Synthesis and antioxidant activity of new tetraarylpyrroles

The synthesis and in vitro antioxidant activity of 17 new tetraarylpyrroles are investigated by 2 tests highly documented in the literature: capability to prevent Fe(2+)-induced lipid peroxidation on microsomes, which is a membrane preparation rich in polyunsaturated fatty acids, and direct scavenging effect on a stable free radical, 1,l-diphenyl-2-picryl-hydrazyl (DPPH). For the Fe(2+)-induced microsomal lipid peroxidation system, the results show that molecules which possess 2-pyrazinyl or 2-pyridyl in the 3- and 4-positions on the pyrrole ring are the most efficient. Introduction of methoxy groups on the phenyl ring in the 2- and 5-positions increases the effects but the higher activity is obtained with 2-furyl or 2-thienyl. The only compounds which possess a direct scavenger effect on trapping the stable free radical DPPH are those which have 2-pyridyl in the 3- and 4-positions and 2-furyl or 2-thienyl in the 2- and 5-positions.