Studies On The Extraction, Characterization, And Anti-Diabetic Effects Of Mycelia Polysaccharides From Pleurotus Djamor

The diabetes mellitus(DM), a globally multi-factorial endocrine metabolic disease, usually characterized by hyperglycemia resulting from defects of insulin secretion, can lead to the imbalance of acid-base and impaired metabolism in carbohydrate, lipid and protein. It is usually accompanied by many complications such as diabetic nephropathy(DN), diabetic hepatopathy(DH), and diabetic-pancreatic diseases(DPD), resulting the high raise of disabling and fatality. Clinically, the therapies for DM mainly include the use of insulin and oral hypoglycemia agents, however, these approaches can also induce negative effects in the long-term use. Therefore, it is vital to seek the natural and non-toxic anti-diabetic medicines for diabetic therapy.The Pleurotus djamor, a common edible, medicinal, and visual mushroom, belongs to the kingdom of Fungi, phylum of Basidimycota, subphylum of Agaricomycotina, class of Agaricomycets, subclass of Agaricomycetidea, order of Agaricales, family of Pleurotaceae, and genus of Pleurotus. Up till now, scare papers about the anti-diabetic effects of mycelia polysaccharides(MPS) by P. djamor had been published.In the present study, the liquid fermentation of P. djamor was processed to yield the mycelia. The extraction conditions of three MPS including acidic-extractable MPS(Ac-MPS), alkalic-extractable MPS(Al-MPS) and enzymatic-extractable MPS(En-MPS) were determined by single-factor test(SFT) and response surface methodology(RSM). Furthermore, the characterization and anti-diabetic activities of these three MPS were analyzed. These results demonstrated that Ac-, Al-, and En-MPS possessed potent antioxidant activities, and could be used as a potentially functional food for the prevention of diabetes and its complications. The present conclusions were listed as follows.(1) Extraction conditions for Ac-, Al-, and En-MPS were optimized by SFT and RSM. The results showed that(a) the optimum conditions of Ac-MPS extraction were water multiples of 37.25, extracting time of 42.95 min, concentration of HCl of 0.20 M, and extraction temperature of 83.98 oC, and the Ac-MPS yield reached 1.97%,(b) the optimum conditions of Al-MPS were water multiples of 41.56, extracting time of 88.91 min, concentration of Na OH of 0.36 M, and extraction temperature of 74.90 oC, and the Al-MPS yield reached 2.36%, and(c) the optimum conditions of En-MPS were p H of 7.36, water multiples of 56.78, extraction time of 44.77 min, and extraction temperature of 35.36 oC, and the En-MPS yield reached 3.61%. The analysis of ANOVA, desirability, adequacy, and outlier showed that all the models can be applied to optimize the extraction parameters for the extraction of Ac-, Al- and En-MPS.(2) The characterizations of MPS were investigated by gas chromatography(GC), Fourier transform infrared spectroscopy(FT-IR), and high performance liquid chromatography(HPLC). The GC results displayed that both Ac-MPS and En-MPS were composed of arabinose, galactose and glucose showing the difference in monosaccharide and contents, Al-MPS contained arabinose, galactose and glucose, and En-MPS contained rhamnose, glucose, xylose, mannose and galactose. The HPLC analysis showed that the weight-average molecular weights(Mw), the number average molecular weights(Mn), and Z-average molecular weights(Mz) of Ac-MPS were 2.33×104, 1.68×104, and 3.14×104Da, with the dispersion coefficient(d) of 1.39, the Mw, Mn, and Mz of Al-MPS were 5.26×104, 3.47×104, and 7.16×104Da, with d of 1.52, and the Mw, Mn, and Mz of En-MPS were 1.97×104, 1.56×104, and 2.93×104, with d of 1.26, respectively, indicating the En-MPS were in superior homogeneous. The FT-IR results showed that the Ac-MPS was α-glycosidic bond connection furanose, Al-MPS was β-glycosidic bond connection furanose, and En-MPS was β-pyranose glycosidic bond connection.(3) The effects of Ac-, Al-, and En-MPS against oxidative stress. The results showed that Ac-, Al-, and En-MPS had potential effects against oxidative stress by increasing the activities of superoxide dismutase(SOD), glutathione peroxidase(GSH-Px), catalase(CAT) and the total antioxidant capacity(T-AOC) activity, and decreasing the contents of lipid peroxide(LPO) and malondialdehyde(MDA) in streptozotocin(STZ) induced diabetic mice, respectively. Furthermore, compared with Ac-MPS and Al-MPS, the En-MPS had superior anti-diabetic effects.(4) The recovery effects of Ac-, Al-, and En-MPS on lipid metabolism. The results showed that Ac-, Al- and En-MPS had significant effects against the elevation of triglycerides(TG), total cholesterol(TC), low-density lipoprotein cholesterol(LDL-C), very low density lipoprotein cholesterol(VLDL-C) and atherosclerosis index(AI), and the reduction of high-density lipoprotein cholesterol(HDL-C), indicating that the MPS can improve the disordered lipid metabolism in STZ induced diabetic mice.(5) The recovery effects of MPS on organs. The results showed that Ac-, Al-, and En-MPS had significant activities in reducing the activities of alanine transaminase(ALT) and aspertate aminotransferase(AST), and levels of blood urea nitrogen(BUN) and creatinine(CRE). Furthermore, the histopathological observations of liver, kidney and pancreas indicated that MPS could attenuate the organ damage induced by hyperglycemia. The En-MPS showed superior recovery effects than Ac-MPS and Al-MPS, demonstrating that En-MPS had the protective effects on liver, kidney, and pancreas against hyperglycemia. And the enhancing recovery abilities may considered as the possible mechanisms in curing the DM.The present conclusions showed that the MPS extracted from P. djamor had clinical effects in curing the STZ-induced DM by improving the glucose and lipid metabolism, and reducing the damage of oxidative stress, indicating that MPS had broad market prospect in developing functional foods due to its relaxative properties and non-toxic effects.