Browsing by Author "Madiehe, Abram M"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Antioxidant and antimicrobial activities of green-synthesized silver nanoparticles using a cocktaila aqueous extract of capparis sepiaria root and tabernaemontana elegans bark
    (Wiley, 2025) Mashilo, Cate M.; Sibuyi Nicole RS; Botha, Subelia; Meyer, Mervin; Madiehe, Abram M
    The increasing incidence of antimicrobial resistance (AMR) poses a serious threat to public health, which necessitates the development of alternative countermeasures to combat it. Green nanotechnology, in particular the use of silver nanoparticles (AgNPs), shows promise in combating AMR. Although the synthesis of AgNPs using medicinal plant extracts has been explored, combining extracts from two medicinal plants to synthesize AgNPs with enhanced properties has received less attention. Therefore, this study addresses this gap by presenting the green synthesis of AgNPs using a cocktail of Capparis sepiaria–Tabernaemontana elegans (CsTe) aqueous extract as reducing, stabilizing, and capping agents. The focus is on assessing the antioxidant and antimicrobial activities of the synthesized CsTe-AgNPs. Various parameters, such as pH, temperature, extract and silver concentrations, reaction ratio, and synthesis time, were optimized to enhance the efficiency of CsTe-AgNPs synthesis. The CsTe- AgNPs were monodispersed and spherical, with an average core size of 14 ± 2.953 and 7 ± 3.849 nm, and hydrodynamic size of 23 ± 12.260 and 138 ± 2.086 nm for pH = 6 and pH = 11, respectively. The FTIR analysis revealed a shift in peaks of biomolecules present in the CsTe extracts that could be responsible for the reduction of Ag salt to form CsTe-AgNPs. Notably, CsTe-AgNPs_pH11 had potent antimicrobial activity, with a minimum inhibitory concentration (MIC) of 12.5 ± 0 μg/mL against K. pneumoniae and P. aeruginosa, and a slightly higher MIC for C. albicans of 25 ± 5.449 μg/mL. This study demonstrated the effectiveness of using a mixture of two extracts to synthesize AgNPs with enhanced antioxidant and antimicrobial activities, and therefore, could serve as a promising reagent to combat AMR.
  • Thumbnail Image
    Item
    Catalytic reduction of 4-nitrophenol and methylene blue by biogenic gold nanoparticles synthesized using Carpobrotus edulis fruit (sour fig) extract
    (SAGE Publications, 2022) Madiehe, Abram M; Moabelo, Koena L; Modise, Keletso
    Along with the increasing requirement for efficient organic conversions using green chemistry, there is a need to develop highly efficient and eco-friendly catalytic reaction systems. Gold nanoparticles (AuNPs)-based nanocatalysts are promising candidates for the reduction of environmental pollutants, such as nitroaromatics and dyes. This study reports on the green synthesis of AuNPs using Carpobrotus edulis (C. edulis) fruit aqueous extract (CeFE) and their catalytic activities. The CeFE induced rapid reduction of gold (III) salt to form monodispersed and spherical AuNPs, with a core and hydrodynamic sizes of 40 and 108.7 nm, respectively. CeFE alone had no effect on 4-nitrophenol, whereas incubation with methylene blue (MB) caused reduction of the peak at 665 nm. Addition of CeFE-AuNPs in the presence of NaBH4, caused the reduction of 4-nitrophenol to 4-AP, and MB to leucoMB within 10 min. These reactions followed the pseudo first-order kinetics. Therefore, biogenic CeFE-AuNPs could be used for the elimination of noxious environmental pollutants.