International Journal of Chemistry

International Journal of Chemistry | Vol. 15, No. 12, December 2024 | pp. 89–96

DOI: 10.46882/2024/IJC/000194

Article Type: Original Research Paper

Title: GC-MS Chemical Profiling, Quantitative Phytochemical Mapping, and Insecticidal Efficacy of Rosmarinus officinalis Essential Oils

Names of Authors: S. A. Abdulrahman¹, G. E. D. M. Santos²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.
²Department of Chemistry, University of Campinas, Campinas, Brazil.

Abstract: The continuous emergence of chemical resistance among stored-grain insect pests requires the formulation of alternative botanical insecticides to minimize chemical pesticide hazards in agricultural facilities. This research reports the qualitative chemical characterization, volatile compound identification via Gas Chromatography-Mass Spectrometry (GC-MS), and in vitro insecticidal efficacy of Rosmarinus officinalis leaf essential oil against Acanthoscelides obtectus (Bean weevil). Essential oils obtained via hydro-distillation in a Clevenger apparatus were separated into 20 distinct peaks through GC-MS profiling, with 1,8-cineole (42.5%), alpha-pinene (18.2%), and camphor (12.4%) emerging as the primary bioactive constituents. Insecticidal bioassays were conducted utilizing contact toxicity tests across a suite of oil concentrations (10 to 50 microliters/square meter) over 24-hour exposure periods. The essential oil demonstrated significant lethal potency, yielding an LC50 value of 18.4 microliters/square meter and an LC90 value of 34.2 microliters/square meter against the weevil populations. A linear correlation was observed between the concentration of oxygenated monoterpenes and insect mortality rates. This confirms that volatile monoterpenoids actively disrupt the respiratory and acetylcholinesterase enzymes of weevils, providing a sustainable botanical framework for grain storage protection.

Keywords: Rosmarinus officinalis; Essential oils; GC-MS analysis; 1,8-Cineole; Contact toxicity; Acanthoscelides obtectus

Manuscript Timeline: Received: June 15, 2023; Revised: July 28, 2023; Accepted: August 22, 2023; Published: December 04, 2024.

Citation: Abdulrahman, S. A., & Santos, G. E. D. M. (2024). GC-MS Chemical Profiling, Quantitative Phytochemical Mapping, and Insecticidal Efficacy of Rosmarinus officinalis Essential Oils. International Journal of Chemistry, 15(12), 89–96.

International Journal of Chemistry | Vol. 15, No. 1, January 2024 | pp. 1–8

DOI: 10.46882/2024/IJC/000183

Article Type: Original Research Paper

Title: Transesterification Kinetics, Thermodynamic Modeling, and Engine Emissions of Methyl Esters from Ricinodendron heudelotii Seed Oil

Names of Authors: M. C. Okonkwo¹, T. H. Nguyen²*

Authors’ Affiliations:
¹Department of Industrial Chemistry, Enugu State University of Science and Technology, Enugu, Nigeria.
²Department of Chemical Engineering, Hanoi University of Science and Technology, Hanoi, Vietnam.

Abstract: Utilizing non-edible agricultural crop lipids as chemical feedstocks for alternative biodiesel synthesis promotes green energy targets without competing with global food security reservoirs. This study investigates the transesterification kinetics and chemical properties of biodiesel synthesized from essessang (Ricinodendron heudelotii) seed oil. Because of an elevated initial free fatty acid content (5.84 mg KOH/g), a two-step acid-base catalyzed transesterification route was deployed. The first step reduced the acid value below 1.0 mg KOH/g using 1.2% v/v sulfuric acid in methanol, followed by standard base-catalyzed transesterification with sodium methoxide. Fatty acid methyl ester (FAME) yield was optimized at 93.8% using a 6:1 methanol-to-oil molar ratio, a catalyst concentration of 1.0 wt% NaOH, and a process temperature of 60°C for 90 minutes. Kinetic analysis confirmed that the transesterification process followed pseudo-first-order reaction mechanics with an activation energy of 41.5 kJ/mol. Fuel properties of the prepared biodiesel, including kinematic viscosity (4.32 mm²/s at 40°C), flash point (164°C), and cetane number (53), matched international ASTM D6751 regulatory specifications. Diesel engine tests using a B20 blend showed a 14.5% reduction in smoke opacity compared to conventional diesel.

Keywords: Ricinodendron heudelotii; Biodiesel; Transesterification; Reaction kinetics; Activation energy; Fuel properties

Manuscript Timeline: Received: July 02, 2022; Revised: August 14, 2022; Accepted: September 10, 2022; Published: January 04, 2024.

Citation: Okonkwo, M. C., & Nguyen, T. H. (2024). Transesterification Kinetics, Thermodynamic Modeling, and Engine Emissions of Methyl Esters from Ricinodendron heudelotii Seed Oil. International Journal of Chemistry, 15(1), 1–8.

International Journal of Chemistry | Vol. 15, No. 8, August 2024 | pp. 57–64

DOI: 10.46882/2024/IJC/000190

Article Type: Original Research Paper

Title: Ultrasonic Speeds, Excess Volumetric Parameters, and Dipolar Hydrogen Bond Networks of Binary Systems of Hexanol with Aliphatic Esters

Names of Authors: E. C. Chiemeka¹, A. M. H. Al-Ghamdi²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Owerri, Nigeria.
²Department of Chemistry, University of Khartoum, Khartoum, Sudan.

Abstract: Experimental determination of ultrasonic velocities and fluid densities across varied temperature states yields critical baseline data needed to map hydrogen bond associations and molecular packing dynamics in multi-component chemical systems. This paper presents the measurement of ultrasonic velocity (u), density (rho), and dynamic viscosity (eta) for binary liquid mixtures of n-hexanol with methyl acetate, ethyl acetate, and propyl acetate across the entire composition matrix at temperatures of 298.15 K, 308.15 K, and 318.15 K under atmospheric pressure. From these raw data metrics, excess molar volumes (V^E) and excess isentropic compressibilities (kappa_s^E) were calculated. The calculated excess datasets were successfully fitted to the Redlich-Kister polynomial expression to compute the binary interaction coefficients and standard deviations. All investigated binary mixtures exhibited significant negative excess molar volumes (V^E) and negative excess isentropic compressibilities (kappa_s^E) across all composition bounds. These strong negative deviations reveal dense interstitial molecular packing and strong intermolecular hydrogen bond formation between the hydroxyl protons of n-hexanol and the ester carbonyl centers, which decrease in intensity as thermal motion breaks the dipole networks.

Keywords: Ultrasonic velocity; Excess molar volume; Isentropic compressibility; Aliphatic esters; Redlich-Kister equation; Hydrogen bonding

Manuscript Timeline: Received: February 05, 2023; Revised: March 12, 2023; Accepted: April 08, 2023; Published: August 03, 2024.

Citation: Chiemeka, E. C., & Al-Ghamdi, A. M. H. (2024). Ultrasonic Speeds, Excess Volumetric Parameters, and Dipolar Hydrogen Bond Networks of Binary Systems of Hexanol with Aliphatic Esters. International Journal of Chemistry, 15(8), 57–64.

International Journal of Chemistry | Vol. 15, No. 5, May 2024 | pp. 33–40

DOI: 10.46882/2024/IJC/000187

Article Type: Original Research Paper

Title: Synthesis, Computational Modeling, and Enzymatic Inhibition Screening of Novel N-Substituted Maleimide Derivatives

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 N-substituted maleimide derivatives were synthesized via the condensation of maleic anhydride with various substituted aniline compounds 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 maleimide carbonyl 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: Maleimide; Chemical synthesis; Alpha-glucosidase; Enzyme inhibition; Molecular docking; Antidiabetic drug design

Manuscript Timeline: Received: September 02, 2022; Revised: October 12, 2022; Accepted: November 05, 2022; Published: May 04, 2024.

Citation: Kolawole, O. M., & Watson, E. R. (2024). Synthesis, Computational Modeling, and Enzymatic Inhibition Screening of Novel N-Substituted Maleimide Derivatives. International Journal of Chemistry, 15(5), 33–40.

International Journal of Chemistry | Vol. 15, No. 9, September 2024 | pp. 65–72

DOI: 10.46882/2024/IJC/000191

Article Type: Original Research Paper

Title: Synthesis, Microcharacterization, and Antifungal Activity of Novel Aminosalicylic Acid Transition Metal Complexes

Names of Authors: A. A. Yusuf¹, P. K. Ghosh²*

Authors’ Affiliations:
¹Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria.
²Department of Pharmaceutical Technology, Jadavpur University, Kolkata, India.

Abstract: The emergence of drug resistance among opportunistic fungal strains requires the structural modification of classic therapeutic agents via coordination to transition metal ions to boost clinical performance. This research outlines the synthesis, structural characterization, and in vitro antifungal testing of novel copper(II), nickel(II), and cobalt(II) complexes coordinated with 4-aminosalicylic acid ligands. The synthesized coordination compounds were profiled utilizing elemental analysis, molar conductance measurements, magnetic susceptibility, and FT-IR spectroscopy. Analytical metrics established a 1:2 metal-to-ligand stoichiometric coordination pattern for all complexes, corresponding to a general structural configuration of [M(ASA)₂Cl₂], where ASA represents the neutral aminosalicylic acid molecule. Molar conductance tests in DMSO indicated a non-electrolytic nature. FT-IR spectra confirmed that the ligand acts as a bidentate chelator, binding to the metal centers via the amino nitrogen and the carboxylate oxygen atoms. In vitro antifungal evaluation was conducted against Candida albicans and Aspergillus niger isolates via the disk diffusion test. The copper(II)-aminosalicylic acid complex demonstrated a two-fold increase in mycelial growth inhibition compared to standalone uncoordinated aminosalicylic acid, which is explained via cell permeability and chelation principles.

Keywords: Aminosalicylic acid; Metal complexes; Antifungal activity; FT-IR spectroscopy; Candida albicans; Chelation theory

Manuscript Timeline: Received: February 12, 2023; Revised: March 20, 2023; Accepted: April 15, 2023; Published: September 09, 2024.

Citation: Yusuf, A. A., & Ghosh, P. K. (2024). Synthesis, Microcharacterization, and Antifungal Activity of Novel Aminosalicylic Acid Transition Metal Complexes. International Journal of Chemistry, 15(9), 65–72.

International Journal of Chemistry | Vol. 15, No. 10, October 2024 | pp. 73–80

DOI: 10.46882/2024/IJC/000192

Article Type: Original Research Paper

Title: Synthesis, Photoluminescence Properties, and Carcinogenic Cell Imaging of Novel Thulium(III) Complexes

Names of Authors: A. O. Balogun¹, J. E. Kim²*

Authors’ Affiliations:
¹Department of Chemistry, University of Ilorin, Ilorin, Nigeria.
²Department of Chemistry, Seoul National University, Seoul, South Korea.

Abstract: Rare-earth coordination materials displaying highly sensitive photoluminescent behaviors are increasingly sought for biochemical sensor and cellular imaging fabrications due to their specific emission bands and high signal-to-noise ratios. This study reports the synthesis, material characterization, and analytical sensor optimization of a novel thulium(III) complex using hexafluoroacetylacetone and 1,10-phenanthroline ligands. Structural configurations were verified using elemental analysis, molar conductance, and Fourier-transform infrared (FT-IR) spectroscopy. Analytical calculations confirmed a 1:3:1 metal-to-ligand stoichiometric coordination pattern, conforming to the formula [Tm(HFA)₃(phen)]. Molar conductivity tests in acetonitrile confirmed a completely non-electrolytic layout. Photoluminescence scanning at room temperature showed narrow blue emission lines characteristic of the central Tm(III) ion framework. The analytical potential of the complex as a cell-permeable fluorimetric sensor for tracking cancerous cellular structures was evaluated in vitro. The complex demonstrated exceptionally low cytotoxicity and high photostability within cellular networks over extended tracking periods. Fluorescent imaging confirmed distinct accumulation inside target cytoplasmic zones, establishing this coordination matrix as a promising bio-imaging candidate for clinical pathology fields.

Keywords: Thulium complexes; Rare earth elements; Photoluminescence; Fluorimetric sensor; Cell imaging; Coordination chemistry

Manuscript Timeline: Received: May 12, 2023; Revised: June 25, 2023; Accepted: July 18, 2023; Published: October 05, 2024.

Citation: Balogun, A. O., & Kim, J. E. (2024). Synthesis, Photoluminescence Properties, and Carcinogenic Cell Imaging of Novel Thulium(III) Complexes. International Journal of Chemistry, 15(10), 73–80.