New antibiotics, resorcinomycins A and B, were isolated from the culture broth of a streptomycete strain identified as Streptoverticillium roseovertidllatum. The antibiotics are water-soluble amphoteric substances, positive to SAKAGUCHI'S reagent. The molecular formulas C₁₄H₂₀N₄O₅ and C₁₃H₁₈N₄O₅ for A and B were indicated by elemental analysis and secondary ion MS. The structures of these antibiotics were determined by ¹H and ¹³C NMR spectrometry and some chemical evidences to be N-[(S)-α-guanidino-3, 5-dihydroxy-4-isopropylphenylacetyl]glycine and N- [(S) - α - guanidino -3, 5-dihydroxy -4-ethylphenylacetyl]glycine, respectively.

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Methyl 2, 3, 6-trideoxy-3-hydroxyamino-3-C-methyl-α-D-ribo-hexopyranoside (2) and the corresponding amino sugar (4) were isolated from reduced viriplanin A by acidic methanolysis and esterified to the di-p-bromobenzoates (3 and 5), respectively. The absolute configuration of crystalline 3 was determined by X-ray analysis to be α-D. This result could be confirmed by oxidation of 2 to methyl α-D-decilonitroside (6) and from the CD spectra of 3 and 5. Thus, the nitrogen-containing sugars of viriplanin A and probably those of decilorubicin and arugomycin belong to the D-series.

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Myxochelin A, a new catechole siderophore, was isolated from the culture broth of the myxobacterium, Angiococcus disciformis strain An d30. As is the case with other iron-chelating compounds the production of myxochelin A could be markedly increased up to 44 mg/liter by fermentation at low iron concentrations (10^-7 M FeCl₃). The new substance showed weak activity against some bacteria.

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Two new carbapenem antibiotic-producing actinomycetes, the cell-walls of which contain LL-diaminopimelic acid and meso-diaminopimelic acid, were isolated from soil. The two strains were subjected to taxonomic studies, which involved morphological, cultural, physiological and chemotaxonomical characterization, the latter including the cell-wall chemotype, whole-cell sugar composition, phospholipid composition, menaquinone system and DNA base composition. These strains were identified as new species of the genus Kitasatosporia. The proposed names are Kitasatosporia papulosa for strain AB-110 (IAM 13637, PERM 9000, JCM 7250) and Kitasatosporia grisea for strain AA-107 (IAM 13638, JCM 7249).

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In freshly harvested Aspergillus terreus cultures grown for the production of lovastatin (formerly called mevinolin), no monacolin L could be detected. However, during the isolation of lovastatin, significant quantities of monacolin L appeared. It has been discovered that a new metabolite structurally related to the members of the monacolin series is present. This metabolite is unstable and under mildly acidic conditions and elevated temperature, it converts to monacolin L. The subject metabolite is proven to be a hydroxylated derivative of dihydromonacolin L identified as 3α-hydroxy-3, 5-dihydromonacolin L. It seems that all monacolin L found later during various treatments of the broth and broth extracts is formed from that precursor via a dehydration reaction. The new metabolite was converted to its phenacyl ester, by means of extractive alkylation, for isolation and structure elucidation by chemical, chromatographic and spectroscopic methods. This ester, on standing, gradually formed the corresponding lactone.

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Endusamycin formerly called CP-63, 517 (C₄₇H₇₇O₁₄Na), is a novel polycyclic ether antibiotic produced by a new strain of Streptomyces endus subsp. aureus (ATCC 39574). Recovery, fractionation and purification were achieved using standard procedures. Forms include the endusamycin free acid, mp 95 - 105°C, λ_max 232 nm (log E 4.16), [α]²⁵_D +47.4° (c 0.5, methanol) and a crystalline sodium salt, mp 215-220°C, λ_max 232 nm, (log E 4.15), [α]²⁵_D +25° (c 0.5, methanol). The structure is shown below, Fig. 1. Endusamycin exhibited; antibacterial activity, in vitro against Gram-positive and anaerobic bacteria, effectiveness against coccidia in poultry, and stimulation of propionic acid production in an in vitro system.

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Antibiotics containing a quinone group show characteristic reduced pseudo-molecular ions (M+2)⁺ and (M+3)⁺ during the measurements of secondary ion mass spectra using glycerol as a matrix. The ratios of peak intensities (M+2)⁺ and (M+3)⁺ over (M+1)⁺ increase with time. As this phenomenon is not found using sulfolane as a matrix, the quinone group seems to be hydf ogenated to a hydroquinone by active hydrogen which is produced from a free hydroxyl group of the glycerol by bombardment with the Xe⁺ beam. This hydrogenation reaction is specific for the quinone group.

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The synthesis and structure-activity relationships of a series of 3-(2-imidazolyl)thiomethyl cephalosporins are described. Among the compounds, 7β-[2-(2-amino-1, 3-thiazol-4-yl)-(Z)-2-methoxyiminoacetamido]-3-[(4, 5-dicarboxyimidazol-2-yl)thiomethyl]-3-cephem-4-carboxylic acid (1) exhibited potent activity against both Gram-positive and Gram-negative bacteria including Pseudomonas aeruginosa. We also estimated lipophilicity of the compounds from the chromatographic log k' value of reversed-phase HPLC. The relationship between lipophilicity and biological activity showed that compound 1 had the most suitable lipophilicity.

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Over eighty N-alkyl vancomycins were synthesized by reductive alkylation of vancomycin with the appropriate aldehydes. The N-alkyl vancomycins exhibit greater antibacterial activity than the corresponding N-acyl vancomycins and the parent antibiotic. Some of these semisynthetic vancomycins are five times more active than vancomycin. The N-alkyl vancomycins also show longer elimination half-lives in rats than vancomycin.

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An improved screening system in a search for carbapenem antibiotics from actinomycetes was developed, involving (1) effective isolation of carbapenem antibiotic producers, (2) favorable cultivation as to antibiotic production and (3) simplified identification of the carbapenem antibiotics: (1) A frequency of isolation of carbapenem antibiotic producers from soils was increased by the use of an amoxicillin/clavulanate-contaimng medium. As many as 20% of the actinomycetes isolated in this medium were found to be carbapenem antibiotic producers, as compared with 0.6% when conventional media were employed. (2) An agar-surface cultivation on oatmeal - yeast extract - malt extract (OMYM) medium, containing oatmeal, yeast extract, malt extract, glucose and trace elements, was most suitable for the antibiotic production. (3) An agar-diffusion assay for identification of carbapenem antibiotics was developed. Although the carbapenem antibiotics are stable against β-lactamases, they were hydrolyzed completely with excess amounts of common β-lactamases. So they could be discriminated from other β-lactam antibiotics and non-β-lactam antibiotics by comparison of the susceptibility profiles for such enzymes.

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Lactivicin is moderately active against a wide range of Gram-negative bacteria and highly active against Gram-positive bacteria. It shows various biological activities commonly observed with β-lactam antibiotics, such as higher activity against β-lactam hypersensitive mutants than against their parents, sensitivity to β-lactamases, inhibitory activity against β-lactamases and ability to induce β-lactamase activity. The primary lethal target of lactivicin in Escherichia coli is highly likely to be penicillin-binding protein (PBP) 1; lactivicin strongly lysed E. coli cells with induction of spheroplasts at its MIC, and showed high affinity for PBPs 1A and IB. At concentrations above × 5 MIC, however, lactivicin dominantly exhibited secondary antibacterial action possibly owing to inhibition of crucial SH proteins engaged in the fundamental membrane functions. In contrast, against Bacillus subtilis, lactivicin showed the typical β-lactam action under a wide range of concentrations. It showed high affinity for PBPs 1, 2 and 4, the possible lethal targets of β-lactam antibiotics in this organism. In conclusion, lactivicin is the first non-β-lactam antibiotic showing β-lactam action through binding to PBPs.

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Phenelfamycins A, B, C, E, F and unphenelfamycin make up a recently isolated group of elfamycin-type antibiotics. All of the phenelfamycins were active against Gram-positive anaerobes, including Clostridium difficile. Phenelfamycin A was also active in vitro against Neisseria gonorrhoeae and Streptococci. Phenelfamycin A was found to be effective in prolonging the survival of hamsters in an animal model of C. difficile enterocolitis. After oral administration of phenelfamycin A to hamsters, antibiotic was detected in the caecal contents but not in the blood.

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During the screening for the inhibitors of protein kinase C (PKC), we found that a streptomycete produced an inhibitor in our bleb-forming assay (OSADA et al., J. Antibiotics 41: 925, 1988). The inhibitor was isolated and identified as sangivamycin (4-amino-5-carboxamide-7-(D-ribofuranosyl)pyrrolo[2, 3-d]pyrimidine). Biological activity of sangivamycin was compared with that of other 7-deazaadenosine group antibiotics, tubercidin and toyocamycin. Sangivamycin showed a strong inhibitory activity against bleb-formation of K562 cells and PKC. On the other hand, tubercidin and toyocamycin had only weak activities in both assays. This paper deals with a new biological activity of sangivamycin, that of an inhibitor of protein kinases, especially PKC.

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The inhibition of human immunodeficiency virus (HIV) reverse transcriptase by certain antibiotics and related compounds was studied in comparison with that of avian myeloblastosis virus (AMV) reverse transcriptase and cellular DNA polymerases α and β. In general, compounds that inhibited HIV reverse transcriptase also inhibited AMV reverse transcriptase. For example, 10 μg/ml of the isoquinoline quinones used in this study inhibited approximately 80 % of the activity of reverse transcriptases of HIV and AMV, but did not inhibit the activity of DNA polymerases α and β even at 50 μg/ml. AMV enzyme was more sensitive than HIV enzyme to colistin, enduracidins A and B, janiemycin, glysperin A, and thielavins A and B. The streptonigrin alkyl esters, however, inhibited HIV reverse transcriptase only. Sakyomicin A, luzopeptins, ellagic acid and suramine inhibited the activities of reverse transcriptases and cellular DNA polymerases.

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Spergualin (SG) and 15-deoxyspergualin (DSG) were more slowly incorporated into L5178Y cells than spermidine. SG and DSG inhibited carrier-mediated transport of [³H]spermidine competitively with inhibition constants of 0.67 mM and 0.45 mM, respectively. Addition of calf serum stimulated uptake of [³H]spermidine into the cells in a serum concentration-dependent manner. The effect was not observed when horse serum was used in place of calf serum. Preincubation of spermidine in calf serum for 1 hour before addition to cells remarkably decreased cellular incorporation of tritium. Three amine oxidase inhibitors, aminoguanidine, 3-hydroxybenzyloxyamine, and semicarbazide, inhibited stimulation of uptake of [³H]spermidine by calf serum and the decrease of it by preincubation in calf serum. So we propose that cellular incorporation or binding of products generated by oxidation of spermidine by amine oxidase in calf serum was much faster than that of spermidine itself and they were unstable and transformed quickly to unincorporable or non-binding substances if cellular targets were not present.
Effect of amine oxidase inhibitors on cytotoxic activity of SG and DSG were determined in low and high concentrations of calf serum. In the presence of 10% calf serum in the basal medium, cytotoxicity to L5178Y cells by SG and DSG was suppressed at high drug concentrations (above 10 μg/ml) and enhanced at low drug concentrations (below 2.5 μg/ml) by amine oxidase inhibitors. In the presence of 0.5 % calf serum suppression of cytotoxicity at high drug concentrations by amine oxidase inhibitors was also observed, but enhancement at low drug concentrations was obscure. These data may suggest the existence of two kinds of cytotoxic mechanism of SG and DSG, one dependent on and one independent of amine oxidase in serum.

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