Synthesis of guanylhydrazones derived from 3-pyridinol and evaluation of their effect on serum thromboxane B2 and prostaglandin E2 production.

3-Pyridyloxyacetaldehyde guanylhydrazone and the guanylhydrazones of pyridine-2- and -4-aldehydes substituted at the 3-position with the omega-carboxypentyloxy chain were synthesized in order to evaluate their activity as thromboxane synthase inhibitors in vitro. The tested compounds inhibit thromboxane B2 biosynthesis in human serum. The first appears to be a selective inhibitor of thromboxane synthase, since there was a concomitant rise in Prostaglandin E2 (PGE2) level. The derivative of 4-pyridinealdehyde was the more active one of the other two compounds but it also markedly lowered PGE2 biosynthesis proving to be an inhibitor of cyclooxygenase.