Oluyomi Stephen Adeyemi

Interaction of metal nanoparticles with recombinant arginine kinase from Trypanosoma brucei: thermodynamic and spectrofluorimetric evaluation.

BACKGROUND Trypanosoma brucei, responsible for African sleeping sickness, is a lethal parasite against which there is need for new drug protocols. It is therefore relevant to attack possible biomedical targets with specific preparations and since arginine kinase does not occur in humans but is present in the parasite it becomes a suitable target. METHODS Fluorescence quenching, thermodynamic analysis and FRET have shown that arginine kinase from T. brucei interacted with silver or gold nanoparticles. RESULTS The enzyme only had one binding site. At 25°C the dissociation (Kd) and Stern-Volmer constants (KSV) were 15.2nM, 0.058nM(-1) [Ag]; and 43.5nM, 0.052nM(-1) [Au] and these decreased to 11.2nM, 0.041nM(-1) [Ag]; and 24.2nM, 0.039nM(-1) [Au] at 30°C illustrating static quenching and the formation of a non-fluorescent fluorophore-nanoparticle complex. Silver nanoparticles bound to arginine kinase with greater affinity, enhanced fluorescence quenching and easier access to tryptophan molecules than gold. Negative ΔH and ΔG values implied that the interaction of both Ag and Au nanoparticles with arginine kinase was spontaneous with electrostatic forces. FRET confirmed that the nanoparticles were bound 2.11nm [Ag] and 2.26nm [Au] from a single surface tryptophan residue. CONCLUSIONS The nanoparticles bind close to the arginine substrate through a cysteine residue that controls the electrophilic and nucleophilic characters of the substrate arginine-guanidinium group crucial for enzymatic phosphoryl transfer between ADP and ATP. GENERAL SIGNIFICANCE The nanoparticles of silver and gold interact with arginine kinase from T. brucei and may prove to have far reaching consequences in clinical trials.

Evaluation of metal nanoparticles for drug delivery systems.

Abstract Diminazene aceturate is a trypanocide with unwanted toxicity and limited efficacy. It was reasoned that conjugating diminazene aceturate to functionalized nanoparticle would lower untoward toxicity while improving selectivity and therapeutic efficacy. Silver and gold nanoparticles were evaluated for their capacities to serve as carriers for diminazene aceturate. The silver and gold nanoparticles were synthesized, functionalized and coupled to diminazene aceturate following established protocols. The nanoparticle conjugates were characterized. The free diminazene aceturate and drug conjugated nanoparticles were subsequently evaluated for cytotoxicity in vitro. The characterizations by transmission electron microscopy or UV/Vis spectroscopy revealed that conjugation of diminazene aceturate to silver or gold nanoparticles was successful. Evaluation for cytotoxic actions in vitro demonstrated no significance difference between free diminazene aceturate and the conjugates. Our data suggest that surface modified metal nanoparticles could be optimized for drug delivery systems.

Biochemical changes in the kidney and liver of rats following administration of ethanolic extract of Psidium guajava leaves.

Furtherance to a previous report on the anti-trypanosomal properties of Psidium guajava aqueous leaf extract in rats experimentally infected with Trypanosoma brucei brucei, we have evaluated the effects of the daily intraperitoneal administration of P. guajava leaf extract to rats on the activities of alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and acid phosphatase (ACP) in the kidney, liver and serum. The results obtained revealed that the administration of the extract produced significant increase in the serum activities of AST, ALT, ALP and ACP when compared with the control (p < 0.05). Also AST, ALT and ALP and ACP activities in the tissues of animals administered the extract revealed inconsistent changes (p < 0.05) relative to control. The increase in the serum activity of ALP may be an indicator that there was a likely compromise to the integrity of the plasma membrane as a result of the ethanolic extract administration. This could have caused leakages of the other enzymes investigated, which may explain the corresponding increases in the serum activities of AST, ALT and ACP observed.

Yoyo Bitters, a polyherbal formulation influenced some biochemical parameters in Wistar rats

Abstract Background: Yoyo Bitters is an indigenous polyherbal preparation widely consumed in Nigeria. In spite of its wide consumption there is little scientific data on the safety/toxicity profile of Yoyo Bitters. This study determined the biochemical effect of daily administration of Yoyo Bitters on rat serum, kidney and liver. Methods: A total of 20 Wistar rats, of average weight between 175 and 200 g, were randomly distributed into four groups of five rats each. Group A served as controls and received distilled water. Groups B, C and D were given Yoyo Bitters at various dosages. Treatments were orally administered for 28 days. Results: Yoyo Bitters caused lipid peroxidation as reflected in serum and liver malondialdehyde (MDA) levels which were significantly (p<0.05) elevated in a dose-dependent manner. In groups treated with 1206.5 mg and 804.3 mg/kg dosages of Yoyo Bitters, serum superoxide dismutase (SOD) levels were also significantly (p<0.05) increased. By contrast, Yoyo Bitters caused a dose-dependent reduction in reduced glutathione (GSH) levels. It is not clear if free radicals or lipid peroxidation caused changes in SOD and GSH levels. However, Yoyo Bitters may have enhanced free radical generation and ensuing lipid peroxidation leading to increased SOD and subsequent dose-dependent depletion of GSH levels. Conclusions: In light of this, caution and adherence to dosage prescription is strongly advised. This study is a contribution to scientific knowledge on the safety/toxicity profile of Yoyo Bitters among the growing list of Nigerian herbal remedies.

Antioxidant and Cytotoxicity of β-Amyrin acetate fraction from Bridelia ferruginea Leaves

Abstract Objective The objective of this work was to determine the beta-amyrin acetate fraction in leave extract of Bridelia ferruginea and evaluate for its antioxidant and cytotoxicity potentials. Methods The dried and pulverized leaves of Bridelia ferruginea was extracted with hexane and then with ethyl acetate. The concentrated ethylacetate extract subjected to silica gel column chromatography and eluted with a mixture of equal volume of hexane and dichloromethane afforded two major fractions. The more polar fraction was concentrated and subjected to GCMS analysis which afforded the steroid, 12-Oleanen-3yl acetate commonly known as beta-amyrin acetate (66.14%). Its ability to act as a scavenger of DPPH radical and its cytotoxicity potential based on brine shrimp assay were investigated. Results The DPPH antioxidant assay revealed that the fraction had a higher antioxidant potential with an IC 50 value of 158.2μg/mL relative to gallic acid which had IC 50 of 201.1 μg/mL. The cytotoxicity assay using the brine shrimp a gave LC 50 values of 319 and 5.86 μg/mL for acute and lethal doses respectively indicating extreme toxicity when compared to reference drug, cyclophosphamide which had LC 50 value of 2506 μg/mL. Conclusions Thus, the beta-amyrin acetate has been identified for the first time in the leave of Bridelia ferruginea. The data here suggest that the beta-amyrin acetate fraction of the leave of Bridelia ferruginea could be further explored in biological profiling requiring antioxidant and cytotoxic dependent therapeutics as the plant could be a viable source of antioxidant and cytotoxic agents in cancer chemotherapy in the near future.

Interaction of nanoparticles with arginine kinase from Trypanosoma brucei: Kinetic and mechanistic evaluation

Arginine kinase is not only absent from mammalian hosts but is critical to the survival of trypanosomes under stressful conditions and consequently its inhibition may lead to an effective treatment for trypanosomiasis. The His-tagged enzyme was cloned from Trypanosoma brucei genomic DNA, expressed in Escherichia coli BL21 DE3 cells and purified on a Ni-affinity column and by FPLC on a Superdex 200 HR. The enzyme had a specific activity of 2.92 μmol min(-1) mg protein(-1), molecular mass of 40 kDa, temperature and pH optima of 30 °C and 7.8, and Km and Vmax as 2.94 mM and 0.161 μmol ml(-1) min(-1) (arginine substrate). The interaction of the enzyme with silver and gold nanoparticles showed a non-competitive inhibition with, respectively, 75% and 62% decrease in activity; Ki values ranged from 1.5 nM (Ag) to 3.1 nM (Au). A mechanism for this inhibition was by interaction with Cys(271) positioned 3.3 Å from the reactive NH(1) of substrate arginine. This cysteine controls electrophilic and nucleophilic character of the guanidinium group that is crucial for enzymatic phosphoryl transfer between ADP and ATP.

Biochemical and morphological changes in Trypanosoma brucei brucei-infected rats treated with homidium chloride and diminazene aceturate.

Abstract Background: Chemotherapy which is one of the major methods for controlling trypanosomal infections is beset with several challenges including unwanted toxicity and limited efficacy. These factors and others underscore research efforts aimed at finding safer and more effective therapeutic agents for trypanosomiasis. Homidium chloride and diminazene aceturate are registered drugs for the treatment of animal trypanosomiasis. Methods: Study investigated and compared, in an experimental Trypanosoma infection, the effects of two trypanocides on the pathology of tissues and some biochemical indices in rats. Results: Data revealed that the levels of alkaline phosphatase, alanine transaminase and aspartate transaminase in infected positive animals were significantly (p<0.05) elevated relative to uninfected negative controls but showed no significant difference when compared with the trypanocide-treatment groups. The histopathological presentations in the infected and treatment groups are a demonstration of the inimical cellular alterations associated with Trypanosoma brucei brucei infection. Conclusions: The inimical alterations to biochemical and morphological parameters observed in the infected as well as the treatment groups is an implication suggesting shortcomings of the investigated trypanocides to alleviate pathology associated with Trypanosoma brucei brucei infection. We present evidence that further supports the urgent need for the development of safer and more effective trypanocides.

Changes in haematological indices and protein concentrations in Trypanosoma brucei infected rats treated with homidium chloride and diminazene aceturate

Anaemia and immunosuppresion have been shown to be a cardinal feature in African trypanosomosis. In this study, we have evaluated and compared the capacity of two registered veterinary trypanocides Novidium® (homidium chloride) and Berenil® (diminazene aceturate) to reduce haematological and biochemical lesions in rats experimentally infected with T. brucei. Packed cell volume (PCV), lymphocyte and eosinophil values in infected negative control group were significantly different and lower compared to positive control group as well as infected animals treated with homidium chloride and diminazene aceturate (P<0.05). Also the white blood cell (WBC) and neutrophil counts in the negative control group were lower and significantly different from the other groups indicating evidence of infection-induced immunosuppresion. Haematological indices in infected rats treated with homidium chloride and diminazene aceturate were higher (P<0.05) than obtained in infected negative control group and significantly different from positive control (P<0.05). Total protein and albumin concentrations in infected negative control group were higher and significantly different from control and treated animals (P<0.05). In contrast, significantly lower values were obtained for albumin concentrations in treated animals compared to both negative and positive control groups (P<0.05). Results suggest that drugs administered have capacity to improved blood components as well as reverse immunosuppressive action of infecting trypanosomes.

Antimicrobial and toxic potential of aqueous extracts of Allium sativum, Hibiscus sabdariffa and Zingiber officinale in Wistar rats

Abstract Allium sativum, Hibiscus sabdariffa and Zingiber officinale are medicinal plants with wide use in traditional medicine; however, the increasing use of crude extracts for traditional medicine applications raises safety concerns. We made a preliminary determination of the phytochemical constituents and antimicrobial and safety profiles of aqueous extracts of A. sativum, H. sabdariffa and Z. officinale. The extracts were administered orally to Wistar rats for 30 days: a control group received distilled water, three groups received the three extract, and a fifth group received a combination of the three extracts. All three extracts, either individually or in combination, had antimicrobial activity, and all extracts influenced the activities of marker enzymes. The evidence lends credence to use of these plants in traditional medicine but also suggests the probable toxic potential of crude plant extracts.

Moringa oleifera Supplemented Diets Prevented Nickel-Induced Nephrotoxicity in Wistar Rats.

Background. The Moringa oleifera plant has been implicated for several therapeutic potentials. Objective. To evaluate whether addition of M. oleifera to diet has protective effect against nickel-induced nephrotoxicity in rats. Methodology. Male Wistar rats were assigned into six groups of five. The rats were given oral exposure to 20 mg/kg nickel sulphate (NiSO4) in normal saline and sustained on either normal diet or diets supplemented with Moringa oleifera at different concentrations for 21 days. 24 hours after cessation of treatments, all animals were sacrificed under slight anesthesia. The blood and kidney samples were collected for biochemical and histopathology analyses, respectively. Results. NiSO4 exposure reduced the kidney-to-body weight ratio in rats and caused significant elevation in the levels of plasma creatinine, urea, and potassium. Also, the plasma level of sodium was decreased by NiSO4 exposure. However, addition of M. oleifera to diets averted the nickel-induced alteration to the level of creatinine and urea. The histopathology revealed damaged renal tubules and glomerular walls caused by NiSO4 exposure. In contrast, the damages were ameliorated by the M. oleifera supplemented diets. Conclusion. The addition of M. oleifera to diet afforded significant protection against nickel-induced nephrotoxicity.