Triterpenes from the Outer Bark ofBetula nigra

Abstract
Twelve pentacyclic triterpenes were isolated from the outer bark of river birch, Betula nigra. 3β-Acetoxyolean-11-oxo-12-ene-28-oic acid was isolated for the first time from a Betula species. 3β-Caffeatoxyolean-12-ene-28-oic acid has been spectrally characterized for the first time. 3β-Acetoxyolean-12-ene-28-oic acid and 3β-acetoxyolean-11-oxo-12-ene-28-oic acid have been demonstrated to be active as antifeedants for the Colorado potato beetle, Leptinotarsa decemlineata.