Abstract
Four new ansamycins, named divergolides T–W (1–4), along with two known analogs were isolated from the fermentation broth of the mangrove-derived actinomycete Streptomyces sp. KFD18. The structures of the compounds, including the absolute configurations of their stereogenic carbons, were determined by spectroscopic data and single-crystal X-ray diffraction analysis. Compounds 1–4 showed cytotoxic activity against the human gastric cancer cell line SGC-7901, the human leukemic cell line K562, the HeLa cell line, and the human lung carcinoma cell line A549, with 1 being the most active while compounds 5 and 6 were inactive against all the tested cell lines. Compounds 1 and 3 showed very potent and specific cytotoxic activities (IC50 2.8 and 4.7 µM, respectively) against the SGC-7901 cells. Further, the apoptosis-inducing effect of 1 and 3 against SGC-7901 cells was demonstrated by two kinds of staining methods for the first time.
Highlights
Ansamycins are a class of bioactive macrolides that have been isolated from actinomycetes [1,2,3,4].The most representatives of them are geldanamycin with HSP90 inhibitory activity [1], rifamycin with antibacterial activity [2], and maytansinoid with anticancer activity [3]
The above data showed that hydroxylation at C-7 or inversion of the configuration at C-2 or ∆3 double bond in compound 1 could significantly reduce cytotoxic activity
KFD18 was isolated from Mangrove sediment, collected from Danzhou, Theprovince, strain Streptomyces sp
Summary
Ansamycins are a class of bioactive macrolides that have been isolated from actinomycetes [1,2,3,4]. Divergolides represent a family of ansamycins with a 19-membered naphthalenic ansamacrolactam skeleton, which was first discovered from Streptomyces sp. A total of 19 members (divergolides A–S) of this family has been reported [5,6,7]. As part our ongoing search for new bioactive secondary metabolites from marine microorganisms [9,10,11,12], Streptomyces sp. Subsequent chemical investigations on the EtOAc extract from the fermentation broth of this strain led to the isolation and identification of four new ansamycins, named divergolides T–W (1–4), as well as. The 2018, structures and bioactivities of these compounds are reported
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