Use of A Hydroalcoholic Extract of Moringa oleifera Leaves for the Green Synthesis of Bismuth Nanoparticles and Evaluation of Their Anti-Microbial and Antioxidant Activities

Abstract

The employment of plant extracts in the synthesis of metal nanoparticles is a very attractive approach in the field of green synthesis. To benefit from the potential synergy between the biological activities of the <i>Moringa oleifera</i> and metallic bismuth, our study aimed to achieve a green synthesis of phytochemical encapsulated bismuth nanoparticles using a hydroalcoholic extract of <i>M. oleifera</i> leaves. The total phenolic content in the <i>M. oleifera</i> leaves extract used was 23.0 ± 0.3 mg gallic acid equivalent/g of dried <i>M. oleifera</i> leaves powder. The physical properties of the synthesized bismuth nanoparticles were characterized using UV-Vis spectrophotometer, FT-IR spectrometer, TEM, SEM, and XRD. The size of the synthesized bismuth nanoparticles is in the range of 40.4-57.8 nm with amorphous morphology. Using DPPH and phosphomolybdate assays, our findings revealed that the <i>M. oleifera</i> leaves extract and the synthesized bismuth nanoparticles possess antioxidant properties. Using resazurin microtiter assay, we also demonstrate that the <i>M. oleifera</i> leaves extract and the synthesized bismuth nanoparticles exert potent anti-bacterial activity against <i>Escherichia coli</i>, <i>Klebsiella pneumoniae</i>, <i>Staphylococcus aureus</i>, and <i>Enterococcus faecalis</i> (estimated MIC values for the extract: 500, 250, 250, and 250 µg/mL; estimated MIC values for the bismuth nanoparticles: 500, 500, 500, and 250 µg/mL, respectively). Similarly, the <i>M. oleifera</i> leaves extract and the synthesized bismuth nanoparticles display relatively stronger anti-fungal activity against <i>Aspergillus niger</i>, <i>Aspergillus flavus</i>, <i>Candida albicans</i>, and <i>Candida glabrata</i> (estimated MIC values for the extract: 62.5, 62.5, 125, and 250 µg/mL; estimated MIC values for the bismuth nanoparticles: 250, 250, 62.5, and 62.5 µg/mL, respectively). Thus, green synthesis of bismuth nanoparticles using <i>M. oleifera</i> leaves extract was successful, showing a positive antioxidant, anti-bacterial, and anti-fungal activity. Therefore, the synthesized bismuth nanoparticles can potentially be employed in the alleviation of symptoms associated with oxidative stress and in the topic treatment of Candida infections.