A54145 is a complex of acidic lipopeptide antibiotics which are produced by Streptomyces fradiae and are active against Gram-positive bacteria. The A54145 complex was isolated by adsorption on Diaion HP-20nonfunctionalized macroreticular resin and/or ion exchange on Amberlite IRA-68 anion exchange resin. Antibacterial factors A, A1? B,

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A58365A and A58365B, angiotensin converting enzyme inhibitors, were isolated from the culture filtrate of Streptomyces chromofuscus NRRL 15098. A58365A and A58365B are homologous nitrogen-containing bicyclic structures of molecular formulae C,2H,3NOo and C"H,;NO,.Recently, several inhibitors of angiotensin converting enzyme (ACE) have been discovered from fermentation sources1-11)A previous paper in the present series described the development of a high volume, agar-based screen for the detection of ACE inhibitors produced by fermentations and the discovery of ACE inhibitory activity in the culture broth of Streptomyces chromofuscus NRRL 1509812) (culture A58365.1). The conditions for the biosynthesis of the ACE inhibitors A58365A and A58365Bproduced by this microorganism have also been described". This paper describes the isolation and characterization of the two ACE inhibitors. Materials and Methods Assay of Angiotensin Converting Enzyme Inhibitory ActivityThe qualitative agar-plate method of O'CONNOR and SOMERS12) was employed for monitoring purification of ACE inhibitors. Dried preparations were assayed in the quantitative spectrophotometric assay 12) to determine inhibitor potency.HPLC Assay of A58365A and A58365B HPLC determinations of A58365A and A58365B utilized a 4 mm x 30 cm Waters Associates ,uBondapak C,, reversed phase column with a mobile phase consisting of CH3CN -HCOOH -H2O (6.0: 0.3: 93.7). Broths were adjusted to pH 2.0 and filtered (0.45 um) prior to injection. Partially purified materials required no sample preparation.Detection was by either UV absorption at 325 nm or by fluorescence measurement. For accurate quantitation a Schoeffel model FS970 spectrofluorometer with excitation at 327 nm and a 370 nm emission cutoff filter coupled to a Hewlett-Packard 3390A integrator was used. With a mobile phase flow rate of 2.5 ml/minute, A58365A had a retention time of 4.88 minutes; A58365B, 12.47 minutes.General Methods UV spectra were run on a Cary model 118 spectrophotometer.Fluorescence spectra were obtained with an Amino-Boman Spectrophotofluorometer.IR spectra were recorded on a Nicolet MX-1 FT-IR spectrometer. 1H NMR spectra were obtained with a Bruker model WH-360 NMR