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Nuts are dry, single-seeded fruits with a combination of beneficial compounds that aid in disease prevention and treatment. The aims of this research are to evaluate the total antioxidant activity (AI) by ferric reducing antioxidant power (FRAP) assay, fatty acids by acid-catalyzed esterification method, and minerals by inductively coupled plasma optical emission (ICP-OE) spectrometer in hazelnuts, pistachios, and almond seeds and skins. Considering total AI, the results demonstrated that the highest activity was found in hazelnut and pistachio skin. The results considering minerals demonstrated that manganese, zinc, and iron levels are high in almond and hazelnut skins, copper is dominant in pistachio skin and hazelnut seed, and selenium is high in pistachio and almond skins and seed. Finally, the results showed palmitic acid is present in almond skin and pistachio seed, palmitoleic acid is high in almond and pistachio skins, and stearic acid is present in almond and hazelnut skins. Oleic acid was found in hazelnut seeds and their skin, linoleic acid in almond skin and pistachio seeds, and α-linolenic acid in almond and pistachio skins. In conclusion, hazelnut, pistachio, and almond skins are a great source of antioxidants, minerals, and healthy fatty acids, making them useful for nutraceutical development.

Nuts are dry, single-seeded fruits, with a combination of beneficial compounds that aid in disease prevention and treatment. This review aims to summarize the antioxidant components and the nutraceutical properties and applications of hazelnut, almond, and pistachio skins, as well as discuss their ability to prevent and treat specific diseases based on in vitro and in vivo studies. The search strategy included searching PubMed database and Google Scholar for relevant articles published in English. Research articles focusing on hazelnut, pistachio, and almond were included. The nut skin extracts were considered and other by-products were excluded from this search. Pistachio and almond skin hydroalcoholic extracts have antibacterial effects and decrease the risk of liver cancer by eliminating reactive oxygen species. Moreover, hazelnut skin can lower plasma against low-density lipoprotein-cholesterol, thus reducing the risk of colon cancer, and its polyphenolic extract can also decrease the formation of advanced glycation end products in vitro with multidimensional effects. Overall, hazelnut, pistachio, and almond skins are a great source of antioxidants, making them suitable for nutraceuticals’ development.