP) exhibited greater antioxidant capacity compared to the other pomegranate parts, including the juice, pulp, arils and seeds [1]. In this study, we aimed to elucidate the intercontinental variability in the polyphenolic phytochemical profiles and anti-oxidative potentials of pomegranate peel. We measured the differences in the total polyphenolic content, as well as individual phytochemical compositions. The anti-oxidative potentials of pomegranate peel were assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Ferric Reducing Antioxidant Power (FRAP) assay. Our results demonstrated that the methanolic extracts of pomegranate peel from China origin (n=5, PGPChina) contained a greater polyphenolic content (˜1.5-fold; P<0.05) compared to USA (n=5, PGPUSA) and Australia (n=5, PGPAUS). By using HPLC-HESI-MS and HPLC-DAD, punicalagin and ellagic acid were identified as the two principle phenolic constituents in pomegranate peel. Our analyses showed that the chemical contents of all identified phenolic compounds from pomegranate peel extract were significantly higher in the samples from China than from USA and Australia (P<0.05). Likewise, the total anti-oxidative capacity of pomegranate peel as measured by DPPH and FRAP assays was found to be 2 to 5-fold higher (P<0.05) in samples from China than samples from USA and Australia. Therefore, the pomegranate peel from China may have greater therapeutic potential than that from USA and Australia due to the higher polyphenolic content and total anti-oxidative capacity.