Xanthocillin X monomethyl ether, a potent inhibitor of prostaglandin biosynthesis

Xanthocillin X monomethyl ether, known as an antiviral antibiotic, was isolated as a potent inhibitor of Dichotomomyces cejpii. The compound inhibited prostaglandin synthesis from 14C-arachidonic acid in rabbit kidney microsomes by 50% at a concentration of 0.2 microM, while prostaglandin synthesis by microsomes of ram seminal vesicle was inhibited by 50% at 20 microM. The inhibition of xanthocillin X monomethyl ether was reversible. Of the enzymatic steps involved in the synthesis of prostaglandins and thromboxanes tested, conversion of arachidonic acid into prostaglandin H2 was specifically inhibited by xanthocillin X monomethyl ether. Anti-inflammatory activity of this antibiotic on carrageenan-induced oedema in the rat foot was, however, not detectable.