ABSTRACT
The reductive activation of mitomycin C in aqueous bicarbonate buffer resulted in the formation of a previously unknown compound, characterized as an oxazolidinone derivative of cis-1-hydroxy-2,7-diaminomitosene. This compound is the result of a cyclization reaction of bicarbonate with the aziridine ring of aziridinomitosene, and was observed at bicarbonate concentrations close to those present in physiological plasma.
Subject(s)
Antibiotics, Antineoplastic/chemistry , Bicarbonates/chemistry , Mitomycin/chemistry , Mitomycins/chemistry , Oxazolidinones/chemistry , Antibiotics, Antineoplastic/metabolism , Aziridines/chemistry , Cyclization , Isomerism , Mitomycin/metabolism , Mitomycins/isolation & purification , Mitomycins/pharmacology , Oxidation-ReductionABSTRACT
Described herein is a study of the reductive alkylation chemistry of mitosene antitumor agents. We employed a 13C-enriched electrophilic center to probe the fate of the iminium ion resulting from reductive activation. The 13C-labeled center permitted the identification of complex products resulting from alkylation reactions. In the case of DNA reductive alkylation, the type and number of alkylation sites were readily assessed by 13C NMR. Although there has been much excellent work done in the area of mitosene chemistry and biochemistry, the present study provides a number of new findings: (1) The major fate of the iminium ion is head-to-tail polymerization, even in dilute solutions. (2) Dithionite reductive activation results in the formation of mitosene sulfite esters as well as the previously observed sulfonate adducts. (3) The mitosene iminium ion alkylates the adenosine 6-amino group as well as the guanosine 2-amino group. The identification of the latter adduct was greatly facilitated by the 13C-label at the electrophilic center. (4) The mitosene iminium ion alkylates DNA at both nitrogen and oxygen centers without any apparent base selectivity. The complexity of mitosene reductive alkylation of DNA will require continued adduct isolation studies.
Subject(s)
Antineoplastic Agents, Alkylating/chemistry , DNA Adducts/chemistry , Imines/chemistry , Mitomycins/chemistry , Antineoplastic Agents, Alkylating/chemical synthesis , Antineoplastic Agents, Alkylating/isolation & purification , Buffers , Carbon Isotopes , Deoxyadenosines/chemistry , Deoxyguanosine/chemistry , Dithionite/chemistry , Mitomycins/chemical synthesis , Mitomycins/isolation & purification , Nuclear Magnetic Resonance, Biomolecular , Oxidation-Reduction , Reducing Agents/chemistryABSTRACT
Se describe la producción de mitomicina C por vía fermentativa con la cepa Streptomyces caespitosus N1204 (NBIMCC). Durante el desarrollo del estudio se probaron distintos medios de fermentación y se hicieron variaciones en los tipos y tiempos de inóculo a nivel de zaranda rotatoria. Se realizaron, además, ensayos en un fermentador instrumentado de 10 L con resultados satisfactorios. Para la extracción del antibiótico de los caldos, se empleó cloroformo y su detección se efectuó mediante cromatografía líquida de alta presión y cromatografía en placa delgada. Una de las manchas obtenidas en el sistema acetato de etilo: 2-propanol (1:2) presentó actividad antibiótica e inducción de profago marcadas (AU)
Subject(s)
In Vitro Techniques , Mitomycins/isolation & purification , Anti-Bacterial Agents/biosynthesis , Fermentation , Streptomyces/metabolismABSTRACT
Se describe la producción de mitomicina C por vía fermentativa con la cepa Streptomyces caespitosus N1204 (NBIMCC). Durante el desarrollo del estudio se probaron distintos medios de fermentación y se hicieron variaciones en los tipos y tiempos de inóculo a nivel de zaranda rotatoria. Se realizaron, además, ensayos en un fermentador instrumentado de 10 L con resultados satisfactorios. Para la extracción del antibiótico de los caldos, se empleó cloroformo y su detección se efectuó mediante cromatografía líquida de alta presión y cromatografía en placa delgada. Una de las manchas obtenidas en el sistema acetato de etilo: 2-propanol (1:2) presentó actividad antibiótica e inducción de profago marcadas
Subject(s)
Anti-Bacterial Agents/biosynthesis , Fermentation , In Vitro Techniques , Mitomycins/isolation & purification , Streptomyces/metabolismABSTRACT
Vinte e oito olhos foram submetidos à trabeculectomia, sendo que em 14 se utilizou o 5-fluoro-uracil (grupo A) e em 14 mitomicina (grupo B). Ambos os grupos apresentavam 6 pseudofácicos, 4 afácicos e 4 fácicos. Os pseudofácicos e afácicos apresentavam uma cirurgia filtrante prévia e os fácicos duas. Todos apresentavam pressöes intra-oculares inaceitáveis, a despeito do uso de terapia máxima tolerável. As pressöes pré-operatórias näo apresentaram diferenças estatisticamente significantes entre o grupo em que se utilizou a mitomicina (12,43 + ou - 6,14) em relaçäo ao grupo em que se utilizou o 5 FU (15,00 + ou - 5,59). A incidência de complicaçöes como atalamia, descolamento de coróide, deiscência de sutura e presença de teste de Seidel positivo foram mais frequentes no grupo em que se utilizou a mitomicina, embora sem diferença estatistica significante. As alteraçöes epiteliais corneanas foram mais frequentes no grupo em que se utilizou o 5 FU. Säo sugeridas algumas mudanças de técnica cirúrgica para se evitar tais complicaçöes
Subject(s)
Humans , Fluorouracil/isolation & purification , Glaucoma/surgery , Mitomycins/isolation & purification , Trabeculectomy/rehabilitation , BrazilABSTRACT
After anaerobic reductive activation by either NADPH cytochrome P-450 reductase (EC 1.6.2.4) or xanthine oxidase (EC 1.2.3.2), mitomycin C readily alkylated DNA. When the mitomycin C-alkylated DNA is digested by DNase, snake venom phosphodiasterase, and alkaline phosphatase, only partial release of the monofunctionally linked mitomycin C nucleotide adduct occurs. Cross-linked adducts are not released into dinucleotides but resist nuclease digestion and remain in oligonucleotides and insoluble precipitates. Kinetic analyses show that the nuclease-resistant fraction which is indicative of DNA cross-linking by mitomycin C takes place quite readily. This nuclease-resistant fraction is particularly significant when the amount of total bound mitomycin C is less than 15 mumol/mmol of DNA. The cross-linked mitomycin C product accounts for more than half of the total alkylation under all pH conditions tested. Our data suggest that particular DNA sites are available for DNA cross-linking by mitomycin C, and these sites are probably the preferred and immediate alkylating targets. Furthermore, DNA cross-links by mitomycin C are not the secondary product of monofunctional adducts. Activity of both flavoenzymes is pH dependent, hence, mitomycin C activation and the rate of DNA alkylation are pH dependent. At elevated mitomycin C alkylation of DNA, the highest amount of cross-linking occurs at neutral pH. High pressure liquid chromatographic separation of the nuclease-digested DNA detected one major and two less prominent mitomycin C adducts. These were verified to be mononucleotide mitosene types by UV spectra showing maximum absorbance at 312 and 250 nm. The major adduct was purified and identified as O6-(2'-deoxyguanosyl)-2,7-diaminomitosene by NMR, indicating that the O6 position of guanine is a preferred site in DNA for at least monofunctional linkage formation.
Subject(s)
Alkylating Agents , DNA , Mitomycins , Animals , Biotransformation , Cattle , Chromatography, Gel , Chromatography, High Pressure Liquid , Hydrogen-Ion Concentration , Kinetics , Mitomycin , Mitomycins/antagonists & inhibitors , Mitomycins/isolation & purification , Mitomycins/metabolism , NADPH-Ferrihemoprotein Reductase/metabolism , Spectrum Analysis , Xanthine Oxidase/metabolismABSTRACT
A method is given for the determination of the antineoplastic drug mitomycin C in plasma and urine samples. Mitomycin is isolated from the biological matrix with the aid of a Sep-Pak C18 extraction column and eluted with methanol. The methanol is evaporated and the residue is redissolved in the chromatographic mobile phase (methanolic phosphate buffer). Mitomycin C is separated from coextracted compounds by reversed-phase liquid chromatography on a LiChrosorb RP-8 column. A high detection sensitivity and selectivity was obtained by photometric measurements at 365 nm. The precision of the determinations was better than 6% relative standard deviation for plasma samples within the range 2-1000 ng/ml, and for urine samples within the range 0.5-4.4 micrograms/ml. The pH-dependent stability of mitomycin in buffer solutions has been studied.
Subject(s)
Mitomycins/isolation & purification , Buffers , Chromatography, Liquid , Half-Life , Humans , Kinetics , Mitomycin , Mitomycins/blood , Mitomycins/urine , Spectrophotometry , TemperatureABSTRACT
Streptomyces michiganensis strain Tü 1074, was isolated from a Tunesian soil sample and produces in liquid medium an antibiotic active pigment complex. Besides mitomycin A the separation of this complex yielded a nonactive phenoxazone, which hitherto has not been described in the literature. In contrary to all known phenoxazones from micro-organisms the new compound lacks a 2-amino-function. The production of this phenoxazone could be enhanced by optimizing the condtions of fermentation.
