Interaction of Hemoglobin A with Sesamol and Polyphenolics

The interactions of sesamol (I), a monophenolic antioxidant in sesame oil, pyrocatechol (II), p-hydroquinone (III) and pyrogallol (IV) with hemoglobin A were investigated. A large excess of the phenolic (I, II and III) induced methemoglobin (MetHb) formation from oxyhemoglobin (HbO2) at pH 7 and 25°, the rates being in the order I>II>III. The diphenolics (II and III) also reduced MetHb to deoxyhemoglobin (DeoxyHb). Pyrogallol (IV) showed a more powerful ability to produce and reduce MetHb. Sesamol (I) readily produced MetHb from HbO2 and even from DeoxyHb, but did not reduce MetHb. MetHb formation from HbO2 by I prevailed in the acidic range. The amount of MetHb formed by I was characteristically proportional to the concentration of HbO2, and more than 10 equivalents of MetHb was produced at high concentrations of HbO2. MetHb formation by I, II and III from HbO2 was enhanced by inositol hexaphosphate, whereas MetHb formation from DeoxyHb was inhibited. The mechanisms of action of the di-and triphenolics may involve electron transfer to HbO2 and MetHb, but that of I could not be explained analogously.