Browsing by Author "Oselusi, Samson"

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    Phytofabrication of silver nanoparticles using ehretia rigida leaf aqueous extract, their characterization, antioxidant and antimicrobial activities
    (Elsevier Ltd, 2025) Oselusi, Samson; Sibuyi, Nicole; Meyer, Mervin
    The green synthesis of nanoparticles (NPs) offers a sustainable, rapid, and cost-effective alternative to traditional chemical and physical methods, with diverse applications across various fields. This study reports the synthesis of silver nanoparticles (AgNPs) using Ehretia rigida (Er) leaf aqueous extract and evaluates their biological activities. The formation of the NPs was confirmed by the change in colour from clear to dark brown. The synthesis parameters, such as pH, temperature, Er extract and silver nitrate (AgNO3) concentrations, reaction ratio, and incubation time, were optimized for high yields, controlled size, and stability of the NPs. The optimized Er-AgNPs were characterized using ultraviolet–visible (UV–vis) spectroscopy, dynamic light scattering (DLS), Fourier transform infrared (FTIR) spectroscopy, and high-resolution transmission electron microscopy (HR–TEM). The Er-AgNPs sample presented a characteristic absorbance peak at 408 nm, a hydrodynamic size of 74.02 ± 0.19 nm, a polydispersity index (PDI) of 0.39 ± 0.05, and a zeta potential of −25.4 ± 6.26 mV. FTIR analysis revealed the nature of the biomolecules responsible for the reduction and stabilization of the NPs. HR–TEM revealed that the Er-AgNPs were spherical, with core sizes ranging from 6 to 18 nm. The Er leaf aqueous extract and Er-AgNPs possessed antioxidant activities, with the Er leaf extract having higher activity than Er-AgNPs. The Er leaf extract did not exhibit any antimicrobial activity, whereas the Er-AgNPs demonstrated broad-spectrum antimicrobial activities against all the tested pathogens. This study provides a sustainable, easy and cost-effective method to produce AgNPs for biomedical applications.
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    Potential matrix metalloproteinase 2 and 9 inhibitors identified from Ehretia species for the treatment of chronic wounds - Computational drug discovery
    (Elsevier Ltd, 2025) Oselusi, Samson; Martin, Darius; Meyer, Mervin; Madiehe, Abram; Sibuyi, Nicole
    Matrix metalloproteinases (MMPs) serve as prognostic factors in several pathophysiological conditions, including chronic wounds. Therefore, they are considered important therapeutic targets in the intervention and treatment of these conditions. In this study, computational tools such as molecular docking and molecular dynamics simulations were used to gain insight into protein‒ligand interactions and determine the free binding energy between Ehretia species phytoconstituents and gelatinases (MMP2 and MMP9). A total of 74 phytoconstituents from Ehretia species were compiled from the literature, and 46 of these compounds were identified as potential inhibitors of at least one type of MMP. Molecular docking revealed that lithospermic acid B, rosmarinic acid, and danshensu had stronger binding affinities against the two enzymes than the reference ligands. Furthermore, (9S, 10E, 12Z, 15Z)-9-hydroxy-10,12,15-octadecatrienoic (∗-octadecatrienoic) had a higher binding energy for MMP2, whereas caffeic anhydride and caffeic acid established stronger binding energy with MMP9 than the reference ligand. These complexes also demonstrated relatively stable, favourable, and comparable conformational changes with those of unbound proteins at 500 ns. The free energy decomposition results further provide detailed insights into the contributions of active site residues and different types of interactions to the overall binding free energy. Finally, most of the hit phytoconstituents (rosmarinic acid, caffeic anhydride, caffeic acid, and danshensu) had good physicochemical, drug-likeness, and pharmacokinetic properties. Collectively, our findings showed that phytoconstituents from Ehretia species could be beneficial in the search for novel MMP inhibitors as therapeutic agents for the treatment of chronic wounds.