Antimicrobial, antiviral and antioxidant activities of “água-mel” from Portugal

Evaluation of Gold Complexes to Address Bacterial Resistance, Quorum Sensing, Biofilm Formation, and Their Antiviral Properties against Bacteriophages

The worldwide increase in antibiotic resistance poses a significant challenge, and researchers are diligently seeking new drugs to combat infections and prevent bacterial pathogens from developing resistance. Gold (I and III) complexes are suitable for this purpose. In this study, we tested four gold (I and III) complexes, (1) chlorotrimethylphosphine gold(I); (2) chlorotriphenylphosphine gold(I); (3) dichloro(2-pyridinecarboxylate) gold (III); and (4) 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene gold(I) chloride, for their antibacterial, antibiofilm, antiviral, and anti-quorum sensing activities. Results reveal that 1 significantly inhibits Escherichia coli DSM 1077 and Staphylococcus aureus ATCC 6538, while 2, 3, and 4 only inhibit S. aureus ATCC 6538. The minimum inhibitory concentration (MIC) of 1 for S. aureus ATCC 6538 is 0.59 μg/mL (1.91 μM), and for methicillin-resistant S. aureus strains MRSA 12 and MRSA 15, it is 1.16 μg/mL (3.75 μM). For E. coli DSM 1077 (Gram-negative), the MIC is 4.63 μg/mL (15 μM), and for multi-resistant E. coli I731940778-1, it is 9.25 μg/mL (30 μM). Complex 1 also disrupts biofilm formation in E. coli and S. aureus after 6 h or 24 h exposure. Moreover, 1 and 2 inhibit the replication of two enterobacteria phages. Anti-quorum sensing potential still requires further clarification. These findings highlight the potential of gold complexes as effective agents to combat bacterial and viral infections.

The Preyssler-Type Polyoxotungstate Exhibits Anti-Quorum Sensing, Antibiofilm, and Antiviral Activities

The increase in bacterial resistance to antibiotics has led researchers to find new compounds or find combinations between different compounds with potential antibacterial action and with the ability to prevent the development of antibiotic resistance. Polyoxotungstates (POTs) are inorganic clusters that may fulfill that need, either individually or in combination with antibiotics. Herein, we report the ability of the polyoxotungstates (POTs) with Wells-Dawson P2W18, P2W17, P2W15, and Preyssler P5W30 type structures to differently affect Gram-negative and Gram-positive microorganisms, either susceptible or resistant to antibiotics. The compound P5W30 showed the highest activity against the majority of the tested bacterial strains in comparison with the other tested POTs (P2W15, P2W17 and P2W18) that did not show inhibition zones for the Gram-negative bacteria, A. baumanii I73775, E. coli DSM 1077, E. coli I73194, K. pneumoniae I7092374, and P. aeruginosa C46281). Generally, the results evidenced that Gram-positive bacteria are more susceptible to the POTs tested. The compound P5W30 was the one most active against S. aureus ATCC 6538 and MRSA16, reaching <0.83 mg·mL−1 (100 μM) and 4.96 mg·mL−1 (600 μM), respectively. Moreover, it was verified by NMR spectroscopy that the most promising POT, P5W30, remains intact under all the experimental conditions, after 24 h at 37 °C. This prompted us to further evaluate the anti-quorum sensing activity of P5W30 using the biosensor Chromobacterium violaceum CV026, as well as its antibiofilm activity both individually and in combination with the antibiotic cefoxitin against the methicillin-resistant Staphylococcus aureus 16 (MRSA16). P5W30 showed a synergistic antibacterial effect with the antibiotic cefoxitin and chloramphenicol against MRSA16. Moreover, the antibiofilm activity of P5W30 was more pronounced when used individually, in comparison with the combination with the antibiotic cefoxitin. Finally, the antiviral activity of P5W30 was tested using the coliphage Qβ, showing a dose-dependent response. The maximum inactivation was observed at 750 μM (6.23 mg·mL−1). In sum, P5W30 shows anti-quorum sensing and antibiofilm activities besides being a potent antibacterial agent against S. aureus and to exhibit antiviral activities against enteric viruses.

Phenolic compounds of Phellinus spp. with antibacterial and antiviral activities

Phellinus Quél is one of the largest genera of Hymenochaetaceae; it comprises about 220 species widely distributed on Earth. Most Phellinus species are lignicolous mushrooms that accumulate bioactive compounds. This research studied the phenolic composition of Phellinus spp. and their relationship with antibacterial and antiviral capacity. Phenolics were extracted from Phellinus badius, P. fastuosus, and P. grenadensis; their antiviral and antibacterial activities were evaluated against Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica, and Escherichia coli O157: H7; and the bacteriophages MS2 and Φ- × 174. Gallic acid, chlorogenic acid, caffeic acid, epicatechin, ferulic acid, catechin, 1,3-dicaffeoylquinic acid, p-coumaric acid, and rutin were found in different proportions among Phellinus spp. Total phenolic content ranged from 96 to 209 mg GAE/g, and total flavonoids from 10 to 27 QE/g. The minimum inhibitory concentrations of P. badius, P. grenadensis, and P. fastuosus against E. coli O157: H7 were 13, 20, and 27 mg/mL, against S. enterica were 20, 30, and 15 mg/mL, and against L. monocytogenes were 10, 15, and 25 mg/mL, respectively. The phenolic content was better correlated with the antibacterial effect against E. coli O157: H7 and L. monocytogenes (r = 0.8-0.9), but not against S. enterica (r = 0.05). The antiviral activity of the extracts (0.9 mg/mL) was 29 to 41% against MS2 and 27 to 38% for Φ-X174 virus (r = 0.8-0.9). In silico analysis showed binding energy values of - 7.9 and - 4.8 kcal/mol between the identified phenolic compounds and the M and G proteins of each virus. The antibacterial and antiviral properties of Phellinus species were correlated with the phenolic content.

Antiviral effects of Brazilian green and red propolis extracts on Enterovirus surrogates

Propolis is a natural product of bees with biological activities that are mainly associated with bee type and geographic origin. Propolis extract has been proposed with several applications in environmental health. The ethanol extracts have shown good antimicrobial activity. The association of this technique with ultrasound-assisted extraction has been studied to improve the characteristics of the obtained extracts. Thus, the objective of this work is to verify the antiviral action against two strains of bacteriophages of two extracts of Brazilian propolis (green and red) obtained by conventional extraction and ultrasonic extraction. The activities of the propolis red and green extracts were confirmed by the significant ~3 and ~4.5 Log 10 PFU/mL reduction in the concentrations of the MS2 and Av-08 bacteriophages, respectively. It was found that ultrasound-assisted extraction is comparable to the maceration process and demonstrated the best antiviral activities. Brazilian red propolis was more effective than green propolis in viral reduction in all treatments.

Factors determining phage stability/activity: challenges in practical phage application

Introduction: Phages consist of nucleic acids and proteins that may lose their activity under different physico-chemical conditions. The production process of phage formulations may decrease phage infectivity. Ingredients present in the preparation may influence phage particles, although preparation and storage conditions may also cause variations in phage titer. Significant factors are the manner of phage application, the patient's immune system status, the type of medication being taken, and diet. Areas covered: We discuss factors determining phage activity and stability, which is relevant for the preparation and application of phage formulations with the highest therapeutic efficacy. Our article should be helpful for more insightful implementation of clinical trials, which could pave the way for successful phage therapy. Expert opinion: The number of naturally occurring phages is practically unlimited and phages vary in their susceptibility to external factors. Modern methods offer engineering techniques which should lead to enhanced precision in phage delivery and anti-bacterial activity. Recent data suggesting that phages may also be used in treating nonbacterial infections as well as anti-inflammatory and immunomodulatory agents add further weight to such studies. It may be anticipated that different phage activities could have varying susceptibility to factors determining their actions.

Bioactive Constituents and Antioxidant Activity of Some Carpathian Basin Honeys

Unifloral honeys have a high commercial value and should undergo a strict quality control before marketing. This study aimed at determining floral origin, polyphenolic compounds and antioxidant activity in 7 samples marketed as lavender and thyme honeys. The samples were subjected to pollen analysis to confirm their botanical origin. Coupled chromatographic techniques (HPLC-DAD-ESI-MS) were optimized for the separation and identification of polyphenolic compounds. The antioxidant properties of the samples were determined by spectrophotometric methods. Pollen profile analysis revealed that only 3 out of 5 alleged lavender honeys contained a low percentage (0.6-1.5) of lavender pollen; and there were only traces (0.1–0.6%) of thyme pollen in the alleged thyme honeys. Polyphenolic constituents did not allow for the clear separation of honey samples, revealing no marker compounds previously associated with lavender and thyme honeys. All samples contained large amounts of chlorogenic acid, chrysin, hesperetin, kaempferol and p-coumaric acid; as well as abscisic acid, a plant hormone known to be present in floral nectar and honey. Our results suggest that only one of five alleged lavender honeys and neither of the two alleged thyme honeys are true unifloral honeys. However, they can still provide various health benefits, such as being good sources of antioxidants. There was no relationship between the antioxidant activity and the uni- or multifloral character of the honey samples. Total phenolic content and antioxidant activity was the lowest in the honey sample with lavender and the highest in one of the alleged lavender honeys. Our findings highlight the importance of microscopical and phytochemical analyses of honeys before marketing, to ensure satisfactory quality for customers.