The Research On Extraction Of Diosgenin And Synthesis Of 5-Hydroxymethylfurfural As A Platform Chemical Made From Renewable Resources

There is a lot of industrial waste rich in starch from diosgenin production. However, at present, there isn’t an appropriate process that can be used to comprehensive utilize the starch from the waste successfully in practical engineering. Starch are carbon-neutral renewable energy resources for the production of biofuels and valuable chemicals. 5-Hydroxymethylfurfural(HMF), a versatile platform chemical derived from biomass feedstocks, it can produce a variety of value-added chemicals. In recent years, because of Dioscorea composita is rich in saponins and starch, the efficient catalytic transformation of the industrial waste rich in starch from diosgenin production from D. composita into HMF has attracted a great deal of attention worldwide. Because it can utilize the starch from the waste in practical engineering. At the same time, it is significant for solving problems such as global warming, air pollution, and secure energy supply.We obtained the diosgenin by employing the direct hydrolysis-extraction under biphasic reaction conditions and determined the antioxidant activity of diosgenin from D. composita. Futhermore, we report a cost-effective catalytic system for HMF synthesis from D. composita biomass based based on dehydration of glucose, maltose and soluble starch into HMF. The catalytic system is composed of a combination of chromium(III) chloride and lanthanide(III) chloride. The main contents in this work are as follows:(1) Through single factor and orthogonal test, the optimal extraction process conditions for extracting diosgenin from D. composita were determined: 15 ml of sulphuric acid, 70 ml of methanol, 15 ml of H2 O, 150 ml of petroleum ether(boiling range 90–120°C), extracting temperature 90°C, extracting time 6h. Under these conditions, the yield of diosgenin was 1.33%. After recrystallization by methanol(three times),70% pure diosgenin was obtained by the determination of liquid chromatography. The process was convenient, time-saving and efficient.(2) In this paper, the antioxidant activity of diosgenin was initially determined by the Fenton reaction-methylene blue spectrophotometric method. Results indicate diosgenin from D. composita demonstrated superior hydroxyl radical scavenging activity. The percentage of the hydroxyl radical scavenging activity(HRSA) for diosgenin was 94.1% when diosgenin concentration was 5×10-3 mmol/L. But the antioxidant activity of diosgenin for superoxide anion radical and DPPH was nearly zero.(3) The reactivity of glucose in N,N-dimethylacetamide(DMA) was first explored with metal chlorides catalyst, results indicate the catalytic system composed of a combination of chromium(III) chloride and lanthanide(III) chloride is very effective for HMF synthesis from glucose. And the catalytic system yielded 77.6% HMF at 100°C for 1.5h. For the HMF synthesis from D. composita, the catalytic system were also employed in the dehydration of maltose and soluble starch. We found maltose and soluble starch were also successfully converted into HMF with good yields under mild conditions(yield up to 45.2% in the case of maltose, 54.5% in the case of soluble starch). Reaction temperature, catalyst loading and reaction time had noticeable effects on this catalytic system. On the basis of the results, the transformation of D. composita and the industrial waste rich in starch from diosgenin production into HMF was achieved by employed the catalytic system(yield up to 45.2% in the case of maltose, 54.5% in the case of soluble starch).The reaction conditions were as following, 30mol% CrCl3·6H2O, 15mol% LaCl3·6H2O, DMA-LiCl, reaction temperature 120°C, reaction time4 h. And HMF yielded up to 33.2% in the case of D. composita, 3.71% in the case of waste, respectively. At last, we tried to separate HMF from reaction mixtures and convert HMF to 2,5-dimethylfuran for liquid fuel.