A40926 aglycone and pseudoaglycones: preparation and biological activity.

A40926 antibiotics are new glycopeptides which are much more active than other members of this class against Neisseria gonorrhoeae. Their activity against Gram-positive bacteria, including coagulase-negative Staphylococci, is similar to that of other glycopeptides. An A40926 preparation containing factors A and B ("A40926 A + B complex") was hydrolyzed to the aglycone and to the mannosyl and N-acylaminoglucuronyl aglycones. The mannosyl aglycone and the aglycone were less active than A40926 A + B complex against Streptococci and Gram-positive anaerobes and lost the anti-gonorrheal activity. In contrast, the N-acylaminoglucuronyl aglycones were as active as the parent complex against these Gram-positive bacteria and were moderately active against N. gonorrhoeae. The aglycone and, even more so, the N-acylaminoglucuronyl aglycones, had better activity than the parent complex against coagulase-negative Staphylococci. In experimental septicemia in the mouse, A40926 A + B complex and its derivatives had activity proportional to their MIC for the test organism.