Antimicrobially active alkaloids from Tabernaemontana chippii.

From Tabernaemontana chippii root bark, forty-five alkaloids were isolated; thirty-four were fully characterized by means of their spectral data and/or co-tlc; eight alkaloids were new, four of them being 3-hydroxy derivatives of known dimeric voacamine type alkaloids. Most of the twenty-six known alkaloids belonged to the corynanthean, ibogan, or bisindole classes. The structures of eleven other alkaloids--all minor--were only partially elucidated, most of them being new alkaloids. All the dimeric alkaloids were shown to possess strong antimicrobial activity against gram-positive bacteria and moderate to weak activity against gram-negative bacteria.