Phytochemical profiling, antibacterial activity and valorization potential of Cucurbita maxima peel and seed waste

The present study evaluated the valorization potential of Cucurbita maxima (pumpkin) peel and seed waste through phytochemical profiling, oil extraction, GC–MS characterization, and antimicrobial activity. Qualitative phytochemical screening of extracts prepared using water, ethanol, and acetone confirmed the presence of several bioactive constituents, including alkaloids, phenolics, flavonoids, tannins, glycosides, and terpenoids, with tannins detected specifically in peel extracts. Antibacterial activity was evaluated using the Kirby–Bauer disk diffusion method against Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae. Peel extracts generally exhibited greater antibacterial activity than seed extracts, with the aqueous peel extract producing the highest inhibition zone of 16.0 ± 0.4 mm against P. aeruginosa, while inhibition zones across the tested bacterial strains ranged from 10.0 to 16.0 mm. Soxhlet extraction of seeds using n-hexane yielded 18% oil, indicating their potential for value-added applications. GC–MS analysis of the peel extract identified 91 phytocompounds, including 17 major constituents, predominantly belonging to triterpenoids, sterols, and isoprenoids. The major compounds included germanicol acetate (26.62%), 24-norursa-3,12-diene (14.63%), chondrillasterol (8.58%), and phytol (7.23%). Overall, the findings demonstrate that C. maxima peel and seed waste are valuable sources of bioactive compounds with measurable antibacterial activity and oil-recovery potential, supporting their sustainable valorization and agro-industrial utilization.