Marigold flavonoids coordinate emulsion stabilization, epithelial transport and gut microbiota modulation to enhance intestinal lutein absorption

BACKGROUND: Flavonoids naturally coexisting with lutein in marigold (Tagetes erecta L.) extracts have been suggested to influence carotenoid bioavailability; however, their coordinated roles in intestinal lutein absorption remain insufficiently understood. This study systematically explored the synergistic effects of six major marigold flavonoids on lutein absorption via a multilevel strategy integrating emulsion behavior, intestinal epithelial transport and gut microbiota modulation. RESULTS: In vitro, flavonoids stabilized lutein-containing mixed emulsion, reduced particle size, increased ζ-potential and enhanced bioaccessibility. In Caco-2 cells, they promoted lutein uptake and trans-epithelial transport, upregulated key transporters (SR-BI, CD36, NPC1L1) and reinforced tight junction integrity. In vivo, their co-administration increased lutein accumulation in eyes, liver and intestinal tissues, enhanced carotenoid cleavage enzyme activities, and reshaped gut microbiota and short-chain fatty acid production. CONCLUSION: Marigold flavonoids facilitate intestinal lutein absorption via multiple pathways, improving the in vivo bioavailability of lutein. This study clarifies the synergistic interaction between marigold flavonoids and lutein, providing a theoretical basis for the rational application of marigold-derived flavonoids and carotenoids in functional food development.