Trikoramides B–D,Bioactive Cyanobactins from the Marine Cyanobacterium Symploca hydnoides |
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| Authors: | Ma Yadanar Phyo Teo Min Ben Goh Jun Xian Goh Lik Tong Tan |
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| Institution: | Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Singapore; (M.Y.P.); (T.M.B.G.); (J.X.G.) |
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| Abstract: | Three new cyanobactins, trikoramides B (1)–D (3), have been isolated from the marine cyanobacterium, Symploca hydnoides, following a preliminary bioassay-guided isolation of the two most active polar fractions based on the brine shrimp toxicity assay. These new cyanobactins are new analogues of the previously reported cytotoxic trikoramide A (4) with differences mainly in the C-prenylated cyclotryptophan unit. Their planar structures were elucidated from their 1D and 2D NMR spectral data in combination with the HRMS/MS data. Marfey’s method, 2D NOESY NMR spectroscopic and ECD spectra analyses were used to determine the absolute stereochemistry of trikoramides B (1)–D (3). Trikoramides B (1) and D (3) exhibited cytotoxicity against MOLT-4 acute lymphoblastic leukemia cell line with IC50 values of 5.2 µM and 4.7 µM, respectively. Compounds 1 and 3 were also evaluated for their quorum-sensing inhibitory assay based on the Pseudomonas aeruginosa PAO1 lasB-gfp and rhlA-gfp bioreporter strains. Although trikoramide B (1) exhibited weak quorum-sensing inhibitory activity, the Br-containing trikoramide D (3) exhibited moderate to significant dose-dependent quorum-sensing inhibitory activities against PAO1 lasB-gpf and rhlA-gfp bioreporter strains with IC50 values of 19.6 µM and 7.3 µM, respectively. |
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| Keywords: | Symploca hydnoides microcoleaceae cyanobactin trikoramides cytotoxic quorum-sensing inhibitors |
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