An aporphinoid and epoxytetraynoic acid from Mkilua fragrans verdc and terpenoids from polyceratocarpus scheffleri engl and diels

This Dissertation reports on phytochemical investigations of two hitherto uninvestigated plants of the family Annonaceae, namely Polyceratocarpus scheffleri Engl. & Diels and Mkilua fragrans Verde. The investigations were done on the stem bark of both plants which was collected from the East Usambara Mountains, in Tanga region. Dry and pulverized stem-bark was extracted using organic solvents and chromatographic methods (TLC, VLC, CC, PTLC) were used for the isolation of compounds. The methanol extract of the stem bark of M. fragrans yielded two natural products, an aporphinoid, 1,2,3-trihydroxy-7-oxo-dibenzo-(de,g)-quinoline and a C t g epoxytetraacetylenic fatty acid, 17,18-epoxyoctadeca-9,11,13,15-tetraynoic acid. The structures of the two natural products as proposed in this Dissertation are still tentative due to the inadequate spectral information which was available at the time of writing this Dissertation. The dichloromethane fraction of the methanol extract of the stem-bark of P. scheffleri yielded three known compounds, namely, polyearpol a tetracyclic triterpenoid with reported strong antitumour activity and considered as a chemotaxonomic marker as it occurs in plants of the family Annonaceae only, a mixture of R-D-glucopyranosides of ß-sitosterol and stigmasterol and a mixture of (3-sitosterol and stigmasterol. The isolated compounds were identified on the basis of their spectral data, (iH-NMR, 13C-NMR, COSY, etc.). The crude extracts and the isolated compounds were tested for their bioactivities (possible cytotoxicity) using the brine shrimp bioassay at the Chemistry Department, University of Dar es Salaam. In the brine shrimp bioassay the crude methanol extract of M. fragrans and the epoxytetraacetylenic acids were found to be inactive. For P. scheffleri, the dichloromethane extract was slightly active while the methanol extract and polyearpol were inactive. The remaining compounds, i. e. the aporphinoid, the glycosides and the aglycones of the sugars were not tested for their cytotoxicities.