Valorization of lychee fruit peels waste for the sustainable production of value-added ingredient

Abstract Lychee (Litchi chinensis Sonn.) is an exotic fruit from Asia, recently introduced in Europe. With the increase in the world production of this fruit, many by-products are wasted during industrial processing, including their peels and seeds. Considering the utilization of fruit peels as edible material as a new functional ingredient, this work aimed to assess the nutritional and phytochemical characterization, as well as the antioxidant activity of two lychee peel extracts (alcoholic and hydroalcoholic). Also, it was evaluated the scavenging capacity against reactive species (O2•-, H2O2, NO•) of the two extracts. The peels, at a nutritional level, showed high levels of carbohydrates and total energy (76.8 ± 1.0 g/100 g and 331.4 kcal/100 g, respectively) and low protein and lipid content. Total phenolic and flavonoid contents were higher in alcoholic extraction (1578 mg GAE/g and 55.1 mg CE/g, respectively). The antioxidant activity evaluated in vitro by DPPH and FRAP assays was also higher in the ethanolic extract, verifying a positive correlation with the extractive yield of the bioactive compounds. In general, the ethanolic extracts of lychee peels showed higher antioxidant capacity and the maximum scavenging activity against reactive oxygen (O2-•) and nitrogen species (NO•). The hydrogen peroxide scavenging activity observed in ethanolic extract (64 µg/mL) was like the values obtained in the positive controls (quercetin and ascorbic acid, 62 µg/mL, and 46 µg/mL, respectively). These preliminary results suggest this undervalued ingredient is a promising source of bioactive compounds with high biological potential for the development of new products as functional ingredient, always focusing on sustainability.