Abstract
A Streptomyces sp. (BRA-384) was selected among nine strains of bacteria isolated from the zoanthids Palythoa caribaeorum due to the high cytotoxic activity presented by its EtOAc extract (inhibitory concentration mean (IC50) of 2 ng mL-1) against colon cancer cell line. From the EtOAc extract of BRA-384 three new chemical entities (A6, A7 and A8) and one dextrorotatory chromomycin (A5), a promising class of anticancer compounds, were identified. The cytotoxicity of chromomycins A5 to A8 was tested against five tumor cell lines (HCT 116 (human colon adenocarcinoma), MCF-7 (human breast carcinoma), PC-3M (human metastatic prostate cancer), 501-mel (human metastatic melanoma) and MM200 (metastatic melanoma)). All chromomycins were highly potent showing IC50 values from 0.2 to 133 nM. Chromomycin A5 was consistently the most potent over all tested cells (IC50 values from 0.2 in MM200 to 7.9 nM in PC-3M), inclusive when compared to the standard chemotherapeutic agent doxorubicin, that presented IC50 values ranging from 147 to 568 nM against MM200 and MCF-7, respectively.
Highlights
Marine microorganisms have emerged as an immensurable resource of bioactive compounds
We present the isolation and structure elucidation of four dextrorotatory chromomycins from a cytotoxic extract produced by a Streptomyces bacteria strain recovered from the zoanthid P. caribaeorum, collected at Pedra Rachada Beach, located on the west coast of Ceará State, including the previously described chromomycin A5.10 The cytotoxic activity of the isolated compounds was evaluated in a panel of five tumor cell lines, including melanoma, breast, colon and prostate carcinomas
A total of nine bacterial strains were isolated from the zoanthids P. caribaeorum and P. variabilis collected at Taíba and Pedra Rachada beaches (Ceará State) in the northeastern Brazil coast
Summary
Marine microorganisms have emerged as an immensurable resource of bioactive compounds. As part of a program on marine natural products bioprospection, we have devoted our attention to the study of the zoanthids Palythoa caribaeorum and Palythoa variabilis, two abundant zoanthids in the Brazilian coast.[15] Recently, we have extended the scope of our research investigating the chemical and microbiological profiles of these species from the Brazilian coast through an omics approach which revealed a great chemical and biosynthetic gene clusters diversity.[15] In this paper, we present the isolation and structure elucidation of four dextrorotatory chromomycins from a cytotoxic extract produced by a Streptomyces bacteria strain recovered from the zoanthid P. caribaeorum, collected at Pedra Rachada Beach, located on the west coast of Ceará State, including the previously described chromomycin A5.10 The cytotoxic activity of the isolated compounds was evaluated in a panel of five tumor cell lines, including melanoma, breast, colon and prostate carcinomas
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