Ansamycin

Ansamycins is a family of secondary metabolites that show antimicrobial activity against many gram-positive and some gram-negative bacteria and includes various compounds among which: streptovaricins and rifamycins. In addition, these compounds demonstrated antiviral activity towards bacteriophages and poxviruses. They are named ansamycins—ansa from the Latin for handle—because of their unique structure which comprises an aromatic moiety bridged by an aliphatic chain. The main difference between various derivatives of ansamycins is the aromatic moiety, which can be a naphthalene ring or a naphthoquinone ring as in rifamycin and naphthomycin. Another variation comprises benzene or a benzoquinone ring system as in geldanamycin or ansamitocin. Ansamycins were first discovered in 1959 by Sensi et al from Amycolatopsis mediterranei, an Actinomycete. Rifamycins are a subclass of ansamycins with high potency against mycobacterial activity. This resulted in their wide use in the treatment of tuberculosis, leprosy, and AIDS-related mycobacterial infections. Since then various analogues have been isolated from other prokaryotes.