The NAD(P)-linked 3α-Hydroxysteroid dehydrogenase(3α-HSD) of rat liver cytosol is powerfully inhibited by the non-steroidal anti-inflammatory drugs in rank-order of their therapeutic potency, and this observation has now been developted into a rapid screen for predicting the potency of products that show anti-inflammatory effect. Five-plants were screened by using this method. Among them, BuOH-fraction of Mucuna birdwoodiana showed strong inhibitory effect on 3α-HSD, and three isoflavone compounds were isolated. Inhibitory activites of isolated compounds were compared.