Antitumor Peptides from Streptomyces sp. SSA 13, Isolated from Arabian Sea
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As part of the endeavor for search of effective bioactive compounds, an untapped Arabian Sea environment is selected as a sampling source for the isolation of chemically-talented actinomycete strains. We have isolated an actinomycete strain from the sea sediments belonging to the genus Streptomyces (Accession No. KJ020688) with having potent cytotoxicity (84 %) against brine shrimps nauplii. Isolated strain also showed substantial antibacterial activity against Bacilus subtilis, Escherichia coli and Acinetobacter test strains. Fractions with significant antitumor activity obtained from the extract of 20 l fermentation broth were structurally elucidated and revealed with the production of compounds named as iturin A6 and actinomycin-D. The cyclic lipopeptide iturin A6 display outstanding novel antitumor activities against three tumor cell lines viz. HeLa, MCF-7, Hep G2 with IC50 values of 1.73 ± 0.9, 6.44 ± 0.6 and 8.9 ± 1.09 μg/ml respectively. This peptide is found to be ineffective against RD tumor cells. The second polypeptide actinomycin-D is found to be active against the entire panel of tumor cell lines used. It exhibited stronger activities with IC50-values of <0.9 μg/ml against HeLa and MCF-7, while 11.72 ± 0.9 and 1.19 ± 0.8 against Hep G2 and RD cells respectively. Results from the culture optimization experiments of this strain showed greater yield of secondary metabolites while culturing in glucose–yeast extract–malt extract (M2) medium under culture conditions set as follows, shaking at 95 rpm, pH 7.8, incubation temperature 28 °C, for 168 h. As such this is the first report for the isolation of any iturin family member from actinomycetes group with having antitumor activity.
KeywordsActinomycete Streptomyces Iturin A6 Actinomycin-D HeLa MCF-7 Hep G2 RD cells
The authors are thankful to Higher Education Commission (HEC) Pakistan for providing financial support under IRSIP Scholarship Program for the completion of this research work. We are also thankful to Dr. David L. Zechel and Mr. XiMing Zhu for their help in Mass spectrometric analysis and Dr. Françoise Sauriol for her help regarding NMR experiments.
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Conflict of Interest
Usman Aftab and Imran Sajid confirm that for this article content they have no conflict of interest.
Human and Animal Rights
This article does not contain studies with human or animal subjects that should be approved by Ethical Committee.
The article does not contain any studies related to patients.
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