Anti-inflammatory thiazine alkaloids isolated from the New Zealand ascidian Aplidium sp.: inhibitors of the neutrophil respiratory burst in a model of gouty arthritis.

Ascidiathiazones A (3) and B (4), two new tricyclic thiazine-containing quinolinequinone alkaloids, were isolated from the New Zealand ascidian Aplidium species. Both compounds inhibited the in vitro production of superoxide by PMA-stimulated human neutrophils in a dose-dependent manner with IC50 1.55 +/- 0.32 and 0.44 +/- 0.09 microM, respectively. In vivo inhibition of superoxide production by peritoneal neutrophils in a murine model of gout was observed for both compounds with oral doses of 25.6 micromol/kg. Ascidiathiazone A (3) was synthesized in four steps from 8-hydroxyquinoline-2-carboxylic acid.