Biologically active indole and bisindole alkaloids from Tabernaemontana divaricata

Abstract

The ethanol extract of the leaves of Tabernaemontana divaricata (double flower variety) provided a total of 23 alkaloids, including the new aspidosperma alkaloids, taberhanine, voafinine, N-methylvoafinine, voafinidine, voalenine and the new bisindole alkaloid, conophyllinine in addition to the previously known, biologically active bisindole, conophylline and its congener, conofoline. The structures of the new alkaloids were established by spectroscopic methods. The preparation and characterization of the corresponding quinones of the biologically active bisindoles are also described in relation to a structure-activity study of these compounds with respect to their action in stimulating insulin expression.

Biologically Active Ibogan and Vallesamine Derivatives from Tabernaemontana divaricata

“…The geometry of the double bond was determined from NOE. Irradiation of HÀC(18) (Me) caused enhancement of HÀC (19) and HÀC (15), while irradiation of HÀC (19) resulted in enhancement of HÀC (18) and H a ÀC (21), indicating that the double bond is (E)-configured, as shown in structure 7. The (Z)-isomer 9, which was named ervaticine, was obtained previously from Ervatamia coronaria, and the NOE results, despite the structure drawn, indicated a (Z)-configuration for the C(19)C (20) [29].…”

“…Three bisindole alkaloids were also obtained, viz., conofoline [18], voacamine [34] [35], and conodusarine (17) [36]. Conofoline also occurs in the leaf extract [18], while conodusarine (17) is a new biologically active bisindole alkaloid, which was found to reverse multidrug resistance in vincristine-resistant tumor cells [36].…”

“…Conofoline also occurs in the leaf extract [18], while conodusarine (17) is a new biologically active bisindole alkaloid, which was found to reverse multidrug resistance in vincristine-resistant tumor cells [36].…”

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“…Presence of many kinds of alkaloids from T. divaricata is already reported by T.S. Kam 24 . Antibacterial, antioxidant and antimicrobial studies of the leaves of T. divaricata are also reported.…”

Synthesis of the indole core structures of conophylline

“…We were interested in the anti-diabetic effect of conophylline that was unprecedent as a bisindole and considered that conophylline could be a new lead for the drugs and therapies toward diabetes. Conophylline has a unique structure comprising two indoles segmented via a central dihydrofuran [4]. The dihydrofuran seems crucial for the effect on diabetes, determining the spatial relationships of the indoles of both sides [3].…”