Green synthesis of silver nanoparticles utilizing Gardenia latifolia extract, characterization, and in vitro antibacterial activity

Abstract

Biogenic silver nanoparticle (AgNPs) formulations were synthesized using alcoholic extract from the bark of Gardenia latifolia Ait. as a reducing agent and a capping ligand for the silver ions present in an aqueous silver nitrate solution. The synthesis of AgNPs was noted by color, the presence of notable peaks in Fourier-transformed infrared spectra (FT-IR), and RAMAN spectra. High-resolution transmission electron microscopy (HRTEM) analyses of all the AgNP formulations confirmed the crystalline and spherical characteristics along with smooth surface that was further supported by low particle size (Zavg, <50 nm), low polydispersity index (PDI), and negative Zeta potential. The crude extract and its various fractions did not show significant activity against Staphylococcus aureus MTCC-96 and the Methicillin-resistant S. aureus (MRSA) clinical isolate, yet in a combinatorial study, a concentration of 10 µg/mL, they reduced the MIC of ethidium bromide (EtBr) to half against the MRSA clinical isolate, supporting the drug resistance reversal property of G. latifolia extracts and fractions. The in vitro evaluations of AgNP formulations against MRSA, Staphylococcus epidermidis, Escherichia coli, and Klebsiella pneumoniae revealed MIC ranging from 30.00 to 2.81 µg/mL. Among all, AgNP-F3 may find its use in the development of cost-effective broad-spectrum antibacterial medications.