表棓儿茶素棓酸酯体外氧化及其低聚产物形成的研究

Effects of Reaction Condition on the Oxidation in vitro of Epigallocatechin-3-gallate and the Formation of Its Oligomers

为控制儿茶素类低聚氧化产物形成条件,以表棓儿茶素棓酸酯(EGCG)为代表进行体外化学氧化,通过对产物的HPLC-MS分析确定研究对象,即EGCG氧化低聚物(EOP),其主要有3种低聚产物:产物1m/z911,产物2m/z 929,产物3m/z911。产物1和产物3为EGCG脱氢二聚体;产物2为EGCG醌式二聚体。反应条件的研究表明,随温度升高EGCG氧化程度加剧,EOP生成量也随之增加,但温度达40℃时,EOP的生成量在氧化10 min后下降;体系pH值增大可加剧EGCG氧化,但pH值9.0时,EOP的生成量在15 min后有所下降;随氧化剂所占质量比的增大,EGCG氧化程度加大,但EOP的生成量并不与之成正相关。EOP形成的最佳条件为:反应温度25℃,pH值7.5,氧化剂与底物的质量比1.5∶1,氧化时间15 min。

In order to control the formation condition of oxidation oligomers of flavanols, epigallocatechin-3-gallate （EGCG） was oxidized in vitro and EGCG oligomeric products （EOP） were determined by HPLC-MS analysis. The influences of temperature, pH value, mass ratio of oxidant to EGCG on the oxidation of EGCG and the formation of EOP have been discussed. HPLC-MS analysis showed that there were mainly 3 oligomers, namely product 1 m/z 911, product 2 m/z 929, product 3 m/z 911. Products 1 and 3 were dehydrodimers of EGCG, product 2 was quinone dimer of EGCG. The study of reaction condition showed that oxidation of EGCG was enhanced with increased temperature. However when temperature reached 40 ℃, the formation of EOP decreased after 10 min; EGCG oxidation reaction could be accelerated with increase of pH value. However, at pH value 9. 0, the formation of EOP decreased after 15 min; EGCG oxidation yield was increased with increase of m （oxidant） ： m（EGCG）. However, the formation of EOP did not have a correlated relationship. The optimum conditions of EOP formation were ： temperature 25 ℃, pH value 7.5, m （oxidant） ： m （EGCG） 1.5 ： 1, oxidation time 15 min.