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=H_2, Fe~(3+), Mn ~(3+), Mn~(2+), Cu~(2+), and Zn~(2+)) on superoxide anion radicals (O_2~-) 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]arenete-trasulfonate (H_2-CAS[4]), calix[6]arenehexasulfonate (H_2-CAS[6]) and calix[8]areneoctasulfonate (H_2-CAS[8]) were also examined. The results by the NBT method indicated that Fe ~(3+)- and Mn~(3+)-TCAS[4] exhibited the highest O _2~- scavenging activity among Me-TCAS[4] and H _2-CAS[n] (n=4, 6, 8) in this study. The IC_(50) values of Fe~(3+)-and Mn~(3+)-TCAS[4] for O_2~- scavenging activity were estimated to be 5.3 and 7.8 μM, respectively, and were almost the same as those of tannin acid, catechin and their derivatives, which are known as very effective scavengers of O_2~-. Scavenging activities were in the order of Fe~(3+)- and Mn ~(3+)-TCAS[4]?Mn~(2+)-, Cu~(2+)-, and Zn ~(2+)-TCAS[4]?H_2-TCAS[4] and H_2-CAS[n] (n=4, 6, 8). Each activity of Me-TCAS[4] (Me=Fe~(3+), Mn~(3+), Mn ~(2+), Cu~(2+), and Zn~(2+)) was higher than that of the corresponding metal ion, indicating that H_2-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 Fe~(3+)- and Mn ~(3+)-TCAS[4] showed high O_2~- scavenging activities, similarly to the results by the NBT method.