Browsing by Author "Kyekyeku, James Oppong"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Bioactive constituents from the Ghanaian medicinal plant Chlorophora regia and its root endophytic fungus JK10.
    ( AUGUST, 2016 ) Kyekyeku, James Oppong
    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 iii 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.
  • Thumbnail Image
    Item
    Characterization and HPLC Quantification of Xylopic Acid in the Dried Fruits of Xylopia Aethiopica
    (APRIL, 2010) Kyekyeku, James Oppong
    Xylopia aethiopica is an evergreen, aromatic tree growing up to 15cm high, bark slightly ridged, native to the West, Central and Southern Africa. Flowers appear in clusters of 2-4, fruits turn red when ripe and black when dried. The dried fruit is commonly called African pepper. The dried fruits of Xylopia aethiopica have been used in folklore medicine. The extracts of the fruit have been shown to have antibacterial and antifungal properties. Dried fruits of Xylopia aethiopica used for the project were obtained from the Kumasi Central Market and were authenticated by the Department of Pharmacognosy, KNUST. In order to obtain pure xylopic acid crystals for use as secondary reference xylopic acid was extracted from dried fruits of Xylopia aethiopica with petroleum ether (40-60oC) and recrystallised from ethanol. The melting point of the crystals was determined to be 261-262oC and the Rf value of xylopic acid using petroleum ether (40-60oC): ethylacetate (9:1) as the solvent system to be 0.53. NMR, infrared and mass spectroscopic analyses were carried out to characterise the isolated crystals. HPLC was used to quantify the xylopic acid in the dried fruits using methanol: water (9:1) as the mobile phase and a phenomenex hypersil 20 micron C 18 200 x 3.2 mm reverse column. The percentage content of xylopic acid in the whole fruit was estimated to be 1.15% ± 0.08 (n=8). The percentage content of xylopic acid in the seeds was determined to be 0.07% ± 0.02 (n=6) and the dried pericarp of the fruit was found to contain 0.87% ± 0.20 (n=6) xylopic acid. The purified xylopic acid crystals were subjected to stability studies for a period of three (3) months. The conditions employed for the stability studies were temperatures of 50oC, 60oC and 80oC. The crystals were assayed on the 20th, 50th and 70th days using the HPLC method developed for the assay of the crude fruit extract. The concentration at 50oC was 87.76%, 74.68% and 67.78% on the 20th, 50th and 70th days respectively. The concentration at 60oC was estimated to be 75.86%, 67.19% and 47.97% on the 20th, 50th and 70th days respectively. The concentration at 80oC was found to be 68.13%, 63.10% and 44.51% on the 20th, 50th and 70th days respectively.
  • Thumbnail Image
    Item
    Characterization and HPLC Quantification of Xylopic Acid in the Dried Fruits of Xylopia Aethiopica
    (APRIL, 2010) Kyekyeku, James Oppong
    Xylopia aethiopica is an evergreen, aromatic tree growing up to 15cm high, bark slightly ridged, native to the West, Central and Southern Africa. Flowers appear in clusters of 2-4, fruits turn red when ripe and black when dried. The dried fruit is commonly called African pepper. The dried fruits of Xylopia aethiopica have been used in folklore medicine. The extracts of the fruit have been shown to have antibacterial and antifungal properties. Dried fruits of Xylopia aethiopica used for the project were obtained from the Kumasi Central Market and were authenticated by the Department of Pharmacognosy, KNUST. In order to obtain pure xylopic acid crystals for use as secondary reference xylopic acid was extracted from dried fruits of Xylopia aethiopica with petroleum ether (40-60oC) and recrystallised from ethanol. The melting point of the crystals was determined to be 261-262oC and the Rf value of xylopic acid using petroleum ether (40-60oC): ethylacetate (9:1) as the solvent system to be 0.53. NMR, infrared and mass spectroscopic analyses were carried out to characterise the isolated crystals. HPLC was used to quantify the xylopic acid in the dried fruits using methanol: water (9:1) as the mobile phase and a phenomenex hypersil 20 micron C 18 200 x 3.2 mm reverse column. The percentage content of xylopic acid in the whole fruit was estimated to be 1.15% ± 0.08 (n=8). The percentage content of xylopic acid in the seeds was determined to be 0.07% ± 0.02 (n=6) and the dried pericarp of the fruit was found to contain 0.87% ± 0.20 (n=6) xylopic acid. The purified xylopic acid crystals were subjected to stability studies for a period of three (3) months. The conditions employed for the stability studies were temperatures of 50oC, 60oC and 80oC. The crystals were assayed on the 20th, 50th and 70th days using the HPLC method developed for the assay of the crude fruit extract. The concentration at 50oC was 87.76%, 74.68% and 67.78% on the 20th, 50th and 70th days respectively. The concentration at 60oC was estimated to be 75.86%, 67.19% and 47.97% on the 20th, 50th and 70th days respectively. The concentration at 80oC was found to be 68.13%, 63.10% and 44.51% on the 20th, 50th and 70th days respectively.