Microbial conversion of saframycin A to 25-dihydrosaframycin A and 21-decyano-25-dihydrosaframycin A (25-dihydrosaframycin B) and their biological activities.

Abstract

25-Dihydrosaframycin A(AR1) and 21-decyano-25-dihydrosaframycinA(AR3) were produced by the microbial conversion of saframycin A(SA). Efficient conversion of SA to AR, and AR3 was observed with Rhodococcus amidophifus IFM 144. Though the antimicrobial activity of AR, was one tenth that of SA, the in vitro antitumor activity of AR1 was found to be equivalent to that of SA. In contrast, AR, was biologically less active.Microlial conversion has been studied extensively1~3) for many classes of organic compounds, namely alkaloids, antibiotics and steroids.For antitumor antibiotics, considerable attention has been given to the microbial reduction of carbonyl groups in relation to antitumor activities .4-8)The antitumor activity of a novel antibiotic, saframycin A, with a unique structure consisting of a dimer of 6-methyl-7-methoxy-1,2,3,4-tetrahydroisoquinoline-5,8-dione, as the basic skeleton, has been reported .9-12)In our studies on the microbial conversion of SA into antibiotics possessing antitumor spectra different from those of the parent compound (SA), reduction of the side chain carbonyl group of SA was observed.In this paper, we report our studies on the microbial conversion of SA to AR, and AR, and their biological properties. Materials and MethodsMicroorganisms and Cultivation Rhodococcus amidophih{s IFM 144 was maintained on slants of I % glycerol nutrient medium until used. The strain was grown in 500-ml Erlenmeyer flasks, each containing 100 ml of a medium consisting of: meat extract 1 %, peptone 1 %, yeast extract 1 %, NaCl 0.3 % (pH 7.2). After 48 hours incubation at 27°C on a rotary shaker at 250 rpm, the culture was centrifuged, washed and suspended in a small volume (23 ml) of 0.1 M phosphate buffer (pH 7.5).Microbial Conversion of Saframyicn A(SA) Two ml of the suspension was mixed with 2 ml of the 10% aqueous methanol solution of SA (0.5 mg/ ml) in a test tube and the mixture incubated at 37°C for 18 hours. The reaction mixture was centrifuged at 500 rpm, and the supernatant extracted with ethyl acetate. The ethyl acetate layer was concentrated in vacuo, and the residue extracted with 1 N HCl solution. After adjustment to pH 7.5 with conc.

Mode of action of saframycin antitumor antibiotics: sequence selectivities in the covalent binding of saframycins A and S to deoxyribonucleic acid

“…The fact that dithiothreitol-inducible binding of saframycin A to DNA was blocked by the addition of excess cyanide ion (40) indicates that the iminium ion or a-carbinolamine is the actual species involved in the interaction with DNA. Additional supporting evidence is that chemical reduction at the C-21 position of the basic skeleton of saframycin A, i.e., at the attachment site of the cyano group, which removes the nitrile, resulted in almost complete loss of biological activity (41). These results are consistent with covalent binding of the activated antibiotic to a guanine-2NH2 site in the central position of the triplet recognition sequence as proposed earlier (18).…”

Advances in Solution- and Solid-Phase Synthesis toward the Generation of Natural Product-like Libraries

“…[233][234][235][236][237][238] Myers and co-workers 239 reported the successful adaptation of their earlier developed solution-phase synthesis of saframycin A 240 to a 10-step solid-phase protocol with the potential of building a large number of its analogs with structural modifications.…”

“…Saframycin A ( 27.1 , Scheme ) is a bis-quinone alkaloid with a bridged complex polycyclic framework with a characteristic cyanopiperazine core and is known to act as an antiproliferative agent. − Myers and co-workers reported the successful adaptation of their earlier developed solution-phase synthesis of saframycin A to a 10-step solid-phase protocol with the potential of building a large number of its analogs with structural modifications.…”