Journal
JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
Volume 13, Issue 12, Pages 1158-1164Publisher
TAYLOR & FRANCIS LTD
DOI: 10.1080/10286020.2011.622720
Keywords
Usnea undulata; antibacterial activity; depsidones; (+) usnic acid; beta-orcinol
Funding
- National Research Foundation of South Africa
- Govan Mbeki Research and Development Centre of the University of Fort Hare
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Usnea undulata Stirton (Usneaaceae) is a fruticose lichen used locally in ethnoveterinary medicine to treat mammary infections in cattle while human beings use it for the treatment of wounds in Eastern Cape, South Africa. Bioactivity-guided fractionation of its extracts led to the isolation and characterization of a new depsidone, 2'-O-methylhypostictic acid (8), together with seven known compounds, i.e. methyl beta-orsellinate (1), norstictic acid (2), menegazziaic acid (3), (+) usnic acid (4), hypoconstictic acid (5), salazinic acid (6), and galbinic acid (7). The structures of the compounds were elucidated on the basis of their spectral analysis including homo-and hetero-nuclear correlation NMR experiments (COSY, NOESY, HMQC, and HMBC) and mass spectra as well as by comparison with available data in the literature. The minimum inhibitory concentrations (MICs) values of the compounds against six bacteria were determined. Compound 8 showed inhibitory activity against Bacillus cereus, Bacillus subtilis, and Staphylococcus epidermidis with MICs of 31, 62.5, 62.5 mu g/ml, respectively. (+) Usnic acid was most active against B. subtilis, B. cereus, Staphylococcus aureus, and Escherichia coli with MICs of 8, 8, 31, and 31 mu g/ml, respectively, while other compounds exhibited moderate activity.
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