Scavenging Effects of Metal Complexes of Water-Soluble Thiacalix[4]arenetetrasulfonate on Superoxide Anion Radicals

摘要

The scavenging effects of metal complexes of thiacalix[4]arenetetrasulfonate (Me-TCAS[4], Me=H₂, Fe3+, Mn3+, Mn2+, Cu2+, and Zn2+) on superoxide anion radicals (O₂?) generated from the xanthine–xanthine oxidase system were investigated by the nitroblue tetrazolium (NBT) method and electron spin resonance (ESR) spin-trapping method using 5,5-dimethyl-1-pyrroline- N -oxide as a trapping reagent. As a reference, calix[4]arenetetrasulfonate (H₂-CAS[4]), calix[6]arenehexasulfonate (H₂-CAS[6]) and calix[8]areneoctasulfonate (H₂-CAS[8]) were also examined. The results by the NBT method indicated that Fe3+- and Mn3+-TCAS[4] exhibited the highest O₂? scavenging activity among Me-TCAS[4] and H₂-CAS[ n ] ( n =4, 6, 8) in this study. The IC₅₀ values of Fe3+- and Mn3+-TCAS[4] for O₂? scavenging activity were estimated to be 5.3 and 7.8 μ M , respectively, and were almost the same as those of tannin acid, catechin and their derivatives, which are known as very effective scavengers of O₂?. Scavenging activities were in the order of Fe3+- and Mn3+-TCAS[4]Mn2+-, Cu2+-, and Zn2+-TCAS[4]H₂-TCAS[4] and H₂-CAS[ n ] ( n =4, 6, 8). Each activity of Me-TCAS[4] (Me=Fe3+, Mn3+, Mn2+, Cu2+, and Zn2+) was higher than that of the corresponding metal ion, indicating that H₂-TCAS[4] has the ability to raise the activity of the metal ion itself by forming a complex. Also, the ESR spin-trapping method revealed that Fe3+- and Mn3+-TCAS[4] showed high O₂? scavenging activities, similarly to the results by the NBT method.