ANTIOXIDANT ACTIVITY OF GREEN TEA CATECHINS IN A β-CAROTENE-LINOLEATE MODEL SYSTEM

A crude mixture of catechins was isolated from Chinese green tea leaves using a hot water extraction. Individual catechins were then separated by chromatographic means using Sephadex LH-20 followed by semi-preparative HPLC. The antioxidant activity of crude and individual catechins was then determined in a β-carotene-linoleate model system. Results indicated that (−)-epicatechin-3-gallate (ECG) possessed the strongest antioxidative activity and (−)-epigallocatechin (EGC) showed the weakest effect. The antioxidative efficacy of (−)-epicatechin (EC) and (−)-epigallocatechin-3-gallate (EGCG) was similar and in between those of ECG and EGC. Furthermore, the antioxidant activity of a reconstituted catechin mixture in the proportions present in the crude extract was lower than that of the crude mixture itself, thus indicating that noncatechin components in the mixture possessed their own antioxidant activity or acted synergistically with the catechins.     

茶多酚制备高纯度EGCG的工艺研究

选择聚酰胺为柱填料,以荼多酚为原料,考察洗脱剂pH值、温度、溶剂的不同比例、流速和不同上样量对纯化分离(-)-EGCG影响.获得的工艺条件是:在玻璃层析柱(规格500 mm×20mm)中,装填聚酰胺(粒径150 μm～75μm)树脂,上样量为42.9 mgTP/g树脂,用洗脱剂(甲醇:水=4:1),pH值3.5～4.5,温度为室温(或25℃),流速为4.0 mL/min的情况下洗脱,可以得到(-)-EGCG的纯度达93%以上,回收率达86.83%以上的产品.     

普洱茶多糖的提取工艺及抗氧化活性研究

用单因素实验研究茶多糖(TSP)提取工艺条件,并进一步通过连苯三酚自氧化测定所得普洱茶茶多糖的抗氧化活性.研究结果表明:普洱茶多糖的适宜提取条件为料液比1:30、浸提温度70℃、浸提时间40min,提取次数4次,所得普洱茶多糖具有一定的抗氧化活性,其抗氧化活性与Vc的抗氧化活性相近.     

SEPARATION OF INDIVIDUAL CATECHINS FROM GREEN TEA USING SILICA GEL COLUMN CHROMATOGRAPHY AND HPLC

Crude catechin mixtures from green tea were separated into six fractions using a silica gel column chromatography and a chloroform-methanol-water (65:35:10, v/v/v, lower phase) solvent system. Fraction I was free of catechins, fraction II contained epicatechin (EC), fraction III had epicatechin and epigallocatechin (EGC), fraction IV possessed EGC, fraction V contained EGC, epicatechin gallate (ECG) and epigallocatechin gallate (EGCG), and fraction VI had EGCG. EC and EGC were separated from fractions II, III and IV using HPLC with a RP-18 semipreparative column and a water-dimethylformamide-methanol-acetic acid (157:40:2:1, v/v/v/v) solvent system. For isolation of EGC, ECG and EGCG from fractions V and VI a water-acetonitrile-methanol-acetic acid (159:36:4:1, v/v/v/v) solvent system was employed. Chemical structures of purified catechins were further confirmed by ESI-MS.     

四种茶花的抗氧化性研究

对4种常见饮用茶花中的总黄酮类物质及其抗氧化性与稳定性进行了研究。实验结果表明：4种茶花金银花、白菊花、茄瑰紫、千日紫的黄酮类物质得率依次为15．29％、12．35％、10．80％和6．53％。利用DPPH法对茶花提取液的抗氧化性测定结果表明，4种茶花都具有一定的抗氧化作用，且可与0．01％BHT的抗氧化能力相媲美。金银花、千日紫、白菊花和茄瑰紫的抑制率依次是94．33％、89．14％、85．46％、和82．79％。稳定性研究结果表明，4种茶花中的黄酮类物质均具有较好的稳定性。     

ENZYMATIC SYNTHESIS OF STRUCTURED LIPIDS: TRANSESTERIFICATION OF TRIOLEIN AND CAPRYLIC ACID

Structured lipids were successfully synthesized by lipase-catalyzed trans-esterification (acidolysis) of caprylic acid and triolein in nonaqueous medium. Twelve commercially available lipases (10%, w/w substrates) were screened for their ability to form structured lipid by incubating 100 mg triolein and 65.3 mg caprylic acid in 3 ml hexane at 55C for 24 h. The products were analyzed by reverse-phase high performance liquid chromatography (HPLC) with evaporative light scattering detection. Monocapryloolein was the major component of the products (57.4 mol %) and IM60 lipase from Rhizomucor miehei was the best biocatalyst. Dicapryloolein and triolein contents were 35.4% and 5.3%, respectively. Temperature, mole ratio, time course, incubation media, added water, enzyme load, and substrate concentration were also investigated in this study. The results suggest that it is possible to synthesize structured lipids with lipase as biocatalyst.     

竹黄多糖BSP-1的组成和抗氧化活性分析

对竹黄子实体总多糖进行提取,分离纯化出2种均一的组分BSP-1和BSP-2.采用气相色谱和凝胶渗透色谱研究BSP-1的组成和分子量,并研究其对猪油的抗氧化作用.结果表明:BSP-1分子量为45.64 ku,主要由葡萄糖和甘露糖组成,摩尔比为2.46:1,红外光谱分析表明含有B-糖苷键,体外抗氧化实验证明BSP-1具有一定的抗猪油自动氧化能力.     

仙人掌水溶性粗多糖提取及抗氧化性能研究

研究仙人掌水溶性粗多糖的提取工艺及抗氧化性能。采用单因素试验和L9（3^3）正交试验设计,考察提取温度、时间、料液比等因素对提取率的影响,并采用水杨酸法考察仙人掌粗多糖抗氧化性能。结果表明：温度是影响粗多糖提取的重要因素。优化工艺条件为：提取温度80℃,提取时间1h,固液比为1：60。抗氧化试验表明仙人掌粗多糖有较好的抗氧化活性。