Phenolic compounds characterisation of peaches and nectarines

Natural products, commonly known as 'phytochemicals', are presently arousing great attention in the scientific community for their nutritional and dietetic value as antioxidant molecules. Fruits and vegetables are the principle sources of antioxidant compounds and, among these molecules, phenolic compounds are considered as the more active and powerful phytochemicals. Quality and quantity of phenolic compounds are both two relevant aspects to investigate in order to evaluate the potential antioxidant property of a specific fruit species. Information on peaches phenolics composition, specifically in relation to the large number of cultivars actually present on the market, is still incomplete. This research is therefore aimed to develop a suitable analytical methodology for the analysis of phenolic compounds of peaches and nectarines common on the Italian peach cultivars scenario. Yellow and white pulp peaches ('Redhaven' and 'Fidelia') and nectarines ('Stark Red Gold' and 'Silver Rome') were compared for their phenolic contents at harvest stage and the potential intake of these molecules was estimated for the different fruit tissues. Qualitative differences among skin and pulp tissues were detected. In details, specific chromatographic peaks were characteristic of skin samples only, therefore showing the presence of a certain number of tissue-specific phenolic compounds (quercetin derivatives and anthocyanins, for instance). As regarding the average total phenolics concentrations of the different analysed cultivars, values ranged from 3 to 4 mg/g DW (skin) and from 1 to 1.5 mg/g DW (pulp), with the relevant exception of nectarine 'Silver Rome' that showed clearly higher concentrations. Skin tissue concentrations were approximately 3 fold higher than pulp tissue concentrations, showing therefore the putative nutritional difference of a peach consumed after peeling or as a whole.