David Kehinde Adeyemi

Residual antibiotics pollution is one of the main drivers of antibiotic resistance, demanding effective and sustainable technologies for remediation. Adsorption was found to be an effective process for antibiotic contaminant remediation, particularly on surfaces of lignocellulosic materials, which have gained attention as low-cost adsorbents. This study investigated the adsorption mechanisms and the optimisation of rifampicin removal from water using sawdust. Adsorption mechanisms were proposed based on kinetic and isotherms, while response surface methodology (RSM) was employed to optimise and identify the critical operating parameters. The results revealed that the adsorption of rifampicin by both adsorbents could be best described by the pseudo-first-order model, while the experimental results fitted perfectly into the Temkin isotherm model, which suggests that the adsorption of rifampicin on sawdust occurred via multi-interaction on a varying, energetically heterogeneous surface. Optimal conditions resulting in an uptake of 0.71 mg/g were established as follows: initial concentration of 20 mg/L, an adsorbent dosage of 0.5 g per 40 mL, pH 6 and at 250 min. The initial concentration of rifampicin and the adsorbent dosage were found to be the most critical parameters that influenced its uptake. The findings revealed that sawdust is a sustainable and cost-effective material to remove rifampicin from water, with adsorption occurring mainly via physisorption on a varying, energetically heterogeneous surface.

Background : Toxicity accounts for nearly one-third of candidate drug attrition, underscoring the need for robust preclinical toxicological evaluation early in the drug development pipeline. To the best of our knowledge, this is the first comprehensive toxicological profiling of Spondias mombin hydroethanolic leaf extract in rodent models in Nigeria. Traditionally used for the treatment of dysentery, gonorrhea, wounds, and anemia, S. mombin hydroethanolic extract warrants systematic evaluation to support its safe therapeutic use and guide the optimization of lead compounds. Methods : Acute toxicity was assessed in mice using a limit test following a single oral dose and a 14-day observation period. Subacute and subchronic toxicity were evaluated in female Wistar rats (n = 6/group and n=10/group) administered 40, 200, or 1000 mg/kg/day of extract for 28 and 60 days, respectively. A control group received distilled water. Hematological and biochemical analyses were conducted post-treatment before humane euthanasia. Results : No mortality or observable signs of toxicity were recorded at doses up to 2000 mg/kg. The extract significantly reduced white blood cell count, absolute lymphocytes, and total bilirubin (WBC: 5.60 × 10³/µL vs. 9.35 × 10³/µL; lymphocytes: 2.08 × 10³/µL vs. 4.28 × 10³/µL; bilirubin: 1.99 µmol/L vs. 2.39 µmol/L). S. mombin extract also exhibited dose-dependent increases in red blood cell and hemoglobin counts, alongside reductions in AST, ALT, and ALP levels in the subacute phase. In the subchronic study, S. mombin significantly reduced total cholesterol (40 mg/kg: 1.96 mmol/L vs. control: 2.85 mmol/L) and bilirubin (1000 mg/kg: 10.69 µmol/L vs. control: 22.58 µmol/L). Conclusion : The validated safety profile of S. mombin hydroethanolic leaf extract supports its continued ethnomedicinal use and highlights its promise as a candidate for further pharmacological development—particularly as a potential hematinic, anti-infective, and hepatoprotective agent.

Background: Key mechanisms of antimicrobial resistance (AMR) include the presence of efflux pumps and the production of drug-degrading enzymes upon exposure to antimicrobial drugs. Levofloxacin, a widely prescribed fluoroquinolone, has marked antimicrobial activity against Gram-positive pathogens like Streptococcus pneumoniae and Gram-negative pathogens like Pseudomonas aeruginosa . However, additional multidrug resistance (MDR) mechanisms in microbes, such as mutations in DNA gyrase and topoisomerase IV or altered efflux pump activity (EPA), threaten its clinical efficacy. To the best of our knowledge, no study has reported the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of levofloxacin against genetically validated MDR isolates in Nigeria. Methods: A cross-sectional study assessing levofloxacin’s potency, MIC and MBC was conducted against 20 validated bacterial isolates with resistance mechanisms such as efflux pump activity, oxacillin resistance, ESBL, and carbapenemase production, following CLSI guidelines. The American Type Culture Collection (ATCC 25922) Escherichia coli reference isolate was used as the standard drug-susceptible control and all assays were performed in triplicate to ensure reproducibility and minimise observer bias. All data were expressed as mean ± standard deviation (S.D.). Significant differences among the groups were determined by one-way analysis of variance (ANOVA), and Graphs were plotted using Microsoft Excel. Results were considered to be significant at p ≤ 0.05. Results: Three MDR Klebsiella pneumoniae strains exhibited non-susceptibility and intermediate resistance to levofloxacin. MICs ranged from 0.0625–8.00 µg/ml for Gram-positive and 0.015625–1.00 µg/ml for Gram-negative organisms. Levofloxacin demonstrated greater inhibitory activity against Gram-negative (72.73% susceptible) than Gram-positive (55.56% susceptible) organisms. MBCs ranged from 0.125–8.00 µg/ml (Gram-positive) and 0.015625–8.00 µg/ml (Gram-negative), with Micrococcus spp. showing marked susceptibility (IZD 50 µg/ml: 37.33 mm ± 0.58; MIC: 0.125 µg/ml). Conclusion: Our study findings underscore the need for continuous surveillance, molecular characterisation of resistance mechanisms, and MIC-guided antimicrobial stewardship. While levofloxacin remains effective for many infections, emerging resistance among previously susceptible organisms highlights the urgent need for informed prescribing practices and the development of novel antimicrobials to combat MDR.

Introduction: The presence of antibiotic residues in the aquatic environment is a likely contributor to the current increase in antibiotic resistance, posing a significant threat to global health. This study investigated the use of a low-cost and sustainable material based on sawdust with the purpose of removing rifampicin residues from water. Methods: The sawdust was pretreated with 2M sulfuric acid and was characterized using Fourier Transform Infrared spectroscopy (FT-IR), a Mastersizer, scanning electron microscopy (SEM), an elemental analyser, and the pH point of zero charge (pH_pzc). The batch adsorption process was conducted using both raw and treated sawdust to determine the effect of contact time, temperature, pH, adsorbent dosage, and the initial concentration of antibiotic dissolved in water. Results and Discussion: The results revealed that the chemical pretreatment of raw sawdust significantly improved its adsorption capacity. The highest removal efficiency of 65% was achieved using an adsorbent dosage of 31.3 g/L. The thermodynamic studies demonstrated that the process was spontaneous and governed by physisorption within the studied temperature range (293.15 K–318.15 K), being more favourable at higher temperatures. The interactions between the functional groups of sawdust and the rifampicin molecules included electrostatic attraction, hydrogen bonding, and π-π interactions. Conclusions: This research highlights the potential of utilizing waste as a valuable and effective adsorbent of residual antibiotics from water, thus contributing to the sustainable practices of solid waste management and water treatment.

Background: Nanotechnology offers an advantage as a green route for synthesis of metal nanoparticles (NPs) with plant extracts as capping agent. Spondias mombin is a fruit-bearing tree and its leaf extracts have been reported to possess anxiolytic, hypoglycaemic, antiepileptic, antipsychotic, sedative, antioxidant, and antimicrobial properties. The objective of the study is to determine the antibacterial potential of a simple non-toxic product of green synthesis of metallic (Ag, Zn and Cu) nanoparticles using the leaf of Spondias mombin aqueous extracts (SMAE) as a reducing and capping agents of the metal ions.Methodology: Nanoparticles were characterized by UV visible spectrophotometeric analysis, Fourier Transform Infra-Red (FT-IR) spectrophotometer and scanning electron microscope (SEM). Antimicrobial activities of synthesized NPs against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were determined by agar well diffusion technique.Results: The synthesized NPs varied in colour from dark brown to green and appears dominantly spherical, occasionally rod or triangular shaped with size ranging from 65-90 nm. UV spectroscopy absorption spectra of Ag, Zn and Cu NPs had absorbance peak at 267, 262 and 765 nm respectively. FT-IR spectrometry of Zn NP, Cu NP, and SMAE gave wave number ranging from 895.71-3320.67, 747.02-3225.45 and 658.25-3674.49 respectively. FT-IR analysis showed that SMAE acted as reducing and stabilizing agent while the NPs exhibited lower energy absorption band when compared to the plant extract. The NPs demonstrated higher antimicrobial activities against S. aureus than Ps. aeruginosa and E. coli. The antimicrobial activity was higher with copper NP than Ag and Zn NPs, and also higher than SMAE.Conclusion: The result from this study presents an indication for an alternative means for development of novel antimicrobial agents for clinical and biotechnological applications.Keywords: synthesis, nanoparticles, FT-IR, UV-visible spectrophotometry, antibacterial activitiesFrench Title: Synthèse verte de nanoparticules d'Ag, de Zn et de Cu à partir d'extrait aqueux de feuilles de Spondias mombin et évaluation de leur activité antibactérienneContexte: La nanotechnologie offre un avantage en tant que voie verte pour la synthèse de nanoparticules métalliques (NP) avec des extraits de plantes comme agent de coiffage. Spondias mombin est un arbre fruitier et ses extraits de feuilles possèdent des propriétés anxiolytiques, hypoglycémiques, antiépileptiques, antipsychotiques, sédatives, antioxydantes et antimicrobiennes. L’objectif de l’étude est de déterminer le potentiel antibactérien d’un simple produit non toxique de synthèse verte de nanoparticules métalliques (Ag, Zn et Cu) à l’aide de la feuille d’extraits aqueux de Spondias mombin (SMAE) en tant qu’agent réducteur et coiffant de la ions métalliques.Méthodologie: Les nanoparticules ont été caractérisées par analyse spectrophotométrique UV visible, spectrophotomètre à transformée de Fourier infrarouge (FT-IR) et microscope électronique à balayage (MEB). Lesactivités antimicrobiennes de NP synthétisées contre Escherichia coli, Staphylococcus aureus et Pseudomonas aeruginosa ont été déterminées par une technique de diffusion sur puits d’agar.Résultats: Les NP synthétisés ont une couleur allant du brun foncé au vert et apparaissent principalement sphériques, parfois en bâtonnets ou en triangles, avec des tailles allant de 65 à 90 nm. Les spectres d'absorption par spectroscopie UV des NP Ag, Zn et Cu présentaient des pics d'absorbance à 267, 262 et 765 nm respectivement. La spectrométrie FT-IR de Zn NP, Cu NP et SMAE a donné un nombre d'onde allant de 895,71 à 3320,67, 747,02 à 3225,45 et 658,25 à 3674,49 respectivement. L'analyse FT-IR a montré que le SMAE agissait en tant qu'agent réducteur et stabilisant, alors que les NP présentaient une bande d'absorption d'énergie inférieure à celle de l'extrait de plante. Les NP ont démontré des activités antimicrobiennes plus élevées contre S. aureus que Ps. aeruginosa et E. coli. L'activité antimicrobienne était plus élevée avec les NP en cuivre que dans les NP Ag et Zn, et également supérieure à celle du SMAE.Conclusion: le résultat de cette étude présente une indication d'un autre moyen de développement de nouveaux agents antimicrobiens pour des applications cliniques et biotechnologiques.Mots-clés: synthèse, nanoparticules, FT-IR, spectrophotométrie UV-visible, activités antibactériennes