Nutraceutical properties and health-promoting biological activities of fruits of watermelon cultivars with different origins

This study was focused on biologically active compounds extracted from pulp and rind of watermelon fruits (Citrullus lanatus (Thunb.) Matsum. & Nakai, 1916) cultivars with different origins (Italy, Costa Rica, Brazil, Ecuador and Santana-Romania). Total polyphenols and flavonoids, lycopene and L-citrulline, were extracted from the pulp and their content determined spectrophotometrically. L-citrulline was also measured in the rind. In addition, the determination of some biological activities (antioxidant activity and inhibition of the amylase and lipase enzymes) of watermelon pulp was carried out. The examined pulp of the watermelon cultivars revealed to have a high content of antioxidants (e.g., lycopene up to 39.68 ± 0.13 μg/g FW in an Italian cultivar) and bioactive molecules (e.g., L-citrulline up to 0.87 mg/g FW in the Ecuadorian cultivar). Watermelon rind had higher contents of L-citrulline (up to 2.60 mg/g FW) compared to pulp. The comparisons between watermelons cultivars revealed the significant inhibitory of lipase (values ranging from 117.10 to 312.12 IC50) and α-amylase (values ranging from 145.52 to 322.13 IC50), so confirming their health-promoting potential. All these factors taken together make watermelon a high-value food with evident benefits on human health. The results of this study could facilitate the discovery, improvement and utilization of new watermelon cultivars with high nutraceutical properties.