International Journal of Chemistry

International Journal of Chemistry | Vol. 5, No. 5, May 2014 | pp. 33–40

DOI: 10.46882/2014/IJC/000068

Article Type: Original Research Paper

Title: Development and Validation of an RP-HPLC Method for Quantitative Monitoring of Ciprofloxacin Formulations

Names of Authors: E. O. Effiong¹, A. G. Silva²*

Authors’ Affiliations:
¹Department of Chemistry, University of Uyo, Uyo, Nigeria.
²Department of Pharmacy, University of Porto, Porto, Portugal.

Abstract: Developing simple, automated, and accurate analytical methods is essential for routine quality monitoring and the detection of counterfeit antibiotics in commercial pharmacies. This paper describes the development and validation of a rapid Reversed-Phase High-Performance Liquid Chromatography (RP-HPLC) method for the quantitative determination of ciprofloxacin in tablet dosage forms. Separation was achieved using a C18 stationary phase column under an isocratic mobile phase composed of water-acetonitrile-triethylamine (75:25:0.1 v/v/v), adjusted to pH 3.0 using orthophosphoric acid, at a flow rate of 1.0 mL/min. Eluent monitoring was executed spectrophotometrically at a wavelength maximum of 278 nm. Method validation parameters followed the International Council for Harmonisation (ICH) guidelines. Excellent linearity was established over a concentration range of 1.0 to 50.0 mg/L with a correlation coefficient (R²) of 0.999. The limit of detection (LOD) and limit of quantification (LOQ) were determined to be 0.05 mg/L and 0.15 mg/L, respectively. Precision assessments yielded relative standard deviations (RSD) below 1.5%. The validated method was successfully applied to screen six commercial ciprofloxacin tablet brands, producing recovery percentages between 98.4% and 101.2% with no interference from common tablet excipients.

Keywords: RP-HPLC; Ciprofloxacin; Quantitative analysis; Method validation; Pharmaceuticals; Quality control

Manuscript Timeline: Received: May 02, 2013; Revised: June 15, 2013; Accepted: July 20, 2013; Published: May 09, 2014.

Citation: Effiong, E. O., & Silva., A. G. (2014). Development and Validation of an RP-HPLC Method for Quantitative Monitoring of Ciprofloxacin Formulations. International Journal of Chemistry, 5(5), 33–40.

International Journal of Chemistry | Vol. 5, No. 10, October 2014 | pp. 73–80

DOI: 10.46882/2014/IJC/000073

Article Type: Original Research Paper

Title: Isolation, Kinetic Optimization, and Characterization of Thermophilic Alkaline Lipases from Spent Bleaching Earth Soil

Names of Authors: C. N. Nwosu¹, Y. S. Takahashi²*

Authors’ Affiliations:
¹Department of Biochemistry, Nnamdi Azikiwe University, Awka, Nigeria.
²Department of Biomolecular Engineering, Tokyo Institute of Technology, Tokyo, Japan.

Abstract: Industrial biocatalysis in detergent formulations and biodiesel production requires robust lipolytic enzymes that maintain activity under high temperatures and alkaline pH conditions. This study focuses on the isolation, kinetic optimization, and biochemical characterization of thermophilic alkaline lipases produced by a novel fungal strain sourced from oil refinery spent bleaching earth dumpsites. Soil suspensions underwent enrichment cultures in olive oil-infused media at 45°C. The highest-yielding isolate was identified via 18S rRNA gene sequencing as Aspergillus flavus strain SBE-L1. Solid-state fermentation parameters were optimized using response surface methodology. Maximum lipase activity (42.5 U/mL) was achieved at an incubation temperature of 45°C, an initial substrate pH of 8.5, and a fermentation period of 96 hours using palm kernel cake as a solid matrix. Characterization profiles showed that the crude enzyme complex retained over 85% of its initial catalytic activity across a temperature range of 40 to 60°C and a pH stability window of 7.5 to 9.5 for 12 hours. The enzyme exhibited high tolerance toward commercial anionic surfactants, proving its industrial viability for bio-detergent product lines.

Keywords: Alkaline lipase; Aspergillus flavus; Response surface methodology; Thermal stability; Surfactant tolerance; Biocatalysis

Manuscript Timeline: Received: February 18, 2014; Revised: March 25, 2014; Accepted: May 02, 2014; Published: October 05, 2014.

Citation: Nwosu, C. N., & Takahashi, Y. S. (2014). Isolation, Kinetic Optimization, and Characterization of Thermophilic Alkaline Lipases from Spent Bleaching Earth Soil. International Journal of Chemistry, 5(10), 73–80.

International Journal of Chemistry | Vol. 5, No. 9, September 2014 | pp. 65–72

DOI: 10.46882/2014/IJC/000072

Article Type: Original Research Paper

Title: Biochemical Composition, Functional Properties, and Antinutritional Profiles of Non-Conventional Legume Seeds from West Africa

Names of Authors: A. E. Ogunkoya¹, M. G. R. S. Dias²*

Authors’ Affiliations:
¹Department of Chemistry, Ekiti State University, Ado-Ekiti, Nigeria.
²Department of Food and Nutrition, National Institute of Health Dr. Ricardo Jorge, Lisbon, Portugal.

Abstract: Non-conventional underutilized legumes are promising nutritional resources for mitigating protein-energy malnutrition in developing countries, though their baseline chemical characteristics require detailed mapping. This research examines the proximate composition, mineral fingerprinting, and antinutritional profiles of three wild legume seeds (Mucuna pruriens, Sphenostylis stenocarpa, and Canavalia ensiformis) harvested in West Africa. Proximate analysis established high crude protein contents ranging from 26.4% to 32.5% on a dry weight basis, low fat contents (2.1% to 4.5%), and total carbohydrate profiles spanning 48.5% to 54.2%. Mineral profiling using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) revealed high concentrations of potassium (840 to 1120 mg/100g) and phosphorus, while toxic heavy metals like lead remained below hazardous legal thresholds. Quantified antinutritional matrices showed high initial levels of phytic acid (4.2 to 6.8 mg/g) and total oxalates (3.1 to 5.2 mg/g). Processing simulations proved that combined soaking and autoclaving treatments effectively reduced antinutrient levels by over 78% without significant loss of core structural proteins, establishing these seeds as safe, functional dietary additives.

Keywords: Underutilized legumes; Proximate composition; Mineral fingerprinting; Antinutrients; Food chemistry; Protein-energy malnutrition

Manuscript Timeline: Received: February 10, 2014; Revised: March 18, 2014; Accepted: April 20, 2014; Published: September 09, 2014.

Citation: Ogunkoya, A. E., & Dias, M. G. R. S. (2014). Biochemical Composition, Functional Properties, and Antinutritional Profiles of Non-Conventional Legume Seeds from West Africa. International Journal of Chemistry, 5(9), 65–72.

International Journal of Chemistry | Vol. 5, No. 11, November 2014 | pp. 81–88

DOI: 10.46882/2014/IJC/000074

Article Type: Original Research Paper

Title: Synthesis, Rheological Profiling, and Adsorptive Features of Sodium Alginate Grafted Polyacrylamide Composite Hydrogels

Names of Authors: J. K. Mensah¹, R. P. Sharma²*

Authors’ Affiliations:
¹Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
²Department of Chemistry, Indian Institute of Technology, Bombay, India.

Abstract: The development of durable biopolymeric hydrogel networks is essential for industrial wastewater treatment due to the requirement for specific structural coordination sites. This study describes the chemical synthesis and rheological optimization of a hybrid hydrogel fabricated via the free-radical graft copolymerization of acrylamide onto a high-viscosity sodium alginate backbone. The grafting reaction was initiated using potassium persulfate (KPS) and crosslinked via N,N'-methylenebisacrylamide (MBA) under optimized gas environments. Structural networks and morphology features were characterized using FT-IR spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Swelling kinetics were evaluated as a function of time, pH, and saline concentration. The hydrogel showed highly responsive pH-dependent swelling profiles, achieving a maximum water absorption capacity of 380 g/g at pH 8.0 due to structural carboxylate ionizations causing intermolecular chain repulsions. Rheological analysis confirmed strong non-Newtonian shear-thinning characteristics with a storage modulus (G') that remained constant up to 75°C. Batch adsorption tests showed high affinity for divalent nickel and zinc ions, matching the Langmuir isotherm with monolayer capacities of 64.2 mg/g and 78.4 mg/g at 298 K, confirming high remediation potential.

Keywords: Sodium alginate; Acrylamide; Graft copolymerization; Hydrogel; Rheological profiling; Heavy metal adsorption

Manuscript Timeline: Received: March 04, 2014; Revised: April 15, 2014; Accepted: May 20, 2014; Published: November 02, 2014.

Citation: Mensah, J. K., & Sharma, R. P. (2014). Synthesis, Rheological Profiling, and Adsorptive Features of Sodium Alginate Grafted Polyacrylamide Composite Hydrogels. International Journal of Chemistry, 5(11), 81–88.

International Journal of Chemistry | Vol. 5, No. 8, August 2014 | pp. 57–64

DOI: 10.46882/2014/IJC/000071

Article Type: Original Research Paper

Title: Green Synthesis of Bimetallic Cu-Ag Nanoparticles Using Aqueous Leaf Extract of Azadirachta indica and Catalytic Reduction of 4-Nitrophenol

Names of Authors: S. I. Musa¹, T. A. Al-Shehri²*

Authors’ Affiliations:
¹Department of Chemistry, University of Jos, Jos, Nigeria.
²Department of Chemistry, King Abdulaziz University, Jeddah, Saudi Arabia.

Abstract: The fabrication of bimetallic nanoparticles using plant extracts represents an active frontier in sustainable heterogeneous catalysis due to synergistic electronic interactions at the nano-interface. This study details the green synthesis of stable copper-silver (Cu-Ag) core-shell nanoparticles utilizing the aqueous leaf extract of Azadirachta indica as a co-reducing and capping agent. The bioreduction process was monitored via UV-Vis spectrophotometry, which revealed a broad surface plasmon resonance peak at 495 nm, indicating alloyed structure formations. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) showed spherical particles with an average diameter of 22 nm and uniform copper-silver atomic distributions. X-ray diffraction (XRD) confirmed the highly crystalline nature of the bimetallic system. Fourier-transform infrared (FT-IR) spectroscopy showed that plant polyphenols and flavonoids actively capped the metallic surfaces, preventing structural agglomeration. The catalytic efficiency of the synthesized Cu-Ag nanoparticles was evaluated by tracking the reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride (NaBH₄). The bimetallic nanocatalyst accelerated the reaction, achieving 98.6% conversion within 6 minutes, outperforming monometallic equivalents. Kinetic modeling conformed to the pseudo-first-order model with a rate constant of 0.384 min⁻¹, confirming high efficacy for nitro-aromatic wastewater remediation.

Keywords: Bimetallic nanoparticles; Green synthesis; Azadirachta indica; Core-shell structure; Heterogeneous catalysis; 4-Nitrophenol

Manuscript Timeline: Received: January 12, 2014; Revised: February 20, 2014; Accepted: March 15, 2014; Published: August 03, 2014.

Citation: Musa, S. I., & Al-Shehri, T. A. (2014). Green Synthesis of Bimetallic Cu-Ag Nanoparticles Using Aqueous Leaf Extract of Azadirachta indica and Catalytic Reduction of 4-Nitrophenol. International Journal of Chemistry, 5(8), 57–64.

International Journal of Chemistry | Vol. 5, No. 6, June 2014 | pp. 41–48

DOI: 10.46882/2014/IJC/000069

Article Type: Original Research Paper

Title: Synthesis, Molecular Docking, and In Vitro Evaluation of Novel Isatin Derivatives as Potential Acetylcholinesterase Inhibitors

Names of Authors: O. M. Kolawole¹, E. J. Cook²*

Authors’ Affiliations:
¹Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria.
²Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.

Abstract: Inhibiting acetylcholinesterase (AChE) represents a vital clinical strategy for managing Alzheimer's disease by maintaining systemic acetylcholine neurotransmitter levels. In this work, five novel N-substituted isatin derivatives were synthesized via nucleophilic substitution reactions of isatin with various benzyl bromides in the presence of potassium carbonate. The molecular structures of the synthesized targets were verified using elemental analysis, FT-IR, and ¹H-NMR spectroscopy. In vitro AChE enzyme inhibition assays revealed that compound 5b, bearing a p-fluorobenzyl substituent, possessed the highest inhibitory potency, showing an IC50 value of 8.4 μM compared to the donepezil clinical standard (IC50 = 2.1 μM). To investigate specific binding modes, in silico molecular docking simulations were run inside the catalytic active site of human AChE using AutoDock Vina software. The computational docking models demonstrated that the isatin core forms stable hydrogen bonds with Gly121 and Ser203 residues. The aromatic ring extensions fit well into the peripheral anionic site, engaging in significant edge-to-face pi-pi stacking interactions with Trp286. These structural contacts stabilize the ligand-protein topology, explaining the sub-micromolar inhibition constants and presenting a potential scaffold for further antidementia drug design.

Keywords: Isatin derivatives; Chemical synthesis; Acetylcholinesterase; Enzyme inhibition; Molecular docking; Alzheimer's disease

Manuscript Timeline: Received: June 12, 2013; Revised: July 25, 2013; Accepted: August 18, 2013; Published: June 03, 2014.

Citation: Kolawole, O. M., & Cook., E. J. (2014). Synthesis, Molecular Docking, and In Vitro Evaluation of Novel Isatin Derivatives as Potential Acetylcholinesterase Inhibitors. International Journal of Chemistry, 5(6), 41–48.