ABSTRACT
BACKGROUND: Artemisia sieberi (mugwort) is a member of the daisy family Asteraceae and is widely propagated in Saudi Arabia. A. sieberi has historical medical importance in traditional societies. The current study aimed to assess the antibacterial and antifungal characteristics of the aqueous and ethanolic extracts of A. sieberi. In addition, the study investigated the effect of silver nanoparticles (AgNPs) synthesized from the A. sieberi extract. METHODS: The ethanolic and aqueous extracts and AgNPs were prepared from the shoots of A. sieberi. The characteristics of AgNPs were assessed by UV-visible spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and dynamic light scattering (DLS). The antibacterial experiments were performed against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. The fungal species used were Candida parapsilosis, Candida krusei, Candida famata, Candida rhodotorula, and Candida albicans. The antibacterial and antifungal characteristics were evaluated by measuring the diameter of growing organisms in Petri dishes treated with different concentrations of either extracts or AgNPs compared to the untreated controls. Furthermore, TEM imaging was used to investigate any ultrastructure changes in the microbes treated with crude extracts and AgNO3. RESULTS: The ethanolic and aqueous extracts significantly decreased the growth of E. coli, S. aureus, and B. subtilis (p < 0.001), while P. aeruginosa was not affected. Unlike crude extracts, AgNPs had more substantial antibacterial effects against all species. In addition, the mycelial growth of C. famata was reduced by the treatment of both extracts. C. krusei mycelial growth was decreased by the aqueous extract, while the growth of C. parapsilosis was affected by the ethanolic extract and AgNPs (p < 0.001). None of the treatments affected the growth of C. albicans or C. rhodotorula. TEM analysis showed cellular ultrastructure changes in the treated S. aureus and C. famata compared to the control. CONCLUSION: The biosynthesized AgNPs and extracts of A. sieberi have a potential antimicrobial characteristic against pathogenic bacterial and fungal strains and nullified resistance behavior.
ABSTRACT
The widespread use of chemical control agents and pesticides for plant-pathogen control has caused many human health and environmental issues. Plant extracts and biocontrol agents have robust antimicrobial activity against different plant pathogens. However, their antiviral activities are still being investigated. In the present study, the methanol extract of Paronychia argentea was characterized and evaluated for its protective activity against the tobacco mosaic virus (TMV) infection in tomato plants under greenhouse conditions at 21 days post-inoculation. The results showed that the foliar application of P. argentea extract (10 µg/mL) enhanced tomato plant growth, resulting in significant increases in shoot and root parameters and total chlorophyll contents. Moreover, a significant reduction in TMV accumulation level in P. argentea-treated plants of 77.88% compared to non-treated plants was reported. Furthermore, induction of systemic resistance with significant elevation in production of antioxidant enzymes (PPO, CAT, and SOD) and transcriptional levels of the pathogenesis-related proteins (PR-1 and PR-7) and polyphenolic genes (CHS and HQT) were also observed. Out of 16 detected compounds, HPLC analysis revealed that the most abundant polyphenolic compounds found in P. argentea extract were gallic acid (5.36 µg/mL), kaempferol (7.39 µg/mL), quercetin (7.44 µg/mL), ellagic acid (7.89 µg/mL), myricetin (8.36 µg/mL), and ferulic acid (8.69 µg/mL). The findings suggest that the use of P. argentea extract as an effective and safe source for the production of bioactive compounds may offer a solution for a promising approach for the management of plant viral infections. To the best of our knowledge, this is the first report of the protective activity of P. argentea extract against plant viral diseases.