Humic acid: inhibitor of plasmin

Synthetic humic acid, well water humic acid and commercial humic acid (Aldrich) all have the ability to inhibit human plasmin activity. At a concentration of 20 micrograms/ml, all three species will result in 93%, 70% and 40% of residual plasmin activity, respectively. The components of humic acid, such as protocatechuic acid, resorcinol, vanillic acid and ferulic acid do not have such inhibitory activities. The ability of humic acid to inhibit human plasmin has not been reported. It is, therefore, a new plasmin inhibitor.