S 3 1 is a simplified synthetic analogue of the active principle of Salvia miltiorrhioza. Electron spin resonance spectrometry using 5

5′ dimethyl 1 pyrroline N oxide as a scavenger of free radicals indicated that 200 μg/ml of S 3 1 scavenged 1

1 diphenyl 2 picrylhydrazyl radicals completely. 25μg/ml of this compound quenched 100% of superoxide anion and a concentration of 250 μg/ml of S 3 1 quenched 63% of hydroxyl radicals. It was also shown that 3 56 mg/ml of S 3 1 could inhibit lipid peroxidation in microsome fraction from rat liver induced by FeSO 4 and cysteine. These results show that S 3 1 is an effective antioxidant by scavenging free radicals.