Abstract
Plant extracts serve as reducing and coating agents and are, therefore, commonly employed for the generation of silver (Ag) nanoparticles (NPs). Plant extract mediated synthesis of Ag NPs is a green, environmentally friendly and cost-effective technique which offers a new and potential alternative to chemically synthesized NPs, decreasing the utilization of hazardous and toxic chemicals and protecting the environment. Origanum vulgare L. extracts were evaluated for total flavonoid and phenol content. The free radical scavenging activity was determined employing 2,2-diphenyl-1-picrylhydrazyl assay. Ag NPs were produced exploiting ethanolic extracts of O. vulgare L. leaves. The generation of Ag NPs was carried out both in light and dark conditions. The biosynthesized Ag NPs were characterized employing microscopic and spectroscopic techniques. Antibacterial activities of Ag NPs were determined following appropriate methods. The results revealed that energy of photons was required to reduce Ag+ to Ag0. According to scanning electron microscopy reports, biologically formed Ag NPs ranged in size from 1 to 50 nmand were presented instability causing aggregation. They indicated that O. vulgare L. extracts were rich in flavonoids and phenols and exhibited strong antioxidant activity. Ag NPs exhibited good antibacterial activity immediately after production. Gram-positive strains showed higher sensitivity to Ag NPs compared to Gram-negative stains. Ag NPs can serve as an effective antibacterial agent against antibiotic-resistant strains. The kanamycin-resistant strain was more sensitive to Ag NPs than the ampicillin-resistant strain. Thus, Origanum extract-mediated synthesized Ag NPs can be recommended as alternative effective antibacterial agents, but their activity depended on bacterial species and strains.
Highlights
The emergence of resistance to currently available antibiotics is a huge challenge faced by the humanity
The total content of flavonoids in different O. vulgare extracts was determined from the calibration curve of Q (y = 2.3083x + 0.0369, R2 = 0.9947)
The highest amount of flavonoid was observed in the sample collected from Tavush region (69.65 ± 1.09 mg (QE) g−1) followed by the sample collected from Gegharkunik region (53.54 ± 0.75 mg (QE) g −1)
Summary
The emergence of resistance to currently available antibiotics is a huge challenge faced by the humanity. According to estimates by the European Center for Disease Prevention and Control, 25,000 people die in Europe from drug-resistant bacterial infections every year. The most recent pandemic Covid-19 situation which has affected more than twenty million people across the globe until now is the latest example which highlights the need to develop cure against these species. The emergence of resistance has, provoked the need to Hambardzumyan et al AMB Expr (2020) 10:162 develop alternative agents against the pathogenic bacterial strains (Trchounian et al 2018; Kraemer et al 2019). The utilization of Ag nanoparticles (NPs) for medical purposes has attracted great attention of researchers because of their exceptional antimicrobial activities especially against a wide range of pathogenic microorganisms (Srirangam and Rao 2017; Trchounian et al 2018)
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