New antibiotic napyradiomycins A2 and B4 and stereochemistry of napyradiomycins

Napyradiomycins A2 and B4, new members of the napyradiomycins, have been isolated from the culture broth of Chainia rubra MG802-AF1. The structure of napyradiomycin A2 was elucidated as 16-hydroxy-17-methylenenapyradiomycin A1 by NMR studies. The absolute structure of napyradiomycin B4 was determined as 13-hydroxy-13-methylnapyradiomycin B1 by X-ray crystallography and therefore the configuration of C(4a) in other napyradiomycins is assumed as the R configuration. The geometrical isomerism of napyradiomycin C1 was estimated as 12E and 16E by nuclear Overhauser effect experiments.

Synthesis and antitumor activity of spergualin analogues. III. Novel method for synthesis of optically active 15-deoxyspergualin and 15-deoxy-11-O-methylspergualin

Optically active 15-deoxyspergualin (II) and 15-deoxy-11-O-methylspergualin (IIa) were synthesized, and their antitumor activities were examined. The (-)-enantiomers of both II and IIa were active against mouse leukemia L1210, while the (+)-enantiomers were almost inactive. The optical resolution of the key intermediate, (+/-)-N-(7-guanidinoheptanoyl)-alpha-alkoxyglycine (VI) was achieved by use of an exopeptidase, serine (acid) carboxypeptidase [EC 3.4.16.1] and (+/-)-N-(7-guanidinoheptanoyl)-alpha-alkoxyglycyl-L-amino acid (VIII) as the substrate. Considering the enzymatic susceptibility of the substrate (VIII), we deduced that the absolute configuration of the carbon at 11 (C-11) of the bioactive (-)-enantiomer, and so that of natural spergualin (I), is S. This is, to our knowledge, the first report of the use of carboxypeptidase for the resolution of N-acyl amino acid.

Synthesis and antitumor activity of spergualin analogues. II. Chemical modification of the spermidine moiety

Chemical modifications of the spermidine moiety of an antitumor antibiotic, spergualin (Ia), and the structure-activity relationship are described. Replacement of spermidine with other polyamines decreased the antitumor activity against mouse leukemia L1210. Analogues containing an oxidized spermidine moiety that probably formed during oxidation with amine oxidase were inactive. Spermidine is indispensable for the antitumor activity. A facile method for the synthesis of glyoxyloyl polyamine, a key intermediate of spergualin-related compounds, is also reported.

Synthesis of p-hydroxyubenimex

p-Hydroxyubenimex, (2S,3R)-3-amino-2-hydroxy-4-p-hydroxyphenylbutyryl-L-leucine, was synthesized starting from D-tyrosine. The structure and stereochemistry of the synthesized product were confirmed by comparison with p-hydroxyubenimex that was chemically transformed from ubenimex, an aminopeptidase inhibitor of microbial origin. Compared to ubenimex, p-hydroxyubenimex is more active against aminopeptidase B but less active against leucine aminopeptidase. By using the synthetic p-hydroxyubenimex as a reference sample, one of the metabolites of ubenimex was identified as p-hydroxyubenimex. The (2R,3R)-stereoisomer of p-hydroxyubenimex was also prepared. However, its activity against aminopeptidases was much weaker.

Analgesic effect of actinonin, a new potent inhibitor of multiple enkephalin degrading enzymes

Actinonin, previously isolated as an antibiotic and shown to be an inhibitor of aminopeptidase M (EC 3.4.11.2), has now been shown to inhibit three enkephalin-degrading enzymes from guinea-pig striatum. The values of IC50 were 0.39 microM for striatal membrane aminopeptidase ("enkephalin-aminopeptidase") and 5.6 microM striatal membrane neutral endopeptidase ("enkephalinase A"). Furthermore, soluble dipeptidylaminopeptidase in a rat whole brain homogenate was also inhibited by actinonin with the IC50 value of 1.1 microM. Actinonin administered intracisternally (i.cist., 50 micrograms) or intraperitoneally (i.p., 100 mg/kg), potentiated the analgesic action of met-enkephalin (50 micrograms i.cist.). analgesia by a tail-flick test. The potentiating activity of actinonin i.p. to met-enkephalin analgesia was almost the same potency as that of thiorphan, whereas the inhibitory activity of actinonin against enkephalinase A was 1/1000 that of thiorphan. Actinonin alone, administered either i.cist. or i.p., showed an analgesic action as estimated by the tail-flick test.

Morphometrical observations on the mandible of five strains of rabbits and strain identification using mandible measurements

In order to clarify the relationships between five strains of rabbits and to identify the strains, principal component and discriminant analyses were carried out using 12 mandibular measurements of three inbred strains (JW-NIBS/Y (JW/Y), NW-NIBS/Y (NW/Y) and Dutch-NIBS/Y (D/Y)) and two outbred strains (JW-NIBS (JW) and NW-NIBS (NW] which were maintained at the Nippon Institute for Biological Science. The results obtained were as follows. (1) Principal component analysis revealed that in the males the mandible of JW was the largest but with considerable variation. D/Y was the smallest of all strains examined. The mandibles of NW and NW/Y were similar to the JW mandibles but had a shape which was shorter and higher. In the females the mandible of NW was the largest of all strains and, as in the males, D/Y was the smallest and JW varied markedly. (2) Discriminant analysis showed the probability of erroneous discrimination to be 14.8% (34/229) when the inbred and outbred strains were combined. In both sexes erroneous discrimination mostly occurred between NW and NW/Y, which have the same origin, and between JW and NW, which have a common ancestor. However, when the inbreds and outbreds were identified separately by discriminant analysis, the probability of erroneous discrimination was low in both cases (4.5% (5/112) and 7.7% (9/117) respectively). These results indicate that strain differences are found in the size and shape of rabbit mandibles and that mandible analysis is effective for strain identification of laboratory rabbits.

Involvement of cytotoxic T-lymphocytes in the antitumor activity of spergualin against L1210 cells

Spergualin exhibited a strong antitumor effect against L1210(IMC), a tumor cell line which has been maintained in BALB/c X DBA/2 F1 (hereafter called CD2F1) mice in the Institute of Microbial Chemistry. Mice inoculated i.p. with 10(5) cells of L1210(IMC) survived more than 60 days by daily i.p. administration of spergualin for 9 days at 5 mg/kg/day, which was started 1 day after the tumor inoculation. These cured mice rejected a second inoculation of 10(6) cells of L1210(IMC), but they did not reject the inoculation of 10(2) P388 cells. In Winn's tumor neutralization assay and in the 51Cr release assay, the T-cell fraction prepared from the spleens of the cured mice had higher cytotoxic activity against L1210(IMC) than whole spleen cells. The cytotoxic activity of spleen cells was diminished by treatment with anti-Thy-1.2 or anti-Lyt-2.1 antibody and complement. Therefore, the effector cells involved in the immunological rejection should be regarded as cytotoxic T-lymphocytes. The cytotoxic activity of these T-lymphocytes was measured during and after the spergualin administration for 9 days, and high activity was observed from 1 day after the final spergualin administration. The antitumor effect of spergualin against L1210(IMC) was much lower in T-cell-deficient athymic mice. These results suggest that cytotoxic T-lymphocytes are involved in the antitumor action of spergualin against L1210(IMC) in vivo.

Enhancement of colony formation of mouse bone marrow cells by ubenimex

Ubenimex enhanced colony formation of bone marrow cells from CDF1 mice induced by L920 cell supernatant, which shows a macrophage-colony-stimulating activity (M-CSA), and also enhanced the colony formation induced CDF1 mouse spleen cell conditioned medium, which shows a granulocyte and macrophage-colony-stimulating activity. The maximal effect was obtained at 0.01 microgram/ml. But, ubenimex showed no effect on the nature of the colonies induced by each CSA. By preincubation of the bone marrow cells with ubenimex, M-CSA-induced colony-forming and the M-CSA-binding activities of the cells were increased. These results suggest that ubenimex enhances the CSA-induced colony formation of bone marrow progenitor cells of CDF1 mouse by increasing the amount of the CSA-binding to the cells.

Composite effects of actinonin when inhibiting enkephalin-degrading enzymes

Actinonin which has been found to be an inhibitor of aminopeptidase M (EC 3.4.11.2) also inhibited enkephalinase A (EC 3.4.24.11) and enkephalin aminopeptidase which were partially purified from the corpus striatum membrane of guinea-pig brain. The IC50 values were 5.6 microM for enkephalinase A and 0.39 microM for enkephalin aminopeptidase. Actinonin also inhibited with an IC50 value of 1.1 microM dipeptidyl aminopeptidase tested on whole brain homogenate of rats in the presence of thiorphan and bestatin. Analgesia was assessed by measuring the tail-flick latency of mice. The analgesic effect of [Met5]enkephalin injected intracisternally (i.cist., 50 micrograms) was potentiated by an intraperitoneal (i.p., 100 and 300 mg/kg) as well as an i.cist. (25 micrograms) injection of actinonin. Actinonin was found to inhibit all three enzymes of enkephalin metabolism and, when given peripherally, to potentiate enkephalin analgesia.

Antitumor cells found in tumor-bearing mice given ubenimex

Antitumor effector cells in spleens of tumor-bearing mice given ubenimex were investigated. The administration of ubenimex, starting 7 days after the tumor inoculation, was effective in inhibiting growth of IMC carcinoma. Spleen cells taken from these mice showed a marked suppression of the tumor growth by the WINN assay. The antitumor activity of spleen cells was reduced by treatment to remove T cells or NK cells, whereas spleen cell preparations enriched for T cells showed the strongest antitumor activity. Moreover, NK activity against YAC-1 cells was found in the spleen. These results indicate that the administration of ubenimex to IMC carcinoma-bearing mice generates cytotoxic T cells and NK cells in the spleen. The antitumor effect of ubenimex was not observed in X-ray-irradiated and in anti-asialo GM1 serum-treated mice.

Antitumor activity of erbstatin, a tyrosine protein kinase inhibitor

A tyrosine protein kinase inhibitor, erbstatin, showed no antineoplastic effect on L-1210 mouse leukemia when it was injected alone. Erbstatin was found to be inactivated by incubation in serum, but not in dialyzed serum. It was also inactivated in reconstituted serum containing dialyzed serum components and ferric or ferrous ion. Because erbstatin was considered to be inactivated by the ferric or ferrous ion in serum, foroxymithine, which is a potent chelator for the ferric ion, was given to the mice together with erbstatin. Administration of both erbstatin and foroxymithine showed antineoplastic activity against L-1210 leukemia.

Syntheses of 23-C-alkylidene, and 23-N-containing derivatives of 5-O-mycaminosyltylonolide

Several derivatives of 5-O-mycaminosyltylonolide substituted at C-23 have been prepared; these are 23-deoxy-23-C-methylene (3), 23-deoxy-23-C-(methoxycarbonylmethylene) (5), 23-deoxy-23-C-(ethoxycarbonylmethylene) (7), and 23-deoxy-23-C-(butoxycarbonylmethylene) (9), 23-deoxy-23-C-[(2E)-3-(ethoxycarbonyl)-2-propenylene] (11), and 23-deoxy-23-(dimethylaminoimino) (13), and 14-de(hydroxymethyl)-14-nitrile (16) derivatives. The key steps in these syntheses are the reactions of 2',4'-di-O-acetyl-3-O-tert-butyldimethylsilyl-23-deoxy-23-oxo-5-O- mycaminosyltylonolide diethyl acetal (1) with several Wittig reagents, 1,1-dimethylhydrazine and hydroxylamine. Antibacterial activities of these compounds are also described.

Activation of bleomycin-Fe(III) by bleomycin-Cu(II) and cysteine

When bleomycin (BLM) was incubated with DNA at 37 degrees C for 30 minutes in the presence of BLM-Cu(II) and cysteine, the DNA became more acid-soluble compared with the reaction without BLM-Cu(II). Superoxide dismutase did not suppress this increased DNA chain breakage. This combination of BLM-Cu(II) and cysteine did not enhance BLM-Fe(II)-induced DNA chain breakage, but caused the DNA chain breakage by inactive BLM-Fe(III). Combination of BLM-Fe(III) with BLM-Cu(II) and cysteine also caused production of malondialdehyde-like product from DNA. Anaerobic incubation of DNA with BLM-Fe(III) and BLM-Cu(I) followed by aerobic incubation produced malondialdehyde-like product, but the incubation with CuCl instead of BLM-Cu(I) did not. These results suggest that activation of BLM-Fe(III) by BLM-Cu(II) and cysteine seems to be due to the reduction of BLM-Fe(III) to BLM-Fe(II) by BLM-Cu(I) formed in the reaction of BLM-Cu(II) and cysteine.