Objective: To establish a method to assay antioxidant activity in vitro of Leonuri Herba and Leonuri Fructus

as a guide for clinical rational use of Leonuri Herba and Leonuri Fructus. Method: 75% ethanol extracting solutions of Leonuri Herba and Leonuri Fructus were prepared with ultraphonic for 30 min at 25℃

and their antioxidant capacity were evaluated with 1

1-Diphenyl-2-picrylhydrazyl radical-2

2-Diphenyl-1-(2

4

6-trinitrophenyl) hydrazyl (DPPH·) spectrometry

compared with vitamin E. Result: The extracts of Leonuri Herba and Leonuri Fructus both had good scavenging effects on DPPH·. IC50 of Leonuri Herba extract

Leonuri Fructus extract and vitamin E solution were 2.70

1.28

5.89 g·L-1

respectively. In other words the antioxidant capability was:Leonuri Fructus extract>Leonuri Herba extract>vitamin E. The repeatability inspection were:Leonuri Herba

RSD 3.34%; Leonuri Fructus

RSD 2.25%. Conclusion: Leonuri Fructus has a stonger antioxidant than Leonuri Herba in vitro.