Synergistic activity of luteolin and amoxicillin combination against amoxicillin-resistant Escherichia coli and mode of action

Botanical Origin and Biological Properties of Honey and Propolis from Cuautitlan, State of Mexico, Mexico

Beekeeping is an activity that generates various products, mainly honey and propolis, with different biological activities that are studied extensively using various methodologies. The influence of various phenolic compounds, such as phenols and flavonoids, which are synthesized and concentrated differently in each product depending on the melliferous flora and sources of resources, on the manufacture of propolis or honey has been investigated. However, the analysis of these products has been performed separately and is outdated in time, and depending on the area and the flowering periods, different crops may be harvested. The analysis of the honey and propolis produced in Cuautitlan, State of Mexico, in the high plateau beekeeping zone, for a period of four years, both in the dry and rainy seasons, was proposed to determine the botanical origin of the honey and propolis. The primary pollen type in both honey and propolis was from Brassica rapa. Physicochemical tests were conducted, revealing higher concentrations of antimicrobial activity in the dry season than in the rainy season. Honey, propolis, and a vegetation extract showed activity against S. aureus, while only honey had an effect on E. coli in both seasons. For antifungal activity, only propolis collected in the rainy season had this activity. The biological properties of these products are closely related to the flora that varies both annually and between seasons, influencing the concentrations of phenolic compounds, as well as the biological activity of honey and propolis.

In silico analysis of luteolin derivatives as antibacterial agents targeting DNA gyrase and CTX-M-15 extended-spectrum β-lactamase of Escherichia coli

Luteolin exhibited antibacterial activity against Escherichia coli and its chemical structure similar to that of ciprofloxacin (CPF) which works by inhibiting DNA gyrase. Filtrate from passion fruit extract containing luteolin and its derivatives could inhibit extended-spectrum β-lactamase (ESBL)-producing E. coli. Antibacterial compounds that can also inhibit ESBL will be valuable compounds to overcome the problem of resistant bacteria. This study aimed to ensure the potency of luteolin and luteolin derivatives targeting DNA gyrase and ESBL by in silico approach. Docking simulation of ligands L1-L14 was performed using AutoDock Vina, and pharmacokinetics and toxicity (absorption, distribution, metabolism, excretion, and toxicity) profiles were predicted by pKCSM online. The docking result revealed higher binding affinity on DNA gyrase (PDB.1KZN) of 12 luteolin derivatives (energy <-7.6 kcal/mol) compared to CPF and higher affinity (energy <-6.27 kcal/mol) of all compounds than clavulanic acid against ESBL CTX-M-15 (PDB.4HBU). The compounds could be absorbed through the human intestine moderately, which showed low permeability to blood-brain barrier, nontoxic and nonhepatotoxic. The most active luteolin glycoside (L6) is capable to inhibit DNA gyrase and ESBL from E. coli which provided the potential against resistant bacteria and was promoted as lead compounds to be developed further.

Comparative HPLC–DAD–ESI-QTOF/MS/MS Analysis of Bioactive Phenolic Compounds Content in the Methanolic Extracts from Flowering Herbs of Monarda Species and Their Free Radical Scavenging and Antimicrobial Activities

Comparative analysis of flavonoids and phenolic acids composition, in plants of six species of Monarda from family Lamiaceae was carried out. The 70% (v/v) methanolic extracts of flowering herbs of Monarda citriodora Cerv. ex Lag., Monarda bradburiana L.C. Beck, Monarda didyma L., Monarda media Willd., Monarda fistulosa L. and Monarda punctata L. were analyzed for their polyphenol composition as well as antioxidant capacity and antimicrobial effect. Liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC–DAD–ESI-QTOF/MS/MS) was used to identify phenolic compounds. The in vitro antioxidant activity was assessed using a DPPH radical scavenging assay, while antimicrobial activity was measured by the broth microdilution method allowing for MIC (minimal inhibitory concentration) determination. The total polyphenol content (TPC) was assayed by the Folin–Ciocalteu method. The results showed the presence of eighteen different components including phenolic acids and flavonoids together with their derivatives. The presence of six constituents (gallic acid, hydroxybenzoic acid glucoside, ferulic acid, p-coumaric acid, luteolin-7-glucoside and apigenin-7-glucoside) was found to be dependent on the species. To differentiate the samples, the antioxidant activity of 70% (v/v) methanolic extracts was studied and expressed as a percent of DPPH radical inhibition and in EC50 values (mg/mL). The latter values were as follows: M. media (EC50 = 0.090 mg/mL), M. didyma (EC50 = 0.114 mg/mL), M. citriodora (EC50 = 0.139 mg/mL), M. bradburiana (EC50 = 0.141 mg/mL), M. punctata (EC50 = 0.150 mg/mL) and M. fistulosa (EC50 = 0.164 mg/mL). Moreover, all extracts indicated bactericidal activity against reference Gram-positive (MIC = 0.07–1.25 mg/mL) and Gram-negative bacteria (MIC = 0.63–10 mg/mL) as well as fungicidal effect towards yeasts (MIC = 1.25–10 mg/mL). Staphylococcus epidermidis and Micrococcus luteus were the most sensitive to them. All extracts showed promising antioxidant properties and noteworthy activity against the reference Gram-positive bacteria. Antimicrobial effect of the extracts against the reference Gram-negative bacteria as well as fungi (yeasts) from Candida spp. was slight. All extracts showed bactericidal and fungicidal effect. The obtained results indicated that the investigated extracts from Monarda spp. could be potential sources of natural antioxidants and antimicrobial agents, especially with activity towards Gram-positive bacteria. The differences in the composition and properties of the studied samples may influence the pharmacological effects of the studied species.

Characterization and Potentiating Effects of the Ethanolic Extracts of the Red Seaweed Gracillaria sp. on the Activity of Carbenicillin against Vibrios

β-lactam-resistant Vibrio strains are a significant clinical problem, and β-lactamase inhibitors are generally coadministered with β-lactam drugs to control drug-resistant bacteria. Seaweed is a rich source of natural bioactive compounds; however, their potential as β-lactamase inhibitors against bacterial pathogens remains unknown. Herein, we evaluated the potential β-lactamase inhibitory effect of the ethanolic extracts of the red seaweed Gracilaria sp. (GE) against four Vibrio strains. The minimum inhibitory concentration, half-maximal inhibitory concentration, checkerboard assay results, and time-kill study results indicate that GE has limited antibacterial activity but can potentiate the activity of the β-lactam antibiotic carbenicillin against Vibrio parahemolyticus and V. cholerae. We overexpressed and purified recombinant metallo-β-lactamase, VarG, from V. cholerae for in vitro studies and observed that adding GE reduced the carbenicillin and nitrocefin degradation by VarG by 20% and 60%, respectively. Angiotensin I-converting enzyme inhibition studies demonstrated that GE did not inhibit VarG via metal chelation. Toxicity assays indicated that GE exhibited mild toxicity against human cells. Through gas chromatography and mass spectrometry, we showed that GE comprises alkaloids, phenolic compounds, terpenoids, terpenes, and halogenated aromatic compounds. This study revealed that extracts of the red seaweed Gracillaria sp. can potentially inhibit β-lactamase activity.

In vitro and in silico analysis of Thymus serpyllum essential oil as bioactivity enhancer of antibacterial and antifungal agents

Wild thyme (Thymus serpyllum L.) of family Laminaceae is an unexplored perennial medicinal shrub. Aerial part of this plant is traditionally used for the treatment of respiratory and gastrointestinal problems. The current study was designed to evaluate the GC-MS, antimicrobial and synergistic potential of T. serpyllum essential oil (TEO). Chemical characterization of TEO showed the presence of thymol (15.79%), Phenol, 2-(1,1-dimethylethyl) (11.55%), o-Cymene (10.96%) as major phytocompounds. Antimicrobial activity of TEO in terms zone of inhibition (ZOI) varied from 13.66 ± 0.58 mm to 33.66 ± 1.52 mm, while, thymol (10%, v/v) showed ZOI ranged from 15.5 ± 0.5 mm to 26.33 ± 2.08 mm against tested bacterial and fungal species. MIC of TEO was 0.039% to 0.078% against tested bacterial and fungal species, whereas, thymol showed 1.25% to 2.5% MIC against tested bacterial and fungal species. Different combinations of TEO (2MIC to ½MIC) and thymol (2MIC to ½MIC) with antibacterial and antifungal antibiotics (2MIC to ½MIC) were found to increase the efficacy of antibiotics by 4-130 folds against bacterial and fungal pathogens. Molecular docking showed the good binding of thymol with both bacterial and fungal targets. Whereas MD simulation showed the stability of thymol complexed with target proteins over 100 ns time scale. Thymol also fulfills the Lipinski rule and showed characteristics similar to that of drugs. Therefore, it can be concluded from the present study that TEO and its major phytocompound, thymol can act as a bioactivity enhancer of antibacterial and antifungal antibiotics and could be used as a potential candidate to fight against antimicrobial drug resistance.Communicated by Ramaswamy H. Sarma.

Breaking down the cell wall: Still an attractive antibacterial strategy

Since the advent of penicillin, humans have known about and explored the phenomenon of bacterial inhibition via antibiotics. However, with changes in the global environment and the abuse of antibiotics, resistance mechanisms have been selected in bacteria, presenting huge threats and challenges to the global medical and health system. Thus, the study and development of new antimicrobials is of unprecedented urgency and difficulty. Bacteria surround themselves with a cell wall to maintain cell rigidity and protect against environmental insults. Humans have taken advantage of antibiotics to target the bacterial cell wall, yielding some of the most widely used antibiotics to date. The cell wall is essential for bacterial growth and virulence but is absent from humans, remaining a high-priority target for antibiotic screening throughout the antibiotic era. Here, we review the extensively studied targets, i.e., MurA, MurB, MurC, MurD, MurE, MurF, Alr, Ddl, MurI, MurG, lipid A, and BamA in the cell wall, starting from the very beginning to the latest developments to elucidate antimicrobial screening. Furthermore, recent advances, including MraY and MsbA in peptidoglycan and lipopolysaccharide, and tagO, LtaS, LspA, Lgt, Lnt, Tol-Pal, MntC, and OspA in teichoic acid and lipoprotein, have also been profoundly discussed. The review further highlights that the application of new methods such as macromolecular labeling, compound libraries construction, and structure-based drug design will inspire researchers to screen ideal antibiotics.

Fingolimod Promotes Antibacterial Effect of Doripenem against Carbapenem-Resistant Escherichia coli

The aim of this study was to determine whether fingolimod could synergize the antibacterial activity of doripenem against carbapenem-resistant Escherichia coli (CREC) and its potential as an antibiotic adjuvant for doripenem. The E. coli used in this study had the bla_KPC gene and became resistant to many classes of antibiotics, particularly carbapenems. The minimum inhibitory concentrations (MICs) of fingolimod and doripenem were determined. To investigate the synergistic action between fingolimod and doripenem, synergy checkerboard, growth curve, and time-kill analyses were performed. A motility test was also performed using a semi-solid medium to determine whether fingolimod could inhibit the motility of E. coli, one of its virulence mechanisms. The expression levels of carbapenemase-, motility-, and efflux pump-related genes suppressed by fingolimod were analyzed by quantitative polymerase chain reaction (qPCR). Our study demonstrated that the combination of fingolimod and doripenem inhibited carbapenemase, biological activity and other CREC virulence factors. This study findings suggest the potential of fingolimod as an adjuvant to prevent antibiotic resistance in CREC.

Luteolin Phosphate Derivatives Generated by Cultivating Bacillus subtilis var. Natto BCRC 80517 with Luteolin

Luteolin (LUT), a plant-derived flavone, exhibits various bioactivities; however, the poor aqueous solubility hampers its applications. Here, we revealed bioconversion of LUT by Bacillus subtilis BCRC 80517, yielding three water-soluble phosphate conjugates. These derivatives were identified as luteolin 4'-O-phosphate (L4'P), luteolin 3'-O-phosphate (L3'P), and luteolin 7-O-phosphate (L7P) by LC-ESI-MS/MS and NMR. Besides, we found that Bacillus subtilis BCRC 80517 was able to convert different levels of LUT but showed a limited conversion rate. By observing bacterial morphology with transmission electron microscopy and confocal fluorescence microscopy, we found that LUT disrupted the bacterial membrane integrity, which explained the incomplete conversion. Additionally, we revealed a spontaneous intramolecular transesterification of L4'P to L3'P, the thermodynamically more stable form, under acidic conditions and proposed the possible mechanism involving a cyclic phosphate as the intermediate. This study provides insight into development of a potent structural modification strategy to enhance the solubility of LUT through biophosphorylation.

Effects of Traditional Chinese Medicine and its Active Ingredients on Drug-Resistant Bacteria

The increasing and widespread application of antibacterial drugs makes antibiotic resistance a prominent and growing concern in clinical practice. The emergence of multidrug-resistant bacteria presents a global threat. However, the development and use of novel antibacterial agents involves time-consuming and costly challenges that may lead to yet further drug resistance. More recently, researchers have turned to traditional Chinese medicine to stem the rise of antibiotic resistance in pathogens. Many studies have shown traditional Chinese medicines to have significant bacteriostatic and bactericidal effects, with the advantage of low drug resistance. Some of which when combined with antibiotics, have also demonstrated antibacterial activity by synergistic effect. Traditional Chinese medicine has a variety of active components, including flavonoids, alkaloids, phenols, and quinones, which can inhibit the growth of drug-resistant bacteria and be used in combination with a variety of antibiotics to treat various drug-resistant bacterial infections. We reviewed the interaction between the active ingredients of traditional Chinese medicines and antibiotic-resistant bacteria. At present, flavonoids and alkaloids are the active ingredients that have been most widely studied, with significant synergistic activity demonstrated when used in combination with antibiotics against drug-resistant bacteria. The reviewed studies show that traditional Chinese medicine and its active ingredients have antimicrobial activity on antibiotic-resistant bacteria, which may enhance the susceptibility of antibiotic-resistant bacteria, potentially reduce the required dosage of antibacterial agents and the rate of drug resistance. Our results provide direction for finding and developing alternative methods to counteract drug-resistant bacteria, offering a new therapeutic strategy for tackling antibiotic resistance.

Auranofin promotes antibacterial effect of doripenem against carbapenem-resistant Acinetobacter baumannii

AIMS

This study was performed to identify the potential for repurposing auranofin as an antibiotic adjuvant against carbapenemase-producing A. baumannii.

METHODS AND RESULTS

The clinically isolated A. baumannii strains used in this study were all resistant to carbapenems and harbored the bla_OXA-23 gene. The synergistic effect of auranofin and doripenem against carbapenemase-producing A. baumannii was confirmed through checkerboard and growth kinetic analyses. This study also demonstrated the inhibitory effects of auranofin against A. baumannii biofilms. The anti-biofilm effects of auranofin were visualized by confocal laser scanning microscopy (CLSM). Furthermore, auranofin inhibited motility, one of the virulence factors. Additionally, the changes in the expression of carbapenemase-, biofilm- and efflux pump-related genes induced by auranofin were confirmed via quantitative polymerase chain reaction (qPCR).

CONCLUSIONS

Our results demonstrated that auranofin has an antibacterial effect with doripenem and an inhibitory effect on several factors related to carbapenem resistance.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study suggests that auranofin is a promising antibiotic adjuvant that can be used to prevent antibiotic resistance in carbapenem-resistant A. baumannii.

Preparation of antibacterial nanofibers by electrospinning polyvinyl alcohol containing a luteolin hydroxypropyl-β-cyclodextrin inclusion complex

Nanofibers have exhibited excellent water solubility, significant antibacterial effects and effective concentration in vitro release.

Plant Bioactive Compounds as an Intrinsic and Sustainable Tool to Enhance the Microbial Safety of Crops

Outbreaks of produce-associated foodborne illness continue to pose a threat to human health worldwide. New approaches are necessary to improve produce safety. Plant innate immunity has potential as a host-based strategy for the deactivation of enteric pathogens. In response to various biotic and abiotic threats, plants mount defense responses that are governed by signaling pathways. Once activated, these result in the release of reactive oxygen and nitrogen species in addition to secondary metabolites that aim at tempering microbial infection and pest attack. These phytochemicals have been investigated as alternatives to chemical sanitization, as many are effective antimicrobial compounds in vitro. Their antagonistic activity toward enteric pathogens may also provide an intrinsic hurdle to their viability and multiplication in planta. Plants can detect and mount basal defenses against enteric pathogens. Evidence supports the role of plant bioactive compounds in the physiology of Salmonella enterica, Escherichia coli, and Listeria monocytogenes as well as their fitness on plants. Here, we review the current state of knowledge of the effect of phytochemicals on enteric pathogens and their colonization of plants. Further understanding of the interplay between foodborne pathogens and the chemical environment on/in host plants may have lasting impacts on crop management for enhanced microbial safety through translational applications in plant breeding, editing technologies, and defense priming.

A synergy interaction of artocarpin and tetracycline against Pseudomonas aeruginosa and its mechanism of action on membrane permeability

The emergence of antibacterial resistance has significantly increased. Pseudomonas aeruginosa is associated with nosocomial infection and difficult to control. Artocarpin, a flavonoid from Artocarpus heterophyllus Lam. exhibits several pharmacological properties including antibacterial. The study was performed to evaluate interaction between artocarpin and antibiotics including tetracycline against P. aeruginosa. Its mechanism of action on membrane permeability was also investigated. Broth microdilution was conducted for the susceptibility assay. The interaction of artocarpin and antibiotics was evaluated using checkerboard method, the effect on alteration of membrane cell was investigated using bacteriolysis and the released of 260 nm materials. Artocarpin showed moderate to weak activity against the Gram-negative bacteria including P. aeruginosa with MIC values in the range of 31.25-250 μg/mL. A synergistic effect against P. aeruginosa was produced by the combination of artocarpin (31.25 μg/mL) and tetracycline (1.95 μg/mL) with FICI of 0.37. The time-killing assay showed that artocarpin enhance the antibacterial activity of tetracycline against P. aeruginosa by completely inhibiting the bacterial growth. Additionally, the mixture of artocarpin (31.25 μg/mL) and tetracycline (1.95 μg/mL) disrupted membrane permeability and lead to cell death. These results proposed that the combination of artocarpin and tetracycline may be used to overcome P. aeruginosa infection.

Cinnamomum Species: Bridging Phytochemistry Knowledge, Pharmacological Properties and Toxicological Safety for Health Benefits

The genus Cinnamomum includes a number of plant species largely used as food, food additives and spices for a long time. Different traditional healing systems have used these plants as herbal remedies to cure diverse ailments. The aim of this comprehensive and updated review is to summarize the biodiversity of the genus Cinnamomum, its bioactive compounds, the mechanisms that underlie the pharmacological activities and molecular targets and toxicological safety. All the data in this review have been collected from databases and recent scientific literature including Web of Science, PubMed, ScienceDirect etc. The results showed that the bioactive compounds of Cinnamomum species possess antimicrobial, antidiabetic, antioxidant, anti-inflammatory, anticancer and neuroprotective effects. The preclinical (in vitro/in vivo) studies provided the possible molecular mechanisms of these action. As a novelty, recent clinical studies and toxicological data described in this paper support and confirm the pharmacological importance of the genus Cinnamomum. In conclusion, the obtained results from preclinical studies and clinical trials, as well as reduced side effects provide insights into future research of new drugs based on extracts and bioactive compounds from Cinnamomum plants.

Combination between antibacterial and antifungal antibiotics with phytocompounds of Artemisia annua L: A strategy to control drug resistance pathogens

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia annua L. is a traditional Chinese medicine used for the treatment of malaria, jaundice and intense fever.

AIM OF THE STUDY

The aim of the present study was to investigate the phytochemicals, antioxidants, antimicrobial and synergistic potential of methanolic and petroleum ether extracts of A. annua against bacterial and fungal pathogens.

METHOD

Antioxidant activity of different concentrations of methanolic and petroleum ether extracts of A. annua was determined by DPPH free radical scavenging assay. Antimicrobial activity was determined by agar well diffusion, whereas MIC and synergistic activity was done by broth dilution method.TLC and GC-MS were done to identify active phytocompounds present in methanolic and petroleum ether extracts.

RESULTS

Methanolic extract of A. annua showed higher antioxidant potential (IC50 37 0.75 ± 0.34 μg ml^-1) as compared to petroleum ether extract. In antimicrobial analysis, methanolic and petroleum ether extracts of A. annua produced potent inhibitory activity against Candida strains as compared to bacterial strains. Methanolic and petroleum ether extracts of A. annua produced synergistic potential with decrease in MIC from 4 to 264 folds against bacterial (S. aureus and E. coli) and Candida strains in combination with antibacterial and antifungal antibiotics. Sub fraction I of methanolic and petroleum ether extracts was isolated through silica TLC and showed 10-fold more antimicrobial activity as compared to crude extract. GC-MS analysis of sub-fraction I of A. annua revealed 13 major phytocompounds with area more than 1%. Interestingly, 2-Propenoic acid and ridecyl ester (25.88%) were the major phytocompounds.

CONCLUSION

Phytocompounds of A. annua can be used as bioenhancer of antibacterial and antifungal agents to control drug resistance.

Synergistic Activity of Equol and Meropenem against Carbapenem-Resistant Escherichia coli

The emergence of carbapenem-resistant Enterobacterales (CRE) seriously limits treatment options for bacterial infections. Combined drugs are an effective strategy to treat these resistant strains. This study aimed to evaluate the synergistic effect of equol and meropenem against carbapenem-resistant Escherichia coli. First, this study investigated the antibacterial activity of carbapenems on clinically isolated E. coli strains by analyzing the minimum inhibitory concentrations (MICs). The E. coli strains were all resistant to carbapenem antibiotics. Therefore, we confirmed the cause of carbapenem resistance by detecting bla_KPC and bla_OXA-48 among the carbapenemase genes using polymerase chain reaction (PCR) analysis. Checkerboard and time-kill analyses confirmed that equol restored the susceptibility of carbapenem-resistant E. coli to meropenem. Also, the transcription levels of specific carbapenemase genes in E. coli were significantly suppressed by equol. The study also evaluated the anti-virulence effects of equol on bacterial biofilm and motility through phenotypic and genotypic analyses. In conclusion, our results revealed that equol had a synergistic effect with meropenem on carbapenem-resistant E. coli. Therefore, this study suggests that equol is a promising antibiotic adjuvant that prevents the expression of carbapenemases and virulence factors in carbapenem-resistant E. coli.

Role of Antioxidant Molecules and Polymers in Prevention of Bacterial Growth and Biofilm Formation

Background:

Antioxidants are multifaceted molecules playing a crucial role in several cellular functions. There is by now a well-established knowledge about their involvement in numerous processes associated with aging, including vascular damage, neurodegenerative diseases and cancer. An emerging area of application has been lately identified for these compounds in relation to the recent findings indicating their ability to affect biofilm formation by some microbial pathogens, including Staphylococcus aureus, Streptococcus mutans, and Pseudomonas aeruginosa.

Methods:

A structured search of bibliographic databases for peer-reviewed research literature was performed using a focused review question. The quality of retrieved papers was appraised using standard tools.

Results:

One hundred sixty-five papers extracted from pubmed database and published in the last fifteen years were included in this review focused on the assessment of the antimicrobial and antibiofilm activity of antioxidant compounds, including vitamins, flavonoids, non-flavonoid polyphenols, and antioxidant polymers. Mechanisms of action of some important antioxidant compounds, especially for vitamin C and phenolic acids, were identified.

Conclusion:

The findings of this review confirm the potential benefits of the use of natural antioxidants as antimicrobial/antibiofilm compounds. Generally, gram-positive bacteria were found to be more sensitive to antioxidants than gram-negatives. Antioxidant polymeric systems have also been developed mainly derived from functionalization of polysaccharides with antioxidant molecules. The application of such systems in clinics may permit to overcome some issues related to the systemic delivery of antioxidants, such as poor absorption, loss of bioactivity, and limited half-life. However, investigations focused on the study of antibiofilm activity of antioxidant polymers are still very limited in number and therefore they are strongly encouraged in order to lay the foundations for application of antioxidant polymers in treatment of biofilm-based infections.

Gut Microbiota-Polyphenol Interactions in Chicken: A Review

The gastrointestinal tract of the chicken harbors very complex and diverse microbial communities including both beneficial and harmful bacteria. However, a dynamic balance is generally maintained in such a way that beneficial bacteria predominate over harmful ones. Environmental factors can negatively affect this balance, resulting in harmful effects on the gut, declining health, and productivity. This means modulating changes in the chicken gut microbiota is an effective strategy to improve gut health and productivity. One strategy is using modified diets to favor the growth of beneficial bacteria and a key candidate are polyphenols, which have strong antioxidant potential and established health benefits. The gut microbiota-polyphenol interactions are of vital importance in their effects on the gut microbiota modulation because it affects not only the composition of gut bacteria but also improves bioavailability of polyphenols through generation of more bioactive metabolites enhancing their health effects on morphology and composition of the gut microbiota. The object of this review is to improve the understanding of polyphenol interactions with the gut microbiota and highlights their potential role in modulation of the gut microbiota of chicken.

Bioassay guided fractionation of rhizome extract of Rheum emodi wall as bio-availability enhancer of antibiotics against bacterial and fungal pathogens

ETHNOPHARMACOLOGICAL RELEVANCE

Rheum emodi Wall., is an important medicinal plant extensively used in Ayurvedic and Unani systems of traditional medicine. It is known to possess antioxidant, antibacterial, antifungal, anticancer, wound healing and immune enhancing activities.

AIM OF THE STUDY

The aim of the current study was to investigate the antimicrobial activity and synergistic potential of different solvent fractions and phytocompounds of Rheum emodi rhizome against bacterial and fungal pathogens.

MATERIAL AND METHODS

The antimicrobial and synergistic potential of the crude methanolic extract, different solvent fractions (n-hexane, chloroform, ethyl acetate, and residual aqueous) and isolated phytocompounds of the rhizome of Rheum emodi were assayed by broth microdilution method. The bioactive phytocompounds were isolated through silica TLC and quantified using HPTLC and HPLC. The bioactive phytocompounds were identified by LC-MS analysis.

RESULTS

Phytochemical analysis of the sub-fractions showed that the TPC (417.94 ± 1.2 mg g^-1 GAE) and TFC (187.40 ± 0.5 mg g^-1 RE) were highest in residual aqueous extracts. The chloroform sub-fraction possessed the highest antimicrobial activity against bacterial (Escherichia coli, Staphylococcus aureus and Klebsiella pneumoniae) and fungal strains (Candida albicans MTCC 277 and ATCC 90028). The MIC of chloroform sub-fraction against S. aureus, K. pneumoniae, E. coli, C. albicans was 1.95, 3.91, 15.62 and 62.5 μg ml^-1, respectively. TLC and LC-MS analysis of chloroform sub-fraction identified phytocompounds namely emodin D4 (m/z 274.262), rhein13c6 (m/z 290.176), chrysophanol dimethyl ether (m/z 282.291), and resveratrol (m/z 340.456). Quantification of emodin content showed that the chloroform sub-fraction (101.4543 μg mg^-1, 194.8037 μg mg^-1 measured through HPTLC and HPLC, respectively), and its TLC fraction (II) (75.18 μg mg^-1, 232.384 μg mg^-1 measured through HPTLC and HPLC, respectively) are rich in emodin. Furthermore, chloroform sub-fraction, its TLC fractions and emodin showed profound synergistic activity in combination with antibacterial and antifungal antibiotics and lowered the dosage of antibiotics by 4-257 folds.

CONCLUSIONS

The bioassay guided fractionation of R. emodi rhizome methanolic extract identified phytocompounds (emodin, rhein13c6, chrysophanol dimethyl ether and resveratrol) that act as bioavailability enhancers of antibacterial and antifungal antibiotics, hence revealing their potential in treating multidrug resistance.

Thymus algeriensis Bioss & Reut: Relationship of phenolic compounds composition with in vitro/in vivo antioxidant and antibacterial activity

Thymus algeriensis Bioss & Reut is an Algerian native plant traditionally used for culinary and medicinal purposes. To evaluate the in vivo antioxidant and antimicrobial properties of T. algeriensis, phenolic compounds were extracted using hydromethanolic solutions and administrated to Swiss albinos mice. It was observed that the plasma antioxidant capacity increased, as well as catalase and glutathione levels, whereas malondialdehyde decreased. In vitro assays confirmed that the extract scavenged 2,2-diphenyl-1-picrylhydrazyl, DPPH^• (7 µg/mL), chelated (EC₅₀: 512 µg/mL) and reduced iron ions (5.3 mM FeSO₄/g), and inhibited β-carotene bleaching (90% at 2 mg/mL). Antibacterial effects were also observed towards Salmonella typhimurium and Proteus mirabilis. However, the methanolic fraction obtained by reversed solid phase cartridge, showed antibacterial activity against Escherichia coli (MIC = 9.37 mg/mL), Proteus mirabilis (MIC = 4.68 mg/mL), Salmonella typhimurium (MIC = 7.06 mg/mL), Micrococcus luteus (MIC = 7.03 mg/mL), and Bacillus cereus (MIC = 2.34 mg/mL). UHPLC-DAD-ESI-MSⁿ analysis showed that these properties could result from rosmarinic acid, caffeoyl rosmaniric acid, and kaempferol and eriodictyol glycoside derivatives. These results pave the way for the understanding of T. algeriensis traditional applications and its use for the development of novel food applications.

Antimicrobial activity of Citrus spp. and Anethum graveolens components against Candida metapsilosis in ranch sauce

In this paper, a study was carried out to test the inhibitory effect of a natural food compound (NFC), based on flavonoids (naringenin, hesperetin, tangeritin, luteolin, apigenin and kaempferol) from citrus and dill, in ranch sauce. A strain of C. metapsilosis, isolated from a spoiled sample of ranch sauce, was used as target pathogen microorganism. The inhibitory effect of NFC was compared with a common mixture of chemical preservatives used in this type of sauces: potassium sorbate and sodium benzoate (S/B). An in vitro test was performed by the microtiter plate assay at 10, 25 and 37 °C for 24 h in modified Tryptic Soy Broth. An additive antimicrobial effect had been observed in the combination of acetic acid and NFC. The results of the microtiter assay were validated in a challenge test in ranch sauce at 5, 25 and 37 °C for 10 weeks. NFC showed partial fungicidal effect against C. metapsilosis, reducing two logarithmic units at 5 °C for 10 weeks. At 5 °C, the traditional doses of S/B used in ranch sauce decreased viable cells to non-detectable counts from the second week of the experiment. At 25 and 37 °C, the use of S/B mixture or the use of NFC showed the same fungicidal effect. The incorporation of NFC, alone or in combination with acetic acid, opens the possibility of formulating clean label sauces with good protection against the development of the acid resistant yeast C. metapsilosis.

Size and Shape-Dependent Antimicrobial Activities of Silver and Gold Nanoparticles: A Model Study as Potential Fungicides

Plant-based pathogenic microbes hinder the yield and quality of food production. Plant diseases have caused an increase in food costs due to crop destruction. There is a need to develop novel methods that can target and mitigate pathogenic microbes. This study focuses on investigating the effects of luteolin tetraphosphate derived silver nanoparticles (LTP-AgNPs) and gold nanoparticles (LTP-AuNPs) as a therapeutic agent on the growth and expression of plant-based bacteria and fungi. In this study, the silver and gold nanoparticles were synthesized at room temperature using luteolin tetraphosphate (LTP) as the reducing and capping agents. The synthesis of LTP-AgNPs and LTP-AuNP was characterized by Transmission Electron Microscopy (TEM) and size distribution. The TEM images of both LTP-AgNPs and LTP-AuNPs showed different sizes and shapes (spherical, quasi-spherical, and cuboidal). The antimicrobial test was conducted using fungi: Aspergillus nidulans, Trichaptum biforme, Penicillium italicum, Fusarium oxysporum, and Colletotrichum gloeosporioides, while the class of bacteria employed include Pseudomonas aeruginosa, Aeromonas hydrophila, Escherichia coli, and Citrobacter freundii as Gram (-) bacteria, and Listeria monocytogenes and Staphylococcus epidermidis as Gram (+) bacterium. The antifungal study demonstrated the selective size and shape-dependent capabilities in which smaller sized spherical (9 nm) and quasi-spherical (21 nm) AgNPs exhibited 100% inhibition of the tested fungi and bacteria. The LTP-AgNPs exhibited a higher antimicrobial activity than LTP-AuNPs. We have demonstrated that smaller sized AgNPs showed excellent inhibition of A. nidulans growth compared to the larger size nanoparticles. These results suggest that LTP-AuNP and LTP-AgNPs could be used to address the detection and remediation of pathogenic fungi, respectively.

Demonstration of bactericidal and synergistic activity of quercetin with meropenem among pathogenic carbapenem resistant Escherichia coli and Klebsiella pneumoniae

Rapid dissemination of carbapenem resistant Enterobacteriaceae (CRE) is considered to be a global issue. Quercetin is a well known antimicrobial agent. Hence, it would be important to investigate bactericidal and synergistic interaction of quercetin with meropenem and elucidate effects of quercetin alone and quercetin-meropenem combination on bla_NDM, bla_VIM,acrB, ompC, ompF, ompk35 and ompk36 expressions, cellular morphology and cell-wall/membrane integrity. MIC, Time-kill and Baclight assays were performed to determine antibacterial/bactericidal activity of quercetin. Synergism with meropenem was evaluated by checkerboard assay followed by dose-response, isobologram analysis and FIC index, combination index calculation. Effects of meropenem, quercetin and their combinations on bla_NDM, bla_VIM,acrB, ompC, ompF, ompk35 and ompk36 expressions were evaluated by qRT-PCR. SEM was performed to evaluate effects of aforesaid combinations on cellular morphology. Quercetin alone exhibited at least four-fold reduced MIC value (16-256 μg/mL) than that of meropenem against CRE. It exhibited synergism with meropenem against 89.25% CRE. Again, only 128 μg/mL quercetin killed upto 99.95% bacteria within 4-6 h of dosing, which increased further to 99.99% in MIC combination of meropenem-quercetin. Thus, effective bactericidal activity of quercetin-meropenem combination might have been achieved through alteration of bla_VIM, ompC expression and cellular morphology of bacteria. Quercetin exhibited bactericidal and synergistic activity with meropenem.

Interaction of apigenin-7-O-glucoside with pyrimethamine against Toxoplasma gondii growth

Apigenin-7-O-glucoside, a flavonoid glucoside known to inhibit cancer cell growth, fungi growth, both intra and extracellular reactive oxygen species generation, causing cell arrest and damage to the plasma membrane, was tested alone or in combination with a dihydrofolate inhibitor (pyrimethamine) against Toxoplasma gondii (T. gondii) growth. The anti-T. gondii activity was carried out using a high throughput antiparasitic drug screening cell-based assay known as 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H tetrazolium, monosodium salt (WST-8) and fluorescence plate reader. The 50% effective concentration inhibition and 95% confidence interval values for individual and combination treatments against T. gondii were 0.80 (0.38-1.29) µg/mL, 1.05 (0.275-2.029) µg/mL, and 0.40 (0-1.06) µg/mL for apigenin-7-O-glucoside, pyrimethamine, and apigenin-7-O-glucoside plus pyrimethamine, respectively. Interestingly, the apigenin-7-O-glucoside plus pyrimethamine combination showed an additive inhibition effect against T. gondii growth in vitro using the fractional inhibitory concentration index method. It was discovered that the apigenin-7-O-glucoside combination with pyrimethamine had a high selectivity index 62.5, which implies 62-fold inhibition activity against the parasite versus human foreskin fibroblast cell cytotoxicity. This new combination hit is novel and will have the potential for future effective, safe, and less costly anti-Toxoplasma drug development, if its in vivo activity shows similar findings.

Plant extract supplementation as a strategy for substituting dietary antibiotics in broiler chickens exposed to low ambient temperature

The present study was conducted to investigate the effects of two plant extracts as alternatives to dietary antibiotics in broiler chickens exposed to low ambient temperature. A total of 300 one-day-old male broiler chickens were randomly assigned to four dietary treatments (5 replicate pens; 15 broiler chickens each) which consisted of starter (d 0 to 10), and grower (d 10 to 28) diets. Dietary treatments included a basal diet (negative control, NC) and three similar diets that were either supplemented with 200 mg/kg of Prosopis farcta extract (PFE), Rhus coriaria L. extract (RCE) or an antibiotic premix containing oxytetracycline (positive control, PC). In order to simulate low ambient temperature, room temperature was maintained at 32°C during the first 3 d of the trial and afterwards, the temperature was gradually reduced by approximately 1.5°C each day to 14°C on d 21. PFE and PC treatments exerted a significant effect on body weight gain at d 28. Diet PFE was effective in reducing mortality when compared with diet NC (p < 0.05). Furthermore, diet PFE caused increases in ileal  digestibility of gross energy, dry matter and organic matter when compared with diet NC (p < 0.05). Diets PFE and PC decreased coliforms, total aerobic bacteria and total anaerobic bacteria loads in the caeca when compared with diet NC (p < 0.05). Moreover, the addition of PFE to the diet improved villous height in all small intestinal segments as well as villous height:crypt depth ratio in the duodenum when compared with diet NC (p < 0.05). The results indicated that PFE is not only a valid alternative to oxytetracycline under cold stress conditions, with no antibiotic resistance, but also has the potential to increase the resistance of broiler chickens against ascites syndrome. Moreover, the addition of RCE at the concentration of 200 mg/kg to the diet was not sufficient to improve the performance of broiler chickens (similar to diet PC) but maybe more effective at higher concentrations.

4-Chloromercuribenzoic acid enhances carbapenem sensitivity among pathogenic Gram negative bacteria by altering blaVIM, adeB and ompC expression

BACKGROUND

Rapid global dissemination of carbapenem resistant Gram negative bacteria (CRGNB) is supposed to be clinically most alarming. Since, p-chloromercuribenzoic acid (pCMB) is a well known metallo-beta-lactamase inhibitor; evaluation of its bactericidal and carbapenem resistance reversing potential would be important.

METHODS

In this study, bactericidal and meropenem resistance reversing potential of pCMB was investigated against CRGNB by MIC determination, checkerboard assay, time-kill assay and cellular viability assay. Effect of pCMB on cellular morphology was visualized by Scanning Electron Microscopy. Further, quantitative Real Time-PCR was performed to evaluate effects of pCMB on clinically relevant metallo-beta-lactamases, major efflux pumps and outer membrane proteins expression.

RESULTS

pCMB exhibited at least four fold reduced MIC value (2-256μg/ml) than that of meropenem against CRGNB. Moreover, pCMB exhibited synergism with meropenem against 86.06% of CRGNB. MIC of pCMB (16-32μg/ml) could kill upto 99.96% bacteria within 6-8h of dosing. pCMB exerted bactericidal activity by severely disrupting cell wall integrity. Reversal of carbapenemase property of CRGNB by pCMB might have developed through alteration of bla_VIM, acrB, mexB and ompk36 expression.

CONCLUSIONS

Hence, the current study identified pCMB as a potential bactericidal agent which enhanced meropenem sensitivity by altering bla_VIM, acrB, mexB and ompk36 expression.

Agro food by-products and essential oil constituents curtail virulence and biofilm of Vibrio harveyi

Vibrio harveyi causes severe loss to the aquaculture industry due to its virulence, which is mediated by Quorum sensing (QS) and biofilm formation. In the current study, we have explored the anti-virulent properties and biofilm disruption ability of luteolin (extracted from coconut shell) and linalool against this important aquaculture pathogen. HPLC analysis of the methanolic extract of coconut shells revealed a single major peak which matched to the standard luteolin which was further elucidated by NMR studies. Further, luteolin and linalool were screened for their ability to inhibit biofilms and various quorum sensing mediated virulence factors of V. harveyi. The Minimum Inhibitory Concentration (MIC) of the two compounds was determined and the sub-inhibitory concentrations of the compounds were able to inhibit biofilm formation. Both the compounds disrupted about 60-70% mature biofilms, which was also visually observed by light microscopy. Both linalool and luteolin exhibited a significant reduction in the production of EPS and alginate in the biofilms matrix of V. harveyi which was confirmed by Scanning Electron Microscopy (SEM). Both compounds inhibited the swarming and swimming motility, the crucial quorum sensing (QS) mediated virulence of V. harveyi. The present study shows the presence of valuable polyphenolic compound like luteolin in coconut shells that are discarded as a waste. From the present study we envisage that luteolin and linalool can serve as potent anti-virulent agents to combat QS mediated infections against aquaculture pathogens.

Antimicrobial Effects of Chemical Compounds Isolated from Traditional Chinese Herbal Medicine (TCHM) Against Drug-Resistant Bacteria: A Review Paper

Infectious diseases caused by pathogenic bacteria seriously threaten human lives. Although antibiotic therapy is effective in the treatment of bacterial infections, the overuse of antibiotics has led to an increased risk of antibiotic resistance, putting forward urgent requirements for novel antibacterial drugs. Traditional Chinese herbal medicine (TCHM) and its constituents are considered to be potential sources of new antimicrobial agents. Currently, a series of chemical compounds purified from TCHM have been reported to fight against infections by drug-resistant bacteria. In this review, we summarized the recent findings on TCHM-derived compounds treating drug-resistant bacterial infections. Further studies are still needed for the discovery of potential antibacterial components from TCHM.

The Effect of Pluchea indica (L.) Less. Tea on Adipogenesis in 3T3-L1 Adipocytes and Lipase Activity

Obesity and hyperlipidemia are a major problem in the world. Pluchea indica (L.) Less. tea (PIT) is a beverage that has various indications. This study focused on the effect of the PIT on inhibiting adipogenesis of 3T3-L1 cells and pancreatic lipase enzyme activity. The viability of 3T3-L1 cells was not significantly decreased after exposure to 200 to 1000 μg mL-1 PIT compared to controls (p > 0.05). The PIT at 750 to 1000 μg mL-1 exhibited a significantly reduced lipid accumulation compared to the control (p < 0.05). The inhibitory effects of the PIT at 250 to 1000 μg mL-1 on lipase activity were significantly increased compared to control (p < 0.05). The FTIR results showed that the integrated areas of lipids, proteins, nucleic acids, glycogen, and carbohydrates of the PIT-treated 3T3-L1 adipocytes were significantly lower than the untreated 3T3-L1 adipocytes (p < 0.05). These findings may indicate that the PIT is not only capable of inhibiting lipids and carbohydrate accumulation in adipocytes but also has a potential to inhibit pancreatic lipase activity. So, the PIT may be further developed to the novel lipid-lowering herbal supplement for the management of overweight or obesity.

The Synergy and Mode of Action of Cyperus rotundus L. Extract Plus Ampicillin against Ampicillin-Resistant Staphylococcus aureus

Cyperus rotundus L. has been used for pharmaceutical applications including antibacterial infections. Nevertheless, there is still no data regarding the mode of actions. This study aimed to determine the antibacterial activity and mode of actions of Cyperus rotundus extract (CRE) against ampicillin-resistant Staphylococcus aureus (ARSA) which poses a serious problem for hospitalized patients. The majority of chemical compounds of CRE were flavonoids and alkaloids. The minimum inhibitory concentrations (MICs) for ampicillin and CRE against all ARSA strains were 64 μg/ml and 0.5 mg/ml, respectively. Checkerboard assay revealed synergistic activity in the combination of ampicillin and CRE at the lowest fractional inhibitory concentration index (FICI) at 0.27. The killing curve assay had confirmed the synergistic and bactericidal activity of the combination against ARSA. Electron microscopic results showed that these ARSA cells treated with this combination caused peptidoglycan and cytoplasmic membrane (CM) damage and average cell areas significantly smaller than control. Also, this combination caused an increase in CM permeability of ARSA. CRE revealed the inhibitory activity against β-lactamase. It is normally known that some drugs are derived from flavonoids or alkaloids. So, this CRE proposes the potential to develop a novel adjunct phytopharmaceutical to ampicillin for the remedy of ARSA.

A synergistic effect of artocarpanone from Artocarpus heterophyllus L. (Moraceae) on the antibacterial activity of selected antibiotics and cell membrane permeability

Aim/Backgrounds:

Artocarpanone isolated from Artocarpus heterophyllus L. (Moraceae) exhibits antibacterial activity. The present study investigated synergistic activity between artocarpanone and tetracycline, ampicillin, and norfloxacin, respectively, against methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Escherichia coli.

Materials and Methods:

A broth microdilution method was used for evaluating antibacterial susceptibility. Synergistic effects were identified using a checkerboard method, and a bacterial cell membrane disruption was investigated by assay of released 260 nm absorbing materials following bacteriolysis.

Results and Discussion:

Artocarpanone exhibited weak antibacterial activity against MRSA and P. aeruginosa with minimum inhibitory concentrations values of 125 and 500 μg/mL, respectively. However, the compound showed strong antibacterial activity against E. coli (7.8 μg/mL). The interaction between artocarpanone and all tested antibiotics revealed indifference and additive effects against P. aeruginosa and E. coli (fractional inhibitory concentration index [FICI] values of 0.75-1.25). The combination of artocarpanone (31.2 μg/mL) and norfloxacin (3.9 μg/mL) resulted in synergistic antibacterial activity against MRSA, with an FICI of 0.28, while the interaction between artocarpanone and tetracycline, and ampicillin showed an additive effect, with an FICI value of 0.5. A time-kill assay also indicated that artocarpanone had a synergistic effect on the antibacterial activity of norfloxacin. In addition, the combination of artocarpanone and norfloxacin altered the membrane permeability of MRSA.

Conclusion:

These findings suggest that artocarpanone may be used to enhance the antibacterial activity of norfloxacin against MRSA.

Synergistic interactions between phenolic compounds identified in grape pomace extract with antibiotics of different classes against Staphylococcus aureus and Escherichia coli

Synergy could be an effective strategy to potentiate and recover antibiotics nowadays useless in clinical treatments against multi-resistant bacteria. In this study, synergic interactions between antibiotics and grape pomace extract that contains high concentration of phenolic compounds were evaluated by the checkerboard method in clinical isolates of Staphylococcus aureus and Escherichia coli. To define which component of the extract is responsible for the synergic effect, phenolic compounds were identified by RP-HPLC and their relative abundance was determined. Combinations of extract with pure compounds identified there in were also evaluated. Results showed that the grape pomace extract combined with representatives of different classes of antibiotics as β-lactam, quinolone, fluoroquinolone, tetracycline and amphenicol act in synergy in all S. aureus and E. coli strains tested with FICI values varying from 0.031 to 0.155. The minimal inhibitory concentration (MIC) was reduced 4 to 75 times. The most abundant phenolic compounds identified in the extract were quercetin, gallic acid, protocatechuic acid and luteolin with relative abundance of 26.3, 24.4, 16.7 and 11.4%, respectively. All combinations of the extract with the components also showed synergy with FICI values varying from 0.031 to 0.5 and MIC reductions of 4 to 125 times with both bacteria strains. The relative abundance of phenolic compounds has no correlation with the obtained synergic effect, suggesting that the mechanism by which the synergic effect occurs is by a multi-objective action. It was also shown that combinations of grape pomace extract with antibiotics are not toxic for the HeLa cell line at concentrations in which the synergistic effect was observed (47 μg/mL of extract and 0.6-375 μg/mL antibiotics). Therefore, these combinations are good candidates for testing in animal models in order to enhance the effect of antibiotics of different classes and thus restore the currently unused clinical antibiotics due to the phenomenon of resistance. Moreover, the use of grape pomace is a good and low-cost alternative for this purpose being a waste residue of the wine industry.

Evaluation of the Antibacterial Effects of Flavonoid Combination from the Leaves of Dracontomelon dao by Microcalorimetry and the Quadratic Rotary Combination Design

Skin infectious disease is a common public health problem due to the emergence of drug-resistant bacteria caused by the antibiotic misuse. Dracontomelon dao (Blanco) Merr. et Rolfe, a traditional Chinese medicine, has been used for the treatment of various skin infectious diseases over 1000 of years. Previous reports have demonstrated that the leaves of D. dao present favorable antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtitles. The flavonoids are the main components of the ethyl acetate extract of D. dao leaf. However, the correlation between flavonoids and antibacterial activities is yet to be determined. In this study, the combined antibacterial activities of these flavonoids were investigated. Three samples with the different concentrations of flavonoids (S1–S3) were obtained. By microcalorimetric measurements, the results showed that the IC₅₀ value of S2 was lower than those of S1 and S3. The contents of main flavonoids (including Luteolin, L-Epicatechin, Cianidanol, and Quercetin) in S1–S3 were various, confirmed by the method of the Ultra High Performance Liquid Chromatography (UPLC). Based on the method of quadratic general rotary unitized design, the antibacterial effect of single flavonoid, and the potential synergistic effects between Luteolin and Quercetin, Luteolin and Cianidanol were calculated, which were also proved by microcalorimetric analysis. The antibacterial activities of main flavonoids were Luteolin > Cianidanol > Quercetin > L-Epicatechin. Meanwhile, the synergistic effects of Luteolin and Cianidanol (P_L+C = 1.425), Quercetin and Luteolin (P_L+Q = 1.129) on anti-microbial activity were validated. Finally, we found that the contents of Luteolin, L-Epicatechin, Cianidanol, Quercetin were 1061.00–1061.00, 189.14–262.86, 15,990.33–16,973.62, 6799.67–7662.64 ng·ml⁻¹ respectively, with the antibacterial rate over 60.00%. In conclusion, this study could provide reference for quality evaluation and pharmacodynamics research of D. dao.

Luteolin, a novel p90 ribosomal S6 kinase inhibitor, suppresses proliferation and migration in leukemia cells

Ribosomal S6 kinases (RSKs) are directly regulated by extracellular signal-regulated kinase (ERK) signaling and are implicated in cell growth, survival, motility and senescence. The present study observed that RSK1 was overexpressed in primary untreated leukemia patient bone marrow samples compared with the expression at the complete remission stage, using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). In addition, a high RSK1 expression (relative expression ≥10) was associated with a significantly shorter overall survival (P=0.038) compared with that in patients with low RSK1 expression (relative expression <10). The current study also investigated the effect of luteolin, a novel p90 ribosomal S6 kinase (RSK) inhibitor extracted from Reseda odorata L., which shows strong biochemical functions including anti-allergy, anti-inflammation and anti-cancer functions, in MOLM-13 and Kasumi-1 leukemic cells. The cell viability, apoptosis and migration ability analysis were assessed by performing a cell counting kit-8 assay, Annexin V-FITC/PI double staining and migration filter assay, respectively. The results indicated that luteolin inhibited the growth of the leukemic cell lines through induction of apoptosis, while the migration ability was also suppressed. Overexpression of RSK1 by plasmid transfection was found to decrease the luteolin-induced apoptosis and migration capabilities. By contrast, knockdown of the RSK1 expression by small interfering RNA appeared to induce the same effect as luteolin on MOLM-13 and Kasumi-1 leukemic cells. In conclusion, these results suggest that luteolin inhibits leukemic cell proliferation and induces apoptosis by inhibition of the RSK1 pathways.

Phytochemicals for human disease: An update on plant-derived compounds antibacterial activity

In recent years, many studies have shown that phytochemicals exert their antibacterial activity through different mechanisms of action, such as damage to the bacterial membrane and suppression of virulence factors, including inhibition of the activity of enzymes and toxins, and bacterial biofilm formation. In this review, we summarise data from the available literature regarding the antibacterial effects of the main phytochemicals belonging to different chemical classes, alkaloids, sulfur-containing phytochemicals, terpenoids, and polyphenols. Some phytochemicals, besides having direct antimicrobial activity, showed an in vitro synergistic effect when tested in combination with conventional antibiotics, modifying antibiotic resistance. Review of the literature showed that phytochemicals represent a possible source of effective, cheap and safe antimicrobial agents, though much work must still be carried out, especially in in vivo conditions to ensure the selection of effective antimicrobial substances with low side and adverse effects.

Effects of Luteolin and Quercetin in Combination with Some Conventional Antibiotics against Methicillin-Resistant Staphylococcus aureus

The present study was designed to evaluate the effects of flavonoids luteolin (L) and quercetin + luteolin (Q + L) in combination with commonly used antibacterial agents against methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates and S. aureus (ATCC 43300). Minimum inhibitory concentrations (MICs) of L and Q + L, as well as the MICs of flavonoids in combination with antibiotics were determined and results showed an increased activity of flavonoids with antibiotics. The synergistic, additive, or antagonistic relationships between flavonoids (L and Q + L) and antibiotics were also evaluated, and additive and synergistic effects were observed for some antibiotic + flavonoid combinations. In addition, some combinations were also found to damage the bacterial cytoplasmic membrane, as assessed through potassium leakage assay. The effects of flavonoids and flavonoids + antibiotics on mecA gene mutations were also tested, and no functional variation was detected in the coding region.

Antimicrobial activity and bioguided fractionation of Rumex tingitanus extracts for meat preservation

This study was undertaken to investigate the antibacterial and antifungal activities of Rumex tingitanus leaves extracts as well as the identification of bioactive components and their performance in meat preservation. Total phenolics and flavonoids showed the highest content of phenolics and flavonoids in the ethyl acetate fraction (Rt EtOAcF). For antimicrobial efficacy, leaves extract and derived fraction were tested for their capacity to inhibit bacterial and fungal proliferation in vitro and in vivo. The ethyl acetate fraction showed the most potent antibacterial and antifungal activities compared to the others extracts. Thus, the efficacy of this extract to inhibit the proliferation of Listeria monocytogenes in minced beef meat model was examined. This fraction eradicates the L. monocytogenes population in meat in a concentration- and time-dependent manner. A bio-guided purification of the Rt EtOAc fraction resulted in the isolation of the compound responsible for the observed antimicrobial activity. This compound was identified as luteolin by analysis of spectroscopic data.

CHEMICAL COMPOUNDS ISOLATED IN THIS ARTICLE

Luteolin (PubChem CID: 5280445); p-iodonitrotetrazolium chloride (PubChem CID: 64957); Amphotericin B (PubChem CID: 5280965); Gentamicin and (PubChem CID: 6419933); Hexane (PubChem CID: 8058); Methanol (PubChem CID: 887); Ethanol (PubChem CID: 702); Dimethylsulfoxide (PubChem CID: 679); Quercetin (PubChem CID: 5280343); Gallic acid (PubChem CID: 370).

Synergism and the mechanism of action of the combination of α-mangostin isolated from Garcinia mangostana L. and oxacillin against an oxacillin-resistant Staphylococcus saprophyticus

Background

Globally, staphylococci have developed resistance to many antibiotics. New approaches to chemotherapy are needed and one such approach could be to use plant derived actives with conventional antibiotics in a synergestic way. The purpose of this study was to isolate α-mangostin from the mangosteen (Garcinia mangostana L.; GML) and investigate antibacterial activity and mechanisms of action when used singly and when combined with oxacillin against oxacillin-resistant Staphylococcus saprophyticus (ORSS) strains. The isolated α-mangostin was confirmed by HPLC chromatogram and NMR spectroscopy. The minimum inhibitory concentration (MIC), checkerboard and killing curve were determined. The modes of action of these compounds were also investigated by enzyme assay, transmission electron microscopy (TEM), confocal microscopic images, and cytoplasmic membrane (CM) permeabilization studies.

Results

The MICs of isolated α-mangostin and oxacillin against these strains were 8 and 128 μg/ml, respectively. Checkerboard assays showed the synergistic activity of isolated α-mangostin (2 μg/ml) plus oxacillin (16 μg/ml) at a fractional inhibitory concentration index (FICI) of 0.37. The kill curve assay confirmed that the viability of oxacillin-resistant Staphylococcus saprophyticus DMST 27055 (ORSS-27055) was dramatically reduced after exposure to isolated α-mangostin (2 μg/ml) plus oxacillin (16 μg/ml). Enzyme assays demonstrated that isolated α-mangostin had an inhibitory activity against β-lactamase in a dose-dependent manner. TEM results clearly showed that these ORSS-27055 cells treated with this combination caused peptidoglycan and cytoplasmic membrane damage, irregular cell shapes and average cell areas were significantly larger than the control. Clearly, confocal microscopic images confirmed that this combination caused considerable peptidoglycan damage and DNA leakage. In addition, the CM permeability of ORSS-27055 was also increased by this combination of actives.

Conclusions

These findings provide evidence that isolated α-mangostin alone has not only some activity but also shows the synergistic activity with oxacillin against ORSS-27055. The chromone and isoprenyl structures could play a significant role in its action. This synergistic activity may involve three mechanisms of action. Firstly, potential effects of cytoplasmic membrane disruption and increases permeability. Secondly, inhibit β-lactamase activity. Finally, also damage to the peptidoglycan structure. We proposes the potential to develop a novel adjunct phytopharmaceutical to oxacillin for the treatment of ORSS. Future studies require clinical trials to establish if the synergy reported can be translated to animals and humans.

The synergy and mode of action of quercetin plus amoxicillin against amoxicillin-resistant Staphylococcus epidermidis

Background

Staphylococcus epidermidis is one of the most multiple resistances to antibiotics in the recent years. Therefore, practically-prescribed antibiotics in the treatment of these strains are not effective. Plant-derived antibacterial is one of the most interesting sources of new therapeutics. The present study was to investigate antibacterial, synergy and modes of action of quercetin and amoxicillin against amoxicillin-resistant Staphylococcus epidermidis (ARSE).

Methods

The MICs, checkerboard assay, viability curves, cytoplasmic membrane (CM) permeability, enzyme assay, transmission electron microscopy, confocal microscopy and FT-IR microspectroscopy measurement was performed.

Results

The MICs of amoxicillin, penicillin, quercetin and kaempferol against all ARSE strains were 16, 200, 256-384 and >1024 μg/mL respectively. Synergistic effects were exhibited on amoxicillin plus quercetin and penicillin plus kaempferol against these strains at FIC index 0.50 and <0.38 respectively. The synergistic activity of quercetin plus amoxicillin was confirmed by the viable count. This combination increased CM permeability, caused marked morphological, peptidoglycan and cytoplasmic membrane damage, increased protein amide I and II, but decreased fatty acid in bacterial cells. The quercetin had an inhibitory activity against β-lactamase.

Conclusions

So, these findings are the first report that quercetin has the synergistic effect with amoxicillin against ARSE via four modes of actions, inhibit peptidoglycan synthesis and β-lactamases activity, increase CM permeability and protein amide I and II but decrease fatty acid in bacterial cells. Of course, this flavonol has the dominant potential to develop a brand-new collateral phytochemical agent plus amoxicillin to treat ARSE. Future work should focus on the bioavailability, efficacy and toxicity in animal and human studies, as well as, the synergistic effect on blood and tissue should be evaluated and achieved.

C-Geranylated flavonoids from Paulownia tomentosa fruits with antimicrobial potential and synergistic activity with antibiotics

Context C-6-Geranylated flavonoids possess promising biological activities. These substances could be a source of lead compounds for the development of therapeutics. Objective The study was designed to evaluate their antibacterial and antileishmanial activity. Materials and methods C-6-Geranylated flavanones were tested in micromolar concentrations against promastigote forms of Leishmania brazilensis, L. donovani, L. infantum, and L. panamensis against methicillin-resistant Staphylococcus aureus (MRSA); and synergistic potential with antibiotics was analyzed. IC50 values (after 72 h) were calculated and compared with that of miltefosine. Flow cytometry and DNA fragmentation analysis were used the mechanism of the effect. Geranylated flavanones or epigallocatechin gallate were combined with oxacillin, tetracycline, and ciprofloxacin, and the effects of these two-component combinations were evaluated. Minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) were established (after 24 h), the synergy was measured by the checkerboard titration technique, and the sums of the fractional inhibitory concentrations (∑FICs) were computed. Results 3'-O-Methyl-5'-O-methyldiplacone and 3'-O-methyldiplacone showed good antileishmanial activities (IC50 8-42 μM). 3'-O-Methyl-5'-hydroxydiplacone activates the apoptotic death at leishmanias, the effect of 3'-O-methyl-5'-O-methyldiplacone has another mechanism. The test of the antibacterial activity showed good effects of 3'-O-methyldiplacol and mimulone against MRSA (MIC 2-16 μg/mL), and in six cases, the results showed synergistic effects when combined with oxacillin. Synergistic effects were also found for the combination of epigallocatechin gallate with tetracycline or oxacillin. Conclusion This work demonstrates anti-MRSA and antileishmanial potential of geranylated flavanones and uncovers their promising synergistic activities with antibiotics. In addition, the mechanism of antileishmanial effect is proposed.

Environmentally oriented models and methods for the evaluation of drug × drug interaction effects

This detailed review compares known and widely used methods for drug interaction estimation, some of which now have historical significance. Pharmaceutical application has been noted as far back as several thousand years ago. Relatively late in the 20th century, however, researchers became aware that their fate and metabolism, which still remain a great challenge for environmental analysts and risk assessors. For the patient's well-being, treatment based on the mixing of drugs has to be effective and should not cause any side effects (or side effects should not have a significant impact on health and mortality). Therefore, it is important to carefully examine drugs both individually and in combinations. It should be also stated that application form/way of entering the living organism is of great importance as well as the age and the place in the trophic system of the organism in order to eliminate harmful dosages in the case of infants' accidental intoxication.

Synergy and Mode of Action of Ceftazidime plus Quercetin or Luteolin on Streptococcus pyogenes

Streptococcus pyogenes causes streptococcal toxic shock syndrome. The recommended therapy has been often failure through the interfering of beta-lactamase-producing bacteria (BLPB). The present study was to investigate antibacterial activity, synergy, and modes of action of luteolin and quercetin using alone and plus ceftazidime against S. pyogenes. The MICs of ceftazidime, luteolin, and quercetin against all S. pyogenes were 0.50, 128, and 128 µg mL⁻¹, respectively. A synergistic effect was exhibited on luteolin and quercetin plus ceftazidime against these strains at fractional inhibitory concentration indices 0.37 and 0.27, respectively, and was confirmed by the viable count. These combinations increased cytoplasmic membrane (CM) permeability, caused irregular cell shape, peptidoglycan, and CM damage, and decreased nucleic acid but increased proteins in bacterial cells. Enzyme assay demonstrated that these flavonoids had an inhibitory activity against β-lactamase. In summary, this study provides evidence that the inhibitory mode of action of luteolin and quercetin may be mediated via three mechanisms: (1) inhibiting of peptidoglycan synthesis, (2) increasing CM permeability, and (3) decreasing nucleic acid but increasing the protein contents of bacterial cells. So, luteolin and quercetin propose the high potential to develop adjunct to ceftazidime for the treatment of coexistence of the BLPB and S. pyogenes infections.

Bioavailability of dietary polyphenols and gut microbiota metabolism: antimicrobial properties

Polyphenolic compounds are plant nutraceuticals showing a huge structural diversity, including chlorogenic acids, hydrolyzable tannins, and flavonoids (flavonols, flavanones, flavan-3-ols, anthocyanidins, isoflavones, and flavones). Most of them occur as glycosylated derivatives in plants and foods. In order to become bioactive at human body, these polyphenols must undergo diverse intestinal transformations, due to the action of digestive enzymes, but also by the action of microbiota metabolism. After elimination of sugar tailoring (generating the corresponding aglycons) and diverse hydroxyl moieties, as well as further backbone reorganizations, the final absorbed compounds enter the portal vein circulation towards liver (where other enzymatic transformations take place) and from there to other organs, including behind the digestive tract or via blood towards urine excretion. During this transit along diverse tissues and organs, they are able to carry out strong antiviral, antibacterial, and antiparasitic activities. This paper revises and discusses these antimicrobial activities of dietary polyphenols and their relevance for human health, shedding light on the importance of polyphenols structure recognition by specific enzymes produced by intestinal microbial taxa.

Synergistic activity and mechanism of action of Stephania suberosa Forman extract and ampicillin combination against ampicillin-resistant Staphylococcus aureus

Background

Ampicillin-resistant S. aureus (ARSA) now poses a serious problem for hospitalized patients, and their care providers. Plant-derived antibacterial that can reverse the resistance to well-tried agents which have lost their original effectiveness are the research objectives of far reaching importance. To this aim, the present study investigated antibacterial and synergistic activities of Stephania suberosa extracts (SSE) against ARSA when used singly and in combination with ampicillin.

Results

The majority chemical compounds of SSE were alkaloid (526.27 ± 47.27 mg/1 g of dried extract). The Minimum inhibitory concentration (MICs) for ampicillin and SSE against all ARSA strains were >512 μg/ml and 4 mg/ml, respectively. Checkerboard assay revealed synergistic activity in the combination of ampicillin (0.15 μg/ml) and SSE (2 mg/ml) at fractional inhibitory concentration index (FICI) <0.5. The killing curve assay had confirmed that the viability of ARSA was dramatically reduced from 5x10⁵ cfu/ml to 10³ cfu/ml within 6 h after exposure to SSE (2 mg/ml) plus ampicillin (0.15 μg/ml) combination. Electron microscopic study clearly revealed that these ARSA cells treated with this combination caused marked morphological damage, peptidoglycan and cytoplasmic membrane damage, and average cell areas significant smaller than control. Obviously, Immunofluorescence staining and confocal microscopic images confirmed that the peptidoglycan of these cells were undoubtedly disrupted by this combination. Furthermore, the CM permeability of ARSA was also increased by this combination. Enzyme assay demonstrated that SSE had an inhibitory activity against β-lactamase in concentrations manner.

Conclusions

So, these findings provide evidence that SSE has the high potential to reverse bacterial resistance to originate traditional drug susceptibility of it and may relate to three modes of actions of SSE: (1) inhibits peptidoglycan synthesis, resulting in morphological damage, (2) inhibits β-lactamases activity, and (3) increases CM permeability. It is widely recognized that many types of drugs are derived from alkaloids. So, this SSE offers the prominent potential to develop a novel adjunct phytopharmaceutical to ampicillin for the treatment of ARSA. Further active ingredients study, toxicity of it, and the synergistic effect on blood and tissue should be performed and confirmed in an animal test or in humans.

Luteolin decreases the attachment, invasion and cytotoxicity of UPEC in bladder epithelial cells and inhibits UPEC biofilm formation

Urinary tract infection (UTI), primarily caused by uropathogenic Escherichia coli (UPEC), is one of the most common infectious diseases worldwide. Emerging antibiotic resistance requires novel treatment strategies. Luteolin, a dietary polyphenolic flavonoid, has been confirmed as a potential antimicrobial agent. Here, we evaluated the sub-MICs of luteolin for potential properties to modulate the UPEC infection. We found that luteolin significantly decreased the attachment and invasion of UPEC J96 or CFT073 in human bladder epithelial cell lines T24. Meanwhile, obvious decreased expression of type 1 fimbriae adhesin fimH gene, lower bacterial surface hydrophobicity and swimming motility, were observed in luteolin-pretreated UPEC. Furthermore, luteolin could attenuate UPEC-induced cytotoxicity in T24 cells, which manifested as decreased activity of lactate dehydrogenase (LDH). Simultaneously, the inhibition of luteolin on UPEC-induced cytotoxicity was confirmed by ethidium bromide/acridine orange staining. Finally, the luteolin-pretreated UPEC showed a lower ability of biofilm formation. Collectively, these results indicated that luteolin decreased the attachment and invasion of UPEC in bladder epithelial cells, attenuated UPEC-induced cytotoxicity and biofilm formation via down-regulating the expression of adhesin fimH gene, reducing the bacterial surface hydrophobicity and motility.