Abstract
BackgroundThe present work aimed to evaluate the antimycobacterial activity and cytotoxicity of Microcystis aeruginosa toxins, the MC-LR variant and purified extract of [D-Leu1] microcystin-LR.MethodsThe antimicrobial activity of M. aeruginosa extract and microcystin was evaluated by resazurin microtiter assay against Mycobacterium tuberculosis, M. terrae, M. chelonae and M. kansasii. The cytotoxicity assay was performed by trypan blue exclusion against the HTC cell line.ResultsAntimicrobial activity was observed in the hexanic extract of M. aeruginosa (RST 9501 strain) against M. tuberculosis, including sensitive and resistant strains with minimal inhibitory concentrations (MIC) between 1.93 μM and 0.06 μM. The high activity of M. aeruginosa hexanic extract could be attributed to the major presence of the toxins MC-LR and [D-Leu1] MC-LR that showed activity at MIC between 53 and 0.42 μM against tested mycobacterial strains. Even at the highest concentration tested, no toxicity of M. aeruginosa extracts was identified against HTC cells.ConclusionsThese preliminary results suggest that [D-Leu1] MC-LR is a promising candidate for the development of a new antimycobacterial agent.
Highlights
The present work aimed to evaluate the antimycobacterial activity and cytotoxicity of Microcystis aeruginosa toxins, the MC-LR variant and purified extract of [D-Leu1] microcystin-LR
The present study evaluated the antimycobacterial activity and cytotoxicity of Microcystis aeruginosa toxins, the variant MC-LR and purified extract of [D-Leu1] microcystin-LR against Mycobacterium tuberculosis, M. chelonae, M. terrae and M. kansasii
M. aeruginosa RST 9501 extracts were evaluated against M. tuberculosis pan-susceptible (H37Rv), rifampicin(RIFr) and isoniazid-resistant strains (INHr)
Summary
The antimicrobial activity of M. aeruginosa extract and microcystin was evaluated by resazurin microtiter assay against Mycobacterium tuberculosis, M. terrae, M. chelonae and M. kansasii. Microcystis culture conditions Microcystis RST 9501 (UPC Culture Collection, Federal University of Rio Grande) isolated from the estuary of Patos Lagoon is the [D-Leu1] MC-LR producing variant and was grown in BG-11 medium with nitrate as previously described [23,24]. The cells were dissolved in absolute methanol (Sigma, USA), sonicated three times and centrifuged (10,000 × g) at 4°C, for ten minutes. Extracts were evaporated at 40°C and redissolved in ultrapure water (Direct Q3, Millipore, USA). The other extract preparations, presented, replaced methanol with hexane, chloroform or water. Microcystin content was determined using a commercial enzymelinked immunosorbent assay (ELISA) with polyclonal antibodies (EnviroLogix Inc., USA). Characterization of microcystins produced by the strain RST 9501 was previously reported by Matthiensen et al [17,25].
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