Enhanced Anti-Bacterial Activity Of Biogenic Silver Nanoparticles Synthesized From Terminalia mantaly Extracts

Michele Stella Majoumouo,1,2 Nicole Remaliah Samantha Sibuyi,2 Marius Belmondo Tincho,2 Michele Mbekou,1 Fabrice Fekam Boyom,1 Mervin Meyer2 1Antimicrobial & Biocontrol Agents Unit, Laboratory for Phytobiochemistry and Medicinal Plants Studies, Department of Biochemistry, University of Yaoundé 1, Yaoundé, Cameroon; 2Department of Science and Technology (DST)/Mintek Nanotechnology Innovation Centre, Biolabels Node, Department of Biotechnology, University of the Western Cape, Bellville, South AfricaCorrespondence: Mervin MeyerUniversity of the Western Cape, Department of Biotechnology, New Life Science Building, Robert Sobukwe Road, Bellville 7535, South AfricaTel +27 21 9592032Fax +27 21 9593505Email memeyer@uwc.ac.zaBackground: The global increase in outbreaks and mortality rates associated with multi-drug-resistant (MDR) bacteria is a major health concern and calls for alternative treatments. Natural-derived products have shown potential in combating the most dreadful diseases, and therefore serve as an effective source of bioactive compounds that can be used as anti-bacterial agents. These compounds are able to reduce metal ions and cap nanoparticles to form biogenic nanoparticles (NPs) with remarkable anti-bacterial activities. This study explores the use of Terminalia mantaly (TM) extracts for the synthesis of biogenic silver NPs (TM-AgNPs) and the evaluation of their antibacterial activity.Methods: TM-AgNPs were synthetized by the reduction of AgNO3 with aqueous and methanolic TM extracts. UV–visible (UV-vis) spectrophotometry, Dynamic Light Scattering (DLS), Transmission Electron Microscopy, and Fourier Transform Infrared (FTIR) analyses were used to characterise the TM-AgNPs. Anti-bacterial activity of the TM extracts and TM-AgNPs was evaluated against eight bacterial strains using the broth microdilution assay. The growth inhibitory kinetics of the bio-active TM-AgNPs was assessed on susceptible strains for a period of 8 hrs.Results: Polycrystalline biogenic AgNPs with anisotropic shapes and diameter range of 11 to 83 nm were synthesized from the TM extracts. The biogenic TM-AgNPs showed significant antibacterial activity compared to their respective extracts. The MIC values for TM-AgNPs and extracts were 3 and 125 μg/mL, respectively. Biogenic AgNPs synthesised from the aqueous TM leaf extract at 25°C (aTML-AgNPs-25°C) showed significant antibacterial activity against all the bacterial strains tested in this study. Their bactericidal effect was particularly higher against the Streptococcus pneumoniae and Haemophilus influenzae.Conclusion: This study demonstrated the ability of TM extracts to synthesize biogenic AgNPs. The NPs synthesized from the aqueous TM extracts demonstrated higher antibacterial activity against the tested microorganisms compared to the methanolic extracts. Studies are underway to identify the phytochemicals involved in NP synthesis and their mechanism of action.Keywords: antimicrobial resistance, green synthesis, nanotechnology, Terminalia mantaly, antibacterial activity