Inhibition of human plasmin activity using humic acids with arsenic

In this study, we examined the effects of natural humic acid ŽHA. purified from drinking well-water in Blackfoot disease ŽBFD. endemic areas, using synthetic humic acid ŽSHA., such as protocatechuic acid, ferulic acid, vanillic acid or catechol, and trivalent arsenic on human plasmin activity. Data in this report indicated that both HA and SHA inhibited human plasmin activity by 20 80 and 5 95%, respectively, at concentrations of 20 480 g ml. Organometallic complexes composed of HA and arsenic show enhanced inhibition of plasmin activity as compared with either HA or arsenic alone. Monomers of HA or arsenic alone do not inhibit plasma activity. Oxidative stress may play a role in the inhibition of plasma activity, as various free-radical scavengers, such as ascorbic acid, -tocopherol, catalase and superoxide dismutase ŽSOD., abrogate the inhibitory effects of HA and HA arsenic complexes. The notion that HA organometallic complexes ŽHA OR. impaired plasmin activity was significant, due to the fact that both of these agents ŽHA and arsenic. are etiological factors in the development of peripheral vascular diseases, such as BFD. This report substantiates the inhibitory effects of HA OR on plasmin activity, and thus provides evidence for the partial mechanism of action of HA OR in BFD.