Study on the inhibitory effect and mechanism of Monascus yellow pigments (ankaflavin and monascinon) on porcine pancreatic lipase

Pancreatic lipase inhibitors are promising agents for reducing dietary fat absorption and improving obesity-related complications. This study systematically investigated the inhibitory effects of two Monascus yellow pigments, ankaflavin (AK) and monascin (MS), on porcine pancreatic lipase (PPL) using enzyme kinetics, spectroscopy, and molecular docking approaches. Both AK and MS exhibited dose-dependent and reversible non-competitive inhibition, with IC 50 values of 50.2 ± 1.4 μM and 120.6 ± 1.8 μM, respectively. Fluorescence and circular dichroism (CD) analyses revealed that AK and MS binding induced conformational changes in PPL, as evidenced by an increase in α-helix content and altered micro-environment around tyrosine (Tyr) and tryptophan (Trp) residues. Notably, AK elicited more pronounced structural perturbations than MS. UV–visible spectroscopy confirmed the formation of intermolecular charge-transfer (CT) complexes upon the binding of AK and MS to PPL, verifying their direct interaction. Molecular docking and chemical modification identified key residues (Lys, Arg, Glu, and Tyr) that were essential for inhibitor binding. Furthermore, the combination of AK, MS, and Orlistat produced a synergistic inhibitory effect on PPL activity (combination index <0.57). These results establish AK and MS as potent natural PPL inhibitors and suggest that their anti-obesity potential stems from the structural modulation of PPL.