A culture of Micromonospora species MK-70 was found to produce two new antibiotics, fortimicins A and B. Antibacterial and paper chromatographic data on an eluate from IRC-50 treatment of fermentation beers indicated that fortimicins A and B are new antibiotics with broad-spectrum, basic and water-soluble properties. Fortimicin A exhibited potent, unique, broad-spectrum antibacterial activity against Gram-positive and negative bacteria both in vitro and in vivo, while fortimicin B was only weakly active.In the course of screening for new antibiotics, a complex of antibacterial antibiotics was obtained from the culture broth of Micromonospora sp. MK-70. This antibiotic complex XK-70 contained two main components designated as XK-70-1 and XK-70-A, both of which exhibited broad-spectrum antibacterial activities. Subsequent studies showed that the two antibiotics are new aminoglycosides, as reported both in the present report and in other papers describing isolation, characterization and structure determination1,2). Therefore we designated XK-70-1 and XK-70-A as fortimicin A and fortimicin B, respectively. This paper deals with the producing organism, fermentation and the biological properties of fortimicins A and B.

A novel inhibitor of angiotensin I converting enzyme (ACE), designated K-26, was isolated from the broth filtrate of an actiomycete K-26. K-26 is a water soluble, acidic peptide composed of an equal mol of L-isoleucine, L-tyrosine and l(R)-l-amino-2-(4-hydroxyphenyl)-ethylphosphonic acid. The IC50 of K-26 for ACE inhibition was 6.7 ng/ml when hippuryl-Lhistidyl-L-leucine was used as a substrate of ACE. K-26 possesses hypotensive activity in vivo.Angiotensin I converting enzyme (ACE) has been found to play a critical role in the regulation of blood pressure in man and animals.Ever since the discovery of captoprill1) a specific inhibitor of ACE, and its successful application to the therapy of hypertension, attempts have been made to develop

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Thin-layer chromatography of the mixed neomycin sulfates on carbon plates. Anal.