Extraction, purification, structural characterization, and hepatoprotective effect of the polysaccharide from purple sweet potato

Abstract BACKGROUND Purple sweet potato Ipomoea batatas (L.) has long been used as a medicine and a food. It contains various bioactive substances such as polysaccharides, anthocyanins, and flavonoids. Purple sweet potato polysaccharides are known to have anti‐oxidant, anti‐tumor, and immunomodulatory functions. Nevertheless, studies on the structural characterization of purple sweet potato polysaccharides and their ability to prevent non‐alcoholic fatty liver disease (NAFLD) have rarely been reported. RESULTS A novel polysaccharide (PSPP‐A) was extracted and isolated from purple sweet potato, and its structural characteristics and preventive effects on NAFLD were investigated. The results indicated that PSPP‐A was composed of l ‐rhamnose, d ‐arabinose, d ‐galactose, d ‐glucose, and d ‐glucuronic acid with molar ratios of 1.89:8.45:1.95:1.13:1. Its molecular weight was 2.63 × 10 3 kDa. Methylation and nuclear magnetic resonance (NMR) analysis indicated that the glycosidic linkages were →3)‐ α ‐L‐Ara f ‐(1→, α ‐L‐Ara f ‐(1→, →2,4)‐ α ‐L‐Rha p ‐(1→, 4‐O‐Me‐ β ‐D‐GlcA p ‐(1→, →4)‐ α ‐D‐Glc p ‐(1→, →4)‐ β ‐D‐Gal p ‐(1→, and →6)‐ β ‐D‐Gal p ‐(1→. Scanning electron microscopy (SEM) indicated that the structure of PSPP‐A was irregular. Subsequently, the protective effect of PSPP‐A on NAFLD was investigated. The results indicated that bodyweight, liver index, and triglyceride (TG), total cholesterol (TC), aspartate transaminase (AST), and alanine transaminase (ALT) content were significantly reduced by intervention of purple sweet potato polysaccharide‐A (PSPP‐A) compared with the ‐ high‐fat diet group. Liver histopathological analysis indicated that PSPP‐A attenuated irregular hepatocyte patterns and excessive lipid vacuoles. CONCLUSIONS The novel polysaccharide, PSPP‐A, mainly contains arabinose, which has certain preventive effects on NAFLD. This study provides a theoretical basis for further elucidating the hepatoprotective effect of purple sweet potatoes as a functional food. © 2022 Society of Chemical Industry.