The kinetics and mechanism of the antioxidant activities of the methanolic extract of the leaves of two vegetables [ Corchorus olitorius ( C. olitorius ) and Vernonia amygdalina ( V. amygdalina )] have been studied using experimental and theoretical approaches. The kinetics (second order and pseudo-first order) of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities of the leaf extracts at varying times (30–90 min) were determined using the UV–visible spectrophotometry method at λ max = 517 nm, whereas the mechanism was studied by density functional theory at two levels of functionals (B3LYP and LC-ωPBE) using bond dissociation enthalpy and adiabatic ionization potential values. Molecular properties such as the highest occupied molecular orbital, lowest unoccupied molecular orbital, electronegativity (χ), electrophilicity (ω), hardness (η), and softness ( S ) of the predominant phenolic antioxidants were also compared. The second-order kinetics is favored by both plants rather than pseudo-first order; however, V. amygdalina with a second-order rate constant k 2 of 0.0152 (mM) −1 min –1 is faster in scavenging DPPH radicals than C. olitorius with a k 2 value of 0.0093 (mM) −1 min –1 . Chlorogenic acid and luteolin-7-O-β-glucuronide, which are the most abundant phenolic acid antioxidant in C. olitorius and V. amygdalina , both preferably scavenge the DPPH radical via a hydrogen atom transfer mechanism. This is evident from their lower bond dissociation enthalpy values than the adiabatic ionization potential values. Successful molecular docking of these phenolic compounds indicates that both compounds form favorable interactions with the therapeutic target, xanthine oxidase.

The biosorption of Cr (III) ions from aqueous solutions by groundnut husk, a low-cost biosorbent was studied on a laboratory scale batch experiments. The effects of pH, contact time, particle size, biosorbent dosage and temperature on the adsorption of Cr (III) ions were investigated. Determination of Chromium ion concentration in solution was done using Atomic Absorption Spectrophotometer (AAS). The results show that the removal mechanism is predominantly by chemisorption and it is dependent on the physical and chemical characteristics of the biosorbent material. From the initial concentration of 0.5 mM, optimum Cr (III) ions removal was obtained at pH of 4, particle size of 0.15 nm, contact time of 180 minutes and biosorbent dosage of 50 mg, with the highest biosorption efficiency of 81.15 %. The biosorption process was best described by the BET adsorption isotherm with R2 value 0.9814 indicating multiplayer adsorption. Analysis of the experimental data revealed that the biosorption of Cr (III) ions from aqueous solution by groundnut husk is a spontaneous process with a ?Go value of -24.38 kJmol-1 at 298 K and follow the pseudo second order kinetics with a rate constant of 0.0151 min-1. The results indicate that groundnut husk can be employed as a low cost alternative to commercial adsorbents in the removal of Cr (III) ions from wastewater.

This study evaluated the chemical composition, physicochemical properties, toxicological and environmental potentials of the Datura metel (D. metel) leaves extracts. Fresh leaves of D. metel were harvested at three different times of the day (morning, afternoon and evening), extraction done in succession using n-hexane and ethanol solvents respectively. Preliminary phytochemical screening, physicochemical analysis for specific gravity, pH, colour, total ash and moisture contents of the dried extracts were determined. The characterisation of the bioactive compounds using Gas Chromatography-Mass Spectrometry, showed the presence of different compounds at the three different times of the day, out of which phytol and 9,12,15-octadecatrienoic acid were present at all times. These results confirmed that some bioactive compounds present in this plant are dependent on environmental factor , time of harvest and the choice of solvent used while the presence of others are independent on these factors. Each extract was administered orally to Wistar rats for two weeks. There were significant difference (p < 0.05) in activities of AST (serum and heart), ALT (liver and serum) and ALP (Serum, liver and kidney), as well as the concentrations of albumin and protein in the liver and serum and urea in the serum of experimental rats given n-hexane and ethanolic extracts of D. metel. Generally it also suggest that the leaf extracts collected at three different times of the day had some significant toxicological effect, thus may not be totally safe for consumption at the dosage indicated since tissues membranes integrity of the Wistar rats were not potentially preserved.