Non-alcoholic fatty liver disease is associated with gut microbiota, oxidative stress, and inflammation. We aimed to investigate the possible mechanism by which noni fruit polysaccharide (NFP) improved hepatic oxidative stress and inflammation in rats under a high-fat diet (HFD) by modulating short-chain fatty acids (SCFAs), the intestinal barrier, and gut microbiota. Hepatic oxidative stress, inflammation, and gut dysbiosis in rats were induced through HFD feeding for 4 weeks, followed by intervention with NFP treatment (100 mg per kg bw) for 5 weeks. The results showed that NFP reduced body weight gain and improved lipid metabolism, hepatic oxidative stress, and inflammation in rats under a HFD. Aside from these beneficial effects, NFP positively affected the SCFA production and reversed the HFD-induced gut dysbiosis as indicated by improved microbiota diversity and composition. The levels of Lactobacillus, Ruminococcaceae_UCG_014, Parasutterella, [Eubacterium]_coprostanoligenes_group, and Ruminococcus_1 improved, whereas the levels of Prevotella_9, Collinsella, Bacteroides, and Turicibacter decreased. Furthermore, NFP maintained the colonic barrier integrity (increased the mRNA relative expression of CCL5, ZO-1, and occludin in the colon, and decreased the serum CCL5 level), and decreased the serum lipopolysaccharide level. Thus, NFP may modulate the gut microflora and SCFA production and reduce the permeability of the colonic barrier and metabolic endotoxemia, thereby alleviating hepatic oxidative stress and inflammation in rats under a HFD.
Iridoid glycosides (IGs) are secondary metabolites found in plants such as the noni plant ( Morinda citrifolia L.), known for their diverse biological activities and potential health benefits. Herein, we screened fifteen natural deep eutectic solvents (NADES) and two conventional solvents (CS, 70% (V/V) methanol and 70% (V/V) ethanol) for extraction of IGs from noni fruit pomace. Our findings indicate that non-acidic NADES promote IG extraction. Glycerol/glycine combined with β-cyclodextrin was selected, and a molecular simulation was performed to elucidate the interaction between NADES components and IGs. Further, the structure-activity relationship and interaction mechanisms of IGs with α-glucosidase were investigated using multispectral and molecular docking tools. The results demonstrated that deacetylation of the B-ring's C-10 improved the inhibitory potential of IGs. Deacetylation produces hydrophobic contacts, which enhance the inhibitory effect of deacetylasperulosidic acid on α-glucosides. Additionally, hydrogen bonds and van der Waals forces drive the formation of non-covalent complexes between IGs and enzymes.