In-Vitro Evaluation of Antimicrobial Activity of Silver Nanoparticles of Plectranthus neochilus Leaf Extract

Abstract

Abstract

Infectious diseases have continued to be problematic due to globalization, an increasing number of patients affected,

increasing cost of treating bacterial infections, adverse and side effects associated with antibacterial drugs, as well as

resistance associated with antibacterial drugs. The study is aimed at assessing the antimicrobial activity of silver

nanoparticles (AgNPs) synthesized using the aqueous extract of Plectranthus neochilus Schltr leaf. Silver nanoparticles

were synthesized by mixing the aqueous extract prepared from leaves of P. neochilus and 1mM silver nitrate solution under

controlled conditions. The silver nanoparticles were then analyzed through spectroscopic methods (Fourier transform

infrared (FTIR) and Ultraviolet (UV)-visible spectroscopy) as well as physical characterization (particle size distribution)

and antimicrobial activity. Results from FTIR analysis showed that silver nanoparticles of P. neochilus leaf contain

flavonoids. In the UV analysis, absorbance spectra of the AgNPs of P. neochilus leaf extract indicated higher peaks at longer

time intervals. Particle size distribution analysis of the AgNPs of P. neochilusleaf extract had a good size distribution ranging

from 13.88 - 82.37nm. The antimicrobial assay showed minimum inhibitory concentrations of Staphylococcus aureus and

Escherichia coli being 10 and 9µg/mL, respectively, and the highest zones of inhibition for the AgNPs at the concentrations

of 50 and 100 µg ranged from 6 to 8 mm. There were higher zone diameters with the gram-positive organisms (S. aureus, 8

mm; B. subtilis, 7mm) relative to the gram-negative organisms (P. aeruginosa, 7 mm; E. coli, 7 mm). AgNPs synthesized

from P. neochilus leaf extract were stable with good size distribution, thereby increasing the bioavailability of the particle,

and may be useful in the treatment of gram-negative and gram-positive organisms as well as fungal organisms.