A novel antitumor antibiotic, DC-52 was found in the culture broths of Actinomycete DO-52. The producing organism was subsequently determined to be a new species and named Streptomyces melanovinaceus nov. sp. For the production of the antibiotic, soluble starch served as a good carbon source and soybean meal was a good nitrogen source tested. The antibiotic DC-52 is active against Bacillus subtilis, Staphylococcus aureus and Klebsiella pneumoniae, but not active against most Gram-negative bacteria. The antibiotic is also active against mouse leukemia P388.

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DC-52, C₁₈H₂₂N₂O₄, is a new antitumor antibiotic produced by Streptomyces melanovinaceus nov. sp. The structure of DC-52 has been determined by consideration of spectral data. It has the novel skeleton, 8, 11-iminoazepinoisoquinoline.

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Extracellular polysaccharides of marine bacteria were screened for their antitumor activity against sarcoma-180 solid tumor in mice. An active polysaccharide was purified and named marinactan. The producing microorganism has a typical marine bacterial nature requiring sea water for growth and was identified as Flavobacterium uliginosum. Marinactan is a novel heteroglycan consisting of glucose, mannose and fucose in a ratio of approximately 7:2:1. Marinactan, 10- 50 mg/kg daily for 10 days i.p., produced 70-90% inhibition of the growth of solid sarcoma 180. Complete regression of the tumor was observed in some treated mice. Its administrations before and after tumor transplantation showed almost the same inhibitory effect. Marinactan prolonged markedly the survival period of mice bearing ascites sarcoma 180.

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WF-3161 is an antitumor antibiotic produced by a strain of fungus, Petriella guttulata. The antibiotic was purified by solvent extraction and a combination of silica gel and reverse phase column chromatography. The chemical structure of the antibiotic (C31H44N4O6, mp 181-183°C) was found to be a cyclic tetrapeptide consisting of phenylalanine, leucine, pipecolinic acid and 2-amino-8-oxo-9, 10-epoxydecanoic acid. WF-3161 inhibited the growth of Trichophyton asteroides. It prolonged survival period of mice bearing leukemia P-388 with a high therapeutic index.

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Two new ansamycin antibiotics, the naphthomycins B and C, were isolated from two different strains of Streptomyces. The structures were determined by comparison of the spectra (UV, ¹H NMR, ¹³C NMR) with those of the known naphthomycin A, by spin decoupling experiments (300 MHz) and in one case by a two dimensional NMR analysis. Naphthomycin B (II) is 30-chloronaphthomycin C. Strikingly, naphthomycin A (I) differs from B and C not only by the presence of an additional methyl group at C (2), but also in the configuration of some of the double bonds. A fourth ansamycin antibiotic of the naphthomycin subgroup, actamycin, is 30-hydroxynaphthomycin C.

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New antibiotic, isohematinic acid, was found in the culture broth of an actinomycete strain SANK 61681, which was identified as a strain of Actinoplanes philippinensis. Fermentation of isohematinic acid was performed by conventional submerged culture in a 600-liter fermentor. Isolation of isohematinic acid was performed by adsorption of the antibiotic from the culture filtrate on a column of Diaion HP-20 followed by elution with aqueous acetone and extraction with ethyl acetate. Isohematinic acid was finally crystallized from hot methanol.

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Physico-chemical characterization of isohematinic acid revealed that this antibiotic has a succinimide nucleus. From elemental analysis, the molecular formula of isohematinic acid was determined to be C₈H₉NO₄. Isohematinic acid showed weak antimicrobial activities against anaerobic bacteria, such as Bacteroides fragilis and Propionibacterium acnes.

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Strain Au-3, a mutant of Streptomyces hygroscopicussubsp. aureolacrimosus, obtained with ultraviolet irradiation, was a high-yield strain of milbemycins D, E, F, G and H. Fermentation studies on the strains were conducted in shake flasks and 30-liter jar fermentors. Isolation of the metabolites was performed by adsorption on resinous adsorbent followed by elution with aqueous MeOH and separated by silica gel column chromatography. Milbemycin D was obtained as colorless needles after recrystallization and milbemycins E, F, G and H were purified to homogeneity by column chromatography. Physico-chemical characterization revealed that milbemycins D, E, F, G and H were new antibiotics possessing the 16-membered macrocyclic lactone with a 6, 6-membered spiroketal ring system.

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Strain Rf-107, a mutant of Streptomyces hygroscopicus subsp. aureolacrimosus, obtained with ultraviolet irradiation, produced two new macrolide antibiotics, milbemycins J and K without production of any of the other milbemycins described in the previous paper. Fermentation studies on the strain were conducted in shake flasks and 30-liter jar fermentors. Isolation of the antibiotics was performed by adsorption on resinous adsorbent followed by elution with aqueous MeOH. Purification of milbemycins J and K was completed with Lobar Si 60 column chromatography to give colorless crystals. Physico-chemical data, such as UV, IR and NMR spectra are described. Milbemycins J and K were readily converted by the intact cells of the parent strain to milbemycins α₁ and α₃, respectively. Physico-chemical characterization and the bioconversion studies revealed that milbemycins J and K were new antibiotics having the 16-membered macrocyclic lactone with a 6, 6-membered spiroketal ring system.

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Rifamycins are supposed to bind to, and inhibit the bacterial DNA-dependent RNA polymerase (DDRP) by the formation of hydrogen bonds through O (1), O (2), O (9), O (10). Therefore, with the aim of increasing the intrinsic activity of rifamycin S (1), the 25-deacetoxy-25-epi-hydroxyrifamycin S (8), was synthesized, which displays an additional hydroxyl available for the inhibiting interaction with the bacterial enzyme. The configuration and conformation of the new compound were as expected, but the biological evaluation did not confirm the hypothesis.

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The synthesis and the antibacterial activity of 7β-[D-2-[(4-hydroxy-1, 5-naphthyridine-3-carbonylamino)- and (4-hydroxypyridine-3-carbonylamino)]-2-(4-hydroxyphenyl)acetamido]-cephalosporins with various substituents at the 3-position in the cephem nucleus are described. These compounds exhibited strong antibacterial activities against a variety of Gram-positive and Gram-negative bacteria, including Pseudomonas aeruginosa and Enterobacter aerogenes, which are insensitive to cefazolin and cefmetazole. The compounds (3e, 4e) having a 1-methyl-1H-tetrazolylthiomethyl group at the 3-position appeared to show the best activity in each series. The 4-hydroxypyridine-3-carbonylamino derivative 4e gave higher peak serum concentrations and urinary recovery rates than those of the 4-hydroxy-1, 5-naphthyridine derivative 3e when administered subcutaneously to mice and intramuscularly to rats.

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The influence of the chirality of the 7-acyl side chain and of various N-acyl moieties (ACO-) on the in vitro activity of 7β-[2-acylamino-2-(4-hydroxyphenyl)acetamido]-3-[(1-methyl-1 H-tetrazol-5-yl)thiomethyl]ceph-3-em-4-carboxylic acids (6) was investigated. A cephalosporin having a 7-acyl side chain of S-configuration (6r) was only weakly active against Staphylococcus aureus and Klebsiella pneumoniae and was inactive against the other species tested. Among the various N-acyl moieties in the cephalosporins having a 7-acyl side chain of the R-configuration, the 4-hydroxypyridine-3-carbonyl moiety, unsubstituted or substituted with 5-bromo and/or 6-alkyl groups and the 4-hydroxy-1, 5-naphthyridine-3-carbonyl moiety, unsubstituted or substituted with a 6-methyl and a 6-methoxy group gave the most active compounds. N-Ethylation of the 4-hydroxy-1, 5-naphthyridine-3-carbonyl derivative and the -hydroxypyridine-3-carbonyl derivative (6p, 6q) resulted in a decrease of the in vitro activity.

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The influence of various 3-substituents on the antibacterial activity of 7β-[D-2-(4-hydroxy-6-methylpyridine-3-carbonylamino)-2-(4-hydroxyphenyl)acetamido]ceph-3-em-4-carboxylic acids (III) was investigated. Introduction of an acidic substituent, such as a sulfo or a carboxyl group, to a 3-(1-methyl-1H-tetrazolyl)thiomethyl substituent (IIIf-i) resulted in a marked loss of activity against Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus faecalis, Escherichia coli, Klebsiella pneumoniae, and Enterobacter aerogenes, in contrast to an in crease of activity against Proteus mirabilis. Displacement of the acetoxy group of IIIb with pyridines (IIIm-p) enhanced the activity against P. aeruginosa and E. aerogenes: their activity against those strains were superior to that of the cephalosporin IIId having a 3-(1-methyl-1H-tetrazolyl)thiomethyl substituent. As a result of extensive studies in addition to the study of in vitro activity in this series, 7β-[D-2-(4-hydroxy-6-methylpyridine-3-carbonylamino) -2-(4-hydroxyphenyl)acetamido]-3-[(1-methyl-1H-tetrazol-5-yl)thiomethyl]ceph-3-em-4-carboxylic acid, code No. SM-1652, cefpiramide (generic name), was selected as a candidate for further biological and clinical investigations.

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The carbazomycin-producing microorganism, strain H 1051-MY 10, was determined to a strain of Streptoverticillium ehimense. Biosynthesis of carbazomycin B was studied using ¹⁴C-labeled and ¹³C-enriched precursors in combination with ¹³C NMR spectroscopy. The C-2 carbon of [2-¹³C]tryptophan was shown to be involved at the C-3 carbon in carbazomycin B and both carbons of [1, 2-¹³C] acetate at the C-1 and C-10 moiety of the antibiotic. [CH₃-¹³C]Methionine was involved at the methoxyl group but not at the methyl group on the C-2 carbon of the antibiotic. Neither of the labeled carbons, [1-¹⁴C]tryptophan nor [2, 3-¹³C]propionic acid, was detected in the antibiotic, and a progenitor of the C-2 and C-11 moiety of the antibiotic has not been determined.

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The antitumor activity of 7-N-(p-hydroxyphenyl)mitomycin C (M-83) against 7 kinds of ascitic tumors and 4 kinds of solid tumors was compared with that of mitomycin C (MMC). M-83 showed more potent activities than MMC against ascites sarcoma 180, fibrosarcoma Meth 1, sarcoma Meth A, melanoma B-16, leukemia P388 and lymphoma EL4, by a single intra-peritoneal injection. Furthermore, M-83 gave markedly higher chemotherapeutic ratio than MMC in these tumor systems. M-83 was also markedly effective against solid tumors of sarcoma 180, Meth 1, Meth A and Lewis lung carcinoma, by a single intravenous injection. M-83 gave lower myelo-suppression than MMC at the doses which gave almost equal inhibition on the tumor growth of solid Meth 1. M-83 and MMC significantly inhibited the growth of HeLa S₃ cells. Cell growth was observed at 24 hours after addition of 3×10^-3 mm of drugs, but no growth was shown thereafter. M-83 inhibited more strongly the incorporation of the radioactive precursor into DNA than that into RNA or protein at the concentration of 3×10^-3 mM.

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Effects produced by intratumor or systemic application of FK-156 and its synthetic derivatives on the syngeneic P388-DBA/2 mouse system were investigated. Among 21 compounds tested, FK-156, FK-565, FR-46758, FR-48217, FR-46091 and FR-47920 substantially suppressed tumor growth when directly injected into a tumor mass and further experiments showed that FK-156, FK-565 and FR-46758 were effective even when administered subcutaneously into site remote from tumor. The mechanisms of growth inhibition are strongly suggested to be host mediated, because these three compounds have remarkably low cytotoxicity against P388 cells in vitro. A single dose of FK-565, however, markedly decreased body weight in healthy DBA/2 mice, whereas FK-156 and FR-46758 did not. These results indicate the superiority of FK-156 and FR-46758 as immunotherapeutic agents over FK-565 with respect to their safety for treatment of cancer. Although significant life-span prolongation could not be seen in the two-injection regimen of six compounds in either system, systemic multiple injections of FK-156 and FR-46758 provided a statistically significant increase in the median survival time of P388 tumor bearing mice.

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The in vitro DNA-cutting activities of macromomycin (MCR), auromomycin (AUR), and their free chromophores were quantitatively analyzed by agarose gel electrophoresis of radioactive supercoiled pBR322 DNA. Methanol extract (chromophore) of MCR inhibited growth of cultured L5178Y cells and caused DNA strand scission without addition of reducing agents, whereas MCR required dithiothreitol (DTT) for its DNA cleavage. In the absence of DTT, concentrations of MCR chromophore, AUR and AUR chromophore to induce 50% degradation of form I DNA were 320μg eq./ml, 44μg/ml and 60 μg eq./ml, respectively. DTT stimulated DNA breakage by the drugs to a similar degree (ca. 4-fold). Since both chromophores showed the same biological activity, further studies were performed with AUR and its free chromophore. DNA strand breakage by AUR occurred rapidly and completed in 5 minutes. The rate of strand scission did not significantly change in a range of pH 7.0 to 10.5, but gradually declined below pH 7.0. Of 4 sulfhydryl compounds tested, DTT and cysteine exhibited potent stimulation, but glutathione and 2-mercaptoethanol weak or no enhancement. The DNA-cleaving activity of AUR and its free chromophore is blocked by addition of ethidium bromide, suggesting that the chromophore binds to DNA by an intercalation mechanism. Addition of poly[dG], poly[dG]• poly[dC], poly[dG-dC]• poly[dG-dC] or poly[Da-dT]• poly[dA-dT] protected DNA against degradation by AUR. Differential protecting effects of synthetic polynucleotides suggest that the chromophore shows higher affinity for guanine than for adenine, cytosine and thymine, and binds preferentially to a purine-pyrimidine neighboring sequence.

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The DNA-cleaving activity of auromomycin (AUR) was prevented by the free radical scavengers α-tocopherol and isopropanol. Participation of a free radical in DNA strand scission by AUR and macromomycin (MCR) was confirmed by electron spin resonance (ESR) spectroscopy, using spin trapping technique. In the mixture of AUR and the spin-trap, phenyl N-tert-butyl nitron (PBN), a definite signal was observed in the presence of ethanol or methanol, and addition of dithiothreitol increased the signal intensity about 5-fold, giving a hyperfine coupling constant of a^N=15.9 G and aβ^H=3.6 G. MCR exhibited no distinct signals in the same reaction mixture, but addition of dithiothreitol induced signals with ESR parameters similar to those of AUR. 2-Mercaptoethanol did not significantly affect the appearance and intensity of the ESR spectra generated by MCR or AUR. Chromophores, extracted from MCR and AUR, showed spectra similar to those of native MCR and AUR. The intensity of ESR signals parallels the degree of DNA strand scission by MCR, AUR and their free chromophores, suggesting that a free radical generated by these antibiotics is involved in the DNA breakage reaction. The ESR parameters of AUR or MCR radical adduct with spin-traps were compared to •OH, •O₂^- or CH₃CHOH adduct, suggesting that the free radical formed in the presence of ethanol is CH₃CHOH. A plausible intermediate radical species, generated by the antibiotics and transferred to ethanol, may be •OH (hydroxyl radical). The current experiments present evidence for involvement of free radical(s) in DNA breakage by macromomycin and auromomycin, although the precise radical species has not been identified.

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No transposition of plasmid-coded gentamicin resistance from more than fifty different R-plasmids onto a deletion derivative of bacteriophage λ was found. In contrast, 13 out of 17 R-plasmids gave rise to the formation of high frequency transducing (hft) hybrids of phage P1Cm. All the hft P1Cm derivatives transduced other antibiotic resistances in addition to gentamicin resistance. The DNA sequences found to be integrated in the prophage genomes of hft phages were generally longer than 15 kb, and ranged up to 60 kb. In most cases analyzed the points of insertions were close to the IS1 elements resident in P1Cm. In part of the hybrid phages the entire R-plasmids were cointegrated. One plasmid (pWP14a) cointegrated preferentially into a BglII fragment of P1Cm containing an invertible structure (C-loop). Eleven out of 16 R-plasmids showed homology to IS1.

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