Phytochemical analyses and biological activities of four South African ficus species (moraceae)

Doctor of Philosophy in Chemistry. University of KwaZulu-Natal, Durban 2015.Abstract available in PDF file

Soil-to-plant transfer of 40K, 238U and 232Th and radiological risk assessment of selected mining sites in Nigeria

One of the major route through which humans are exposed to ionizing radiation is via food chain, which is consequent of soil-to-plant transfer of radionuclides. This work reported the activity concentrations of 40K, 238U and 232Th in samples of water, soil and guinea corn grains collected from Beryllium and Gold mining sites in Kwara, Nigeria. In-situ measurements at approximately 1 m in the air was carried out using a well-calibrated portable Gamma Spectrometer (Super Spec RS-125), while the soil, water and the guinea corn samples were analyzed using a ‘3 × 3’ inch lead-shielded NaI (Tl) detector. The measured activity concentrations of the natural radionuclides in the soil from both mines are lower than the in-situ measurements. This was attributed to the contribution from other terrestrial materials on-site. The estimated mean transfer factors (TFs) for 40K, 238U and 232Th are 0.21, 0.17 and 0.31, and 0.46, 0.19 and 0.28 respectively for the Beryllium and Gold mining sites. While the TFs for 238U and 232Th exceeded the mean value of 0.0062 and 0.0021 for 238U and 232Th respectively, the TFs for 40K are well below the 0.74 for cereals grains provided by International Atomic Energy Agency (IAEA). The radiation impact assessment using the Monte Carlo simulations reveals values that were generally less than the global average values provided by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Hence, the risk of cancer inducement due to radiation exposure is within the acceptable limits for both mining sites

Inhibition of key enzymes linked to type 2 diabetes by compounds isolated from Aframomum melegueta fruit

Context: The use of Aframomum melegueta K. Schum. (Zingiberaceae) fruit for treatment of diabetes has recently been established in Nigeria. However, compounds responsible for the antidiabetic action have not been identified. Objective: The present study carried out the bioassay-guided isolation of possible bioactive compounds responsible for the antidiabetic action of A. melegueta fruit. Materials and methods: The A. melegueta fruit was sequentially extracted using ethyl acetate (EtOAc), ethanol and water, and the most active extract (EtOAc) was subjected to column chromatography on a silica gel column using solvent gradient systems of hexane (HEX):EtOAc and EtOAc:MeOH and the isolation of compounds was guided by α-glycosidase and α-amylase inhibitory activities at various concentrations (30–240 μg/mL). Results: According to the results, 3 arylalkanes, 6-paradol (1), 6-shogaol (2) and 6-gingerol (3) and a pentacyclic triterpene, oleanolic acid (4) were isolated from A. melegueta fruit. All the compounds exhibited inhibitory effects against α-amylase and α-glucosidase. 6-Gingerol (3) and oleanolic acid (4) showed higher inhibitory activity against α-amylase (IC50: 6-gingerol: 81.78 ± 7.79 μM; oleanolic acid: 91.72 ± 1.63 μM) and α-glucosidase (IC50: 6-gingerol: 21.55 ± 0.45 μM; oleanolic acid: 17.35 ± 0.88 μM) compared to the standard drug, acarbose and other isolated compounds. The kinetics of the enzyme action of the compounds showed a noncompetitive mode of inhibition. Conclusion: The data of this study suggest that the 6-gingerol (3) and oleanolic acid (4) showed higher α-amylase and α-glucosidase inhibitory action and therefore could be responsible for the antidiabetic activity of A. melegueta fruit

Inhibition of key enzymes linked to type 2 diabetes by compounds isolated from <i>Aframomum melegueta</i> fruit

<p><b>Context:</b> The use of <i>Aframomum melegueta</i> K. Schum. (Zingiberaceae) fruit for treatment of diabetes has recently been established in Nigeria. However, compounds responsible for the antidiabetic action have not been identified.</p> <p><b>Objective:</b> The present study carried out the bioassay-guided isolation of possible bioactive compounds responsible for the antidiabetic action of <i>A. melegueta</i> fruit.</p> <p><b>Materials and methods:</b> The <i>A. melegueta</i> fruit was sequentially extracted using ethyl acetate (EtOAc), ethanol and water, and the most active extract (EtOAc) was subjected to column chromatography on a silica gel column using solvent gradient systems of hexane (HEX):EtOAc and EtOAc:MeOH and the isolation of compounds was guided by α-glycosidase and α-amylase inhibitory activities at various concentrations (30–240 μg/mL).</p> <p><b>Results:</b> According to the results, 3 arylalkanes, 6-paradol (<b>1</b>), 6-shogaol (<b>2</b>) and 6-gingerol (<b>3</b>) and a pentacyclic triterpene, oleanolic acid (<b>4</b>) were isolated from <i>A. melegueta</i> fruit. All the compounds exhibited inhibitory effects against α-amylase and α-glucosidase. 6-Gingerol (<b>3</b>) and oleanolic acid (<b>4</b>) showed higher inhibitory activity against α-amylase (IC₅₀: 6-gingerol: 81.78 ± 7.79 μM; oleanolic acid: 91.72 ± 1.63 μM) and α-glucosidase (IC₅₀: 6-gingerol: 21.55 ± 0.45 μM; oleanolic acid: 17.35 ± 0.88 μM) compared to the standard drug, acarbose and other isolated compounds. The kinetics of the enzyme action of the compounds showed a noncompetitive mode of inhibition.</p> <p><b>Conclusion:</b> The data of this study suggest that the 6-gingerol (<b>3</b>) and oleanolic acid (<b>4</b>) showed higher α-amylase and α-glucosidase inhibitory action and therefore could be responsible for the antidiabetic activity of <i>A. melegueta</i> fruit.</p