Extraction, Structural Characterization, and Lipid-Lowering Activity of Phyllanthus emblica Polysaccharides

This study aimed to elucidate the structural characteristics and lipid-lowering mechanism of Phyllanthus emblica polysaccharides, providing a theoretical basis for the development of natural functional foods with dyslipidemia-ameliorating effects for metabolic-associated fatty liver disease (MAFLD). The crude polysaccharides were isolated from Phyllanthus emblica by aqueous extraction followed by ethanol precipitation, and further purified on a C18YE reversed-phase cartridge followed by dialysis through a 3500 Da membrane. The resulting fraction exhibited an average molecular weight of 464 kDa and was composed predominantly of galactose (37.59%), galacturonic acid (27.13%) and glucose (18.18%). Fourier-transform infrared spectroscopy identified the typical functional groups of the Phyllanthus emblica polysaccharides were O—H (3384 cm^-1), C—H (2920 cm^-1), uronic C＝O (1737 cm^-1) and α/β-glycosidic linkages. Scanning electron microscopy revealed a folded lamellar morphology interwoven with filamentous networks and multi-strand aggregates, indicating a hierarchical supramolecular organization in Phyllanthus emblica polysaccharides. In vitro antioxidant assays revealed that the polysaccharides (5 mg/mL) scavenged ABTS radicals as effectively as vitamin C (P>0.05), indicating pronounced antioxidant activity, and inhibited pancreatic lipase by 76.00%. In the oleic acid/palmitic acid induced AML12 cell model, high dosage of 5 mg/mL polysaccharides lowered intracellular triglycerides significantly (P＜0.005). Mechanistically, it increased AMPK and PPARα expression to regulate lipid metabolism, and selectively activated the AMPK/PPARα signal pathway to enhance fatty acid oxidation, thereby exerting lipid-lowering effect. This study systematically characterized the structure of Phyllanthus emblica polysaccharides with potential lipid-lowering activity and demonstrated that it produced significant effects at both the in vitro and cellular levels by suppressing pancreatic lipase activity and activating the AMPK/PPARα pathway. This study aimed to provide a scientific basis for developing natural lipid-lowering functional foods based on Phyllanthus emblica polysaccharides.