Biology subjects

Ntoumba, A. A.

Publications and source records attributed to Ntoumba, A. A..

3 recordsLinked to original sources

bioRxiv2024

Phytoassisted synthesis of biogenic silver nanoparticles using Vernonia amygdalina leaf extract: characterization, antibacterial, anti-inflammatory, and acute toxicity profile

Increasing antimicrobial resistance and pathological consequences from long-term anti-inflammatory drug use necessitate the urgent discovery and rational design of new, effective antimicrobial and anti-inflammatory agents. This study reports the antibacterial, anti-inflammatory, and acute toxicity profile of Vernonia amygdalina leaf extract-mediated silver nanoparticles (VA-AgNPs). VA-AgNPs were synthesized by mixing Ag+ ions with an aqueous leaf extract from Vernonia amygdalina and characterized using UV-Visible (UV-Vis) spectroscopy, powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). Antibacterial activity against Escherichia coli strains, carrageenan-induced rat paw edema, and oral acute toxicity assays were performed. The change in color from light brown to dark brown indicated the formation of VA-AgNPs, which was further confirmed by the surface plasmon resonance peaks between 400 and 450 nm in the UV-Vis spectrum. Stability studies showed increased VA-AgNPs formation at basic pH and with higher reactant quantities. The X-ray pattern showed nanocrystalline particles of Ag and AgCl with mean sizes of 13 and 18 nm, respectively. The SEM images depict aggregates of spherical shapes. The synthesized VA-AgNPs inhibited Escherichia coli growth with a minimum inhibition concentration of 0.125 mg/mL and rat paw edema with a maximum inhibition percentage of 96% at a dose of 0.4 mg/kg body weight. Oral administration of VA-AgNPs was not associated with any toxicity, supporting their use in the development of new effective antibacterial and anti-inflammatory drugs.

pharmacology and toxicology↗

bioRxiv2024

Chitosan nanocapsules with Alstonia boonei extract modulate the immune system in Wistar rats

The development of biosynthetic methods for nanoparticles using plants presents an exciting opportunity to better utilize our rich and diverse medicinal flora. We are particularly interested in creating nanocapsules using Alstonia boonei, a Cameroonian plant known for its immunomodulatory properties. Chitosan nanocapsules were synthesized from the methanol/dichloromethane extract of the powdered stem bark of A. boonei after harvest and drying. The encapsulation of the secondary metabolites was achieved using the ionic gelation method, which involved the agitation of a chitosan solution, extract, and tripolyphosphate. Subsequently, the encapsulation efficiency was calculated. Infrared spectroscopy identified the various functional groups present in the nanocapsules. The acute toxicological profile of these chitosan nanocapsules at a limit dose of 2000 mg/kg, along with their immunomodulatory activities, was evaluated in Wistar rats. The immunomodulatory potential was assessed in dexamethasone-induced immunosuppressed rats by measuring total blood count, delayed-type hypersensitivity response, and hemagglutinating antibody titre between groups of animals after 14 days of treatment. The data collected on the synthesis and characterization confirmed the formation of nanocapsules. This was evidenced by infrared spectroscopy and an entrapment efficiency of 69%. Powder X-ray diffraction confirmed the presence of chitosan in the polymer material. SEM imaging further confirmed the formation of nanocapsules. The toxicological profile of these nanocapsules was found to be satisfactory. Administration of chitosan nanocapsules containing Al. boonei methanol/dichloromethane extracts at doses of 100 mg/kg, 200 mg/kg, and 500 mg/kg body weight significantly prevented dexamethasone-induced immunosuppression in rats. This was achieved by increasing the parameters of total blood count (hematocrit, mean corpuscular volume, platelets, lymphocytes, and granulocyte counts), hemagglutinating antibody titre values, and delayed type hypersensitivity response induced by chicken red blood cells. However, doses of 500 mg/kg of crude A. boonei extract and 500 mg/kg body weight of empty chitosan nanocapsules did not show this effect. The nanocapsules generated from the extracts of chitosan and A. boonei are responsible for immunostimulatory activity and possess therapeutic potentials for the prevention of depressed immune depressed conditions with satisfactory safety at acute dose.

pharmacology and toxicology↗

bioRxiv2024

Magnesium hydroxide nanoneedles derived from Anthocleista schweinfurthii Gilg (Loganiaceae) support mesenchymal stromal cell proliferation and wound healing

Multiple metallic nanoparticles are able to promote cellular and tissue health, but these nanoparticles can be difficult to synthesize and can also cause unintended side-effects. Here, we study the effects on wounds healing and bone reparation of Mg(OH)2 from Anthocleista schweinfurthii Gilg (Loganiaceae) leaves (AS), which are local to the Africa region and have been used in traditional medicine to treat injuries. Mg(OH)2 nanoneedles were synthesized from aqueous extracts of Anthocleista schweinfurthii Gilg (Loganiaceae) leaves (AS) and magnesium nitrate. The quick polydispersing and crystallized Mg(OH)2-metal interface was found to be covered in plant secondary metabolites. We call this compound Mg(OH)2-AS. Using an acute dermal toxicity experiment on animal model, we determined that Mg(OH)2-AS is safe for topical application. In vitro experiments suggest that Mg(OH)2-AS has anti-inflammatory potential, and in vivo wound healing assays in Wistar rats indicate that Mg(OH)2-AS can enhance wound healing. To investigate Mg(OH)2-AS effects on the cellular level, we used bone marrow mesenchymal stromal cells (BM-MSCs). In contrast to pure Mg(OH)2 or AS, cell viability and proliferation were not impaired by Mg(OH)2-AS. Cell morphology remained unchanged upon media supplementation with Mg(OH)2-AS. Preliminary results further indicate enhanced osteogenic differentiation of BM-MSCs in media supplied with ascorbic acid, {beta}-glycerophosphate and dexamethasone and addition of Mg(OH)2-AS. These findings motivate further research towards the inclusion of the material in implants for bone fracture healing.

pharmacology and toxicology↗