RESUMO
Antibiotic resistance is an important and emerging alarm for public health that requires development of new potential antibacterial strategies. In recent years, nanoscale materials have emerged as an alternative way to fight pathogens. Many researchers have shown great interest in nanoparticles (NPs) using noble metals, such as silver, gold, and platinum, even though numerous nanomaterials have shown toxicity. To overcome the problem of toxicity, nanotechnology merged with green chemistry to synthesize nature-friendly nanoparticles from plants. Here, we describe the synthesis of NPs using silver (AgNPs) and platinum (PtNPs) alone or in combination (AgPtNPs) in the presence of Ocimum basilicum (O. basilicum) leaf extract. O. basilicum is a well-known medicinal plant with antibacterial compounds. A preliminary chemical-physical characterization of the extract was conducted. The size, shape and elemental analysis were carried out using UV-Visible spectroscopy, dynamic light scattering (DLS), and zeta potential. Transmission electron microscopy (TEM) confirmed polydisperse NPs with spherical shape. The size of the particles was approximately 59 nm, confirmed by DLS analysis, and the polydisperse index was 0.159. Fourier transform infrared (FTIR) demonstrated an effective and selective capping of the phytoconstituents on the NPs. The cytotoxic activities of AgNPs, PtNPs and AgPtNPs were assessed on different epithelial cell models, using the 3-[4.5-dimethylthiazol-2-yl]-2.5-diphenyltetrazolium bromide (MTT) cell proliferation assay, and discovered low toxicity, with a cell viability of 80%. The antibacterial potential of the NPs was evaluated against Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis), Klebsiella pneumonia (K. pneumoniae), and Staphylococcus aureus (S. aureus) strains. Minimum inhibitory concentration (MIC) assays showed AgPtNP activity till the least concentration of NPs (3.15-1.56 µg/mL) against ATCC, MS, and MDR E. coli, E. faecalis, and S. aureus and the Kirby-Bauer method showed that AgPtNPs gave a zone of inhibition for Gram-positive and Gram-negative bacteria in a range of 9-25 mm. In addition, we obtained AgPtNP synergistic activity in combination with vancomycin or ampicillin antibiotics. Taken together, these results indicate that bimetallic nanoparticles, synthesized from O. basilicum leaf extract, could represent a natural, ecofriendly, cheap, and safe method to produce alternative antibacterial strategies with low cytotoxicity.
RESUMO
Ficus rubiginosa plant extract showed antimicrobial activity, but no evidence concerning its antiviral properties was reported. The antiviral activity of the methanolic extract (MeOH) and its n-hexane (H) and ethyl acetate (EA) fractions against Herpes simplex virus-1 (HSV-1), Human coronavirus (HCoV) -229E, and Poliovirus-1 (PV-1) was investigated in the different phases of viral infection in the VERO CCL-81 cell line. To confirm the antiviral efficacy, a qPCR was conducted. The recorded cytotoxic concentration 50% was 513.1, 298.6, and 56.45 µg/mL for MeOH, H, and EA, respectively, assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay after 72 h of treatment. The Ficus rubiginosa leaf extract inhibited the replication of HSV-1 in the early stages of infection, showing a complete inhibition up to 0.62, 0.31, and 1.25 µg/mL. Against HCoV-229E, a total inhibition up to 1.25 µg/mL for MeOH and H as well as 5 µg/mL for EA was observed. Otherwise, no activity was recorded against PV-1. The leaf extract could act directly on the viral envelope, destructuring the lipid membrane and/or directly blocking the enriched proteins on the viral surface. The verified gene inhibition suggested that the treatments with M, H, and EA impaired HSV-1 and HCoV-229E replication, with a greater antiviral efficiency against HSV-1 compared to HCoV-229E, possibly due to a greater affinity of Ficus rubiginosa towards membrane glycoproteins and/or the different lipid envelopes.