Abstract: In the course of a screening for inhibitors of PAI - 1 from natural products with small molecular weight, preliminay "hits" were found from several natural products. Further investigation and selectivity experiments indicated that compound 1 (expoxyrolin B), compound 4 (cherimolin - 2) and compound 6 (damnacanthal) showed some inhibition on plasmin; compound 2 (muricatin C) showed week specific PAI - 1 inhibition activity. Compound 5 (morindone) inhibited thrombin, trypsin and plasmin, compound 7 (16a - hydroxy - cleroda - 4 (18),13 (14) Z-dien-15, 16-olide), compound 8 (hedergenin) and compound 9 (ocetadecanoic acid - 9 - yne) inhibited thrombin and plasmin. This report deals with the re-sults of the effect of several natural products on the fibrinolytic system.

Key words: Natural products