Chemical Composition and Antioxidant Properties of Peels of Five Pumpkin (Cucurbita sp.) Species

By-products from the fruit and vegetable processing industry represent a substantial source of bioactive compounds, which can be extracted and utilized in the development of functional foods or nutraceuticals, thereby contributing to sustainable nutrition and waste valorization. Pumpkin peels are particularly abundant in bioactive components and contain significant fiber, protein, and minerals such as calcium and magnesium. This study determined the chemical composition, the content of water- and fat-soluble vitamins, and the antioxidant activity of peels from five pumpkin species: <i>Cucurbita pepo</i> 'Kamo Kamo', <i>C. maxima</i> 'Bambino', <i>C. moschata</i> 'Butternut', <i>C. argyrosperma</i> 'Chinese Alphabet', and <i>C. ficifolia</i> 'Chilacayote Squash'. The highest moisture content was observed in the peels of <i>C. ficifolia</i> (89.2 mg 100 g⁻¹ WW). In contrast, the highest amounts of protein (14.82 mg 100 g⁻¹ DW), fat (1.59 mg 100 g⁻¹ DW), and ash (7.46 mg 100 g⁻¹ DW) were recorded in <i>C. maxima</i> peels. The peels of <i>C. moschata</i> contained the highest levels of total sugars (9.17 mg 100 g⁻¹ DW), reducing sugars (8.48 mg 100 g⁻¹ DW), and fiber (19.04 mg 100 g⁻¹ DW). The peels of all analyzed pumpkin species were rich in amino acids and water- and fat-soluble vitamins. The highest levels of polyphenols and flavonoids and the most potent antioxidant properties (DPPH and FRAP) were found in the extract from <i>C. argyrosperma</i> peels. The findings of this study highlight the potential of pumpkin peels as a valuable source of bioactive compounds.