Browsing by Author "Mubofu, Egid B."
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Item The Activity of Invertase Immobilized on Cashew Nut Shell Liquid-Templated Large Pore Silica Hybrids(2011) Mubofu, Egid B.; Mdoe, James; Kinunda, GraceThe characterization and activity of invertase enzymes immobilized on large pore micelle templated silica (LP-MTS) hybrid materials is reported. The LP-MTS hybrid materials were prepared by a co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyltrimethoxysilane (AMPTS) in a cashew nut shell liquid (CNSL) template. A commercially available dodecylamine template was also used to afford similar materials, hereinafter abbreviated as DDA-MTS, for comparison purposes. The prepared materials were characterized by different techniques to determine their physicochemical properties. The maximum loading for the amine groups in LP-MTS and DDA-MTS were 3.3 and 2.8 mmol g�1, respectively. Modification of the materials for immobilization of the invertase enzyme was done by reacting them with glutaraldehyde resulting in Glu-LP-MTS or Glu-DDA-MTS. The as-prepared hybrid materials have surface areas ranging from 100 to 214 m2 g�1 with pore diameters ranging from 3.1 to 25 nm. Scanning electron microscopy (SEM) images show that LP-MTS and DDA-MTS materials comprise of roughly spherical particles whereas enzyme and glutaraldehyde supported micelle templated silicas show a rupture of the spherical particles to a fine powder. The activities of free and immobilized invertases have been determined by measuring the amount of reducing sugar produced upon hydrolysis of sucrose at different temperatures, pH and substrate concentrations. Both free and immobilized invertase enzymes showed a maximum activity at a particular optimum temperature, pH and substrate concentration. The maximum activity for the free invertase was 15 229 U at pH 5.0 and at 40 1C whereas those of the LP-MTS immobilized invertases were 14 833 U and 14 625 U for covalent and cross-linked invertases, respectively, at pH 4.0 and 40 1C. The maximum activity for DDA-MTS covalently immobilized invertase was 4750 U, at pH 4.0 and 40 1C.Item Aromatic Bio-Based Solvents(John Wiley & Sons, 2017-06-30) Mubofu, Egid B.; Mgaya, James; Munissi, Joan J.EThis chapter focuses on alkylresorcinols (AR) and cashew nut shell liquid (CNSL) as bio‐based solvents from agricultural produce and waste. It highlights the possible biological sources for bio‐based aromatics, such as cereals and CNS wastes, and the techniques for their extraction. The chapter also introduces the possible potential applications of these extracts as solvents or reagents in the production of functional or platform chemicals. The competitive advantage of utilizing agricultural by‐products or wastes, such as cereal bran and CNSs, as renewable bio‐resources for the production of aromatic bio‐based solvents is manifested in non‐interference with food supply and their contributions towards waste minimization. Thus, this chapter centres its discussion onaromatic bio‐based solvents from agricultural by‐products and waste materials, and emphases on resorcinolic lipids and CNSL. Basically, there are three methods used to extract CNSL from the shells: solvent extraction, thermal extraction and mechanical extractionItem A Bellows-Shape Electrostatic Microactuator(1999-02) Williford, Clint W.; Li, Z.; Wang, Z.; Bricka, Mark R.; Bahemuka, T. E.; Mubofu, Egid B.; Minami, Kazuyuki; Morishita, H.; Esashi, MasayoshiItem Bis(piperidinedithiocarbamato)pyridinecadmium(II) as a Single-Source Precursor for the Synthesis of CdS Nanoparticles and Aerosol-Assisted Chemical Vapour Deposition (AACVD) of CdS thin films(2014) Lewis, David J.; Revaprasadu, Neerish; Mlowe, Sixberth; Malik, Azad; Mubofu, Egid B.; O'Brien, Paul; Raftery, JamesThe synthesis and single-crystal X-ray structure of bis(piperidinedithiocarbamato)pyridinecadmium(II), [Cd(S2C(NC5H10))2(NC5H5)] are reported and its use as a precursor for the synthesis of hexagonal CdS nanoparticles and CdS thin films is presented. Thermogravimetric analysis (TGA) of this complex showed clean decomposition in two steps to give CdS. Thermolysis of the complex in hexadecylamine at different temperatures in the range 190 ¬ 270 °C gave CdS nanostructures including nanorods and oval shaped particles. The band gap of the as-synthesized CdS nanoparticles varied as the temperature was increased. CdS thin films with optical direct band gaps of ca. 2.4 eV were deposited by aerosol-assisted chemical vapour deposition (AACVD) in the temperature range 350 to 450 oC using the same precursor. Powder X-ray diffraction (p-XRD) patterns of CdS nanoparticles and thin films confirmed the hexagonal phase of CdS.Item Cadmium Sulfide Quantum Dots Stabilized By Castor Oil and Ricinoleic Acid(Elsevier, 2016) Kyobe, Joseph W.; Mubofu, Egid B.; Makame, Yahya M. M.; Mlowe, Sixberth; Revaprasadu, NeerishCastor oil and ricinoleic acid (an isolate of castor oil) are environmentally friendly bio-based organic surfactants that have been used as capping agents to prepare nearly spherical cadmium sulfide quantum dots (QDs) at 230, 250 and 280 °C. The prepared quantum dots were characterized by Ultra violet–visible (UV–vis), Photoluminescence (PL), Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HRTEM) and X-ray diffraction (XRD) giving an overall CdS QDs average size of 5.14±0.39 nm. The broad XRD pattern and crystal lattice fringes in the HRTEM images showed a hexagonal phase composition of the CdS QDs. The calculated/estimated average size of the prepared castor oil capped CdS QDs for various techniques were 4.64 nm (TEM), 4.65 nm (EMA), 5.35 nm (UV–vis) and 6.46 nm (XRD). For ricinoleic acid capped CdS QDs, the average sizes were 5.56 nm (TEM), 4.78 nm (EMA), 5.52 nm (UV–vis) and 8.21 nm (XRD). Optical properties of CdS QDs showed a change of band gap energy from its bulk band gap of 2.42–2.82 eV due to quantum size confinement effect for temperature range of 230–280 °C. Similarly, a blue shift was observed in the photoluminescence spectra. Scanning electron microscope (SEM) observations show that the as-synthesized CdS QDs structures are spherical in shape. Fourier transform infra-red (FTIR) studies confirms the formation of castor oil and ricinoleic acid capped CdS QDs.Item Cdse Quantum Dots Capped with Naturally Occurring Biobased Oils(2015) Kyobe, Joseph W.; Mubofu, Egid B.; Makirita, Yahya M. M.; Mlowe, Sixberth; Revaprasadu, NeerishWe report a green synthesis of CdSe quantum dots (QDs) using bio-based materials (castor oil and ricinoleic acid) as capping agents. The absorption spectra of the as-synthesized CdSe QDs showed typical features of quantum confinement. The particle sizes of QDs were determined using the absorption band edges and found to be 3.81 to 6.80 nm and 5.91 to 8.31 nm for the entire range of reaction temperatures for QD-capped with castor oil (CSTO) and ricinoleic acid (RA), respectively. The photoluminescence spectra showed narrow emission peaks. The transmission electron microscopy (TEM) images showed spherical particles with sizes comparable to those determined from the absorption spectra. Comparatively, large particles were observed for RA capped CdSe QDs than those stabilized by CSTO. X-ray diffraction patterns revealed that the synthesized CdSe quantum dots have cubic structure. The particle sizes of CdSe deduced from X-ray diffraction measurements were in excellent agreement with those deduced from absorption spectra and TEM images. The d-spacings from the HRTEM images were consistent with those reported in literature. The surface area and the agglomeration number for as-synthesized CdSe QDs of different sizes are also reported.Item Current and Future Trends In Food Waste Valorization for the Production of Chemicals, Materials and Fuels: A Global Perspective(Wiley, 2014) Lin, Carol S. K.; Koutinas, Apostolis A.; Stamatelatou, Katerina; Mubofu, Egid B.; Matharu, Avtar S.; Kopsahelis, Nikolaos; Pfaltzgraff, Lucie A.; Clark, James H.; Papanikolaou, Seraphim; Kwan, Tsz H.; Luque, RafaelFood waste is currently generated in significant quantities worldwide. While most of this has generally few uses different from landfilling or composting, advanced valorization alternatives should be developed to maximize the value derived from such an important waste source. This contribution aims to illustrate a series of examples and current valorization strategies proposed in different countries in order to tackle the food waste issue. Proposed processing schemes involve biorefinery approaches based on both chemical and biological technologies. Important legislation aspects in different countries are also presented.Item Dynamics of Kaolinite-Urea Nanocomposites via Coupled DMSO-Hydroxyaluminum Oligomeric Intermediates(Hindawi Publishing Corporation, 2015) Ibahati, Sempeho S.; Kim, Hee T.; Mubofu, Egid B.; Pogrebnoi, Alexander; Shao, Godlisten N.; Hilonga, AskwarKaolinite-urea nanocomposites were prepared via intercalation reactions in an attempt to investigate the dynamic nature of kaolinite morphology for advanced applications in controlled release systems (CRS). Characterization was done using SEM-EDX, XRF, ATR-FTIR, XRD, and DT/DTG; Andreasen pipette sedimentation technique was used to determine the grain size distribution of the raw kaolinite. The X-ray diffraction pattern revealed the existence of an FCC Bravais lattice where the intercalation ratios attained were 51.2%, 32.4%, 7.0%, and 38.4% for hydroxyaluminum oligomeric intercalated kaolinite, substituted urea intercalated kaolinite, calcined DMSO intercalated kaolinite, and hydroxyaluminum reintercalated kaolinite, respectively, along with their respective crystallite sizes of 33.51–31.73 nm, 41.92–39.69 nm, 22.31–21.13 nm, and 41.86–39.63 nm. The outcomes demonstrated that the employed intercalation routes require improvements as the intercalation reactions were in average only ≈32.3%. The observations unveiled that it is possible to manipulate kaolinite structure into various morphologies including dense-tightly packed overlapping euhedral pseudo hexagonal platelets, stacked vermiform morphologies, postulated forms, and unique patterns exhibiting self-assembled curled glomeruli-like morphologies. Such a diversity of kaolinite morphologies expedites its advanced applications in the controlled release systems (CRS) such as drug delivery systems and controlled release fertilizers (CRFs).Item Fatty Acid Profile and Physico-Chemical Parameters of Castor Oils In Tanzania(2014-12) Omari, Athumani; Mgani, Quintino A.; Mubofu, Egid B.This paper reports on the assessment of the quality and quantity of castor oil from castor seeds collected from different regions in Tanzania. The castor seeds from Arusha, Dar es Salaam, Dodo-ma, Iringa, Kagera and Morogoro regions in Tanzania were extracted by Soxhlet method using n-hexane and the oil yields were determined. The yields were 52.78%, 49.95%, 47.89%, 44.23%, 43.71% and 43.69% for Dodoma, Arusha, Iringa, Morogoro, Kagera and Dar es Salaam respectively. The physico-chemical parameters that were determined were refractive index (1.468-1.473), pH 5.7-6.3, viscosity (0.943-0.954), specific gravity (165.50-187.46 mg KOH/g Oil), saponification value (76.68-80 mg KOH/g Oil), iodine value (76.68-80.12 g I2/100 g Oil), acid value (0.44-1.97 mg NaOH/g Oil), free fatty acid (0.22-0.99) and peroxide value (10.79-13.73). Fatty acid profile of castor oil was analysed using Shimadzu GCMS and ricinoleic acid ranged from 83.5% to 92.3% of the total fatty acids in the castor oils.Item Fatty Acid Profile and Physico-Chemical Parameters of Castor Oils in Tanzania(Scientific Research, 2015) Omari, Athumani; Mgani, Quintino A.; Mubofu, Egid B.This paper reports on the assessment of the quality and quantity of castor oil from castor seeds collected from different regions in Tanzania. The castor seeds from Arusha, Dar es Salaam, Dodo-ma, Iringa, Kagera and Morogoro regions in Tanzania were extracted by Soxhlet method using n-hexane and the oil yields were determined. The yields were 52.78%, 49.95%, 47.89%, 44.23%, 43.71% and 43.69% for Dodoma, Arusha, Iringa, Morogoro, Kagera and Dar es Salaam respectively. The physico-chemical parameters that were determined were refractive index (1.468-1.473), pH 5.7-6.3, viscosity (0.943-0.954), specific gravity (165.50-187.46 mg KOH/g Oil), saponification value (76.68-80 mg KOH/g Oil), iodine value (76.68-80.12 g I2/100 g Oil), acid value (0.44-1.97 mg NaOH/g Oil), free fatty acid (0.22-0.99) and peroxide value (10.79-13.73). Fatty acid profile of castor oil was analysed using Shimadzu GCMS and ricinoleic acid ranged from 83.5% to 92.3% of the total fatty acids in the castor oilsItem Fatty Acid Profile And Physico-Chemical Parameters of Castor Oils in Tanzania(2014-12) Omari, Athumani.; Mgani, Quintino A.; Mubofu, Egid B.This paper reports on the assessment of the quality and quantity of castor oil from castor seeds collected from different regions in Tanzania. The castor seeds from Arusha, Dar es Salaam, Dodo-ma, Iringa, Kagera and Morogoro regions in Tanzania were extracted by Soxhlet method using n-hexane and the oil yields were determined. The yields were 52.78%, 49.95%, 47.89%, 44.23%, 43.71% and 43.69% for Dodoma, Arusha, Iringa, Morogoro, Kagera and Dar es Salaam respectively. The physico-chemical parameters that were determined were refractive index (1.468-1.473), pH 5.7-6.3, viscosity (0.943-0.954), specific gravity (165.50-187.46 mg KOH/g Oil), saponification value (76.68-80 mg KOH/g Oil), iodine value (76.68-80.12 g I2/100 g Oil), acid value (0.44-1.97 mg NaOH/g Oil), free fatty acid (0.22-0.99) and peroxide value (10.79-13.73). Fatty acid profile of castor oil was analysed using Shimadzu GCMS and ricinoleic acid ranged from 83.5% to 92.3% of the total fatty acids in the castor oils.Item Food Waste as a Valuable Resource for the Production of Chemicals, Materials and Fuels. Current Situation and Perspective(2013) Lin, Carol S. K.; Pfaltzgraff, Lucie A.; Herrero-Davila, Lorenzo; Mubofu, Egid B.; Solhy, Abderrahim; Clark, James H.; Koutinas, Apostolis A.; Kopsahelis, Nikolaos; Stamatelatou, Katerina; Dickson, Fiona; Thankappan, Samarthia; Zahouily, Mohamed; Brocklesby, Robert; Luquek, RafaelIncreasing demand for fuels and chemicals, driven by factors including over population, the threat of global warming and the scarcity of fossil resources, strain our resource system and make necessary the development of sustainable and innovative strategies for the chemical industry. The strain upon which our resource system is under drives industry to increase its overall efficiency by improving existing processes or finding new uses for waste. Food supply chain waste emerged as a resource with a significant potential to be employed as raw material for the production of fuels and chemicals given the abundant volumes globally generated, its contained diversity of functionalised chemical components and the opportunity to be utilised for higher value applications. The present manuscript is aimed to provide a general overview of current and most innovative uses of food supply chain waste, providing a range of worldwide case studies from around the globe. These studies will focus on examples illustrating the use of citrus peel, waste cooking oil and cashew shell nut liquid in countries such as China, UK, Tanzania, Spain, Greece or Morocco. This work emphasises 2nd generation food waste valorisation and re-use strategies for the production of higher value and marketable products rather than conventional food waste processing (incineration for energy recovery, feed or composting) while highlighting issues linked to the use of food waste as a sustainable raw material. Influence of food regulations on food supply chain waste valorisation will also be addressed as well as our society’s behavior towards food supply chain wasteItem From Cashew Nut Shell Wastes to High Value Chemicals(2015) Mubofu, Egid B.The amount of waste generated in cashew nut processing factories has caused serious problems for a long time. However, this situation is about to change because they are being turned into an opportunity by a variety of bio-based chemicals. Todate, cashew nut shells (CNS) have proven to be among the most versatile renewable resource as they produce cashew nut shell liquid (CNSL). CNSL which is a dark reddish brown viscous liquid (ca. 30–35 wt%) is extracted from the soft honeycomb of the CNS. The shells have been regarded as a by-product of the cashew industry though now it is a cheaper source of natural unsaturated phenols. CNSL offers a multitude of interesting possibilities for the synthesis of speciality chemicals, high value products and polymers. Our recent research efforts have demonstrated that its constituents can be transformed into diverse functional chemicals. This paper reports some key results on how cashew nut shells (an agro waste from cashew nut processing factories) have been employed to produce several functional materials and chemicals. The materials that are highlighted include the synthesis of 3-propylphenol from cardanol and anacardic acid, some polymers prepared from CNSL components, heterogeneous catalysts prepared using CNSL as a templating agent and anacardic acid capped chalcogenide nanoparticles.Item Functionalized Mesoporous Organo-Silica Nanosorbents for Removal of Chromium (III) Ions from Tanneries Wastewater(Springer Link, 2016) Gervas, Charles; Mubofu, Egid B.; Mdoe, James; Revaprasadu, NeerishOrgano-silica mesoporous materials with cyano functional groups were prepared by a one pot co-condensation of 2-cyanoethyltriethoxysilane (CETS) and tetraethoxysilane (TEOS) at ratios of 1:4 and 1:9 using either sunflower oil or n-dodecylamine as templating agents. The tethered cyano groups were used as adsorption sites or hydrolysed to carboxylic surface functional groups. The prepared materials were characterized by diffuse reflectance infrared Fourier transform spectroscopy, atomic force microscopy (AFM), Brunauer, Emmettt and Teller, thermogravimetric analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Results indicated that materials with cyano and carboxylic surface groups were successfully prepared. AFM results indicated that primary particles with irregular shapes and grain size ranging from 0.28 ± 0.03 to 0.46 ± 0.08 µm were obtained depending on the CETS to TEOS ratio used and the structure directing template. SEM and TEM micrographs depict spherical like morphology of the same size as portrayed by AFM results. Sunflower cyano functionalized micelle template silica (MTS-S-CN) at a ratio of 1:9 had surface area of 760.5 m2/g and average pore diameters of 3.5 nm while MTS-S-CN at a ratio 1:4 had pore diameter of 10.1 nm with surface area of 734.1 m2/g. On the other hand, the MTS-S-COOH (1:9) had surface area of 975.9 m2/g with pore diameter of 4.6 nm whereas MTS-S-COOH (1:4) had surface area of 740.1 m2/g with pore diameter of 6.3 nm. The materials were used in adsorption studies of Cr(III) ions from tannery wastewater. Cr(III) ions removal ranged from 48 to 83 % depending on the adsorbent functional group and the organosilyl groups to silica ratio. This study has indicated that materials prepared were good adsorbents with an adsorption maximum of 19.7 mg Cr(III) ions per g of adsorbent.Item Growth of Nanocrystalline Thin Films of Metal Sulfides [CdS, ZnS, CuS and PbS] at the Water-Oil Interface(2015) Thomas, John; Stansfield, Gemma L.; Komba, Nathaniel; Cant, David J. H.; Ramasamy, Karthik; Albrasi, Enteisar M.; Al Chaghouri, Hanan; Syres, Karen L.; O'Brien, Paul; Flavell, Wendy R.; Mubofu, Egid B.; Bondino, Federica; Magnano, ElenaSimple one pot reactions between thiobiuret complexes [M(SON(CNiPr2)2)2], (M = Cd, Zn, Pb or Cu) in toluene and aqueous Na2S lead to well-defined assemblies of nanocrystals. High quality thin films of CdS, ZnS, CuS and PbS nanoparticulates adhered to the interface are produced and are transferable to glass and other substrates. The effect of reaction parameters on the nature and properties of the deposits are examined. The films are characterized by high-resolution transmission electron microscopy, X-ray diffraction, scanning electron microscopy, transport property measurements, X-ray photoelectron and absorption spectroscopy. The ability to obtain thin films of several nanocrystalline semiconductors from a single precursor set significantly expands the scope of a reaction scheme that is still in its infancy.Item Heavy Metals in Edible Green Vegetables Grown Along the Sites of the Sinza and Msimbazi Rivers in Dar Es Salaam, Tanzania(Elsevier, 1999) Bahemuka, T. E.; Mubofu, Egid B.Four heavy metals (cadmium, copper, lead and zinc) were determined in some green vegetables cultivated along the sites of the Sinza and Msimbazi rivers. Atomic absorption spectrophotometry was used to estimate and evaluate the levels of these metals in the vegetables. The contributions of the vegetables to the daily intake of the heavy metals from the vegetables were determined. The results showed the following ranges (mg/100 g): 0.01±0.06, 0.25±1.60, 0.19±0.66, and 1.48±4.93 for cadmium, copper, lead and zinc, respectively. Some vegetables contained high levels beyond the permissible levels given by FAO and WHO for human consumption. When the mean levels of cadmium, copper, lead and zinc (0.20, 7.95, 3.95 and 33.75 mg per kg, respectively) were taken into account, the daily intake contribution of these metals was found to be 21.60 mg, 858.60 mg, 426.60 mg and 3.65 mg for cadmium, copper, lead and zinc, respectively.Item Heterocyclic Dithiocarbamato-Iron (III) Complexes: Single-Source Precursors for Aerosol-Assisted Chemical Vapour Deposition (AACVD) of Iron Sulfide Thin Films(2016) Mlowe, Sixberth; Lewis, David J.; Malik, Mohammad A.; Raftery, James; Mubofu, Egid B.; O'Brien, Paul; Revaprasadu, NeerishThe biomedical potential of flavonoids is normally restricted by their low water solubility. However, little has been reported on their encapsulation into polyamidoamine (PAMAM) dendrimers to improve their biomedical applications. Generation four (G4) PAMAM dendrimer containing ethylenediaminetetraacetic acid core with acrylic acid and ethylenediamine as repeating units was synthesized by divergent approach and used to encapsulate a flavonoid tetramethylscutellarein (TMScu, 1) to study its solubility and in vitro release for potential bioactivity enhancement. The as-synthesized dendrimer and the dendrimer–TMScu complex were characterized by spectroscopic and spectrometric techniques. The encapsulation of 1 into dendrimer was achieved by a co-precipitation method with the encapsulation efficiency of 77.8% ˘ 0.69% and a loading capacity of 6.2% ˘ 0.06%. A phase solubility diagram indicated an increased water solubility of 1 as a function of dendrimer concentration at pH 4.0 and 7.2. In vitro release of 1 from its dendrimer complex indicated high percentage release at pH 4.0. The stability study of the TMScu-dendrimer at 0, 27 and 40 ˝ C showed the formulations to be stable when stored in cool and dark conditions compared to those stored in light and warmer temperatures. Overall, PAMAM dendrimer-G4 is capable of encapsulating 1, increasing its solubility and thus could enhance its bioactivity.Item In Silico Evaluation of Anti-Malarial Agents from Hoslundia opposita as Inhibitors of Plasmodium falciparum Lactate Dehydrogenase (P f LDH) Enzyme(Scientific Research, 2016-06-17) Shadrack, Daniel M.; Nyandoro, Stephen S.; Munissi, Joan J. E.; Mubofu, Egid B.Malaria has continued to be a health and economic problem in Africa and the world at large. Many anti-malarial drugs have been rendered ineffective due to the emergence of resistant strains of Plamodium falciparum. A key malaria parasite enzyme in glycolytic pathway, P. falciparum lactate dehydrogenase (PfLDH) is specially targeted for anti-malarial drugs development. Thus, the aim of this investigation was to determine the in silico inhibition effects of antimalarial compounds from Hoslundia opposita Vahl. namely hoslundin, hoslundal and hoslunddiol on PfLDH enzyme. The compounds were docked to the three-dimensional structure of PfLDH as enzyme using AutoDock Vina in PyRx virtual screening software. Binding affinity and position of the inhibitors were evaluated using PyMol software. The PfLDH enzyme showed two binding sites: the cofactors binding site (Site A) and secondary binding site (Site B). In the absence of the cofactor all ligands showed higher affinity than NADH, and were bound to the cofactors binding site (Site A). When docked in the presence of the cofactor, site B was the preferred binding site. Binding to cofactor site with higher binding energy than NADH suggests that these ligands could act as preferential competitive inhibitors of PfLDH. However, the binding to site B also suggests that they may be non-competitive allosteric inhibitors. Amino acid residues Gly99, Asn140, Phe100 and Thr97 were indicated to form hydrogen bonds with Hoslundin. Hoslunddiol showed hydrogen bonding with Thr97 and Met30, while Hoslundal formed hydrogen bond with Thr101 and Asn140.Item In silico pharmacokinetic, molecular docking and molecular dynamics simulation studies of n-cinnamoyltetraketide derivatives as inhibitors of cyclooxygenase-2 enzyme(Dar es Salaam University Press, 2018-06) Nyandoro, Stephen S.; Shadrack, Daniel M; Munissi, Joan J.E; Mubofu, Egid B.Recent phytochemical analysis of Toussaintia orientalis leaves yielded series of novel bioactive N-cinnamoyltetraketide derivatives namely toussaintines A-G (t_1 - t_8) some portraying cytotoxicity against the triple negative aggressive human breast cancer cell line (MDA-MB-231) among other potencies. Despite having broad bioactivity spectrum, their general drug-likeness profiles and mode of action (simulated or actual) targeting any enzyme remains uninvestigated. In silico pharmacokinetic, drug-likeness descriptors and molecular docking of the compounds t_1-t_8 targeting inhibition of cyclooxygenase-2 (COX-2) enzyme were evaluated. The Lipinski Rule of Five heralded the pharmacokinetic properties of the studied metabolites. The studied compounds were docked with COX-2 following already established protocol. ADMET descriptors fell within the recommended range, except for compound t_3 that was predicted to potentially have positive blood brain barrier (BBB+) penetration. Docking studies indicated N-cinnamoyltetraketide derivatives as potential inhibitors of COX-2 enzyme. Compounds t_3 and t_5 showed lower binding energy of -13 and -12.3 kcal/mol, respectively, being closely comparable to celecoxib (-12.3 kcal/mol) indicating compatibility with the protein receptor. The findings provide baseline information on drug or lead-likeness and potential mode of action of the studied molecules towards inhibition of COX-2 enzymeItem In vivo antimycobacterial studies of toussaintine A-chitosan nanocomposites(Dar es Salaam University Press, 2018-06) Rwegasila, Edward; Munissi, Joan J.E; Mubofu, Egid B.; Nyandoro, Stephen S.; Erasto, PaulChitosan (CS, molecular weight (MW) 20.2 kDA, stability of 210 °C and degree of deacetylation (DD) 73.31%) was obtained by deacetylation of chitin extracted from shrimp (Litopenaeus vannamei) shell wastes. The encapsulation of the studied bioactive natural product, toussaintine A (TA) isolated from the leaves of Toussaintia orientalis, on a chitosan-tripolyphosphate (CS/TPP) nanoformulation was attained through ionotropic gelation. Characterization of pure CS, CS/TPP and TA-CS/TPP nanocomposites was carried out by FTIR and SEM. The encapsulation efficiency and loading capacity of the TA were 69.33 and 0.46%, respectively. The in vitro release kinetics established an initial release of 27% of TA in the initial six hours followed by a slow and maintained release up to 72 h. The in vivo antimycobacterial acitivities of both TA and TA-CS/TPP nanocomposites against Mycobacterium indicus pranii (MIP) employing Galleria mellonella larvae as an infection model were evaluated. TA-CS/TPP nanocomposite formulations exhibited remarkable effectiveness against MIP than free TA
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