PENTACYCLIC TRITERPENE CONSTITUENTS OF YELLOW BIRCH BARK FROM QUEBEC*

ABSTRACT

Birch bark represents an abundant, and currently under-utilized, natural resource. Yellow birch (Betula alleghaniensis), the emblem tree of Quebec, is commercially important and one of the most widespread birch species in the province, but the use of its bark is limited. It is only used as a low value fuel source in solid wood products industries. Yellow birch bark triterpene constituents such as lupeol, betulin and betulinic acid have been described to have high biological activity. The yellow birch bark triterpene constituents such as betulin and certain derivatives of this natural substance have demonstrated interesting therapeutic properties. For example, betulinic acid has been shown to possess anti-tumor activity against human melanoma cells both in vitro and in vivo models. Its mechanism of action consists in the induction of apoptosis or cellular suicide in the cancer cells without affecting healthy cells.14] Pisha, E., Chai, H., Lee, I.-S., Chagwedera, T.E., Farnsworth, N.R., Cordell, G.A., Beecher, C.W.W., Fong, H.H.S., Kinghorn, A.D., Brown, M., Wani, M.C., Wall, M.E., Hieken, T.J., Das Gupta, T.K. and Pezzuto, J.M. 1995. Nature Medicine, 1: 1046Crossref], PubMed], Web of Science ®] , Google Scholar] These natural products confer added value to this tree. In this study, we investigated the triterpenoid composition of the outer bark of B. alleghaniensis from three locations in Quebec: Saint-Damien de Bellechasse, Saint-Félix-d’Otis, and Duchesnay. Eight triterpenes not previously reported in the bark of yellow birch were detected in this research. The betulonic aldehyde was identified as a new yellow birch bark constituent in bark samples from all sites, while the betulinic aldehyde and the oleanane type triterpenes were only detected in the sample from Saint-Félix-d’Otis. To our knowledge, this is the first time that the oleanane-type triterpenes are identified in yellow birch bark.