Phytochemical studies on the ethanolic extract of the roots of Buxus sempervirens of Turkish origin have resulted in the isolation of two new triterpenoidal alkaloids, (+)-16α, 31- diacetylbuxadine (1), (-)-Nb-demethylcyclomikuranine (2) along with three known natural products, (-)-cyclomikuranine (3), (-)-cyclobuxophylline-K (4) and (+)-buxaquamarine (5) isolated for the first time from this species of genus Buxus. The structures of these new natural products were established on the basis of extensive spectroscopic studies. Compound 1 exhibited antibacterial activity against human pathogenic bacteria and weak phytotoxic activity against Lemna minor Linn. © 2002, Verlag der Zeitschrift für Naturforschung. All rights reserved.