Inhibition of trypsin and chymotrypsin by anti-inflammatory triterpenoids from Compositae flowers.

Taraxastane, oleanane, ursane, lupane, taraxane, cycloartane, dammarane and tirucallane triterpenoids isolated from flowers of Compositae plants have been previously reported to exhibit anti-inflammatory effects and are variously competitive and non-competitive inhibitors of the serine proteases trypsin and chymotrypsin. The general features of those triterpenoids found to be protease inhibitors are having a hydroxy group and an appropriate side chain in the region of the molecule distal to the 3-hydroxy group. However, fatty acid esterification of the triterpenoid 3-hydroxy group can have a marked effect on inhibitor effectiveness. This suggests a possible means of rapid alteration of the plant defensive complement in vivo and of the bioactivity of these anti-inflammatory compounds.