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Antibacterial Activity of Steroids Isolated from the Madagascar Marine Sponge Biemna laboutei: Δ7 Steroids as New Potential Agents Against Pathogenic Bacteria

[ Vol. 11 , Issue. 1 ]

Author(s):

Rahanira Ralambondrahety, Aurélie Couzinet-Mossion, Vony Rabesaotra, Onja Andriambeloson, Gilles Barnathan, Marcelle Rakotovao and Gaëtane Wielgosz-Collin*   Pages 57 - 62 ( 6 )

Abstract:


Background: Nowadays, the efficiency of antibiotics is endangered by the development of resistant bacterial strains. Consequently, novel bioactive agents are intensively searched. Marine sponges are well-known for being major sources of bioactive compounds, including unusual sterols. Until now, among sterols, interesting antibacterial activity has been reported exclusively for Δ5 sterols.

Objectives: This study aims to describe the steroid composition of the marine sponge Biemna laboutei collected in the North coast of Madagascar, and the antibacterial activity of steroid mixture against human pathogenic strains.

Methods: Sponge was extracted in CHCl3/MeOH. Free steroids were separated from other lipids by column chromatography with dichloromethane as specific eluent. Free sterols/steroids and sterol acetates were analyzed by gas chromatography coupled with mass spectrometry. Antibacterial activity (Minimum inhibitory concentration, MIC) of steroid fractions was assessed for eight strains using agar diffusion with cellulose disks.

Results: Neutral lipids were the major lipid class (79.1% of total lipids) and the dichloromethane eluted fraction contained only free steroids giving rise to the identification of eleven compounds. These components presented exclusively Δ7 unsaturation, including lathosterol as major one (38.4%) and four 3-oxo-steroids (11.8%). The steroid fraction of B. laboutei has demonstrated efficiency against pathogenic strains but more specifically on the gram(+) Bacillus cereus (MIC of 12.5 µg/mL) and Staphylococcus aureus (MIC of 25 µg/mL). This latter bacterium causes several illnesses, some of those strains being antibiotic-resistant and this becomes a worldwide health problem.

Conclusion: This is the first report for an antibacterial activity of a mixture of Δ7 steroids against a resistant strain of S. aureus to many antibiotics.

Keywords:

Marine invertebrates, Biemnidae sponge, Indian Ocean, lipids, Δ7 steroid compounds, Staphylococcus aureus.

Affiliation:

Laboratoire de Microbiologie de l’Environnement, Centre National de Recherche sur l’Environnement, CNRE, BP 1739, Fiadanana, Antananarivo, Faculty of Pharmaceutical and Biological Sciences, MMS-EA 2160, Institut Universitaire Mer et Littoral FR3473 CNRS, University of Nantes, Nantes, Faculty of Pharmaceutical and Biological Sciences, MMS-EA 2160, Institut Universitaire Mer et Littoral FR3473 CNRS, University of Nantes, Nantes, Laboratoire de Chimie et de Valorisation des Produits Naturels, LCVPN, Faculty of Sciences, University of Antananarivo, BP 906, Antananarivo, Faculty of Pharmaceutical and Biological Sciences, MMS-EA 2160, Institut Universitaire Mer et Littoral FR3473 CNRS, University of Nantes, Nantes, Laboratoire de Microbiologie de l’Environnement, Centre National de Recherche sur l’Environnement, CNRE, BP 1739, Fiadanana, Antananarivo, Faculty of Pharmaceutical and Biological Sciences, MMS-EA 2160, Institut Universitaire Mer et Littoral FR3473 CNRS, University of Nantes, Nantes



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