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Abstract：
Though the instability of polyphenols in cell culture experiment has been investigated previously, the underlying mechanism is not completely clear yet. Therefore, in this study, the stability of epigallocatechin gallate (EGCG) in cell culture medium DMEM was investigated at 4 °C and 37 °C via UPLC-MS-MS analysis followed by determination of the antioxidant capacity of EGCG. EGCG was instable in DMEM and formed various degradation products derived from its dimer with increasing incubation time with many isomers being formed at both temperatures. The dimer products were more stable at 4 °C than at 37 °C. The structure and formation mechanism of five products were analyzed with four unidentified. Ascorbic acid significantly improved the stability of EGCG by protecting EGCG from auto-oxidation in DMEM, particularly at 4 °C. The antioxidative activity of EGCG in DMEM was determined by DPPH, ABTS and FRAP assay. The antioxidative properties of EGCG continuously decreased over 8 h in DMEM, which was consistent with its course of degradation.
摘要：
尽管之前已经研究了多酚在细胞培养实验中的不稳定性，潜在的机制还不完全清楚。因此,在这项研究中，通过UPLC-MS-MS分析，然后测定EGCG的抗氧化能力，在4°C和37°C下研究表没食子儿茶素没食子酸酯（EGCG）在细胞培养基DMEM中的稳定性。EGCG在DMEM中不稳定，并且随着孵育时间的增加，形成了源自其二聚体的各种降解产物，在两个温度下都形成了许多异构体。二聚体产物在4°C下比在37°C下更稳定。分析了5种产物的结构和形成机理，其中4种产物未鉴定。抗坏血酸通过保护EGCG在DMEM中的自动氧化，显着提高了EGCG的稳定性，特别是在4°C用DPPH法测定EGCG在DMEM中的抗氧化活性，ABTS和FRAP测定。EGCG在DMEM中的抗氧化性能持续下降超过8小时，这与它的退化过程是一致的。
