Studies of the triterpenoids from the outer bark of three birch species: Betula lenta, Betula alleghaniensis and Betula nigra

Triterpenoid constituents in the outer bark of three Betula species were investigated. Ten triterpenoids were isolated from the outer bark of B. lenta by chromatography. Spectroscopic evidence and chemical derivatization showed that these triterpenoids were lupeol, betulin, lupenone, betulone, betulinic acid, betulin 3{dollar}beta{dollar}-caffeate, lup-20(29)-ene-3{dollar}beta{dollar}, 30-diol, lup-20(29)-ene-3{dollar}beta{dollar}-ol-30-al, lup-20(29)-ene-3{dollar}beta{dollar},28-diol-30-al and lupan-3{dollar}beta{dollar},20-diol. Betulone and lup-20(29)-ene-3{dollar}beta{dollar},28-diol-30-al, previously prepared synthetically, are new natural products. Lupeol was the most abundant triterpene, and betulin was second in abundance.; From the outer bark of B. alleghaniensis, seventeen triterpenoids were isolated and identified by the same methods. Four of them, including lup-20(29)-ene-3-one-28-ol-30-al, 29-norlupan-3{dollar}beta{dollar},20-dione, 29-norlupan-28-ol-3{dollar}beta{dollar},20-dione and lupan-3-one-20,28-diol, are new natural compounds. Other triterpenes were previously isolated either from the bark of Betula species or from other natural sources. In B. alleghaniensis, lupeol was still the predominant component, but the second most abundant component in B. alleghaniensis was lupenone, which was different from B. lenta. Betulone and lupan-3-one-20-ol were also present at the high level in B. alleghaniensis. Lup-20(29)-ene-3{dollar}beta{dollar}-ol-30-al was tested for insect antifeedant activity against Colorado potato beetle (Leptinotarsa decemlineata) and showed no activity.; From the outer bark of Betula nigra, twelve triterpenoids were isolated and identified. Among them, acetyl methyl betulinate, acetyl betulinic acid and 3{dollar}beta{dollar}-acetoxy-olean-11-oxo-12-ene-28-oic acid were isolated for the first time from a Betula species. Oleanolic acid 3{dollar}beta{dollar}-caffeate was spectrally characterized for the first time. Other triterpenes were previously isolated either from the bark of European birch species or from two dark-barked North American birches. The composition of the triterpenoids in B. nigra was quite different from the previously studied birch species. Instead of lupenone, lupeol and betulin being the major components, acetyl oleanolic acid and betulinic acid were the predominant components in B. nigra. Acetyl oleanolic acid and 3{dollar}beta{dollar}-olean-11-oxo-12-ene-28-oic acid demonstrated activity as antifeedants for the Colorado potato beetle. Oleanolic acid showed lower activity in the same bioassay.; Both the {dollar}beta{dollar}-D- and {dollar}beta{dollar}-L-glucosides of 19{dollar}beta{dollar},28-epoxy-2-hydroxy-18{dollar}alpha{dollar}-olean-1-ene-3-one were synthesized in order to find out the mechanism of action of the betulin-derived active compound. Also, a model compound was synthesized for structure-activity evaluation. These synthetically prepared compounds will be assessed for antifeedant activity.