Osman, K;
Evangelopoulos, D;
Basavannacharya, C;
Gupta, A;
McHugh, TD;
Bhakta, S;
Gibbons, S;
(2012)
An antibacterial from Hypericum acmosepalum inhibits ATP-dependent MurE ligase from Mycobacterium tuberculosis.
International Journal of Antimicrobial Agents
, 39
(2)
124 - 129.
10.1016/j.ijantimicag.2011.09.018.
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Abstract
In a project to characterise new antibacterial chemotypes from plants, hyperenone A and hypercalin B were isolated from the hexane and chloroform extracts of the aerial parts of Hypericum acmosepalum. The structures of both compounds were characterised by extensive one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy and were confirmed by mass spectrometry. Hyperenone A and hypercalin B exhibited antibacterial activity against multidrug-resistant strains of Staphylococcus aureus, with minimum inhibition concentration ranges of 2-128 mg/L and 0.5-128 mg/L, respectively. Hyperenone A also showed growth-inhibitory activity against Mycobacterium tuberculosis H37Rv and Mycobacterium bovis BCG at 75 mg/L and 100mg/L. Neither hyperenone A nor hypercalin B inhibited the growth of Escherichia coli and both were non-toxic to cultured mammalian macrophage cells. Both compounds were tested for their ability to inhibit the ATP-dependent MurE ligase of M. tuberculosis, a crucial enzyme in the cytoplasmic steps of peptidoglycan biosynthesis. Hyperenone A inhibited MurE selectively, whereas hypercalin B did not have any effect on enzyme activity.
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