Mechanistic investigation of carotenoid effects on lipid digestion-related processes: Pancreatic lipase inhibition and bile salt-mediated emulsion destabilization.

Modulation of lipid digestion by food-derived compounds has attracted increasing interest. This study explored the effects of four common carotenoids (lutein, zeaxanthin, lycopene, and β-carotene) on lipid digestion using simplified in vitro model systems from biochemical and interfacial perspectives. Lutein showed noncompetitive inhibition of pancreatic lipase, whereas zeaxanthin, lycopene, and β-carotene exhibited mixed-type inhibition. Spectroscopy and molecular simulation showed that these carotenoids can directly interact with pancreatic lipase, altering its structure and reducing activity. At the oil-water interface, the presence of carotenoids significantly decreased the release of free fatty acids, destabilized bile salt-stabilized emulsions, increased interfacial tension, and reduced emulsion viscosity, phenomena largely arising from interactions between carotenoids and bile salts. Isothermal titration calorimetry combined with oil-water interface dynamics simulation revealed carotenoids binding to bile salts, with lutein and zeaxanthin displaying stronger affinities than lycopene and β-carotene. These findings indicate that carotenoids may modulate lipid digestion through two possible mechanisms.