Study On Extraction, Isolation And Antioxidant Activity Of Lignans Of Sesame Cake

Sesame(Sesamum indicum L.-Pedaliaceae), an important oil-yielding plant, is one of the most ancient crops in the world. Sesame is also one of the four major oil crops in China where it has been cultivated for about 2200 years and it is also an important exporting goods to earn foreign currency. The resource of sesame is very abundant in our country, and the by-product of sesame processing is more than 500 thousand tons annually. The sesame cake contains a lof of 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. The objective of this research was to extract and purify sesamin, sesamolin and sesaminol triglucosides from sesame cake which is the by-products of sesame oil plants. The antioxidant activity of lignans was also studied here. Major tests and results are as follows:Firstly, determination method of sesamol, sesamin and sesamolin in sesame oil was studied firstly. Based on sesame oil was pretreated with chromatographic column packed with Kieselgel 60, then HPLC was applied to qualitatively and quantitatively analyze sesamol, sesamin and sesamolin. The average recoveries of sesamol, sesamin and sesamolin were 97.9%,99.0% and 99.1%. The Relative Sandard Deviation of sesamol, sesamin and sesamolin were 2.32%,1.74% and 1.82%. The minor components of sesamol, sesamin and sesamolin were studied in 20 kinds of sesame oil and 4 kinds of sesame salad oil in Chinese market where sesame is abundant. The results was as follows:a) sesamol and sesamolin were both abundant in most sesame oil, where sesamol and sesamolin were 61% and 29% respectively relative to lignans;b) the contens of sesamol and sesamolin were positive correlated with lignans, sesamol was negative correlated with sesamolin;c) lignans contents of sesame salad oil were fifth respective to that of sesamol oil as a result of admixture with some other vegetable oil.Secondly, methanol was used to extract sesamin and sesamolin from the sesame cake. The influences of several factors for extraction were studied. The effects on yield of extraction temperature, ratio of solid/liquid, extraction time and extraction times were researched. Sesamin and sesamolin of different treatments were determined. The optimization technics parameters of sesamin and sesamolin by orthogonal design of L9(34) were as follows:sesame cake was extracted at 55℃for 3.5h one time, with 1:3.5 as ratio of solid/liquid, whereafter sesamol, sesamolin sesamimol triglusosides'standard specimens were prepared by HPLC.At last, the anti-oxidant activity of the extract was evaluated by soybean oil oxidation process. The fat auto-oxidation is the free radical chain type response, in this reaction process many kinds of peroxidation lipid was produced, these peroxidation lipid not only may cause nutrition and sensual features deterioration, moreover lead to carcinogenic substances produced. Lignans can improve above questions. The antioxidative activity of lignans was obviously in soybean oils and was significant as lignans mount increased. Sesamol showed stronger antioxidative activity than that of BHT. It was also found that the oxidation products of lignans did not affect vegetable oil's color and brightness. So, lignans are widely used in edible oils and oil-based foods, they can be developed as a new antioxidant.