Preparation Of Conjugated Linoleic Acid From Okra Seed Oil And The Study Of Its Anti-oxidant Activity

Conjugated linoleic acid has many physiological functions, such as reducing lipid, anti-oxidation, anti-cancer, bone healthy, immunity regulation and lowering blood glucose, known as the "new type of nutrients in the 21st century". The content of fatty acid in okra seed oil is rich; especially the content of linoleic acid content is 40%, which can be the raw materials for preparation of conjugated linoleic acid. Oil is extracted by ultrasonic-assistant method and with okra seed as raw material, then synthesis of conjugated linoleic is by alkali isomerization. Water-soluble conjugated linoleic acid-arginine complex is prepared and its antioxidant activity is studied. The main results of this paper were as follow:1. The ultrasonic-assistant extraction technique was studied with okra seed as raw material, microwave pretreatment and petroleum ether as extraction agent. The composition and contents of fatty acid in okra seeds were determined by gas chromatography-mass spectrometry (GC-MS). The orthogonal test was designed and the optimal extraction conditions were as follows:ultrasonic time 30min; ultrasonic power 240w; solid-liquid ratio 1:11 and ultrasound temperature 60 ℃, and the extraction rate was 26.41%. The main fatty acids were:linoleic acid (34.89%), oleic acid(26.78%), palmitic acid(25.58%) and stearie acid(5.613%). The oxidation stability of okra oil、soybean oil and corn oil were compared by the method of Rancimat. Selecting Vc、BHT and TBHQ as antioxidants, the oxidation induction effect of okra oil added with antioxidants were explored. The results showed that the oxidation induction time of TBHQ was the longest and its antioxidant effect was best.2. In order to improve the conjugate conversion rate of linoleic acid in okra seed oil, the Box-Benhnken experimental design was performed on the basis of one-factor experiments, and the response surface analysis and corresponding regression model were established with conjugated linoleic acid (CLA) yield as response value. The optimum conditions of conjugate conversion were obtained as follows:reaction time of 4 h, reaction temperature of 162 ℃, oil against KOH at ratio of 1.9 (mL/g), propylene glycol against oil at ratio of 2.0 (mL/mL), and the conversion rate of CLA was 74.20%. The quadratic regression equation was established as follow:Y=72.44+2.40A-3.19B-0.17C-3.00AB-1.12AC+2.83BC-1.67A2-2.33B2-6.81C2. Conversion rate was greatly affected by reaction temperature and the interaction of reaction time and temperature was significant. The measured date (74.20%) was almost accorded with the predicted data (76.99%). It demonstrated that the conversion condition parameter optimized by response surface method was credible and feasible.3. Water-soluble conjugated linoleic acid-arginine (CLA-Arg) Complex had been prepared by dissolving, mixing, concentration and vacuum freeze drying from same mole of CLA and Arg. The antioxidant activity of CLA-Arg was studied by measuring its scavenging effects on DPPH radical and ABTS radical, inhibition effect on liposome peroxide and influence on oxidation induction time by Rancimat. The results showed that CLA-Arg had strong scavenging capacity on DPPH radical (IC50 2.76mg/mL) and ABTS radical (IC50 1.43mg/mL); The inhibition rate of liposome peroxide system was 41.8% when the concentration was 1.0mg/mL; The oxidation induction time extended to 1.79h and was higher than BHT when the content was 0.1%. CLA-Arg had a significant antioxidant activity.