Further phytochemical and cytotoxicity studies of the indole alkaloids of Kopsia arborea STEM-BARK / Wong Soon Kit

Wong , Soon Kit (2024) Further phytochemical and cytotoxicity studies of the indole alkaloids of Kopsia arborea STEM-BARK / Wong Soon Kit. PhD thesis, Universiti Malaya.

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Abstract

Two Malaysian plants of Kopsia arborea Blume (family: Apocynaceae) of different geographical locations, one of which was collected in Petaling Jaya, Selangor (Sample A), and the other in Penang Island (Sample B), were investigated for their alkaloidal composition. A total of 60 alkaloids (1−60) were isolated and characterized from the stem-bark extracts of these sources, of which eight are new alkaloids. Of these, arbophyllidine (1) and arboduridine (2) are distinguished by incorporation of novel molecular skeletons, and arbophyllinines A (6) and B (7) are two corynanthean alkaloids incorporating a substituted tetrahydrofuranone ring. The aspidofractinine-aspidofractinine bisindole alkaloid, arbolodinine A (58), is notable for being a rare instance of a bisindole alkaloid branched from an iminium ion, while arbolodinines B (59) and C (60) represent the first examples of strychnan-aspidofractinine and strychnan-kopsine bisindole alkaloids, respectively. Among the new alkaloids, arbophyllidine (1) showed pronounced in vitro growth inhibitory activity against HT-29 human cancer cell line (IC50: 6.2 M), and arbolodinine B (59) displayed strong cytotoxicity against KB, vincristine-resistant KB, PC-3, HCT 116, HT-29, MDA-MB-231, MCF7, and A549 cells (IC50: 1.3−9.6 M). The alkaloid compositions of the two plants are summarized in Table 2.1.

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