Actaplanin (A4696), a new complex of broad spectrum Gram-positive antibiotics is produced by Actinoplanes inissouriensis. High performance liquid chromatography was used to show that this complex is composed of several actaplanins. Hydrolytic experiments with actaplanins A, B1, B2, B3, C1 and G showed that these actaplanins were composed of the same peptide core, an amino sugar and varying amounts of glucose, mannose and rhamnose. The neutral sugar content was determined for each actaplanin. A bioautographic study of aglycone formation during hydrolysis of the actaplanin complex showed that within a short time a simple mixture of two antimicrobially active hydrolysis products was obtained. These substances retained the antimicrobial spectrum and a high percentage of the antibiotic activity of the parent actaplanin complex. Methanolysis of the actaplanin complex as well as the individual actaplanins resulted in the selective loss of the neutral sugar moieties and the isolation of actaplanin Ψ(pseudo)-aglycone-the core peptide which still retained an amino sugar group. The 1H NMR spectrum of this substance indicated a similarity to many features of ristocetin Ψ-aglycone. Hydrolytic studies showed that the amino sugar present in actaplanin was identical with L-ristosamine. It is concluded that the aglycone of actaplanin is a complex peptide composed of aromatic amino acids, and that the actaplanins each possess this aglycone and L-ristosamine but are differentiated by their neutral sugar composition.
Antibiotic U-64846 is a new entity with the molecular formula C18H35ClN4O9 (MW 486). It is a very water soluble, reddish solid which decomposes above 300°C and which is air-sensitive. The antibiotic is produced by Streptomyces braegensis and it inhibits a variety of Gram-positive bacteria. Acidic hydrolysis gave 3, 7-diaminoheptanoic acid. The antibiotic gives 1H NMR, 13C NMR, IR and UV spectra which indicate it is not closely related to known antibiotic families.
Fermentation of Streptomyces hygroscopicus var. crystallogenes, the copiamycin source, yielded several minor components with antifungal activity. One of these minor components, neocopiamycin A, was isolated and characterized. The structure of neocopiamycin A was determined as N-demethylcopiamycin on the basis of spectroscopic evidence. The antibiotic was found to be more active against Gram-positive bacteria and fungi but less toxic than copiamycin.
The bafilomycins A1, A2, B1, B2, C1 and C2, a new type of macrolide antibiotics with a 16-membered lactone ring, were isolated from the fermentation broth of three Streptomyces griseus strains (TÜ 1922, TÜ 2437, TÜ 2599) by ethyl acetate extraction and column chromatography on silica gel. The bafilomycins exhibit activity against Gram-positive bacteria and fungi. Physico-chemical data, chemical structures and biological activities are reported.
Carbomycin A (deltamycin A4) was deepoxidized to carbomycin A P1 by Streptomyces halstedii subsp. deltae (a deltamycins producer), favorably under anaerobic conditions. Carbomycin A P1 was spontaneously converted to geometric isomers designated carbomycins A P2 and A P3. This type of deepoxidation and subsequent isomerization was not limited to carbomycin A, but generally occurrable in other 16-membered epoxyenone macrolide compounds. Many bacteria and actinomycetes were also found to have an ability to deepoxidize deltamycins reductively. The chemical structures of carbomycins A P1, A P2 and A P3 were elucidated as shown in Fig. 3.
16-Membered epoxyenone macrolide antibiotics were reductively deepoxidized with dissolving metals such as zinc. Angolamycin and rosamicin which have a methyl substituent at C-12 in the epoxyenone structure were deepoxidized, but not isomerized further to the geometric isomers P2 and P3.
Deepoxidation products P1, P2 and P3 of carbomycin A, deltamycin A1 and 4″-phenylacetyldeltamycin showed high in vitro antibacterial and antimycoplasmal activities which were comparable to those of the respective parent compounds. By contrast, the in vitro antimicrobial potencies of angolamycin P1 and rosamicin P1 were about ten-fold lower than those of the parent macrolides. In mice, the increase in the plasma levels of the epoxyenone macrolides due to deepoxidation was highly significant with the P1, P2 and P3 derivatives of carbomycin A and 4″-phenylacetyldeltamycin, whereas angolamycin P1 gave a moderately-improved plasma level compared with angolamycin.
A new soil actinomycete (UC 5762, NRRL 11111) was found to transform novobiocin to 11-hydroxynovobiocin. The product was isolated by solvent extraction and column chromatography, and identified by IR, UV, 1H NMR and 13C NMR spectroscopy. Related structures (8, 9-dihydronovobiocin, novobiocic acid and chlorobiocin) were similarly transformed to their corresponding C-11 hydroxylated analogues. The microbial process is superior to chemical (selenium dioxide) oxidation which yielded a mixture of 11-hydroxy- and 11-oxonovobiocin.
Lividamine and paromamine were converted into two key intermediate ethylenic aldehydes 10a and 10b. Reductive amination of the two aldehydes yielded the protected sisamine 11a and the three analogs 11b, 12a and 12b. These four derivatives were deprotected to yield the four pseudodisaccharides 1a, 1b, 2a and 2b which were less active in vitro than neamine against Escherichia coli ATCC 9637 and Staphylococcus aureus 209P.
The three protected sisamine derivatives 2i, 2j and 3, with a free 5-hydroxyl group, have been synthesized. Glycosylation at the 5 position with various pentofuranose derivatives yielded after deprotection of the 6a-i ribostamycin related aminoglycoside. These pseudotrisaccharides showed only low antibacterial activities with respect to the parent compounds.
The enzyme activities which catalyze the conversion of tryptophan to β-methyltryptophan by two different routes have been demonstrated in cell-free extracts of streptonigrin-producing Streptomyces flocculus. The first route involves direct methylation of tryptophan by a C-methyltransferase. The second involves transamination of tryptophan to indolepyruvate, methylation of indolepyruvate to β-methylindolepyruvate, followed by a reverse transamination reaction to yield β-methyltryptophan. The direct methylation route was confirmed by the fact that the methyltransferase activity is still present after the transaminase has been inactivated by hydroxylamine treatment. The L-tryptophan C-methyltransferase has been purified 30-fold by ammonium sulfate precipitation and a Sephadex G-150 column. The indolepyruvate C-methyltransferase activity copurified with the tryptophan C-methyltransferase activity, but the transaminase did not. These results show that a metabolic grid exists for the first antibiotic-committed step of the streptonigrin biosynthetic pathway.
The effect of cefoperazone on ethanol and acetaldehyde metabolism was studied in rat liver homogenates and with a purified aldehyde dehydrogenase. Rat liver homogenates were incubated with ethanol (30 mM) alone or in combination with cefoperazone (15 or 150 μg/g liver). Ethanol and acetaldehyde concentrations were determined at 6, 12, 18 and 24 minutes. Cefoperazone added to the incubation medium inhibited ethanol and acetaldehyde metabolism in a concentration-dependent manner. The addition of cefoperazone to rat liver homogenates incubated with acetaldehyde (300 μM), however, did not inhibit acetaldehyde disappearance for a period of 15 minutes. Purified aldehyde dehydrogenase was incubated with 300 μM acetaldehyde. When cefoperazone was added, acetaldehyde disappearance was significantly slower than without cefoperazone. The data indicate that cefoperazone inhibits ethanol metabolism in rat liver homogenates in a concentration-dependent manner. The effect of the antibiotic on acetaldehyde elimination in liver homogenate, however, depends on the concentration of acetaldehyde in the medium. The acetaldehyde dehydrogenase obtained from yeast is inhibited by cefoperazone.
Iturin A and bacillomycin L, antibiotics of the iturin group inhibit the growth of Saccharomyces cerevisiae and the lethal doses were respectively 10 and 60 μg/ml. Both antibiotics had an effect on the incorporation of radioactive precursors into macromolecules which decreased with increasing concentrations of antibiotics. However, no specificity was observed on the various macromolecules, proteins, ribonucleic acids and polysaccharides. The site of action on yeast cells was demonstrated to be the cytoplasmic membrane: both antibiotics of iturin group lysed spheroplasts of S. cerevisiae. Moreover, a rapid leakage of potassium ions occurred in the presence of the antibiotics; this leakage was directly associated to the killing effect. These results are consistent with a disruption of the structural integrity of the cytoplasmic membrane correlated to the loss of viability of the yeast cells.