Tabernabovines A–C: Three Monoterpenoid Indole Alkaloids from the Leaves of Tabernaemontana bovina

Three monoterpenoid indole alkaloids (MIAs), tabernabovines A–C (1–3), were isolated from Tabernaemontana bovina. They were elucidated by spectroscopic data and computational calculations. Unlike precursors of MIAs, strictosidine and alstrostine A, alkaloid 1 consists of tryptamine and secologanin in a 2:1 ratio. Alkaloid 2 is a cage compound, and 3 possesses a bridged ring. Tabernabovine A exhibited inhibitory activity against NO production with IC₅₀ 44.1 μM compared to l-NMMA with IC₅₀ of 48.6 μM.