It is well documented that caffeic acid (3,4-dihydroxycinnamic acid) (CA) interacts with and inhibits the oxidative reactions of myoglobin (Mb) and hemoglobin (Hb), and this interaction underlies its antioxidative action in meat. Sickle cell hemoglobin (HbS) is known for its tendency to oxidize more readily than normal HbA in the presence of hydrogen peroxide (H₂O₂), which leads to a more persistent and highly oxidizing ferryl Hb (HbFe⁴⁺). We have investigated the effects of CA on HbS oxidation intermediates, specifically on the ferric/ferryl forms. At a low concentration of H₂O₂ (0.5-fold over heme), we observed a fivefold reduction in the amount of HbFe⁴⁺ accumulated in a mixture of ferric and H₂O₂ solution. Higher levels of H₂O₂ (onefold and twofold over heme) led to a lesser threefold and twofold reduction in the content of HbFe⁴⁺, respectively, possibly due to the saturation of the binding sites on the Hb molecule. The most intriguing finding was that when 5-molar excess CA over heme was used, and a considerable increase in the delay time of HbS polymerization to approximately 200 s was observed. This delay in polymerization of HbS is theoretically sufficient to avoid microcapillary blockage and prevent vasoconstrictions in vivo. Mass spectrometry analysis indicated that CA was more extensively covalently bonded to βCys⁹³ than to βCys¹¹² and αCys¹⁰⁴. The dual antioxidant and antisickling properties of CA may be explored further to maximize its therapeutic potential in SCD.

中文翻译：

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咖啡酸：具有新型抗镰刀特性的抗氧化剂

有充分证据表明，咖啡酸（3,4-二羟基肉桂酸）（CA）与肌红蛋白（Mb）和血红蛋白（Hb）的氧化反应相互作用并抑制，这种相互作用是其在肉类中的抗氧化作用的基础。众所周知，镰状细胞血红蛋白 (HbS) 在过氧化氢 (H ₂ O ₂ ) 的存在下比正常 HbA 更容易氧化，这会导致更持久和高度氧化的ferrl Hb (HbFe ⁴⁺ )。我们研究了 CA 对 HbS 氧化中间体的影响，特别是对铁/铁基形式的影响。在低浓度的 H ₂ O _{2 （血红素的 0.5 倍）下，我们观察到 HbFe} ⁴⁺的量减少了五倍_{在铁和 H 2} O ₂溶液的混合物中积累。较高水平的 H ₂ O ₂（比血红素高一倍和两倍）分别导致 HbFe ⁴⁺含量减少三倍和两倍，这可能是由于 Hb 分子上的结合位点饱和。最有趣的发现是，当使用超过血红素 5 摩尔的 CA 时，观察到 HbS 聚合的延迟时间显着增加至约 200 秒。HbS 聚合的这种延迟理论上足以避免微毛细血管阻塞并防止体内血管收缩。质谱分析表明 CA 更广泛地与 βCys 共价结合⁹³比βCys ¹¹²和αCys ¹⁰⁴。可以进一步探索 CA 的双重抗氧化和抗镰刀特性，以最大限度地提高其在 SCD 中的治疗潜力。