Study On Extraction, Purification And Antioxidant Activity Of Sesamin From Sesame Oil Residue

Sesamin,a lipid-soluble lignan, has many biological activities. The objective of this research was to extract and purify sesamin by crystallization from sesame oil residue which is the by-products of sesame oil plants.The antioxidant activity of sesamin was also studied here.Firstly, determination method of sesamin in sesame oil was studied.Based on it, sesame oil was pretreated with chromatographic column packed with alumina and then HPLC was applied to qualitatively and quantitatively analyze sesamin.The average recoveries and coefficient variation were 95.6% and 1.19% for sesamin respectively. The method was simple and accurate in sesamin determination.Oil and minor components of sesamin were studied in 15 strains of Sesamum indicum L from different regions in China where sesame is abundant.The percentage of sesamin in the oil ranged from 0.1152% to 0.7773%.The oil contents of the seed ranged from 46.48% to 58.28%.There was a significant positive correlation between the oil content of seed and the sesamin content of the oil( r=0.556,significant at the 5% level).No significant difference in sesamin content was found between the means of white and brown seed strains.The average sesamin content of the white seed strains is higher than that of the black seed strains.Secondly,compositions of sesame oil residue were analyzed .The results showed the content of sesamin, total solid and sesame oil in sesame oil residue were 0.251%, 31.0% and 68.9% respectively. Methanol was used to extract sesamin from the sesame oil after sesame oil was extracted from the sesame oil residue by hexane.The influences of several factors for extration were studied. The extraction temperature of 60℃, extraction time of 2.5 h , methanol with the ratio of 3:1 to sesame oil were selected as the optimum parameters .Under these conditions,the extraction rate of the sesamin was 83.7% and the purity of this product was 67.5%. This product was purified by the ethanol solvent with the following conditions: the ratio of sesmin to the ethanol solvent 1:40(w/m), crystallization temperature 25℃, time 2 hours. The purity of the product increased from 67.5% to91.2% by crystallization for four times. Sesamolin and sterol were determined in the product by GC-MS analysis. It was showed from Schaal oven test and Rancimat experiments that sesamin in oil has lower antioxidant activity than that of BHA,BHT,TBHQ and VE.. The free radical scavenging capacity of sesamin was investigated. The results showed sesmin could scavenge the free radical (DPPH·,·0H,O2-·). The mechanism of antioxidative activity of sesamin was discussed on the basis of sesamin molecule structure.