Aclarubicin A

The generation of hydroxyl free radicals in the system consisting of purified NADPH-cytochrome P-450 reductase and anticancer quinone drugs, such as carbazilquinone, mitomycin C, aclacinomycin A and adriamycin, has been confirmed by two methods. In the spin trapping study, using N-tert-butyl-alpha-phenylnitrone as the spin trapping agent, four drugs generated hydroxyl radical-trapped signals, and the formation of the spin adduct was dependent on time and the enzyme concentration. Among the four drugs, the generation time of signal was in the order of carbazilquinone, aclacinomycin A, adriamycin and mitomycin C, but the magnitude of signal intensity was different. In both aclacinomycin A and adriamycin, the signal disappeared in a few minutes. Catalase completely inhibited the formation of the spin adduct, while superoxide dismutase did not significantly inhibit, but effected in some manner. The generation of hydroxyl radical was also confirmed by the ethylene production from methional.

1,4-Dihydroxy-5,8-bis(((2-[(2-hydroxyethyl) amino] ethyl)amino))-9,10-anthracenedione dihydrochloride (mitoxantrone) was tested for antitumor activity against experimental tumors in mice and the results were compared with those of seven antitumor antibiotics: adriamycin (ADM), daunomycin (DM), aclarubicin, mitomycin C (MNC), bleomycin, neocarzinostatin, and chromomycin A3. The drugs were given IP or IV, in general on days 1, 5, and 9 following tumor inoculation. Mitoxantrone given IP at the optimal dose (1.6 mg/kg/day; as a free base) produced a statistically significant number of 60-day survivors (curative effect) in mice with IP implanted L1210 leukemia. The curative effect was not observed with any of the other antibiotics. In the case of IV implanted L1210 leukemia, there was an increase in lifespan (ILS) by more than 100% in the mice following IV treatment with mitoxantrone or DM. In IP implanted P388 leukemia, the curative effect was elicited by IP treatment with mitoxantrone or MMC.

The properties of the interactions of anticancer quinone drugs, aclacinomycin A, adriamycin, carbazilquinone, and mitomycin C with nicotinamide adenine dinucleotide phosphate (NADPH)-cytochrome P-450 reductase and xanthine oxidase under anaerobic and aerobic conditions were studied. Km values of NADPH-cytochrome P-450 reductase for these drugs were in the range of 40-227 microM, and that of deflavo xanthine oxidase in the range of 39-over 200 microM. Under anaerobic conditions, when xanthine was used as an electron donor, deflavo xanthine oxidase catalyzed the reductive glycosidic cleavage reaction of anthracyclines and nicotinamide adenine dinucleotide was ineffective as an electron donor. In the electron spin resonance study, the formation of the semiquinone or free radical state of the quinone drugs in both enzyme systems were evidenced. A weak and symmetric signal was obtained from aclacinomycin A, and a symmetric signal from adriamycin was changed into an asymmetric and strong.

Fluorescence emission spectra from anthracycline-treated cells suspended in buffer have been used to measure the uptake of three anthracycline derivatives: Adriamycin (ADR), 4'-o-tetrahydropyranyl-Adriamycin (THP-ADR) and aclacinomycin (ACM) in drug-sensitive and drug-resistant K562 cells. The concentration of drug bound to the nucleus and free in the cytoplasm, at steady state, as well as the concentration of drug bound to the nucleus at equilibrium state have been determined at temperatures ranging from 6 degrees to 40 degrees. The enthalpies for the binding of ADR, THP-ADR and ACM to nuclei equal -35 +/- 3, -35 +/- 3 and -30 +/- 3 kJ/mol, respectively. These values compare with the enthalpies of binding of these drugs to naked DNA.