Differential Absorption of Components in Buckwheat Polyphenols via MKN28/Caco-2 Continuous Transport Model and Their Lipid-Lowering Effects

Polyphenolic compounds exhibit pronounced lipid-lowering effects, and their absorption in the human gastrointestinal tract varies considerably, which critically influences their bioavailability. Buckwheat, a natural food being rich in polyphenols, has been suggested to possess unique lipid-lowering potential.

This study aimed to investigate the differential absorption of buckwheat polyphenols using an MKN28/Caco-2 sequential transport model, and to systematically evaluate their lipid-lowering effects and underlying mechanisms through cellular assays and gut microbiota fermentation experiments.

Buckwheat polyphenol extract was characterized by ultra-high-performance liquid chromatography coupled with quadrupole Orbitrap mass spectrometry (UHPLC-Q-Orbitrap MS). Based on the MKN28/Caco-2 transport model, the extract was fractionated into readily absorbable and poorly absorbable components. The lipid-lowering effects of the absorbable fraction were assessed in adipocytes using Oil Red O staining and intracellular lipid quantification. In addition, the impact of the non-absorbable fraction on gut microbiota composition was evaluated in vitro fermentation.

Component analysis revealed that there are 23 kinds of polyphenolic compounds rutin and protocatechuic acid exhibited relatively high signal intensities. The absorbable fraction significantly reduced lipid accumulation in adipocytes, with triglyceride (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) levels in 3T3-L1 cells decreased by 17.8%, 28.6%, and 15.2%, respectively. Furthermore, in vitro fermentation demonstrated that the poorly absorbable fraction (BWP-AP) modulated gut microbiota composition by increasing the relative abundance of Bacteroides and Bifidobacterium, while decreasing Escherichia-Shigella and Alistipes.

Buckwheat polyphenol extract contained 23 identified phenolic compounds. The readily absorbable fraction exerted significant intracellular lipid-lowering effects, whereas the poorly absorbable fraction regulated metabolic homeostasis via modulation of gut microbiota. These findings revealed a dual-pathway mechanism involving direct host absorption and microbiota-mediated regulation, providing a theoretical basis for the development of functional foods based on buckwheat polyphenols.