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The study aimed at evaluating the phytochemical composition, antioxidant potentials and the levels of trace elements in the fruit extract of Kigelia africana obtained by different extraction solvents in order to ascertain its numerous pharmacological activities and identify the different chemical compounds responsible for these activities. The crude extract in ethanol and four other solvent fractions (hexane, ethylacetate, butanol and aqueous) were obtained for phytochemical screening. Antioxidant potentials of K. africana fruit were investigated spectrophotometrically using hydroxyl ion scavenging (OH−) activity, metal ion chelating activity, anti-lipid peroxidation activity as well as total antioxidant capacity assays. Trace element (Mn, Zn, Cd, Ni, Cu, Pb, Cr, Co and Fe) levels were measured using a plasma-emission spectrometer that has an auto sampler AS 93-plus and coupled with Nebulizer CETAC U-6000AT+ after microwave acid digestion of the fruit extracts. Chemical identification was performed using ultra-high-pressure liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UHPLC-qTOF-MS2). Kigelia africana fruit extracts obtained showed a variety of bioactive phytochemical compounds including phenolic acids, flavonoids, saponins, tannins and glycosides. The total antioxidant capacity activities of the aqueous, butanol, ethanol, hexane and ethylacetate extracts are 15.04, 52.11, 44.95, 79.27 and 175.20 mg AAE/g. Metal ion chelating activity showed significant correlation with lipid peroxidation inhibition activity at p ≤ 0.01 and with OH− scavenging activity at p ≤ 0.05. PCA analysis revealed that all the extract/fractions have higher total antioxidant activities compared to aqueous extract with hexane extract exhibiting the highest radical scavenging potential. HCA showed similarities with three well-defined clusters and PLS regression was used to predict total antioxidant activity. High sensitivity by low values of limits of detection and quantification was observed ranging from 0.021 to 0.085 mg/ml and 0.063 to 0.258 mg/ml for Zn and Fe respectively. Ethylacetate extract had high concentration of Fe (0.5656 mg/kg). For the standardization of the K. africana fruit extract, 244 chemical compounds were identified by measuring m/z values with threshold override of 100,000 and analysing mass spectrometer fragmentation behaviour while 16 of these were confirmed. Kigelia africana fruit extract is a good source of antioxidant and possess maximum accepted concentration of trace elements according to European legislation (1881/2006/EC). The metabolites identified exhibited numerous pharmacological activities. The method and results suggest the applicability for commercial use of this K. africana fruit in the treatment of oxidative-related diseases.

The purification and characterization of rhodanese, an enzyme that catalyses the detoxification of cyanide, from the gut of the variegated grasshopper (Zonocerus variegatus L.) were carried out to understand the biochemical basis of the survival of this grasshopper living on cyanogenic plants such as cassava. All experiments, including enzyme assay, were carried out at room temperature and all buffers contained 10mM sodium thiosulphate to stabilize the enzyme. Grasshoppers were caught alive from a cassava farm within the locality and kept frozen until analysis. Each grasshopper was dissected and the gut was removed quickly. Approximately 102g of the gut were homogenized in three volumes of 0.1 M acetate glycine buffer (pH 7.8) containing e-amino-n-caproic acid. The supernatant was collected by centrifugation at 12,000 rpm, for 30 min at 40 °C. The enzyme was purified to homogeneity by a combination of procedures such as ammonium sulphate precipitation, ion-exchange chromatography (CM-Sephadex and DEAE-Sephadex), gel filtration (Sephadex G-75) and Agarose-Blue affinity chromatography. Sodium dodecyl sulphate Polyacrylamide gel electrophoresis (SDS-PAGE) and non-SDS-PAGE were used to ascertain the purity of the enzyme. The native and subunit molecular weights of the enzyme were determined by gel filtration on a Bio-Gel P-200 column and SDS-PAGE, respectively. Kinetic parameters were determined by using varying concentrations of one of the substrates at a fixed concentration of the other, and vice versa. Furthermore, the effects of temperature, pH and cations on the activity of the enzyme were investigated. The purified enzyme had a specific activity of 51.7 μmol thiocyanate formed/ml/min/mg protein (U/mg protein) with a yield of about 29%. The apparent molecular weight of the enzyme estimated by Sephadex G-75 gel filtration was 35,400 ± 482 Da and its subunit molecular weight determined by SDS-PAGE was 33,000 ± 212 Da. The Km values of KCN and Na2S2O3 were found to be 29.63 ± 02.87 and 26 ± 03.04mM, respectively. An optimum pH and temperature of 7.0 and 35 °C, respectively, were obtained for the enzyme. The results of enzyme inhibition showed that the activity of the enzyme was not affected by NH4Cl, MgCl2, CoCl2, CaCl2, MnCl2, NiCl2 and SnCl2, but inhibited by ZnCl2 and BaCl2. In conclusion, these results suggest that the survival of Z. variegatus depends on the presence of the enzyme rhodanese, which shows high activity and has suitable kinetic properties in the gut of the grasshopper that feeds mainly on cassava leaves which are cyanogenic.