Logeswari. N and Prabhakaran. S.G.*
Withania somnifera (L.) Dunal (Solanaceae), commonly known as ashwagandha or Indian ginseng is a valuable medicinal plant and it is very potent, far and wide used herb in Ayurveda and other traditional systems of medicine in India. The qualitative and quantitative analysis has shown that methanol, ethanol and isopropanol has rendered a good yield of secondary metabolites. The silver nanoparticles used in W. somnifera AgNPs were characterized using UV-VIS spectrophotometry has shown two characteristic absorbance peaks value at 261.46 nm and 451.67 nm. The W. somnifera AgNPs has been detected with considerable antibacterial effect in comparison with the crude extract. The scanning electron microscopic (SEM) analysis also reveals the influence of W. somnifera AgNPs over the inhibition of biofilm formation in test pathogen Pseudomonas. The present study shows that isopropanolic root extracts of Withania somnifera has exhibited a substantial inhibitory effect towards the test pathogens used which may be due to the high degree of alkaloids retained in the extract that possess the inhibitory effect and renders bioactivity towards the pathogen. The antibacterial activity of isopropanolic root extracts of W. somnifera against the pathogens like E.coli, Klebsiella, Staphylococcus and Pseudomonas was detected and compared along with the standard antibiotics like ciprofloxacin and kanamycin. The maximum zone of inhibition and the activity index were observed in isopropanol extract against Pseudomonas (0.792). The MIC and MBC of crude isopropanol root extract of W. somnifera was determined to be 25 mg/ml and 6.25 mg/ml respectively against Pseudomonas. Similarly, the MIC and MBC of W. somnifera AgNPs extract tested against Pseudomonas was 25 mg/ml and 12.5 mg/ml respectively. The silver nanoparticles acts as an effective carrier of active ingredients of W. somnifera extract into the cells of pathogens which has probably inhibited its growth and thereby rendering an antibacterial activity to the W. somnifera AgNPs as effective as the crude solvent extracts.
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