Cytotoxic bipyridines from the marine-derived actinomycete Actinoalloteichus cyanogriseus WH1-2216-6.

Five new bipyridine alkaloids (1-5) and a new phenylpyridine alkaloid (6), which we name caerulomycins F-K, along with five known analogues (7-11), were isolated from the marine-derived actinomycete Actinoalloteichus cyanogriseus WH1-2216-6. The structures of 1-6 were established on the basis of spectroscopic analyses and chemical methods. Compounds 1-10 showed cytotoxicity against the HL-60, K562, KB, and A549 cell lines, with IC₅₀ values of 0.26 to 15.7 μM. Compounds 7 and 8 also showed antimicrobial activities against Escherichia coli, Aerobacter aerogenes, Pseudomonas aeruginosa, and Candida albicans, with MIC values of 9.7 to 38.6 μM.