Polyphenolic content and biological properties of Avola almond (Prunus dulcis Mill. D.A. Webb) skin and its industrial byproducts

• Natural skin is a rich source of bioactive compounds.
• Twenty one derivatives of phenolic compounds were identified by RP-HPLC-DAD.
• The bioactive compounds shows high antimicrobial and antioxidant activities.

Almonds are cultivated around the world under very different growth conditions, and this leads to substantial differences in terms of nutritional and organoleptic properties between different cultivars. Although several studies are available on the polyphenolic content and bioactivity of Californian almonds, no information is currently available on the Avola almond and its main industrial by-products, blanched skin and blanch water. The industrial processes are currently not standardized, resulting in substantial fluctuations in the polyphenolic content of these byproducts. The aim of the present work was to characterize for the first time the phenol composition, antioxidant power, cytoprotective and anti-bacterial activity of the extracts of the main industrial byproducts of Avola almonds. Twenty-one flavanons, flavonols, flavan-3-ols and phenolic acids were identified by RP-HPLC-DAD analysis. Naringenin is the most abundant identified compound followed by kaempferol-3-O-rutinoside, kaempferol-3-O-glucoside, kaempferol and eriodictyol-7-O-glucoside. Natural skin was found to be the richest in all the classes of compounds analyzed and the highest in scavenging and cytoprotective activity. The extracts also showed antiperoxidative and anti-bacterial potential (mainly against Gram-negative bacteria). The results highlighted interesting and strong biological activities of the extracts under study, indicating how the industrial byproducts from Avola almonds may be used as a source of polyphenols for the cosmetic, pharmaceutical and food industries.

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