Two indolocarbazole alkaloids with apoptosis activity from a marine-derived actinomycete Z2039-2

Bioassay-guided fractionation of the EtOAc extract from the fermentation broth of a marine-derived actinomycete Z(2)039-2 led to the isolation of two known indolocarbazole alkaloids, K252c (1) and arcyriafiavin A (2). 1 and 2 exhibited moderate cytotoxic activities against the K562 cell line, and induced apoptotic activities at 10 and 100 mu M, respectively. This is the first report on the significant apoptosis inducing effect of indolocarbazole alkaloids against K562 cancer cells.