Sulfobacins A and B, Novel von Willebrand Factor Receptor Antagonists: I. Production, Isolation, Characterization and Biological Activities

Sulfobacins A and B, novel von Willebrand factor (vWF) receptor antagonists, have been isolated from the culture broth of Chryseobacterium sp. (Flavobacterium sp.)^† NR 2993 by ethyl acetate extraction, and by Sephadex LH-20 and silica gel column chromatographies. The physico-chemical properties of the sulfobacins indicate that their structures are completely different from that of aurintricarboxylic acid, the one known vWF receptor antagonist. Sulfobacins A and B inhibit the binding of vWF to its receptor with IC₅₀s of 0.47 and 2.2 μM, respectively. Sulfobacin A also inhibits ristocetin-induced agglutination in human platelets fixed with paraformaldehyde with an IC₅₀ of 0.58 μM.