11-Deoxylandomycinone and landomycins X-Z, new cytotoxic angucyclin(on)es from a Streptomyces cyanogenus K62 mutant strain

Four new angucyclin(on)es, 11-deoxylandomycinone (1) and landomycins X–Z (2–4) were isolated from the crude extract of Streptomyces cyanogenus K62 mutant strain, along with the recently reported landomycins S, T and V (5–7) and five other known compounds. The structures of the new compounds 1–4 were elucidated by 1D and 2D NMR studies along with HR-MS analyses. Unique about the structures is that the fourth sugar moiety (sugar D) in landomycins X–Z (2–4) was β- D -amicetose instead of β- D -olivose, usually found in this position. The new angucyclin(on)es were biologically evaluated in comparison with previously known congeners against a small panel of MCF-7 (estrogen responsive) and MDA 231 (estrogen refractory) breast cancer cell lines. 11-deoxylandomycinone (IC 50 2.1±0.3 and 1.2±0.4 μ M ) and landomycin Y (IC 50 1.0±0.1 and 2.0±0.1 μ M ) showed the highest cytotoxic potencies against both the cell lines.