Bioactive constituents from the Ghanaian medicinal plant Chlorophora regia and its root endophytic fungus JK10.
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Date
AUGUST, 2016
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Abstract
The extracts of the Ghanaian medicinal plant Chlorophora regia A. Chev (Moraceae) has been used for the treatment of various ailments in traditional medicine including burns, wounds, snake bite, wasp bite. A search through the literature, however, revealed there were no available data on the phytochemical composition of the plant. Therefore, the main objective of this study was to isolate, characterize and evaluate some biological activities of secondary metabolites from the stem bark of the plant and further investigate the endophytic community harbored in the inner tissues of the plant. Extensive phytochemical investigation of the stem bark resulted in the isolation and characterization of four new metabolites, regiafuran A–C and 6–prenylated–3,5,7,4ʹ–tetrahydroxy–2ʹ–methoxyflavonol in addition to fifteen known compounds. The isolated compounds were tested for their free radical scavenging activities. Regiafuran A–B, mulberrofuran Y, kuwanol E and 5,7,4ʹ–trihydroxy–2ʹ–methoxyflavanone demonstrated significant free radical scavenging activities with IC50 values of 1.9 μg/ml, 2.4 μg/ml, 2.2 μg/ml, 2.1 μg/ml and 1.8 μg/ml respectively. An unidentified endophytic fungus, JK10, was isolated from the root of C. regia. Twelve compounds including seven new 7–desmethyl derivatives of fusarin C and five known compounds were isolated from the endophytic fungus, JK10. The planar and relative configurations of the new compounds were elucidated by combined spectroscopic analyses of their UV, IR, HRESI–MSn, ECD and NMR data. The absolute configuration of solaniol was established for the first time by X–ray diffraction analysis of a single crystal. The antibacterial activities of the isolated compounds were evaluated. 7–desmethyl fusarin C–22/23 and 7–desmethyl fusarin C–25 exhibited remarkable activity at concentrations of 10.0 μg/mL against the soil bacterium Acinetobacter sp. BD4 comparable to the reference standard streptomycin. All the tested compounds demonstrated activity against the environmental strain of E. coli. Based on the results it could be proposed that the endophytic fungus, whose origin is from the roots, contributes a chemical–mediated defensive mechanism to the host plant against
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invading specific soil and environmental bacterial pathogens. This may confirm the existence of a unique cost–benefit endophyte–plant association. The spatial distribution of three kaurane diterpenes, xylopic acid, ent–kaur–16–en–19–oic acid and 15–oxo–ent–kaur–16–en–19–oic acid, in the fruits of Xylopia aethiopica (Dunal) A. Rich (Annonaceae) were visualized by MALDI–HRMS imaging techniques. The distribution of the compounds was predominantly in the pericarp region of the fruit with non-detectable levels in the seed.
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A thesis submitted in fulfillment of the requirements for the degree of
Doctor of Philosophy
in the Department of Pharmaceutical Chemistry,Faculty of Pharmacy and Pharmaceutical Sciences College of Health Sciences, Kwame Nkrumah University of Science and Technology, Kumasi,