LAUSR

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 Hb (HbS) is known for its tendency to oxidize more readily than normal HbA in the presence of hydrogen peroxide (H2 O2 ), which leads to a more persistent and highly oxidizing ferryl Hb. We have investigated the effects of CA on HbS oxidation intermediates, specifically on the ferric/ferryl forms. At a low concentration of H2 O2 (0.5-fold over heme), we observed a 5-fold reduction in the amount of ferryl Hb accumulated in a mixture of ferric and H2 O2 solution. Higher levels of H2 O2 (1-fold and 2-fold over heme) led to a lesser 3 and 2-fold reduction in the content of ferryl Hb 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, a considerable increase in the delay time of HbS polymerization to approximately 200 sec 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 and βCys112 than to αCys104 . The dual antioxidant and antisickling properties of CA may be explored further to maximize its therapeutic potential in SCD.