Four Yellow Monoterpenoid Quinoline Alkaloids fromthe Stem of Tabernaemontana bovina

Four unprecedented yellow alkaloids named as taberbovines A–D (1–4) were isolated from stems of Tabernaemontana bovina Lour. Their structures were elucidated by the comprehensive spectroscopic data, computational chemistry, and X-ray crystal diffraction. Alkaloids 1–4 possessed a unique 6/6/5/6/5 ring system and were assigned to monoterpenoid quinolines. Biosynthetically, the isolated alkaloids may be derived from Aspidosperma-type alkaloid by oxidation and rearrangements. Taberbovines A–D exhibited the good inhibitory activities of formation NO in LPS induced RAW264.7 macrophages.