Antimicrobial activities of the CH₂Cl₂–CH₃OH (1 : 1) extracts and compounds from the roots and fruits of Pycnanthus angolensis (Myristicaceae)

Abstract

This study was designed at evaluating the antimycobacterial, antibacterial and antifungal activities of the CH₂Cl₂–CH₃OH (1 : 1) extracts and isolated compounds, namely 3,4-dimethoxy-3′,4′-methylenedioxy-7,7′-epoxylignan (1), genkwainin (2), pycnanthulignene C (3), 4,5-dimethoxy-3′,4′-methylenedioxy-2,7′-cycloligna-7,7′-diene (4), pycnanthulignene A (5) from the roots, and calycosin (6), biochanin A (7) and prunetin (8), from the fruits of Pycnanthus angolensis. The microplate alamar blue assay and the broth microdilution method were used to determine the minimal inhibitory concentration (MIC) and minimal microbicidal concentration of the samples. The H⁺-ATPase-mediated proton pumping assay was used to evaluate one of the possible mechanisms of action of the extracts and isolated compounds. The results of MIC determinations showed that the extract from roots was able to prevent the growth of all the studied organisms, including mycobacteria, fungi, and Gram-positive and Gram-negative bacteria. All tested compounds showed antimicrobial activities to different extents, compound 1 and 8 exhibiting the best antimicrobial spectrum, with 92.3% of the tested organisms being sensitive. The results obtained in this study also showed that the extracts as well as most of the compounds were able to inhibit the H⁺-ATPase activity. The overall results provided evidence that P. angolensis and some of its components might be potential sources of antimicrobial drugs against tuberculosis, bacterial and fungal diseases.

Keywords:

• Pycnanthus angolensis
• Myristicaceae
• extract
• compounds
• antimicrobial activity

Acknowledgements

Authors acknowledge the financial support of the International Foundation for Science (grant no. F/4579-1 to VK) for antimycobacterial assays. We also thank Mr G. Ngo Teke (University of Dschang) for providing technical support.