International Journal of Chemistry

International Journal of Chemistry | Vol. 10, No. 11, November 2019 | pp. 81–88

DOI: 10.46882/2019/IJC/000133

Article Type: Original Research Paper

Title: Isolation, Structural Profiling, and Optimizing Kinetics of Cellulolytic Complexes Sourced from Thermophilic Aspergillus Strains

Names of Authors: C. N. Nwosu¹, H. M. Sato²*

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

Abstract: The industrial saccharification of lignocellulose into simple glucose syrups requires robust cellulolytic enzymes that can resist thermal denaturation during high-temperature steam hydrolysis loops. This study details the isolation, microstructural profiling, and kinetic optimization of high-yielding endoglucanase complexes produced by a thermophilic fungal strain sourced from processing soil surrounding artisanal rice hulling mills. Enrichment culturing was executed in cellulose-infused Mandels' media at 50°C, isolating a dominant strain identified via internal transcribed spacer (ITS) rRNA gene sequencing as Aspergillus terreus strain Rice-C1. Response surface methodology optimized solid-state fermentation yields using wheat bran matrices. Maximum cellulase activity (54.5 U/mL) was achieved at an incubation temperature of 50°C, an initial substrate pH of 6.0, and a fermentation period of 96 hours. Biochemical characterization showed that the crude enzyme complex retained over 85% of its initial catalytic activity across a temperature range of 45 to 65°C and a pH stability window of 5.5 to 7.0 for 24 hours. The high thermal stability of this enzyme system, along with its independence from calcium ions, makes it a viable candidate for bio-refinery industrial operations.

Keywords: Endoglucanase; Aspergillus terreus; Solid-state fermentation; Thermal stability; Kinetic optimization; Cellulose saccharification

Manuscript Timeline: Received: March 10, 2019; Revised: April 18, 2019; Accepted: May 14, 2019; Published: November 02, 2019.

Citation: Nwosu, C. N., & Sato, H. M. (2019). Isolation, Structural Profiling, and Optimizing Kinetics of Cellulolytic Complexes Sourced from Thermophilic Aspergillus Strains. International Journal of Chemistry, 10(11), 81–88.

International Journal of Chemistry | Vol. 10, No. 6, June 2019 | pp. 41–48

DOI: 10.46882/2019/IJC/000128

Article Type: Original Research Paper

Title: Development and Validation of a Spectrophotometric Method for Quantitative Determination of Ganciclovir in Pharmaceutical Formulations

Names of Authors: E. O. Effiong¹, J. M. S. Cardoso²*

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

Abstract: Developing rapid, low-cost analytical protocols is essential for routine quality monitoring and the detection of substandard antiviral formulations in clinical testing laboratories. This paper describes the development and validation of a simple UV-Vis spectrophotometric method for the quantification of ganciclovir in pharmaceutical injections. The analytical procedure relied on the reaction of ganciclovir with 1,2-naphthoquinone-4-sulfonate in an alkaline medium, generating a highly stable orange-colored derivative monitored spectrophotometrically at its absorption maximum of 460 nm. Method validation parameters followed the International Council for Harmonisation (ICH) guidelines. Excellent linearity was established over a concentration range of 2.0 to 25.0 mg/L with a correlation coefficient (R²) of 0.999. The limit of detection (LOD) and limit of quantification (LOQ) were determined to be 0.08 mg/L and 0.24 mg/L, respectively. Precision assessments yielded relative standard deviations (RSD) below 1.8%. The validated method was successfully applied to screen commercial brands of ganciclovir formulations, producing recovery percentages between 98.6% and 101.4% with no interference from common excipients, making it suitable for routine quality control setups.

Keywords: UV-Vis spectrophotometry; Ganciclovir; Chemical derivation; Method validation; Pharmaceuticals; Quality control

Manuscript Timeline: Received: June 12, 2018; Revised: July 25, 2018; Accepted: August 18, 2018; Published: June 03, 2019.

Citation: Effiong, E. O., & Cardoso, J. M. S. (2019). Development and Validation of a Spectrophotometric Method for Quantitative Determination of Ganciclovir in Pharmaceutical Formulations. International Journal of Chemistry, 10(6), 41–48.

International Journal of Chemistry | Vol. 10, No. 4, April 2019 | pp. 25–32

DOI: 10.46882/2019/IJC/000126

Article Type: Original Research Paper

Title: Geochemical Speciation, Spatial Distribution, and Ecotoxicological Risk Assessments of Cadmium and Chromium in Coastal Estuaries

Names of Authors: C. I. Obi¹, S. H. Kim²*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, University of Port Harcourt, Port Harcourt, Nigeria.
²Department of Chemistry, Seoul National University, Seoul, South Korea.

Abstract: Total concentrations of heavy metals are insufficient to assess ecological risk in coastal bodies because environmental mobility and bioavailability depend heavily on specific chemical binding forms. This study evaluates the total concentration and geochemical speciation fractions of cadmium (Cd) and chromium (Cr) in surface sediments collected from an urban coastal estuary exposed to municipal and industrial waste discharges. Quantitative analysis was performed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) following the modified BCR three-step sequential extraction procedure. The total metal concentrations followed the sequence: Cr > Cd across all sampling locations. Spatial mapping revealed significant pollutant accumulation near industrial discharge channels. Speciation patterns demonstrated that a high proportion of cadmium (45.2%) was associated with the acid-soluble and exchangeable fractions, suggesting high structural instability and bioavailable risks to benthic organisms. Conversely, chromium was primarily bound within the residual and organic matrices, indicating low immediate mobility under baseline pH conditions. The Risk Assessment Code (RAC) calculated for cadmium indicated a high environmental hazard rating, highlighting a strong need for local effluent regulatory frameworks.

Keywords: Coastal estuary; Sediments; Heavy metals; BCR protocol; Geochemical speciation; Bioavailability

Manuscript Timeline: Received: May 11, 2018; Revised: June 22, 2018; Accepted: July 18, 2018; Published: April 02, 2019.

Citation: Obi, C. I., & Kim, S. H. (2019). Geochemical Speciation, Spatial Distribution, and Ecotoxicological Risk Assessments of Cadmium and Chromium in Coastal Estuaries. International Journal of Chemistry, 10(4), 25–32.

International Journal of Chemistry | Vol. 10, No. 7, July 2019 | pp. 49–56

DOI: 10.46882/2019/IJC/000129

Article Type: Original Research Paper

Title: Synthesis, Computational Docking, and Enzymatic Screening of Novel Indole-Linked Hydrazone Compounds

Names of Authors: O. M. Kolawole¹, E. R. Watson²*

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

Abstract: Inhibiting alpha-glucosidase represents a critical therapeutic target for managing postprandial hyperglycemia in type 2 diabetes mellitus. In this work, five novel indole-linked hydrazone derivatives were synthesized via the condensation of indole-3-carboxaldehyde with various substituted benzohydrazides in the presence of catalytic glacial acetic acid. The molecular frameworks of the synthesized targets were verified using elemental analysis, FT-IR, and ¹H-NMR spectroscopy. In vitro alpha-glucosidase enzyme inhibition assays revealed that compound 3c, bearing a p-nitro substituent, possessed the highest inhibitory potency, showing an IC50 value of 12.4 μM, compared to the acarbose clinical standard (IC50 = 38.2 μM). To investigate specific binding configurations, in silico molecular docking simulations were run inside the catalytic domain of alpha-glucosidase using AutoDock Vina software. The computational docking models demonstrated that the indole core forms stable hydrogen bonds with Asp214 and Arg315 residues. The aromatic ring extensions fit well into the hydrophobic pocket, engaging in significant pi-pi stacking interactions with Phe178. These structural contacts stabilize the ligand-protein topology, explaining the sub-micromolar inhibition constants and presenting a potential scaffold for further antidiabetic drug design.

Keywords: Indole; Hydrazones; Alpha-glucosidase; Enzyme inhibition; Molecular docking; Antidiabetic drug design

Manuscript Timeline: Received: July 20, 2018; Revised: August 28, 2018; Accepted: September 15, 2018; Published: July 08, 2019.

Citation: Kolawole, O. M., & Watson, E. R. (2019). Synthesis, Computational Docking, and Enzymatic Screening of Novel Indole-Linked Hydrazone Compounds. International Journal of Chemistry, 10(7), 49–56.

International Journal of Chemistry | Vol. 10, No. 12, December 2019 | pp. 89–96

DOI: 10.46882/2019/IJC/000134

Article Type: Original Research Paper

Title: Synthesis, Microcharacterization, and Viscosity Profiling of Alginate-Graft-Polyacrylamide Superabsorbent Hydrogels

Names of Authors: J. K. Mensah¹, S. K. Roy²*

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

Abstract: The development of durable biopolymeric hydrogel networks is essential for agricultural soil water retention and controlled agrochemical delivery 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 atmospheric conditions. 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 410 g/g at pH 7.4 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 80°C. Batch adsorption tests showed high affinity for divalent lead and copper ions, matching the Langmuir isotherm with monolayer capacities of 72.4 mg/g and 85.6 mg/g at 298 K, confirming high remediation potential.

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

Manuscript Timeline: Received: March 15, 2019; Revised: April 22, 2019; Accepted: May 20, 2019; Published: December 08, 2019.

Citation: Mensah, J. K., & Roy, S. K. (2019). Synthesis, Microcharacterization, and Viscosity Profiling of Alginate-Graft-Polyacrylamide Superabsorbent Hydrogels. International Journal of Chemistry, 10(12), 89–96.

International Journal of Chemistry | Vol. 10, No. 1, January 2019 | pp. 1–8

DOI: 10.46882/2019/IJC/000123

Article Type: Original Research Paper

Title: Phytochemical Screening, Volatile Component Identification, and In Vitro Acaricidal Efficacy of Vernonia amygdalina Essential Oils

Names of Authors: S. A. Abdulrahman¹, L. E. G. O. Santos²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.
²Department of Organic Chemistry, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.

Abstract: The widespread development of acaricide resistance among livestock ticks demands the isolation of alternative botanical formulations to minimize chemical toxicities in agrarian systems. This study describes the qualitative chemical characterization, essential oil isolation via Gas Chromatography-Mass Spectrometry (GC-MS), and in vitro acaricidal efficacy of Vernonia amygdalina (Bitter leaf) leaf extracts against Rhipicephalus microplus larvae. Essential oils obtained via hydro-distillation in a Clevenger apparatus were separated into 18 distinct peaks through GC-MS profiling, with beta-caryophyllene (38.4%), alpha-humulene (16.2%), and caryophyllene oxide (12.4%) emerging as the primary bioactive constituents. Acaricidal bioassays were performed utilizing the larval packet test across a suite of oil concentrations (5.0 to 25.0 mg/mL) over 24-hour exposure periods. The essential oil demonstrated significant lethal potency, yielding an LC50 value of 8.4 mg/mL and an LC90 value of 16.5 mg/mL against the tick larvae. A linear correlation was observed between the concentration of sesquiterpenes and larval mortality rates. This confirms that volatile sesquiterpenoids actively disrupt the respiratory and cuticle matrices of arachnid vectors, providing a sustainable botanical framework for veterinary parasite control.

Keywords: Vernonia amygdalina; Essential oils; GC-MS analysis; Beta-caryophyllene; Acaricidal bioassay; Rhipicephalus microplus

Manuscript Timeline: Received: April 02, 2018; Revised: May 15, 2018; Accepted: June 20, 2018; Published: January 03, 2019.

Citation: Abdulrahman, S. A., & Santos, L. E. G. O. (2019). Phytochemical Screening, Volatile Component Identification, and In Vitro Acaricidal Efficacy of Vernonia amygdalina Essential Oils. International Journal of Chemistry, 10(1), 1–8.