Bioactive compounds in Cucurbita spp.: a critical review of functional properties, bioaccessibility, and applications in functional foods

Species of the genus Cucurbita have gained increasing attention because of their rich bioactive compounds and potential applications in functional foods. These matrices contain a wide range of phytochemicals, including carotenoids, phenolic compounds, fatty acids, and cucurbitacins, which have been associated with antioxidant, anti-inflammatory, hypoglycemic, antimicrobial, and antitumoral activities. However, the physiological benefits of these compounds depend largely on their bioaccessibility and bioavailability. This review provides an updated overview of studies published between 2021 and 2025 on the occurrence and biological activity of major bioactive compounds in Cucurbita spp. , examining how physicochemical properties, food matrix interactions, and processing conditions during gastrointestinal digestion influence their bioaccessibility and intestinal absorption. This study also critically evaluates the applicability of in vitro digestion models and Caco-2 cell systems for predicting intestinal absorption and transport. Current evidence highlights Cucurbita spp. as promising sources of functional compounds with well-documented biological activities. However, matrix-dependent and compound-specific factors constrain their bioaccessibility and bioavailability. Carotenoid bioaccessibility varies significantly with processing techniques and formulation, whereas cucurbitacins are further limited by low aqueous solubility and remain comparatively understudied. Processing conditions and matrix composition play a crucial role in determining compound release and absorption during digestion, with effects varying across compound classes. Emerging delivery systems, such as lipid-based carriers and nanoencapsulation strategies, have shown potential to enhance carotenoid bioaccessibility, but similar approaches for cucurbitacins remain limited. Overall, important knowledge gaps remain, particularly for cucurbitacins, highlighting the need for integrated research approaches that combine food science, digestion models, and clinical validation.