The Extraction Of Antioxidants From Clove And Their Anti-LDL Oxidation Activity

The former experiments of the laboratory explored the antioxidant activity of87Chinese medicinal and edible materials proclaimed by China and chose20of them with higher antioxidant activity. This paper screened the antioxidant activity of the selected20materials and discovered clove possesses the strongest antioxidant activity in both aqueous and ethanol extracts among them. Therefore clove was selected as the test material to further study.The simultaneous ultrasonic/microwave assisted extraction (UMAE) technology of extracting antioxidant activity components from clove was optimized by univariate and orthogonal experiments and the reason for high-efficiency of this method was analyzed. The results showed that the optimal parameters of the UMAE technology were as follows, ethanol concentration was50%, ratio of sample to extracting solution was1:30(g:mL), ultrasonic power was50W, microwave power was100W and extracting time was12min. Comparative study showed that the extraction ratio of antioxidant activity components from clove by UMAE was significantly improved compared with water bath oscillator extraction (WBOE) under both optimum conditions (P<0.01). It was also found that the superiority of UMAE was simultaneously acted and mutually reinforced by ultrasonic and microwave through interaction analysis. A comparison of scanning electron microscopy images among UMAE、WBOE、microwave assisted extraction(MAE) and ultrasonic assisted extraction(UAE) treated clove powders indicated the extraction efficiency was higher by UMEA with the more serious disruption of cell structure and the more sufficient interaction.Because of the strong antioxidant activity of clove, the property of anti-low density lipoprotein (LDL) oxidation of clove was studied. The different polar fractions of clove’s extracts were separated by bio-assay guided method. The anti-LDL oxidation activity of clove was determined by thiobarbituric acid reactive substance (TBARS) guided method in vitro copper sulfate induction on LDL. The results showed as follows. The ethyl acetate fraction was the most effective part with significantly higher inhibition rate (P<0.05) compared with n-butyl alcohol fraction、water fraction and crude extract and surpassed the lowest one by63.02%. The inhibition rates of both the crude extract and the ethyl acetate fraction were presented a good dose-effect relationship. Besides, the oxidation progress of oxidized LDL was delayed by the effective ethyl acetate fraction. The absorbance value (OD532) was reached peak at32h when the concentration was1.2mg/mL, extended18h than the promoted oxidation group.Eight main ingredients in effective ethyl acetate fraction were detected through Thin-layer Chromatography(TLC) scanning. Two main aglycones and three glycosides (glucose, rhamnose and glucuronic acid) in acid hydrolysis solution of the effective part were observed by TLC. Ten weak polar monomer compounds in the effective part of clove were identified after separation and purification through Column Chromatography and Nuclear Magnetic Resonance Analyzer. They were oleanolic acid、quercetin、β-sitosterol、 kaempferol、gallic acid、ellagic acid、rhamnetin、flavin resurrectionlily armour、2α hydroxyl oleanolic acid、3,3’,4-triethoxy ellagic acid.This paper provides the basis on enhancing the extraction efficiency of antioxidant activity components from clove and industrializing it and analyzing the function mechanism of UMAE technology. It also lays the foundation for further study of anti-low density lipoprotein oxidation of clove and exploration of anti-atherosclerotic medicines and functional foods.