Durian husk-mediated green synthesis of Cr 2 O 3 nanoparticles exhibiting uncompetitive inhibition of pancreatic lipase for anti-obesity applications

Abstract The global obesity epidemic underscores the urgent need for safer and more sustainable alternatives to conventional lipase inhibitors, which are limited by adverse side effects. In this study, chromium oxide nanoparticles (Cr 2 O 3 NPs) were synthesized via a microwave-assisted green route using durian ( Durio zibethinus or D. zibethinus ) husk extract (DHE), valorising agricultural waste as a natural reducing and stabilising agent. The nanoparticles were comprehensively characterised, confirming a rhombohedral eskolaite crystalline structure, quasi-spherical morphology with an average size of 65.93 ± 13.48 nm, and a bandgap energy of 3.32 eV. Functionally, the Cr 2 O 3 NPs exhibited strong antioxidant activity (91.94 % DPPH, 57.0 % ABTS) and significant pancreatic lipase inhibition (73.82 %). Kinetic analysis revealed an uncompetitive inhibition mechanism, representing the first report of durian husk-derived Cr 2 O 3 NPs with this enzymatic action. These findings highlight the dual antioxidant and enzymatic inhibitory potential of green-synthesised Cr 2 O 3 NPs and their promise as sustainable nanotherapeutics for obesity management within the framework of green nanomedicine and circular bioeconomy.