Chemical constituents of Zanthoxylum capense

Zanthoxylum capense (Thunb.) Harv (Rutaceae) is a small to medium tree distributed in Zimbabwe, South Africa, and Mozambique. The decoction of its roots is used to treat gallsickness in the Eastern Cape, and its fruits are employed in the treatment of colic and paralysis. Similarly to other Zanthoxylum species, such as Z. chalybeum Engl. and Z. davyi (Verdoorn) P.G. Waterman, Z. capense is also used in the treatment of snakebite and severe coughs and colds [1]. Previous studies of this genus have reported the isolation of coumarins, lignans, alkaloids, terpenoids, and flavonoids [2]. In our search for biologically active compounds from plant species, the methanol extract of Z. Capense roots has been studied. The crude methanol extract was suspended on a methanol-water mixture and sequentially extracted with n-hexane and dichloromethane. Preliminary studies of the dichloromethane fraction, using combined chromatographic techniques, have yielded some known benzophenanthridine-type alkaloids, namely decarine, norchelerythrine, and 8-acetonyldihydro-cherlerythrine, and one furoquinoline alkaloid, skimmianine. The lignan, (–)-savinin was also isolated. The structures of these compounds were deduced from their physical and spectroscopic data, including 1D and 2D NMR experiments (¹H, ¹³C, COSY, HMQC, HMBC and NOESY) and comparison with reported data. Further phytochemical study on this plant is going on.

Acknowledgements: This study was supported by a fellowship from FCT, Portugal (reference number SFRH/BPD/37179/2007).

References: 1. Tarus, P.K. et al. (2006) S. African. J. Bot. 72:555–558.

2. Gray, A.I. et al. (1983) Chemistry and Chemical Taxonomy of Rutales. Academic Press, London, p.97.