机构地区: 华中农业大学食品科学技术学院
出 处: 《精细化工》 2006年第11期1094-1098,共5页
摘 要: 为调控儿茶素氧化条件,以表没食子酸儿茶素没食子酸酯(EGCG)为代表,考察温度、反应体系pH、EGCG初始质量浓度、氧化剂与EGCG质量比对氧化反应速率的影响。对EGCG氧化产物进行了HPLC-MS分析,结果表明,EGCG体外氧化符合二级动力学反应特征。随温度的升高,EGCG反应速率加快,在0、25、40℃时的反应速率常数k分别为0.145 9、0.260 9、0.359 1 m in-1;EGCG反应速率在pH≥7.0时,随pH增高而加快,pH=7.0、8.0、9.0时的反应速率常数k分别为0.389 1、0.568 9、0.797 0 m in-1;EGCG初始质量浓度≥1.00 mg/mL时,反应速率随其增大而加快,ρ(EGCG)为1.00、2.00、3.00 mg/mL时的反应速率常数k分别为0.253 1、0.304 6、0.351 1 m in-1;随氧化剂所占质量比的增大,EGCG反应速率加快,m(氧化剂)∶m(EGCG)为1∶1、1.5∶1、2∶1时的反应速率常数k分别为0.145 9、0.229 9、0.480 7 m in-1。在40℃、pH=9.0、m(氧化剂)∶m(EGCG)=2∶1条件下氧化EGCG,氧化体系中w(EGCG)=14.05%。氧化产物的HPLC-MS分析结果表明,EGCG氧化产物Ⅰm/Z:911,产物Ⅱm/Z:929,产物Ⅲm/Z:911。产物Ⅰ、产物Ⅲ为EGCG脱氢二聚体;产物Ⅱ为EGCG邻醌二聚体。 In order to control the oxidation condition of catechins, epigallocatechin-3-gallate (EGCG) was used as an example to investigate the factors influencing the oxidation rate, and HPLC- MS was used to analyze the oxidation products. The results show that the in vitro oxidation of EGCG is in accordance with the second order reaction. The reaction rate increases with increase of temperature( the rate constant k =0. 145 9,0.260 9 and 0.359 1 min^-1 respectively at 0 ℃ ,25℃ and 40℃ ). When pH≥7.0 ,the reaction rate increases with increase of pH (k = 0.389 1,0.568 9 and 0.797 0 min^-1 respectively while pH = 7.0,8.0 and 9.0). When p (EGCG) ≥ 1.00 mg/mL, the reaction rate increases with increase of p (EGCG) ( k = 0. 253 1,0. 304 6 and 0.351 1 min^-1 respectively while p (EGCG) = 1.00,2.00 and 3.00 mg/mL). The reaction rate increases with increase of m(oxidant) :m (EGCG) ( k = 0. 145 9,0. 229 9 and 0. 480 7 rain^-1 respectively while m (oxidant) :m (EGCG) = 1:1,1.5:1 and 2:1 ). When EGCG was oxidized at 40 ℃ and pH = 9.0 with m(oxidant) :m (EGCG) = 2: 1 ,in the final oxidation mixture w(EGCG) = 14.05%. HPLC-MS analysis showes that,for oxidation product Ⅰ m/Z=911,for product Ⅱ m/Z =929,and for product Ⅲ m/Z =911. Product Ⅰ and Ⅲ are dehydrodimers,while product Ⅱ is EGCG quinone dimer.
领 域: [化学工程]