Antiprotease effect of anti-inflammatory lupeol esters

Lupeol-3-palmitate (LP) and lupeol-3-linoleate (LL), two synthetic long chain fatty acid ester analogues of the plant-derived anti-inflammatory pentacyclic triterpenoid lupeol (L), were studied in vitro as potential inhibitors of serine protease activity. With respect to the natural protein substrate bovine serum albumin (BSA), lupeol palmitate and lupeol linoleate inhibited trypsin activity in a manner consistent with mixed inhibition (K(IC) values of 103 and 52 microM respectively; K(IU) values of 30 and 14 microM respectively). However, the lupeol esters showed no inhibitory effect on the catalytic activity of porcine pancreatic elastase (PPE) with respect to the synthetic tetrapeptide substrate succinyl-(alanyl)3-p-nitroanilide (SAAANA). The present paper shows the lupeol triterpenes to be selective protease inhibitors.