FACULTY OF PHARMACY
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Item Visible spectrophotometric determination of Furosemide in dosage forms following its hydrolysis and Diazo coupling with Chromotropic Acid(Nigeria Association of Pharmacists in Academia, 2023) Thomas, O. E.; Adegoke, O. A.; Taiwo-Ojediran, B.Background: Several previously reported visible spectrophotometric methods for the quantification of furosemide in dosage forms are fraught with poor specificity due to background absorptivities of other chemical species in the sample matrices. Objective: To develop a simple, sensitive and specific visible spectrophotometric method for the quantitative determination of furosemide in bulk and dosage forms. Method: The new spectrophotometric method was based on acid-hydrolysis of furosemide followed by its diazotization and coupling with chromotropic acid to generate a red adduct. Reactions variables critical to optimal response were established. Various analytical and validation parameters including repeatability, reproducibility and selectivity were also determined. Results: The calibration graph was linear between 8.09 μg/mL to 161.8 μg/mL at 503 nm with a correlation coefficient of 0.992. The Sandell’s sensitivity of the new method was 0.14 μg.cm-2/0.001 A.U. while the limits of detection and quantification were 0.75 and 2.28 μg/mL respectively. The method was accurate and precise with recovery in the range of 102.24–109.92% and intra- and inter-day precision (%RSD) at three different concentrations less than 2.0%. When applied to the analysis of dosage form, there was no statistical difference between the newly developed and official methods. There was no interference from commonly used excipients or background absorptivities in the sample matrices. Conclusion: In comparison with some previously reported colorimetric methods, the new method reliably quantified furosemide over a wider range of concentration and with a superior level of sensitivity. The new method can serve as a reliable alternative to the official method for analysis of furosemide.Item In vitro cytotoxicity, genotoxicity and apoptoxicity of 8-hydroxy-3,6-disulphonaphthyl azohydroxynaphthalenes using Human Lymphocytes: Experimental and theoretical profiling(Taylor & Francis, 2023) Thomas, O. E.; Adegoke, O. A.; Mukherjee, A.; Banerjee, R.Regulatory agencies require demonstration of non-genotoxicity of new chemical entities prior to their use as pharmaceuticals or additives. Consequently, the in vitro cytotoxicity, genotoxicity and apoptoxicity of five novel monoazo colourants (8-hydroxy-3,6-disulphonaphthyl azohydroxynaphthalenes, 3a-e) on human lymphocytes were evaluated using a cell viability assay, alkaline comet assay, DNA diffusion assay, DFT calculations and molecular docking. The test concentrations of the compounds varied from 0 to 3.4 mM. Relative to negative control, the compounds at concentrations up to 0.5mM induced small dose-dependent reduction (< 20%) in viability of lymphocytes. Statistically significant changes (p<0.05) in DNA damage parameters (percent tail DNA, tail extent moment, olive tail moment) were observed at all concentrations of 3a, 3b while 3c-e showed genotoxicity at 2.8, 0.17 and 3.4 mM respectively. Compounds 3a, 3b, 3d induced apoptosis at concentrations below cytotoxic doses while 3c and 3e were non-apoptoxic at all test concentrations. DFT calculations showed the genotoxicity of 3a-e increased with electrophilicity and ionization potentials of the compounds. Molecular docking of 3a-e with apoptosis-associated proteins revealed binding affinity patterns that were consistent with observed experimental apoptoxicity. The structure-genotoxicity relationships of five novel monoazo compounds, which can be employed in the design of safer congeners, have been elucidated.Item Phytosynthesis, Antimicrobial and Catalytic Activities of Silver Nanoparticles derived using Leaf and Stem Extracts of Indigofera macrophylla(Nigeria Association of Pharmacists in Academia, 2022) Thomas, O. E.; Adegoke, O. A.; Adeniyi, E. M.; Oliver, C. G.Background: The phytosynthesis of metal nanoparticles is a promising green alternative to traditional chemical approaches. Objective: The aim of this study was to synthesize silver nanoparticles (AgNPs) with antimicrobial and biocatalytic activities using aqueous leaf and stem extracts of Indigofera macrophylla. Methods: Critical reaction variables for the biosynthesis of AgNPs were optimized using UV-vis spectroscopy before the biosynthesised AgNPs were characterized using various spectroscopic and microscopic techniques. The biological activities of the biogenic nanoparticles were then investigated with particular focus on their antimicrobial activity and biocatalytic efficiency in the degradation of methylene blue. Results: The surface plasmon resonance of silver nanoparticles biosynthesized using aqueous extracts of leaf (LEAgNPs) and stem (SE-AgNPs) of I. macrophylla occurred at 430 and 426 nm respectively. Scanning electron microscopy images of the nanoparticles showed highly aggregated polymorphs with mostly spherical shape. The particle sizes of LE-AgNPs and SE-AgNPs as determined by Transmission electron microscopy were 48.61±8.60 and 18.09±4.13 nm respectively with Energy dispersive X-ray analysis confirming characteristic absorption band at 3 KeV. In susceptibility assays, LE-AgNPs showed dose-dependent zones of inhibition against Escherichia coli (18mm), Staphylococcus aureus (18 mm), Pseudomonas aeruginosa (20 mm) while SE-AgNP was only active against Staphylococcus aureus (10 mm). Both LE-AgNPs and SE-AgNPs showed good biocatalytic efficiency in the degradation of methylene blue with rate constants of 0.0204 and 0.0182 min-1 respectively. Conclusion: Silver nanoparticles with antimicrobial and catalytic activities have been biosynthesized using the aqueous extract of Indigofera macrophylla.Item Preferential solvation of 4-carboxyl-2, 6-dinitrophenylazohydroxynaphthalenes in mixed hydroxylic solvents(Nigeria Association of Pharmacists in Academia, 2021) Thomas, O. E.; Adegoke, O. A.; Adenmosun, F. G.; Abiodun, O. J.Background: The applications of a group of 4-carboxyl-2,6-dintrophenylazohydroxynaphathalenes, AZ-01 to 04, as colourants, chemosensors or synthetic intermediates have been limited by their solubility. Aim: To investigate the effect of solvent mixture composition on the solubility, solution thermodynamics and position of equilibrium processes of the dyes. Method: The UV-visible spectral patterns of the dyes in binary mixtures including Methanol:Water, Ethanol:Water, Methanol:Ethanol, Methanol:Propan-1-ol, Methanol:Propan-2-ol, Propan-1-ol:Water and Propan-2-ol:Water were acquired. The type and quantitative estimation of solute-solvent interactions at play were determined by fitting spectral patterns to solvent parameters using multilinear regression. Results: Preferential solvation was detected by the non-ideality of the plots of E12 as against the mole fractions of cosolvent in all binary mixtures. In pure solvents, the spectral shifts of AZ-01, 03 and 04, which exist predominantly in the hydrazone form, were affected by polarity of solvent milieu while solvent basicity and acidity, in that order, were the significant parameters for AZ-02. In aqueous alcoholic mixtures, solvent polarity was contributory, although to different degrees, to the observed spectral data of the four dyes. However, solvent acidity and basicity were the primary determinants of spectral shifts observed with AZ-04 and AZ-03 respectively. Spectra-structure relationships identified the formation of the charged hydrazone tautomer which requires stabilisation by polar solvent milieu as responsible for the observed trend. In addition, interactions between new aggregated solvent-solvent species and the propionic acid substituent present in AZ-03 contributed to its spectral shifts. Conclusion: The solvatochromic properties of the phenylazonaphthalene series in binary mixtures have been successfully studied.Item Heavy Metal Contamination of Paediatric Paracetamol and Ascorbic Acid Drug Products in South-West Nigeria.(West African Postgraduate College of Pharmacists (WAPCP), 2019) Thomas, O. E.; Itopa, M. O.; Adegoke, O. A.Background: Water is a primary contributor to human populations’ heavy metals exposure and industrial contamination of products. Consequently, paediatric medications because of their high-water constitution can contribute significantly to intake of heavy metals in excess of allowable limits. There is therefore a need for effective preventive and control strategies. Unfortunately, studies investigating heavy metal content in paediatric formulations in Nigeria are scarce and often limited in the range of elements assayed. Objective: To evaluate elemental impurities in the two most frequently administered paediatric medications-paracetamol and ascorbic acid marketed in South-west Nigeria. Methods: Thirteen paediatric syrup brands were used for the study. Sample pretreatment involved dry ashing followed by digestion using concentrated aqua regia (nitric acid:hydrochloric acid, 3:1). Chromium, lead, copper, cadmium, zinc, nickel, cobalt and manganese were assayed with the atomic absorption spectrophotometer with the limit of detection set at 0.001. Results: The most abundant metal ions present in all the formulations were chromium (1.16-1290.2 mg/) and nickel (2.37-1289.0 mg/L). Cadmium was detected at low concentration in only two of the brands while lead was detected in three brands at concentrations ranging from 0.09 - 0.12 mg/L. The calculated expected daily exposures of lead in the three brands were in excess of the permissible daily exposure for oral drug products. Conclusion: Some of the paracetamol and vitamin C syrups sold in the South-West of Nigeria are contaminated with cadmium, nickel and lead.Item Two New Spectrophotometric Methods for the Determination of Isoniazid in Bulk Form and Tablet Dosage Form.(Istanbul Medipol University, Faculty of Pharmacy, 2019) Adegoke, O. A.; Thomas, O. E.; Babatunde, D. I.; Oyelami, O.; Adediran, A.; Omotosho, A.To develop two new spectrophotometric methods for the analysis of isoniazid in bulk form and tablets. The methods involved condensation of isoniazid with salicylaldehyde and diazo coupling with diazotized p-nitroaniline. Critical factors were optimised; evidence for new product formation, selection of analytical wavelengths, temperature and time and solvent for dilution. Validation was carried out according to ICH guidelines. The new methods were used for isoniazid tablets. Isoniazid formed an imine and azo adduct readily with the two reagents at 30 ⁰C after 5 and 20 mins, and determined at 405 and 420 nm, respectively. Low LODs were obtained for the two methods and recoveries were generally above 98%. The methods were successfully adopted for the assay of isoniazid in tablets and there were no significant differences in the contents when compared with the official titrimetric method of analysis. The methods could find application as in-process method in pharmaceutical industries.Item A New Method for the Microdetermination of Para Aminophenol in Generic Brands of Paracetamol Tablets(Taylor & Francis Group,, 2019) Adegoke, O. A.; Thomas, O. E.; Amao, S. A.; Agboola, S. O.; Omotosho, A. E.In Nigeria, paracetamol is readily available in several retail outlets where the conditions of storage can be poor leading to elevated levels of para-aminophenol (PAP), which is known to be nephrotoxic and hepatotoxic. However, the routine analysis of PAP is mostly by chromatographic separation which requires expensive instrumentation not often available in developing countries. The objective of this research was to develop a sensitive colorimetric method for the quantification of PAP in paracetamol. The method was based on the diazo coupling reaction between diazotised PAP and chromotropic acid. Various reaction parameters critical for optimal detector response were optimized. The validation of the new method was done following the determination of parameters including repeatability, reproducibility and selectivity using current ICH guidelines. The new method was also applied to the assay of PAP in 14 paracetamol tablet samples. The calibration was linear between 0.0297 and 0.2229 mg/mL at 470nm with limits of detection and quantification of 0.0061 and 0.0185 mg/mL, respectively. The recovery was in the range of 95.96 and 102.21 while intra- and inter-day precisions at three different concentrations did not exceed 4.03%. The new method was successfully applied to quantify PAP in paracetamol with percent content varying from 0.14 to 0.21%w/w. A simple and reliable method for the quantification of PAP has been developed and successfully employed to report, for the first time, the presence of the degradation product at levels beyond the allowable limits in paracetamol dosage forms in Nigeria.Item Preferential Solvation of 4-Carboxyl-2,6-dinitrophenylazohydroxynaphthalenes in Aqueous Dimethylformamide and Dimethylsulfoxide Binary Mixtures by UV-Visible Spectroscopy.(Springer New York / Springer Science+Business Media., 2019) Thomas, O. E.; Adegoke, O. A.; Adenmosun, F. G.; Abiodun, O. J.The objective of this study was to evaluate the influence of partly aqueous solvent mixtures on the solubility and azohydrazone equilibrium processes for a group of phenylazohydroxynaphthalenes, AZ-01, AZ-02, AZ-03, and AZ-04, whose applications as potential color additives and chemosensors have been demonstrated in previous studies. The UV-visible spectrum was acquired between 190-900 nm at concentrations of the dyes that precluded molecular aggregation for each dye in aqueous dimethylformamide and dimethylsulfoxide binary mixtures of varying compositions. The plots of E12 against mole fractions of the co-solvent showed deviation from ideality in the behaviors of the four dyes in the aqueous solvent mixtures. The solvation data were largely influenced by the structural chemistry of the dyes. In particular, AZ-01, which contains a free parahydroxyl group that can donate hydrogen to hydrogen bond acceptor solvents showed substantial bathochromic shifts in the aqueous DMF and DMSO mixtures as well as a local accumulation of the organic solvent in its solvation sphere. Conversely, the positional isomer AZ-02 with its ortho hydroxyl group being involved in intramolecular hydrazone rearrangement exhibited dielectric enrichment in both aqueous solvent mixtures. In addition, synergism through formation of the water-DMSO and water-DMF complexes was observed with all the dyes in the solvent mixtures with AZ-01 being solvated by the more polar component of the complex while AZ-02 and AZ-04 were solvated by the less polar solvent mixture component. Thus, the preferential solvation of the phenylazohydroxynaphthalene series from AZ-01 to AZ-04 in the partly aqueous DMSO and DMF solvent mixtures has been successfully studied using UV-visible spectroscopy.Item New spectrophotometric method for the determination of Gabapentin in bulk and dosage forms using p-dimethylaminobenzaldehyde(Taylor & Francis, 2018) Adegoke, O. A.; Adegbolagun, O. M.; Aiyenale, E.; Thomas, O.E.A new simple, accurate and economic spectrophotometric method based on azo dye derivatization for the determination of gabapentin (GBP) was developed. Critical factors were optimized. The method was validated and assay of dosage forms was done. Spot tests and TLC confirmed the formation of azo adduct. A 0.3M NaNO2 solution using 2M HCl was used for diazotization. The optimal temperature and time were 30°C and 10 min. Azo adducts were determined at 430 nm. Methanol was found to be the best solvent. Gabapentin coupled at a ratio of 1:1 with DMAB. The assays of GBP were linear over the range 1–6 μg/mL (r = 0.9973) and LOD of 0.8322 μg/mL. The methods were accurate (error < 2%) and precise (RSD < 0.5%). The methods were successfully applied to the assay of GBP in dosage forms and compared favorably with reference method (p > .05). The successful diazotization of gabapentin and the azo adduct formation with DMAB is reported for the first time.Item Colorimetric determination of Olanzapine via charge-transfer complexation with Chloranilic Acid.(Elsevier B.V., 2016) Adegoke, O. A.; Thomas, O. E.; Emmanuel, S. N.The charge-transfer complexation (CTC) formed between olanzapine and chloranilic acid have been studied and used as a sensitive colorimetric method for the determination of olanzapine. Evidence for the formation of the CTC between chloranilic acid (CAA) and olanzapine (OLP) was established by spot tests and TLC. Method development was carried out through selection of analytical wavelength, optimization and validation studies. Physicochemical parameters such as energy of transition, transition dipole, oscillator frequency and ionization energies were estimated and related to the stability of the formed CT band. Thermodynamic properties of the CT band at four temperature levels were also estimated and their inter-relationship established. The reaction was completed at room temperature within 10 min with the evidence of formation of purple-coloured solution with CAA that absorbed maximally at 520 nm. Linearity was obtained in the concentration range of 2–40 µg/mL for OLP (r = 0.9977) with a limit of detection of 1.57 µg/mL. Estimates of accuracies and precisions gave error values less than 2% for both intra- and inter-day assessments. The transition energies were of the order of 2.303 eV. The Gibbs energy varied with the temperature and room temperature values favoured formation of stable complexes. The thermodynamic studies revealed small positive entropy for slightly negative enthalpy change. The method was successfully applied to estimate OLP in tablets and the method was found to be of equivalent accuracy with the Indian Pharmacopoeia’s HPLC method (p > 0.05). The method could find application as a rapid and sensitive determination technique for olanzapine.