丹参素自氧化与促氧化机理

Autoxidation and Prooxidation Mechanisms of Danshensu

采用过氧化氢电极与电子自旋共振(ESR)技术对不同pH值条件下丹参素的自氧化及Cu2+对丹参素的促氧化反应机理进行了研究.实验结果发现:在碱性条件下(pH=8.5),丹参素自氧化作用异常显著,氧化首先生成O2-·,随后可歧化为H2O2,并且Cu2+对H2O2信号增强也起着显著的促进作用;在弱酸性条件下(pH=6.5),丹参素自氧化过程受到抑制,主要表现为少许Cu2+的促氧化作用;而在生理条件下(pH=7.4),丹参素的自氧化过程缓慢,有少量H2O2生成,并且Cu2+的促氧化作用非常有限.因此,当丹参素作为一种高效抗氧化剂药用时,其自身的自氧化与金属离子促氧化作用都应有所考虑,尤其在偏碱性体液中,更易产生大量的超氧阴离子自由基,并对生物机体造成某种损害.

A hydrogen peroxide （H2O2） electrode and electron spin resonance （ESR） methods were used to continuously monitor and analyze the autoxidation and prooxidation of Danshensu in aqueous solutions with various pH values.We found that Danshensu exhibited obvious autoxidative activity in alkalescence buffer solutions （pH=8.5） and the presence of Cu^2＋ evidently accelerated the generation of H2O2.The primary product of the autoxidation was a superoxide anion radical （O2^-·） and then it could be converted into H2O2.The autoxidation of Danshensu was totally inhibited under weak acidic conditions （pH=6.5） and a partial prooxidation of Danshensu occurred in the presence of cupric ion.However, under physiological conditions （pH=7.4）, the autoxidation of Danshensu was very slow and its prooxidation, initiated by Cu^2＋, was very limited.Consequently, the autoxidation and prooxidation of Danshensu cannot be completely ignored when used in clinical practice especially under alkaline body fluid conditions.