Abstract
In order to find out the seeds of antitumor agents, we focused on potential bioactive materials from marine-derived microorganisms. Marine products include a number of compounds with unique structures, some of which may exhibit unusual bioactivities. As a part of this study, we studied metabolites of a strain of Alternaria sp. OUPS-117D-1 originally derived from the sea urchin Anthocidaris crassispina, and isolated five new decalin derivatives, altercrasins A–E (1–5). The absolute stereostructure of altercrasins A (1) had been decided by chemical transformation and the modified Mosher’s method. In this study, four decalin derivatives, altercrasins B–E (2–5) were purified by silica gel chromatography, and reversed phase high-performance liquid chromatography (RP HPLC), and their structures were elucidated on the basis of 1D and 2D nuclear magnetic resonance (NMR) spectroscopic analyses. The absolute configuration of them were deduced by the comparison with 1 in the NMR chemical shifts, NOESY correlations, and electronic circular dichroism (ECD) spectral analyses. As a result, we found out that compound pairs of 1/2 and 4/5 were respective stereoisomers. In addition, their cytotoxic activities using murine P388 leukemia, human HL-60 leukemia, and murine L1210 leukemia cell lines showed that 4 and 5 exhibit potent cytotoxicity, in especially, the activity of 4 was equal to that of 5-fluorouracil.
Highlights
Marine organisms are a potential prolific source of highly bioactive secondary metabolites with unique structures that may serve as useful seeds for the development of new chemotherapy agents [1,2].Previously, our group has focused on potential new antitumor materials from marine-derived microorganisms that produce several compounds bearing unique structures [3,4,5]
OUPS-117D-1 originally obtained from the sea urchin Anthocidaris crassispina were examined, and a new compound designated as altercrasin A (1)
After incubating at 37 ◦ C for 72 h in 5% CO2, grown cells were labeled with 5 mg/mL MTT in phosphate-buffered saline (PBS), and the absorbance of formazan dissolved in 20% sodium dodecyl sulfate (SDS) in 0.1 N HCl was measured at 540 nm with a microplate reader (MTP-310, CORONA electric)
Summary
Marine organisms are a potential prolific source of highly bioactive secondary metabolites with unique structures that may serve as useful seeds for the development of new chemotherapy agents [1,2]. Our group has focused on potential new antitumor materials from marine-derived microorganisms that produce several compounds bearing unique structures [3,4,5]. In a previously reported study for the absolute stereostructure of 1, our group has successfully determined. Mar. Drugs 2019, 17, x it by experiments via a chemical transformation [6]. Our continuous search for cytotoxic metabolites fromfrom this fungal strain afforded four new decalin derivatives as altercrasins. B–Eas(2–5), metabolites this fungal strain afforded four new decalindesignated derivatives designated altercrasins respectively As these were minor components, the above-mentioned method to elucidate the stereostructures. The chiral centers in these metabolites were assigned by was not used to elucidate the stereostructures. Were assigned by NMR and ECD spectral analyses
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