Cytotoxic indolocarbazoles alkaloids from the streptomyces sp. A65

Abstract

Three new indolocarbazoles alkaloids together with nine known compounds were isolated from the rice solid fermentation of the marine-derived Streptomyces sp. A65. Their structures were elucidated by interpretation of spectroscopic and spectrometric data (1D and 2D NMR, IR, and HRESIMS). The absolute configurations of compounds 1 and 2 were determined by single-crystal X-ray crystallographic analysis, and 3 was assigned on the basis of experimental and calculated electronic circular dichroism spectra. All of these compounds were evaluated for cytotoxic activity assay. Compounds 6 and 10 exhibited significant cytotoxicity against PC3 cell lines with IC50 values of 1.96 and 2.92 μM, respectively; Compounds 2 and 3 showed moderate cytotoxic activity with IC50 values of 9.67 and 6.79 μM, respectively. Additionally, compounds 1–4 also were also tested for enzyme inhibition activities of Protein kinase C and Brution tyrosine kinase. They showed moderate activity with IC50 values ranging from 0.25 μM to 1.91 μM except for compound 1, which has no inhibition activity for protein kinase C.