Phytochemical and nutritional analysis of Plukenetia corniculata Sm. leaves for functional food development and biological activity assessment

Plukenetia corniculata Sm. (Euphorbiaceae), an underutilized leafy vegetable traditionally consumed across South and Southeast Asia, remains scientifically understudied despite its widespread ethnobotanical relevance. This study provides a comprehensive assessment of its phytochemical composition, nutritional profile, heavy metal accumulation, biological activities, and amino acid content using standardized protocols. Qualitative screening of methanolic, ethanolic, and aqueous leaf extracts revealed the presence of alkaloids, flavonoids, terpenoids, phenols, tannins, saponins, proteins, steroids, glycosides, carbohydrates, coumarins, and amino acids. Quantitative analysis indicated that the methanolic extract contained the highest levels of total phenols (80.14 mg GAE/g), flavonoids (56.27 mg QE/g), tannins (184.93 mg TAE/g), and saponins (58.78 mg DE/g). Proximate composition analysis showed substantial moisture (70.77%), fiber (6.17%), and crude fat (7.03%) contents, along with appreciable carbohydrate and protein levels. Heavy metal concentrations, including Zn, Mn, Fe, Cu, Cr, Cd, and Pb, were all below the FAO/WHO permissible limits, confirming their safety for consumption. The methanolic extract exhibited strong antioxidant activity (DPPH IC₅₀: 59.52 µg/mL; TAC: 180.60 mg AAE/g), moderate cytotoxicity (LC₅₀: 75.76 µg/mL), and notable protein denaturation inhibitory activity (47.80% inhibition). The ethanolic extract showed the strongest α-amylase inhibitory activity (IC₅₀: 148.24 µg/mL). HPLC-based amino acid profiling identified 13 amino acids, including six essential amino acids, with histidine being the most abundant (5.05 mg/g). Collectively, these findings demonstrate that P. corniculata leaves are nutrient-dense and phytochemical-rich with multiple in vitro bioactivity-related responses, supporting their potential as a functional food resource and a natural source of bioactive constituents. Further investigations focusing on the isolation of bioactive constituents and in vivo validation of their biological efficacy are warranted.