Volume 165, 13 May 2015, Pages 148–151
Ethnopharmacological communication
Anti-mycobacterial triterpenes from the Canadian medicinal plant Alnus incana
Abstract
Ethnopharmacological relevance
Alnus incana,
commonly known as the gray or speckled alder, is a medicinal plant used
by some Canadian First Nations to treat symptoms associated with
tuberculosis. The aim of this study was to assess the anti-mycobacterial
activity of an Alnus incana bark extract and to identify the active constituents of the extract.
Materials and Methods
Methanolic extracts of the bark of A. incana were subjected to bioassay guided fractionation using Mycobacterium tuberculosis (H37Ra). The active constituents were identified by NMR and MS.
Results
Four
pentacyclic lupane triterpenes were isolated and were identified as
betulin, betulinic acid, betulone and lupenone. Betulin displayed a MIC
of 12.5 μg/mL and an IC50 of 2.4 μg/mL against M. tuberculosis (H37Ra). Betulinic acid and betulone showed lower anti-mycobacterial activities with IC50 values of 84 and 57 μg/mL respectively. Lupenone was inactive against M. tuberculosis (H37Ra).
Conclusions
Betulin, betulinic acid and betulone were identified as the major anti-mycobacterial constituents in the bark of A. incana
and the functionality at carbons 3 and 28 of the lupane skeleton would
seem to be important in determining the anti-mycobacterial activity of
the triterpenes. This work supports the ethnopharmacological use of A. incana by Canadian First Nations communities as a treatment for tuberculosis.
Graphical abstract
Keywords
- Alnus incana;
- Antimycobacterial activity;
- Betulin;
- Betulinic acid;
- Betulone;
- Mycobacterium tuberculosis
- Corresponding author at: Department of Chemistry, University of New Brunswick, Saint John, New Brunswick, Canada E2L 4L5. Tel.:
+1 506 648 5576..
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