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

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 × 103 kDa. Methylation and nuclear magnetic resonance (NMR) analysis indicated that the glycosidic linkages were →3)-α-L-Araf-(1→, α-L-Araf-(1→, →2,4)-α-L-Rhap-(1→, 4-O-Me-ß-D-GlcAp-(1→, →4)-α-D-Glcp-(1→, →4)-ß-D-Galp-(1→, and →6)-ß-D-Galp-(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.

Effects of salinity on the synthesis of 3-methylthiopropanol, 2-phenylethanol, and isoamyl acetate in Zygosaccharomyces rouxii and Z. rouxii 3-2.

Zygosaccharomyces rouxii referred as Yeast S is an important microorganism widely applied in traditional fermented food to accelerate flavor formation. Z. rouxii 3-2 referred as Yeast S 3-2 constructed previously is a new strain having higher salt tolerance than wild type. In this study, salt stress response of synthesis key flavor metabolites 3-methylthiopropanol, 2-phenylethyl alcohol, and isoamyl acetate in Yeast S and S 3-2 were investigated based on SPME-GC-MS and RT-qPCR. Analysis of GC-MS data showed that high salinity led to increase the contents of 3-methylthiopropanol and 2-phenylethyl alcohol both in Yeast S and Yeast S 3-2, while inhibited the synthesis of isoamyl acetate, and the induced effect on Yeast S 3-2 was more pronounced than Yeast S. Furthermore, the RT-qPCR results revealed that the salinity could enhance the genes expression of ARO10 and PDC1, and stronger effect on Yeast S 3-2 than S. However, the gene expression of AFT1 was reduced in high-salt culture conditions, which was consistent with the results of GC-MS data. The results presented in this study can provide theoretical support of Z. rouxii 3-2 application during food fermentation.

The impact of a novel Chinese yam-derived polysaccharide on blood glucose control in HFD and STZ-induced diabetic C57BL/6 mice.

Chinese yam, as a kind of traditional "medicine and food homologous food" in Asia, could assistance to digestion, nourish the lungs and relieve cough. Some research also suggested that Chinese yam could prevention of hyperglycemia, but the specific mechanism of action was not clear. In this paper, an acidic polysaccharide (CYPB) was isolated from Chinese yam with the molecular weight of 1.55 × 102 kDa. The determination of the monosaccharide composition of CYPB with ion chromatography showed that CYPB was composed of rhamnose, glucose, arabinose, galactose, glucose, xylose and glucuronic acid with the ratio of 6 : 3.73 : 7.31 : 10.95 : 4.56 : 1. The structural analysis indicated that the CYPB contain 1 → 3, 1 → 4, 1 → 2, 1 → 6 and 1 → 3, 6 glycoside bonds. The experimental results of diabetic mice model induced by high-fat diet (HFD) and streptozocin (STZ) indicated that CYPB could improve clinical symptoms and alleviate the glucose tolerance damage symptoms effectively. The underlying mechanism of regulate blood glucose of CYPB may be related to improve the ability of synthesize glycogen, insulin resistance and reduce gluconeogenesis by regulating the expression of InsR, PI3K, Akt and FoxO3, GLUT4 proteins in PI3K/Akt signaling pathway in T2DM mice.

Protective effect and mechanism of docosahexaenoic acid on the cognitive function in female APP/PS1 mice.

Docosahexaenoic acid (DHA) has been studied for many years owing to its protective effect on the decline in brain function. DHA intake reduces the risk of Alzheimer's disease (AD) and decreases amyloid deposition; however, the underlying molecular mechanism has not been completed elucidated. In this study, the effect of DHA on the cognitive function of amyloid precursor protein (APP)/PS1 in wild-type mice and its related mechanism were investigated. Results from the Morris water maze test showed that DHA improved learning and memory function in mice. Moreover, DHA reduced neuronal damage in mice brains, as determined using Nissl staining. Unsaturated fatty acid levels in the brain of mice increased (p < 0.01) after DHA administration and saturated fatty acid levels decreased (p < 0.01). The deposition of amyloid-beta (Aß) plaques and tau protein neurofibrillary tangles was significantly inhibited. The mechanism of action of DHA was attributed to the upregulation of the expression of ß-secretase (BACE)2, which competed with BACE1 to cleave APP, thus decreasing the production of extracellular Aß fragments (p < 0.01). The expression level of insulin-degrading enzyme was not significantly different. The expression of N-methyl-D-aspartate receptors was further downregulated and the phosphorylation of glycogen synthase kinase-3ß and tau protein was inhibited (p < 0.01). These data indicated that DHA could protect cognitive function in mice by reducing Aß plaque formation and decreasing tau phosphorylation levels.