Nghiên cứu tách, tinh chế và thủy phân glucomannan từ cây amorphophallus konjac k koch ở lâm đồng và định hướng ứng dụng hạ đường huyết tt tiếng anh

MINISTRY OF EDUCATION VIETNAM ACADEMY OF AND TRAINING SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY Tran Thi Nu STUDIES ON EXTRACTION, PURIFICATION AND HYDROLYSIS OF GLUCOMANNAN FROM MORPHOPHALLUS KONJAC K.KOCH IN LAM DONG, VIETNAM AND ITS ANTI-DIABETIC ACTIVITIES Major: Organic chemistry Code: 9.44.01.14 SUMMARY OF CHEMISTRY DOTORAL THESIS Hanoi – 2020 This thesis was completed at: Graduate University of Science and Technology, Vietnam Academy of Science and Technology Advisor 1:Prof Dr Do Truong Thien Advisor 2: Dr Tran Thi Y Nhi 1st Reviewer: … 2st Reviewer: … 3st Reviewer: … This thesis will be defended at Graduate University of Science and Technology, Vietnam Academy of Science and Technology at .hour date month 2020 The thesis can be found in: - The Library of Graduate University of Science and Technology, Vietnam Academy of Science and Technology - Vietnam National Library INTRODUCTION The urgency of the thesis Glucomannan, a water soluble polysaccharide, is composed of a linear chain of β-1,4-linked D-glucose and Dmannose residues in a molar ratio of 1:1.6, with side branches through β-1,6-glucosyl units The acetyl groups along the glucomannan backbone are located, on average, every 9–19 sugar units at the C-6 position Glucomannan is a low-calorie dietary fiber that has been used as diatary food for dieters to lose weight, reduce blood cholesterol and postprandial glucose response In addition, glucomannan is one of the most viscous dietary fibres known which has been used in various fields such as food thickener, elastic gels, films Glucomannan is extracted from the tubers of some Amorphophallus species In some subtropical Asia countries such as China and Japan Thai Lan, A konjac is regarded as an agronomically important crop which has great potential in both domestic and international markets Glucomannan is found in many different Amorphophallus species which has different structure and properties in each species Amorphophallus konjac K Koch (Amorphophalus konjac K Koch) is a species with high content of glucomannan that become a industrial key crop in some East Asian and Southeast Asian countries such as China, Japan and Thailand There are more than 25 Amorphophallus species in Vietnam which distributed in different regions of the country Amorphophallus konjac K Koch was recently discovered in 2012 in some northern mountainous provinces Despite its hydrophilicity, glucomannan is poorly soluble in water (solubility of around 30%) due to its high molecular weight 1.9  106÷2  106Da, which limits its application range in certain areas [3] In order to increase its solubility, glucomannan is hydrolyzed to lower molecular weigh and the process attracts the attention of many scientists In addition to the general properties of glucomannan (KGM), hydrolyzed glucomannan (LMWG) also has many biological activities such as probiotics, antioxidants, immune regulators, etc Hydrolyzed glucomannan is also used as drug delivery carriers With the potential application in food and pharmaceuticals, studies on the methods of preparing low molecular weight glucomannan have been of interest to many authors worldwide, including enzymatic hydrolysis [13]–[23], combination of -irradiation and β-mannanase [24] hydrochloric acid [14][25], hydrochloric acid combined with ultrasound [26] treatment with -irradiation combined with ethanol [8], alkaline hydrolysis combined with heat [28] However, the abovementioned studies in the world have almost focused on methods of low molecular weight glucomannan preparation Studies on properties, chemical structure, and the relationship between their structure and biological activity have not paid enough attention Especially, the ability to reduce blood sugar absorption when using low molecular weight and mechanism has not been studied Such studies are hardly ever been investigated in Vietnam In order to contribute a new fundamental research on glucomannan originating in Vietnam and to improve the value of glucomannan for pharmaceutical and functional food products, we have chosen the Doctor thesis entitled “Studies on extraction, purification and hydrolysis of glucomannan from Amorphophallus konjac K.Koch in Lam Dong, Vietnam and its anti-diabetic activities” The objectives of the thesis - Extraction, chemical charaterization of glucomannan from the tubers of Amorphophallus Konjac K.Koch in Lam Dong, Vietnam - Parameter optimization for glucomannan hydrolysis reaction to make different types of low molecular weight glucomannan by different methods - Evaluate the hypoglycemic activity and hypoglycemic mechanism of hydrolyzate products The main content of the dotoral thesis * Study on main chemical constituents of tuber from A.Konjac K.Koch Physico-chemical charaterization of glucomannan: chemical constituents, manose/glucose ratio, molecuar weight by IR, NMR, TGA, … * Hydolysis parameter optimization, physico-chemical characterization of low molecular weight gluocomannan * AMPK activation by low molecular weihgt glucomannan in vitro and Oral Glucose Tolerance Test New finding of the thesis Fully investigation on the main composition of tuber of A.konjac planted in Lam Dong province, glucomannan extraction and purification process, physico-chemical characterization of glucomannan The hydrolysis parameters were optimized by response surface methodology, using β-1,4-mannanase from Bacillus sp as catalysis A three level, four variable Box-Behnken factorial designs (BBD) was applied to determine the best combination for viscosity The optimal conditions were pH at 7.24, temperature at 42.4oC, and incubation time at 5.7 h, substrate concentration at 0.54% Under optimized conditions, predicted Y was 57.5 mpa.s and experimentally value Y was 60.85 mpa.s The hydrolysis product (LMWG-E) consisting of beta-(1  4)linked D-glucose (G) and D-mannose (M) in a proportion of 1:1.2; the degree of acetylation was determined to be approximately 7.56%, molecular weight was calculated to be 2051.77 g/mol, solubility of 92.5% LMWG-E significantly increased AMPK phosphorylations in a dose dependent manner Treatment with KGM 100 μg/ml and 50μg/ml caused 1.47-fold and 1.81-fold phosphorylation of AMPK, respectively (p