Inhibition of PGHS-1 and PGHS-2 by Triterpenoid Acids from Chaenomelis Fructus

Abstract

The dichloromethane extract of the dried fruits of Chaenomeles speciosa (Sweet) Nakai (Rosaceae) showed strong inhibitory activity against both prostaglandin-H-synthase isoenzymes [IC50 (PGHS-1) = 5.1 μg/mL; IC50 (PGHS-2) = 2.3 μg/mL]. The lipophilic portion of the extract was mainly responsible for the inhibitory effect. Several triterpenoid acids were isolated and identified as contributing to this inhibitory activity (oleanolic, pomolic, 3β-O-acetylursolic and 3β-O-acetylpomolic acids). Comparison of their inhibitory potential with their selectivity to PGHS-2 showed that 3β-O-acetylursolic acid had the highest potency in the inhibition of PGHS-1 and PGHS-2 enzymes, whilst pomolic and 3β-O-acetylpomolic acid, with a hydroxyl group at position 19α, showed selectivity for PGHS-2. The inhibitory effect of the extract seems to be the result of the activity of the mixture of these different triterpenoid acids.