Tabernaemontana Aspidosperma alkaloids

Tabernaemontana divaricata (double flower variety) provided an unusual minor alkaloid, voaharine (178), whose structure was established by X-ray analysis [137]. Voaharine is exceptional in being in all probability a tryptamine and jccologanine derived alkaloid but possessing a 3-quinolone instead of an indole chromophore. Voaharine is probably derived from voaphylline (180) (which is also present in the plant) via oxidation and rearrangement and represents the first instance of a 3-quinolone-type alkaloid obtained from Tabernaemontana. Besides these, and the known alkaloids N-methylvoaphylline (181), pachysiphine (tabersonine-P-epoxide) and apparicine, as well as two new bisindoles (vide infra), the plant also provided several new alkaloids of the aspidosperma-type including (-)-mehranine (179), voafinine (182), N-methylvoafinine (183), voafinidine (184) and voalenine (185) which were obtained in minute amounts [138-140]. 

The popular garden plant Tabernaemontana divaricata which is extensively grown in gardens in Malaysia as well as in India provided several novel bisindoles, one of which, viz., conophylline (303) has been shown to be a potent inhibitor of ras functions (vide infra). There are two distinct varieties, the single flower variety produces both conophylline (303) and conophyllidine (304) [137,180] while the double flower variety gives in addition, a third dimeric alkaloid, conofoline (305) [ 138] as well as several new aspidosperma-type compounds. 

Zaima K, Hirata T, Hosoya T, Hirasawa Y, Koyama K, Rahman A, Kusumawati I, Zaini NC, Shiro M, Morita H (2009) Biscarpamontamines A and B, an aspidosperma-Zboga bisindole alkaloid and an aspidosperma-aspidosperma bisindole alkaloid, from Tabernaemontana sphaerocarpa. J Nat Prod 72 1686-1690... 

Olivacine (52) occurs in the bark of several Brazilian trees of the genera Aspidosperma and Tabernaemontana (Apocynaceae) ellipticine (53) and 9-methoxyellipticine (54) have been isolated from species of Ochrosia (Apocynaceae) (Neuss, 1980). Similar alkaloids have been isolated from Strychnos dinklagei (Gribble, 1990). Both ellipticine and 9-melhoxyellipticine (54) have been isolated at low levels from callus cultures of Ochrosia elliptica (Gribble, 1990). 

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