Studied On Antioxidant Function And Characteristic Ingredient Of Sesame Cake Fermentation

The resource of sesame is very abundant in our country,and the by-product of sesame processing is more than 50 thousand tons annually.The sesame cake contains 40～60%protein and 0.5～1.0%lignans,and is always used as feed or muck,and the research of deep processing and comprehensive utilization of sesame cake is far away from success.In this paper,the final objective is to improve the antioxidant activity of sesame cake by fermentation and to make full use of sesame cake resources.We optimized the composition of fermentation substrate and the condition of ethanol extraction in fermenting sesame cake with Aspergillus sojae,the antioxidant activity in vitro and decreasing hyperlipidemia in vivo were studied.A characteristic ingredient was isolated and purified from sesame cake fermented extract and named as sesaminol through structural analysis.The antioxidant activity of sesaminol was studied.The major results are as follows:(1) The fermentation substrate composition and extraction condition of increasing antioxidant activity were optimized in sesame cake by Aspergillus sojae.The optimized fermentation substrate composition were as follows:amount of glucose, ammonium sulfate and wheat bran in substrate were 1.9%,1.6%and 2.6% respectively,and fermentation temperature and time were 28℃and 120 h respectively.The optimized extraction conditions were:ethanol concentration 60%, ratio of solution to material 16 mL/g,time 120 min,temperature 50^C and rotary speed 150 r/min.The peak area and height of characteristic material from optimum sesame cake fermentation extraction(SCFE) was increased by 88 and 51 times than that of sesame cake extraction(SCE),respectively.The DPPH radical scavenging activity was increased from 53.4%to 87.9%,and the total phenol content was increased from 1.85%to 2.23%.(2) The antioxidant activity of SCFE in vitro was studied,which is better than SCE.The total antioxidant capacity(TAC) and reduction ability of SCFE accentuated with concentration increasing in the range of 0.1～1.0 mg/mL,and the activity significantly increased at 0.5 mg/mL.The DPPH radical scavenging activity of SCFE at 0.5 mg/mL and 1.0 mg/mL was 72.7%and 87.5%,respectively,while that of SCE was 53.7%and 70.6%,respectively.The O₂^-·scavenging ability of SCFE at 1.0 mg/mL was 20%higher than that of SCE.The inhibition ratio of SCFE on the lipid peroxidation in liver homogenate spontaneously and H202 induced at 1.0 mg/mL was 84.4%and 67%,respectively,while that of SCE was 76.2%and 52.3%,respectively. The antioxidant effect of SCFE was higher than that of SCE on preventing lipid peroxidation of linoleic acid,which was increased in a dose-dependent way within the concentration range of 0.1 ¹.0 mg/mL.The antioxidant activity of SCFE at 0.1%was comparable to that of Vc at 0.02%on inhibition of refrigerated cooked ground pork oxidant.(3) Simulation test of prevention and regulation of SCFE on hyperlipidemian rat were studied.The result showed that SCFE could effectively decrease blood lipid level of SD rats with hyperlipidemia,improve blood lipid metabolism,reduce the formation of atherosclerosis.Meanwhile,SCFE effectively increased antioxidative level of rat body,improved antioxidase activities,reduced peroxidative lipid contents, and the effect of SCFE was much better than SCE.Main features were:the antioxidant activity and antioxidase decreased significantly,and the oxidation metabolin increased significantly in hyperlipidemian rat.When received intragastric administration with SCFE and SCE,they significantly decreased levels of triglyceride (TG),total cholesterol(TC),low density lipoprotein cholesterol(LDL-C) and atherosclerosis index(AI),and significantly increased high density lipoprotein cholesterol(HDL-C).In addition,they significantly increased total antioxidation capacity(TAC),superoxide dismutase(SOD) activities of rat serum,decreased malonyldialdehyde(MDA) contents and displayed significant dose-dependence.The effect of SCFE on decreasing blood lipids in hyperlipidemia rat serum index was much better than that of SCE at the same concentration.Comparing the coefficient of correlation of prevention array with regulation array,the former was better.The blood lipid level and atherosderosis index of rats with hyperlipidemia correlated closely with oxidation and antioxidation levels,both of which were cause and effect mutually and promoted each other.(4) The characteristic ingredient P_x was isolated,purified and identified in SCFE. It was obtained by ethyl acetate abstraction and silica gel column chromatography. The condition of silica gel column chromatography was as follows:petroleum benzin/acetoacetate eluted fraction(3:1 and 1:1,v/v).The UV scan of P_x showed one peak by thin layer chromatography(TLC),and the transport ratio of P_x after sulphuric acid carbonization was 0.20.The UV scanning spectrum max wave of P_x was 228 nm and 287 nrn,respectively.The retention time was 13.5 rain in HPLC.The molecular weight was analyzed by LC-MS and showed to be 370.0.The material was identified as sesaminol and the molecular formula is C₂₀H₁₈O₇.(5) The antioxidant activity of sesaminol was studied.Sesaminol has inhibitory function on lipid peroxidation in liver homogenate spontaneously and H₂O₂ induced, the superoxide dismutase(SOD) activity increased from 130.7 u/mgprot to 198.3 u/mgprot and maleic dialdehyde(MDA) inhibition ratio increased from 21.7%to 61.8%in liver homogenate spontaneously when sesaminol concentration increased from 10μg/mL to 100μg/mL.Sesaminol prevented lipid peroxidation both in linoleic acid-tween emulsion system and linoleic acid-ethanol system.The inhibitory effect of sesaminol was better than BHT in emulsion system.The DPPH radical scavenging activity of sesaminol at 20μg/mL was equivalent with BHT and Vc at 5μg/mL.The deep processing and exploitation of sesame cake were studied through biotransformation of the sesame cake lignans.We carried out the biotransformation of sesame lignan and isolated a characteristic ingredient which named sesaminol,and the result will provide a theoretical basis to deeply develop and utilize sesame cake.