Terpenoid Antibiotics in Clinical Practice

A rather interesting development emanating from the observation that fusidic acid exhibits S5mergism with other antibiotics has been the S5mthesis of tetracychne fusidate which is claimed to exhibit higher antibacterial potency than a mixture of tetracychne and fusidic acid [329]. 

On the basis of its activity and antagonism relationships, fusidic acid has been placed with chloramphenicol, the tetracychnes and the erythromycin 

Investigation of the metabolic effects of fusidic acid in man [334] have shown that, like the tetracycline group, it has a mild catabolic effect upon protein metabolism. It also shows a hypocalciuric effect and a moderate reduc-tion in bromsulphthalein excretion, with the latter probably arising from a competition between the metabolites of fusidic acid and the bromsulphthalein for a common transport mechanism involved in the excretion into the bile. Seven such metabohtes of fusidic acid have been isolated from human bile [335]. 

The structurally related cephalosporin and helvolic acid do not appear to have the same antibacterial potency as fusidic acid [271, 336, 337] and so would not seem destined for equivalent status in medicine. Similarly the antibacterial potency of the triterpenoid antibiotics polyporenic acid A [338] and polyporenic acid C [339], like that [340] of pristimerin (LXI) [341, 342], which is one of the most highly oxidised naturally occurring pentacyclic triterpenes 

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