Influence of plant polyphenols and medicinal plant extracts on antibiotic susceptibility of Escherichia coli

Antimicrobial and Antioxidant Activity of Some Nitrogen-Containing Heterocycles and Their Acyclic Analogues

We investigated antimicrobial and antioxidant activity of nitrogen-containing heterocycles and their acyclic analogues, some of which can be considered as promising in terms of biological activity. Based on structure, 26 tested compounds were divided into 4 groups. In the test with 2,2-diphenyl-1-picrylhydrazyl (DPPH), the compounds of the group 2 had the highest radical-binding activity (RBA) (53-78%), while those of group 3 had the lowest values (1.5-5.2%). In oxygen radical absorbance capacity assay, all compounds from groups 1, 2 and 3 showed high RBA: 44-94% at 50 µM. The highest bacteriostatic activity against Escherichia coli was found for four compounds in group 2 (MIC = 0.25-1 mM) and low bacteriostatic activity for group 3 (MIC > 4 mM). Some relationships between the structure of compounds and the values of the MIC are revealed. It was also found that four substances from different groups had the ability to inhibit the formation of colonies in E. coli from 1.3 to 5.7 times. Four compounds reduced specific biofilm formation by 40-60%. The tested substances did not induce the expression of the sulA gene controlled by the SOS system, which indicates the lack of genotoxic activity. None of the tested compounds had pro-oxidant activity. This was shown by both the absence of production hydrogen peroxide in a bacteria-free medium and inability to induce expression of the katG gene encoding HPI catalase in growing E. coli. The data obtained could be useful in the development of new drugs.

Natural polyphenols for drug delivery and tissue engineering construction: A review

Polyphenols, natural compounds rich in phenolic structures, are gaining prominence due to their antioxidant, anti-inflammatory, antibacterial, and anticancer properties, making them valuable in biomedical applications. Through covalent and noncovalent interactions, polyphenols can bind to biomaterials, enhancing their performance and compensating for their shortcomings. Such polyphenol-based biomaterials not only increase the efficacy of polyphenols but also improve drug stability, control release kinetics, and boost the therapeutic effects of drugs. They offer the potential for targeted drug delivery, reducing off-target impacts and enhancing therapeutic outcomes. In tissue engineering, polyphenols promote cell adhesion, proliferation, and differentiation, thus aiding in the formation of functional tissues. Additionally, they offer excellent biocompatibility and mechanical strength, essential in designing scaffolds. This review explores the significant roles of polyphenols in tissue engineering and drug delivery, emphasizing their potential in advancing biomedical research and healthcare.

Unveiling the Phytochemical Profile and Biological Potential of Five Artemisia Species

The Artemisia L. genus comprises over 500 species with important medicinal and economic attributes. Our study aimed at providing a comprehensive metabolite profiling and bioactivity assessment of five Artemisia species collected from northeastern Romania (A. absinthium L., A. annua L., A. austriaca Jacq., A. pontica L. and A. vulgaris L.). Liquid chromatography–tandem high-resolution mass spectrometry (LC-HRMS/MS) analysis of methanol and chloroform extracts obtained from the roots and aerial parts of the plants led to the identification of 15 phenolic acids (mostly hydroxycinnamic acid derivatives), 26 flavonoids (poly-hydroxylated/poly-methoxylated flavone derivatives, present only in the aerial parts), 14 sesquiterpene lactones, 3 coumarins, 1 lignan and 7 fatty acids. Clustered image map (CIM) analysis of the phytochemical profiles revealed that A. annua was similar to A. absinthium and that A. pontica was similar to A. austriaca, whereas A. vulgaris represented a cluster of its own. Correlated with their total phenolic contents, the methanol extracts from both parts of the plants showed the highest antioxidant effects, as assessed by the DPPH and ABTS radical scavenging, CUPRAC, FRAP and total antioxidant capacity methods. Artemisia extracts proved to be promising sources of enzyme inhibitory agents, with the methanol aerial part extracts being the most active samples against acetylcholinesterase and glucosidase. All Artemisia samples displayed good antibacterial effects against Mycobacterium tuberculosis H37Ra, with MIC values of 64–256 mg/L. In conclusion, the investigated Artemisia species proved to be rich sources of bioactives endowed with antioxidant, enzyme inhibitory and anti-mycobacterial properties.

Absinthe against multi-drug resistant bacterial pathogens? A recent update on the antibacterial effects of Artemisia compounds

The widespread misuse of antibiotics leads to a rapid development of multi-drug resistant (MDR) bacterial pathogens all over the globe, resulting in serious difficulties when treating infectious diseases. Possible solutions are not limited to the development of novel synthetic antibiotics but extend to application of plant-derived products either alone or in combination with common antibiotics. The aim of this actual review was to survey the literature from the past 10 years regarding the antibacterial effects of distinct Artemisia species including Artemisia absinthiae constituting an integral component of the Absinthe drink. We further explored the synergistic antibacterial effects of the Artemisia plant products with established antibiotics. The survey portrays the Artemisia derived compounds as potent antibacterial agents that can even restore the efficacy of antibiotics against MDR bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) and MDR Escherichia coli. This, in turn, is presumably triggered in part by the interaction of the Artemisia ingredients with the efflux pumps of MDR bacteria. In conclusion, biologically active molecules in Artemisia plants enhance the antibiotic susceptibility of resistant bacteria, which provide promising future therapeutic strategies to combat MDR bacterial pathogens.

Effect of resveratrol and quercetin on the susceptibility of Escherichia coli to antibiotics

Activities of plant polyphenols (PPs), resveratrol and quercetin, alone or in combination with four conventional antibiotics against Escherichia coli have been investigated. In medium without antibiotics, both polyphenols caused a dose-dependent growth inhibition. However, pretreatment with resveratrol (40 and 100 μg ml^-1) and quercetin (40 μg ml^-1) reduced the bacteriostatic effect of kanamycin, streptomycin, cefotaxime and partially of ciprofloxacin. With few exceptions, both PPs also reduced the bactericidal effect of tested antibiotics. Paradoxically, low doses of PPs enhanced the bactericidal effect of kanamycin and partially ciprofloxacin. Compared to quercetin, resveratrol showed a weaker effect on the induction of antioxidant genes and the resistance of E. coli to the oxidative stress generated by hydrogen peroxide treatment. Both polyphenols at high doses reduced membrane potential. Altogether, these findings suggest that the decrease in the bactericidal effect of antibiotics by high doses of polyphenols is mostly due to bacteriostatic action of the latter. In the case of quercetin, the contribution of its antioxidant activity for antibiotic protection may be significant. There is a growing interest in the use of plant-derived compounds to enhance the toxicity of traditional antibiotics. This and other studies show that, under certain conditions, the use of polyphenols as adjuvants may not exert the expected therapeutic effect, but rather to decrease antimicrobial activity of antibiotics.

Anti-infective potential of a quorum modulatory polyherbal extract (panchvalkal) against certain pathogenic bacteria

Background

In view of the gravity of the problem of antimicrobial resistance among pathogenic bacteria against conventional bactericidal agents, investigation on alternative approaches to combat bacterial infections is warranted.

Objective

Current study aimed at investigating anti-infective potential of a polyherbal ayurvedic formulation namely panchvalkal against three different pathogenic bacteria.

Materials and methods

The panchvalkal formulation available as Pentaphyte P5® was tested for its possible in vitro quorum-modulatory potential against Chromobacterium violaceum, Serratia marcescens, and Staphylococcus aureus through broth dilution assay. Invivo efficacy was demonstrated employing Caenorhabditis elegans as the model host for test pathogens.

Results

This formulation was found to exert quorum-modulatory effect on C. violaceum, S. marcescens, and S. aureus at 250–750 μg/ml. Besides altering production of the quorum sensing-regulated pigments in these bacteria, the test formulation also had in vitro effect on antibiotic susceptibility, catalase activity and haemolytic potential of the pathogens. Invivo assay confirmed the protective effect of this panchvalkal formulation on C. elegans, when challenged with the pathogenic bacteria. Repeated exposure of S. aureus to panchvalkal did not induce resistance in this bacterium.

Conclusion

To the best of our awareness, this the first report on quorum-modulatory potential of panchvalkal formulation, validating the anti-infective potential and moderate prebiotic property of this polyherbal preparation.

Epilobium spp: Pharmacology and Phytochemistry

The Epilobium species and their extracts are very popular in folk medicine, for a wide range of applications. The purpose of this review is the analysis of the pharmacological properties of Epilobium spp, considering whether their effects (e.g., anti-inflammatory, antioxidant, antitumor, antimicrobial, analgesic, and antiandrogenic) could rationally justify the use of Epilobium as a treatment of numerous diseases. Even if numerous preclinical studies have been reported, randomized controlled clinical trials (for the evaluation of safety and efficacy), and eventually cost-effectiveness studies (to estimate the long-term cumulative costs), are still needed to confirm the usefulness of these medicinal plants in human diseases.

The effect of 20-hydroxyecdysone on the susceptibility of Escherichia coli to different antibiotics

AIMS

The aim of this study was to investigate the influence of 20-hydroxyecdysone (20E) on the susceptibility of growing Escherichia coli to antibiotics.

METHODS AND RESULTS

Susceptibility of E. coli to antibiotics in the presence of 20E was estimated by determination of the colony-forming ability and the specific growth rate. Pretreatment with 20E decreased the bactericidal effect of ciprofloxacin (0·3 and 3·0 μg ml^-1 ), streptomycin (10 and 40 μg ml^-1 ) and kanamycin (10 μg ml^-1 ) and increased the bactericidal action of 0·03 μg ml^-1 ciprofloxacin. To study the influence of 20E on gene expression, we used strains of E. coli carrying fusions of promoters of relevant genes with the structural gene of β-galactosidase. 20E had no marked effect on the expression of antioxidant genes katG, katE, sodA and the rpoS gene (general stress response), while it (alone or combined with ciprofloxacin) markedly stimulated expression of the sulA gene belonging to the SOS regulon (DNA damage response).

CONCLUSION

In growing E. coli, 20E modulated the bactericidal action of antibiotics and stimulated the SOS response.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results of this study may be used to enhance the efficiency of antibacterial therapies.

Ixodicide activity of Eysenhardtia polystachya against Rhipicephalus (Boophilus) microplus

The objective of this study was to evaluate the acaricidal effect of 2 compounds extracted from Eysenhardtia polystachya in vitro, namely coatlines and matlalines. Each extract was obtained by aqueous extraction in a nitrogen atmosphere. Engorged adult females of an amitraz-resistant strain of Rhipicephalus (Boophilus) microplus were used to produce larvae and to carry out the adult immersion test (AIT), while larvae were assayed using the larval packet test (LPT). After exposure to coatlines or matlalines, the mortality of larvae and engorged females, as well as the reproductive parameters of adult ticks were assessed. Coatlines were not lethal against larvae and did not decrease reproductive parameters. Conversely, matlalines showed a 90 to 100% efficacy against adults and larvae at all concentrations tested and a reduction of 76.41 to 80.64% oviposition and a 48.02 to 54.86% reduction in egg hatchability. Therefore, the acaricidal activity of matlalines was more efficient. Further studies are required to elucidate both the mode of action of matlalines as well the structure-activity relationships responsible for the observed differential efficacy between these 2 related isoflavans against the cattle tick.

Medicinal plant extracts can variously modify biofilm formation in Escherichia coli

Low concentrations of black tea and water extracts from medicinal plants Arctostaphylos uva-ursi, Vaccinium vitis-idaea, Tilia cordata, Betula pendula and Zea mays stimulated biofilm formation in Escherichia coli BW25113 up to three times. Similar effect was observed for tannic acid and low concentrations of quercetin. In contrast, the extract from Urtica dioica reduced biofilm production. Pretreatment with plant extracts variously modified antibiotic effects on specific biofilm formation (SBF). Extract from V. vitis-idaea increased SBF, while the extracts from Achillea millefolium, Laminaria japonica and U. dioica considerably decreased SBF in the presence of ciprofloxacin, streptomycin and cefotaxime. Stimulatory effect of the extracts and pure polyphenols on biofilm formation was probably related to their prooxidant properties. The rpoS deletion did not affect SBF significantly, but stimulation of biofilm formation by the compounds tested was accompanied by inhibition of rpoS expression, suggesting that a RpoS-independent signal transduction pathway was apparently used.

Salmonella enterica serovar Typhimurium BaeSR two-component system positively regulates sodA in response to ciprofloxacin

In response to antibiotics, bacteria activate regulatory systems that control the expression of genes that participate in detoxifying these compounds, like multidrug efflux systems. We previously demonstrated that the BaeSR two-component system from Salmonella enterica serovar Typhimurium (S. Typhimurium) participates in the detection of ciprofloxacin, a bactericidal antibiotic, and in the positive regulation of mdtA, an efflux pump implicated in antibiotic resistance. In the present work, we provide further evidence for a role of the S. Typhimurium BaeSR two-component system in response to ciprofloxacin treatment and show that it regulates sodA expression. We demonstrate that, in the absence of BaeSR, the transcript levels of sodA and the activity of its gene product are lower. Using electrophoretic mobility shift assays and transcriptional fusions, we demonstrate that BaeR regulates sodA by a direct interaction with the promoter region.

Medicinal plant extracts variously modulate susceptibility of Escherichia coli to different antibiotics

Antioxidant activity of green and black tea and extracts of medicinal plants and their ability to modulate antibiotic susceptibility in Escherichia coli were studied. Among a number of extracts tested the maximal capacity to scavenge DPPH radicals and chelate iron in chemical tests was found in green and black tea, Arctostaphylos uva-ursi and Vaccinium vitis-idaea. These extracts contained high level of polyphenols and in aerobic conditions exhibited prooxidant features, producing H2O2 and inducing expression of the katG gene encoding catalase HPI in E. coli cells. A good correlation between the polyphenol content and the ability of extracts to protect bacteria against peroxide stress was observed (r = 0.88). Polyphenol-rich extracts and iron chelators demonstrated the highest modulating effect on the antibiotic susceptibility by changing the time period before lysis started and by influencing the colony-forming ability of bacteria. The direction of the modulating effect was dependent on nature of antibiotic applied: under treatment with ciprofloxacin and ampicillin the extracts predominantly provided protective effects, while under treatment with kanamycin a bactericidal action was enhanced. Mechanism of modulating action of extracts on bacterial antibiotic susceptibility probably involves antioxidant, preferentially iron-chelating, or prooxidant properties of polyphenols.