Identification and quantification of phenolic compounds from pomegranate (Punica granatum L.) peel, mesocarp, aril and differently produced juices by HPLC-DAD-ESI/MS(n)

Abstract

Phenolic compounds were extracted from pomegranate (Punica granatum L.) peel, mesocarp and arils. Extracts and juices were characterised by HPLC-DAD-ESI/MS(n). In total, 48 compounds were detected, among which 9 anthocyanins, 2 gallotannins, 22 ellagitannins, 2 gallagyl esters, 4 hydroxybenzoic acids, 7 hydroxycinnamic acids and 1 dihydroflavonol were identified based on their UV spectra and fragmentation patterns in collision-induced dissociation experiments. To the best of our knowledge, cyanidin-pentoside-hexoside, valoneic acid bilactone, brevifolin carboxylic acid, vanillic acid 4-glucoside and dihydrokaempferol-hexoside are reported for the first time in pomegranate fruits. Furthermore, punicalagin and pedunculagin I were isolated by preparative HPLC and used for quantification purposes. The ellagitannins were found to be the predominant phenolics in all samples investigated, among them punicalagin ranging from 11 to 20g per kilogram dry matter of mesocarp and peel as well as 4-565mg/L in the juices. The isolated compounds, extracts and juices were also assessed by the TEAC, FRAP and Folin-Ciocalteu assays revealing high correlation (R(2)=0.9995) of the TEAC and FRAP values, but also with total phenolic contents as determined by the Folin-Ciocalteu assay and by HPLC. Selection of raw materials, i.e. co-extraction of arils and peel, and pressure, respectively, markedly affected the profiles and contents of phenolics in the pomegranate juices, underlining the necessity to optimise these parameters for obtaining products with well-defined functional properties.