Inhibition of growth of Streptococcus mutans, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant enterococci by kurarinone, a bioactive flavonoid isolated from Sophora flavescens

Antibacterial phenolic compounds from the flowering plants of Asia and the Pacific: coming to the light

CONTEXT

The emergence of pan-resistant bacteria requires the development of new antibiotics and antibiotic potentiators.

OBJECTIVE

This review identifies antibacterial phenolic compounds that have been identified in Asian and Pacific Angiosperms from 1945 to 2023 and analyzes their strengths and spectra of activity, distributions, molecular masses, solubilities, modes of action, structures-activities, as well as their synergistic effects with antibiotics, toxicities, and clinical potential.

METHODS

All data in this review was compiled from Google Scholar, PubMed, Science Direct, Web of Science, and library search; other sources were excluded. We used the following combination of keywords: 'Phenolic compound', 'Plants', and 'Antibacterial'. This produced 736 results. Each result was examined and articles that did not contain information relevant to the topic or coming from non-peer-reviewed journals were excluded. Each of the remaining 467 selected articles was read critically for the information that it contained.

RESULTS

Out of ∼350 antibacterial phenolic compounds identified, 44 were very strongly active, mainly targeting the cytoplasmic membrane of Gram-positive bacteria, and with a molecular mass between 200 and 400 g/mol. 2-Methoxy-7-methyljuglone, [6]-gingerol, anacardic acid, baicalin, vitexin, and malabaricone A and B have the potential to be developed as antibacterial leads.

CONCLUSIONS

Angiosperms from Asia and the Pacific provide a rich source of natural products with the potential to be developed as leads for treating bacterial infections.

Estrogenic Prenylated Flavonoids in Sophora flavescens

Sophora flavescens is a medicinal herb distributed widely in Japan and it has been used to treat various diseases and symptoms. To explore its pharmacological use, we examined the estrogenic activity of four prenylated flavonoids, namely kurarinone, kushenols A and I, and sophoraflavanone G, which are characterized by the lavandulyl group at position 8 of ring A, but have variations in the hydroxyl group at positions 3 (ring C), 5 (ring A) and 4' (ring B). These prenylated flavonoids were examined via cell proliferation assays using sulforhodamine B, Western blotting, and RT-PCR, corresponding to cell, protein, and transcription assays, respectively, based on estrogen action mechanisms. All the assays employed here found weak but clear estrogenic activities for the prenylated flavonoids examined. Furthermore, the activities were inhibited by an estrogen receptor antagonist, suggesting that the activities were likely being mediated by the estrogen receptors. However, there were differences in the activity, attributable to the hydroxyl group at position 4', which is absent in kushenol A. While the estrogenic activity of kurarinone and sophoraflavanone G has been reported before, to the best of our knowledge, there are no such reports on kushenols A and I. Therefore, this study represents the first report of their estrogenic activity.

The cancer preventive activity and mechanisms of prenylated resveratrol and derivatives

Resveratrol is regarded as neutraceuticals with multiple health benefits. The introduction of prenyl can enhance the bioactivity. In this work, the cancer preventive activities and mechanisms of 18 prenylated reseveratrol and derivatives were investigated. The results showed that prenyl increased the antiproliferative activities of resveratrol, oxyresveratrol and piceatannol against cancer cells, and their antiproliferative activities were time- and dose-dependent. 4-C-prenylation was important for the antiproliferative activity of stilbenoids. The 4-C-prenyl stilbenoids showed better antiproliferative activities than other prenylated stilbenoids. 4-C-prenyl piceatannol showed the best antiproliferative activity. Human hepatoellular carcinomas (HepG₂) cell was more sensitive to prenylated stilbenoids than human MCF-7 breast carcinoma cell. 4-C-prenyl piceatannol had high affinities to Caspase-3, Caspase-9, CDK2 and Cyclin A2. The possible amino acids involved in binding 4-C-prenyl piceatannol were revealed. The expression of Caspase-3 and Caspase-9 were upregulated by 4-C-prenyl piceatannol and the expression of CDK2 and Cyclin A2 in HepG₂ cells were downregulated, which contributed to apoptosis. The above results eludicated the possible antiproliferative mechanisms of prenylated stilbenoids.

Uncovering heterogeneity of anacardic acids from pistachio shells: A novel approach for structural characterization

Anacardic acids (AnAs) are important secondary metabolites that occur primarily in plants of the Anacardiaceae family, such as pistachio (Pistacia vera L.). Some AnAs have been associated with health benefits, and the position of the CC double bonds is a crucial feature of these metabolites. Herein, we propose a new strategy based on RPLC separation and detection by ESI-MS/MS, preceded by an epoxidation reaction. The procedure was applied to the green extracts of lignified pistachio shells, and a mixture of AnAs bearing alkyl chains 13:0, 15:0, and 17:1 emerged as prevailing. As positional isomers of AnA 15:1 (Δ⁸ and Δ⁶) and AnAs 17:1 (Δ¹⁰ and Δ⁸) were identified for the first time, their discovery paves the way to the systematic study of their potential health-beneficial effects. The developed method was validated and applied to quantify AnAs in pistachio ethanolic extract, showing contents higher than 10 mg/ 100 g of biomass.

Herbal Products and Their Active Constituents Used Alone and in Combination with Antibiotics against Multidrug-Resistant Bacteria

The purpose of this review is to summarize the current knowledge acquired on herbal products and their active constituents with antimicrobial activity used alone and in combination with antibiotics against multidrug-resistant bacteria. The most promising herbal products and active constituents used alone against multidrug-resistant bacteria are Piper betle (methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, extended-spectrum beta-lactamase, Acinetobacter baumannii, Pseudomonas aeruginosa), Glycyrrhiza glabra (methicillin-resistant S. aureus, vancomycin-resistant Enterococcus, P. aeruginosa), and berberine (methicillin-resistant S. aureus, A. baumannii, P. aeruginosa), respectively. The synergistic effect of the combination of herbal products and their active constituents with antibiotics against multidrug-resistant bacteria are also described. These natural antibacterial agents can be promising sources of inhibitors, which can modulate antibiotic activity against multidrug-resistant bacteria, especially as efflux pump inhibitors. Other possible mechanisms of action of herbal therapy against multidrug-resistant bacteria including modification of the bacterial cell wall and/or membrane, inhibition of the cell division protein filamenting temperature sensitive Z-ring, and inhibition of protein synthesis and gene expression, all of which will also be discussed. Our review suggests that combination herbal therapy and antibiotics can be effectively used to expand the spectrum of their antimicrobial action. Therefore, combination therapy against multidrug-resistant bacteria may enable new choices for the treatment of infectious diseases and represents a potential area for future research.

Therapeutic Potential of Flavonoids and Tannins in Management of Oral Infectious Diseases-A Review

Medicinal plants are rich sources of valuable molecules with various profitable biological effects, including antimicrobial activity. The advantages of herbal products are their effectiveness, relative safety based on research or extended traditional use, and accessibility without prescription. Extensive and irrational usage of antibiotics since their discovery in 1928 has led to the increasing expiration of their effectiveness due to antibacterial resistance. Now, medical research is facing a big and challenging mission to find effective and safe antimicrobial therapies to replace inactive drugs. Over the years, one of the research fields that remained the most available is the area of natural products: medicinal plants and their metabolites, which could serve as active substances to fight against microbes or be considered as models in drug design. This review presents selected flavonoids (such as apigenin, quercetin, kaempferol, kurarinone, and morin) and tannins (including oligomeric proanthocyanidins, gallotannins, ellagitannins, catechins, and epigallocatechin gallate), but also medicinal plants rich in these compounds as potential therapeutic agents in oral infectious diseases based on traditional usages such as Agrimonia eupatoria L., Hamamelis virginiana L., Matricaria chamomilla L., Vaccinium myrtillus L., Quercus robur L., Rosa gallica L., Rubus idaeus L., or Potentilla erecta (L.). Some of the presented compounds and extracts are already successfully used to maintain oral health, as the main or additive ingredient of toothpastes or mouthwashes. Others are promising for further research or future applications.

Antibiotic Potentiators Against Multidrug-Resistant Bacteria: Discovery, Development, and Clinical Relevance

Antimicrobial resistance in clinically important microbes has emerged as an unmet challenge in global health. Extensively drug-resistant bacterial pathogens have cropped up lately defying the action of even the last resort of antibiotics. This has led to a huge burden in the health sectors and increased morbidity and mortality rate across the world. The dwindling antibiotic discovery pipeline and rampant usage of antibiotics has set the alarming bells necessitating immediate actions to combat this looming threat. Various alternatives to discovery of new antibiotics are gaining attention such as reversing the antibiotic resistance and hence reviving the arsenal of antibiotics in hand. Antibiotic resistance reversal is mainly targeted against the antibiotic resistance mechanisms, which potentiates the effective action of the antibiotic. Such compounds are referred to as resistance breakers or antibiotic adjuvants/potentiators that work in conjunction with antibiotics. Many studies have been conducted for the identification of compounds, which decrease the permeability barrier, expression of efflux pumps and the resistance encoding enzymes. Compounds targeting the stability, inheritance and dissemination of the mobile genetic elements linked with the resistance genes are also potential candidates to curb antibiotic resistance. In pursuit of such compounds various natural sources and synthetic compounds have been harnessed. The activities of a considerable number of compounds seem promising and are currently at various phases of clinical trials. This review recapitulates all the studies pertaining to the use of antibiotic potentiators for the reversal of antibiotic resistance and what the future beholds for their usage in clinical settings.

Prenylated Flavonoids in Topical Infections and Wound Healing

The review presents prenylated flavonoids as potential therapeutic agents for the treatment of topical skin infections and wounds, as they can restore the balance in the wound microenvironment. A thorough two-stage search of scientific papers published between 2000 and 2022 was conducted, with independent assessment of results by two reviewers. The main criteria were an MIC (minimum inhibitory concentration) of up to 32 µg/mL, a microdilution/macrodilution broth method according to CLSI (Clinical and Laboratory Standards Institute) or EUCAST (European Committee on Antimicrobial Susceptibility Testing), pathogens responsible for skin infections, and additional antioxidant, anti-inflammatory, and low cytotoxic effects. A total of 127 structurally diverse flavonoids showed promising antimicrobial activity against pathogens affecting wound healing, predominantly Staphylococcus aureus strains, but only artocarpin, diplacone, isobavachalcone, licochalcone A, sophoraflavanone G, and xanthohumol showed multiple activity, including antimicrobial, antioxidant, and anti-inflammatory along with low cytotoxicity important for wound healing. Although prenylated flavonoids appear to be promising in wound therapy of humans, and also animals, their activity was measured only in vitro and in vivo. Future studies are, therefore, needed to establish rational dosing according to MIC and MBC (minimum bactericidal concentration) values, test potential toxicity to human cells, measure healing kinetics, and consider formulation in smart drug release systems and/or delivery technologies to increase their bioavailability.

Investigation of the antimicrobial activities of various antimicrobial agents on Streptococcus Mutans Sortase A through computer-aided drug design (CADD) approaches

BACKGROUND AND OBJECTIVE

Tooth decay is a common chronic disease that causes pain, tooth loss, malnutrition, anxiety and significantly affects half of the world's population. Streptococcus mutans (S.mutans), is considered the main pathogen causing tooth decay. Sortase A (SrtA), one of the surface proteins of S. mutans, is a potential target in the development of antimicrobial and caries prevention agents for preventing infections associated with biofilm formation. Recently, various SrtA inhibitors, including small molecules and natural product, especially, trans-chalcone, chlorhexidine (CHX) and flavonoid compounds, which exhibit effective inhibition against SrtA, have been identified. However, due to the limited number of inhibitors, multi-drug resistance and side-effects the discovery of new inhibitors for SrtA is essential.

METHODS

In this case, various compounds aimed at the target enzyme underwent high-throughput screening with small molecule libraries. For this screening of a total of 178 compounds, 163 were found to be pharmacokinetically suitable by performing an absorption, distribution, metabolism, and excretion (ADME) analysis. Molecular docking was then applied to investigate the interaction mechanism among these suitable compounds and the target enzyme structure at the molecular level.

RESULTS

According to the results of the study, six compounds (CHEMBL243796 (kurarinone), CHEMBL2180472, CHEMBL3335591, CHEMBL373249, CHEMBL1395334, CHEMBL253467 (Isobavachalcone)) exhibited lower docking scores (-7.18, -6.59, -6.53, -6.47, -6.43, and -6.39 kcal/mol, respectively) against S. mutans SrtA than the positive control CHX (-6.29 kcal/mol). Finally, the 100 ns molecular dynamic simulations and binding free energy calculations were performed for the structure stability analysis of the enzyme with CHEMBL243796 (kurarinone), which showed the lowest docking score. As a result of these studies, the stability of the critical interactions between kurarinone and the target enzyme was preserved during the simulation time.

CONCLUSIONS

These results indicate that flavonoid and chalcone scaffold compounds are clinically more reliable and potent than CHX as novel inhibitory agents for inhibiting oral biofilm formation. These finding can provide important contribution to the future clinical trials in the development of therapeutically useful inhibitors of SrtA by virtually screening several chemical compounds more rapidly to select suitable compounds for the prevention and treatment of dental caries.

Five-Decade Update on Chemopreventive and Other Pharmacological Potential of Kurarinone: a Natural Flavanone

In the present article we present an update on the role of chemoprevention and other pharmacological activities reported on kurarinone, a natural flavanone (from 1970 to 2021). To the best of our knowledge this is the first and exhaustive review of kurarinone. The literature was obtained from different search engine platforms including PubMed. Kurarinone possesses anticancer potential against cervical, lung (non-small and small), hepatic, esophageal, breast, gastric, cervical, and prostate cancer cells. In vivo anticancer potential of kurarinone has been extensively studied in lungs (non-small and small) using experimental xenograft models. In in vitro anticancer studies, kurarinone showed IC₅₀ in the range of 2–62 µM while in vivo efficacy was studied in the range of 20–500 mg/kg body weight of the experimental organism. The phytochemical showed higher selectivity toward cancer cells in comparison to respective normal cells. kurarinone inhibits cell cycle progression in G2/M and Sub-G1 phase in a cancer-specific context. It induces apoptosis in cancer cells by modulating molecular players involved in apoptosis/anti-apoptotic processes such as NF-κB, caspase 3/8/9/12, Bcl2, Bcl-XL, etc. The phytochemical inhibits metastasis in cancer cells by modulating the protein expression of Vimentin, N-cadherin, E-cadherin, MMP2, MMP3, and MMP9. It produces a cytostatic effect by modulating p21, p27, Cyclin D1, and Cyclin A proteins in cancer cells. Kurarinone possesses stress-mediated anticancer activity and modulates STAT3 and Akt pathways. Besides, the literature showed that kurarinone possesses anti-inflammatory, anti-drug resistance, anti-microbial (fungal, yeast, bacteria, and Coronavirus), channel and transporter modulation, neuroprotection, and estrogenic activities as well as tyrosinase/diacylglycerol acyltransferase/glucosidase/aldose reductase/human carboxylesterases 2 inhibitory potential. Kurarinone also showed therapeutic potential in the clinical study. Further, we also discussed the isolation, bioavailability, metabolism, and toxicity of Kurarinone in experimental models.

Pharmacokinetic and bioavailability study of kurarinone in dog plasma by UHPLC-MS/MS

Kurarinone, a natural prenylated flavonone isolated from Sophora flavescens, has been exhibited various activities. This study aimed to establish a simple and sensitive ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for determining kurarinone in dog plasma. Acetonitrile-mediated precipitation was applied for sample pretreatment. Chromatographic separation was achieved on a Waters ACQUITY HSS T3 (100 × 2.1 mm, i. d., 1.8 μm) column with gradient elution using water containing 0.1% formic acid and acetonitrile as mobile phase. Quantitation was performed using an electrospray ionization source in negative multiple reaction monitoring mode. The linearity of this method was over the concentration range 0.1-500 ng/mL with the lowest limit of quantification (LLOQ) of 0.1 ng/mL. The intra- and inter-day precision was less than 10.51% and the accuracy ranged from 94.85% to 97.72%, respectively. The extraction recovery of kurarinone in dog plasma was more than 82.37% and no significant matrix effect was observed. The analyte was stable under tested storage conditions. The validated method was further successfully applied to a preclinical pharmacokinetic study of kurarinone in dog after a single intravenous (2 mg/kg) and oral (20 mg/kg) administration. The results revealed that kurarinone was rapidly absorbed into plasma with good bioavailability (38.19%) and low clearance.

Maackiain, a compound derived from Sophora flavescens, increases IL-1β production by amplifying nigericin-mediated inflammasome activation

Sophora flavescens is used as a traditional herbal medicine to modulate inflammatory responses. However, little is known about the impact of (-)-maackiain, a compound derived from S. flavescens, on the activation of inflammasome/caspase-1, a key factor in interleukin-1β (IL-1β) processing. Here, we report that (-)-maackiain potently amplified caspase-1 cleavage in macrophages in response to nigericin (Nig). In macrophages primed with either lipopolysaccharide or monophosphoryl lipid A, Nig-mediated caspase-1 cleavage was also markedly promoted by (-)-maackiain. Notably, (-)-maackiain induced the production of vimentin, an essential mediator for the activation of the NOD-, LRR-, and pyrin domain-containing protein 3 inflammasome, thereby contributing to promotion of the formation of the inflammasome complex to activate caspase-1. Taken together, our data suggest that (-)-maackiain exerts an immunostimulatory effect by promoting IL-1β production via activation of the inflammasome/caspase-1 pathway. Thus, the potent inflammasome-activating effect of (-)-maackiain may be clinically useful as an acute immune-stimulating agent.

Integrated metabolomics and network pharmacology strategy for ascertaining the quality marker of flavonoids for Sophora flavescens

Traditional Chinese medicines (TCMs) have been widely used in Asian countries for thousands of years due to their supreme quality and good clinical efficacy. However, the increasing demand for TCMs in recent decades warrants effective quality control methodology to avoid clinical problems. Therefore, comprehensive quality evaluation systems should be established for ensuring TCM's quality, in terms of chemical components, as well as bioactivity for identifying quality markers in TCM and developing suitable analytical methods for quality control. In this study, we selected Sophora flavescens (S. flavescens) as the research object and developed a novel integrated strategy combining metabolomics and network pharmacology to explore the quality markers. Firstly, we determined the targeted metabolomic profiles of seventy-four batches of S. flavescens (aged from 1 to 6 years) by UHPLC/QE-MS. Six potential markers were successfully screened, quantified and reverse-verified as the most influential effective compounds by UHPLC/QE-MS and multivariate statistical analysis. Secondly, the network of "components-targets-pathways" was constructed, and the pharmacological activities of six potential markers were predicted. Finally, we determined the anti-tumor activity of six flavonoids (kurarinone, norkurarinone, kuraridin, kushenol N, trifolirhizin, and genistein) as the quality markers for Sophora flavescens, evaluated their pharmacokinetic profiles and reviewed their existing pharmacological researches. Thus, integrated metabolomics and network pharmacology technology were applied for the effective discovery of quality markers of Chinese material medica.

The RUTI trial: A feasibility study exploring Chinese herbal medicine for the treatment of recurrent urinary tract infections

ETHNOPHARMACOLOGICAL RELEVANCE

Chinese herbal medicine (CHM) is a widely used traditional intervention that may have a role to play in addressing the global problem of antimicrobial resistance in conditions such as recurrent urinary tract infections (RUTIs).

AIM OF THE STUDY

To evaluate the feasibility of administering standardised and individualised formulations of CHM for RUTIs as a Clinical Trial of an Investigational Medicinal Product (CTIMP) within primary care of the UKs National Health Service (NHS).

MATERIALS AND METHODS

Regulatory approval was applied for a placebo controlled, double blinded randomised controlled feasibility trial comparing a) standardised CHM vs placebo administered via General practitioners, and b) individualised CHM vs placebo administered by an experienced CHM practitioner. Primary feasibility outcomes included: gaining regulatory approval, recruitment, randomisation, retention, safety and the relevance of outcomes measures.

RESULTS

Regulatory approval for testing CHM as a CTIMP was successfully obtained. Recruitment to the trial was slow and non-NHS self help networks were required to find participants for the individualised arm (n = 31). Retention and data collection in the standardised arm (n-30) were problematic, but these were acceptable in the individualised arm. The use of a daily symptom diary was not a suitable outcome measure for women with continuous infection. Other measures showed promising preliminary data for the individualised arm on improvement in symptoms, and reduction in antibiotic use during and after the trial.

CONCLUSION

CHM can fulfil the demanding requirements of a CTIMP study but it may not be feasible at this point in time to recruit and treat via NHS primary care. However acceptable rates of recruitment and retention via self-help groups and promising preliminary results in the individualised arm suggest it would be worth testing this approach in a full trial.

Antitumor effect of kurarinone and underlying mechanism in small cell lung carcinoma cells

Background

Kurarinone, a prenylated flavonone isolated from the roots of Sophora flavescens, is known to be cytotoxic against many human cancer cells but not human small cell lung carcinoma (SCLC) yet. Also, the exact molecular mechanism of kurarinone for induction cytotoxicity remains unknown.

Material and methods

We investigated the effects of kurarinone on cell proliferation, apoptosis, and migration in H1688 SCLC cells. Cell viability was determined by the MTT assay. Apoptotic indices such as cell cycle, mitochondrial membrane potential, cytochrome c release, caspase activity, and death receptors were evaluated by flow cytometry. Transwell migration and invasion assays were also included.

Results

Our results indicated that kurarinone significantly decreased H1688 cell viability and induced the accumulation of sub-G1 fractions by activating caspase-3, -9, and PARP cleavage accompanied by the elevated release of cytochrome c and mitochondrial dysfunction in H1688 cells. Additionally, kurarinone promoted Fas and TRAIL receptor-1 and -2 expression via the caspase-8/Bid pathway, suggesting that kurarinone triggered apoptosis via the mitochondria-mediated and receptor-mediated apoptotic pathways. We also observed that kurarinone repressed migration and invasion capabilities of SCLC cells by suppressing the expression of epithelial-mesenchymal transition-related proteins and matrix metalloproteinases.

Conclusion

Our findings provided evidence that kurarinone can induce apoptosis in SCLC cells via multiple mechanisms and delayed the cell migration and invasion of SCLC cells.

Biologically active prenylated flavonoids from the genus Sophora and their structure-activity relationship-A review

The genus Sophora (Fabaceae) has been used in traditional medicine for years. Prenylated flavonoids are one of the constituents of Sophora species that play important roles in their biological properties. Different classes of prenylated flavonoids are produced by Sophora spp. including prenylated flavonol (e.g., sophoflavescenol), prenylated flavanone (e.g., sophoraflavanone G), prenylated flavonostilbene (e.g., alopecurones A and B), and prenylated chalcone (kuraridin). Prenylated flavonoids have a more lipophilic structure, which leads to its high affinity to the cell membranes and enhancement of the biological activity, which includes cytotoxicity, antibacterial, anti-inflammatory, and estrogenic activities. However, it is reported that prenylation decreases the plasma absorption but increases the tissue accumulation. The presence of the prenyl or lavandulyl groups on C8 position of flavonoids plays an important role in the biological activity. It seems that prenylated flavonoids have the potential to be developed as new drugs or supplements for human health.

Sophora flavescens protects against mycobacterial Trehalose Dimycolate-induced lung granuloma by inhibiting inflammation and infiltration of macrophages

The immune system responds to Mycobacterium tuberculosis (MTB) infection by forming granulomas to quarantine the bacteria from spreading. Granuloma-mediated inflammation is a cause of lung destruction and disease transmission. Sophora flavescens (SF) has been demonstrated to exhibit bactericidal activities against MTB. However, its immune modulatory activities on MTB-mediated granulomatous inflammation have not been reported. In the present study, we found that flavonoids from Sophora flavescens (FSF) significantly suppressed the pro-inflammatory mediators released from mouse lung alveolar macrophages (MH-S) upon stimulation by trehalose dimycolate (TDM), the most abundant lipoglycan on MTB surface. Moreover, FSF reduced adhesion molecule (LFA-1) expression on MH-S cells after TDM stimulation. Furthermore, FSF treatment on TDM-activated lung epithelial (MLE-12) cells significantly downregulated macrophage chemoattractant protein (MCP-1/CCL2) expression, which in turn reduced the in vitro migration of MH-S to MLE-12 cells. In addition, FSF increased the clearance of mycobacterium bacteria (Mycobacterium aurum) in macrophages. FSF mainly affected the Mincle-Syk-Erk signaling pathway in TDM-activated MH-S cells. In TDM-induced mouse granulomas model, oral administration with FSF significantly suppressed lung granulomas formation and inflammation. These findings collectively implicated an anti-inflammatory role of FSF on MTB-mediated granulomatous inflammation, thereby providing evidence of FSF as an efficacious adjunct treatment during mycobacterial infection.

Synergism of prenylflavonoids from Morus alba root bark against clinical MRSA isolates

BACKGROUND

Clinical methicillin-resistant Staphylococcus aureus (MRSA) is a thorny problem in current anti-infective therapeutics and a challenge of new drug development. Plant prenylflavonoids possess anti-MRSA activity, but few of the prenylflavonoids have been reported the synergistic anti-MRSA effect when they are used in combination with conventional antibacterial agents.

PURPOSE

This study deals with anti-MRSA activity of four prenylflavonoids from the root bark of Morus alba and their synergism with 11 conventional antibacterial agents.

METHODS

Chromatographic methods and spectral analysis were used to isolate and identify the prenylflavonoids. The antibacterial activity and synergism were assessed by the broth microdilution method, checkerboard dilution test, and time-kill curve assay, respectively.

RESULTS

Four prenylflavonoids, i.e., cyclocommunol (Cy, 1), morusinol (Ml, 2), morusin (Mi, 3) and kuwanon E (Ku, 4), were isolated from Morus alba bark ethanol extract. Compounds 1, 3 and 4 showed high antimicrobial activity on both methicillin-susceptible S. aureus (MSSA) and MRSA strains with MICs/MBCs at 4-16/32-64 and 4-32/16-128 µg/ml, respectively. Ml (2) was not active. Compound 2 showed synergy with amikacin (AK) and streptomycin (SM) against all the ten MRSA isolates. Ml (2) and Ku (4) also showed synergy with ciprofloxacin (CI), etimicin (EM) and vancomycin (VA) against 7-9 isolates. The fractional inhibitory concentration indices (FICIs) ranged 0.09-1.00 and the dose reduction indices (DRIs) of these antibacterial agents ranged 2-128. Cy (1) and Mi (3) showed synergy with the tested antibacterial agents against only 1-3 MRSA isolates except VA. Furthermore, the MRSA resistance could be reversed in the combinations of AK with Cy, Ml, Mi and Ku; EM with Mi and Ku; and SM with Ml by the criteria of MIC interpretive standards for Staphylococcus spp. of CLSI. All the combinations showed only indifference in the 1 × MIC time-killing experiments. The prenylated substitutions play an important role in the activity of the compounds used alone and combined with the tested antibacterials.

CONCLUSIONS

The study revealed for the first time the anti-MRSA synergism of prenylflavonoids 1-4 with eleven antibacterial agents and the reversal of MRSA resistance to aminoglycosides, especially amikacin. The results might be valuable for the development of new antibacterial drugs and synergists against MRSA infection.

Antimicrobial Air Filters Using Natural Euscaphis japonica Nanoparticles

Controlling bioaerosols has become more important with increasing participation in indoor activities. Treatments using natural-product nanomaterials are a promising technique because of their relatively low toxicity compared to inorganic nanomaterials such as silver nanoparticles or carbon nanotubes. In this study, antimicrobial filters were fabricated from natural Euscaphis japonica nanoparticles, which were produced by nebulizing E. japonica extract. The coated filters were assessed in terms of pressure drop, antimicrobial activity, filtration efficiency, major chemical components, and cytotoxicity. Pressure drop and antimicrobial activity increased as a function of nanoparticle deposition time (590, 855, and 1150 µg/cm2(filter) at 3-, 6-, and 9-min depositions, respectively). In filter tests, the antimicrobial efficacy was greater against Staphylococcus epidermidis than Micrococcus luteus; ~61, ~73, and ~82% of M. luteus cells were inactivated on filters that had been coated for 3, 6, and 9 min, respectively, while the corresponding values were ~78, ~88, and ~94% with S. epidermidis. Although statistically significant differences in filtration performance were not observed between samples as a function of deposition time, the average filtration efficacy was slightly higher for S. epidermidis aerosols (~97%) than for M. luteus aerosols (~95%). High-performance liquid chromatography (HPLC) and electrospray ionization-tandem mass spectrometry (ESI/MS) analyses confirmed that the major chemical compounds in the E. japonica extract were 1(ß)-O-galloyl pedunculagin, quercetin-3-O-glucuronide, and kaempferol-3-O-glucoside. In vitro cytotoxicity and disk diffusion tests showed that E. japonica nanoparticles were less toxic and exhibited stronger antimicrobial activity toward some bacterial strains than a reference soluble nickel compound, which is classified as a human carcinogen. This study provides valuable information for the development of a bioaerosol control system that is environmental friendly and suitable for use in indoor environments.

Potential biological applications of bio-based anacardic acids and their derivatives

Cashew nut shells (CNS), which are agro wastes from cashew nut processing factories, have proven to be among the most versatile bio-based renewable materials in the search for functional materials and chemicals from renewable resources. CNS are produced in the cashew nut processing process as waste, but they contain cashew nut shell liquid (CNSL) up to about 30-35 wt. % of the nut shell weight depending on the method of extraction. CNSL is a mixture of anacardic acid, cardanol, cardol, and methyl cardol, and the structures of these phenols offer opportunities for the development of diverse products. For anacardic acid, the combination of phenolic, carboxylic, and a 15-carbon alkyl side chain functional group makes it attractive in biological applications or as a synthon for the synthesis of a multitude of bioactive compounds. Anacardic acid, which is about 65% of a CNSL mixture, can be extracted from the agro waste. This shows that CNS waste can be used to extract useful chemicals and thus provide alternative green sources of chemicals, apart from relying only on the otherwise declining petroleum based sources. This paper reviews the potential of anacardic acids and their semi-synthetic derivatives for antibacterial, antitumor, and antioxidant activities. The review focuses on natural anacardic acids from CNS and other plants and their semi-synthetic derivatives as possible lead compounds in medicine. In addition, the use of anacardic acid as a starting material for the synthesis of various biologically active compounds and complexes is reported.

Review: Chinese herbs as alternatives to antibiotics in feed for swine and poultry production: Potential and challenges in application

Gong, J., Yin, F., Hou, Y. and Yin, Y. 2014. Chinese herbs as alternatives to antibiotics in feed for swine and poultry production: Potential and challenges in application. Can. J. Anim. Sci. 94: 223–241. Traditional Chinese medicine (TCM) has a long history of clinical practice, and its own theoretical framework focused on functions at the whole-body level. However, due to cultural differences, TCM has not been fully recognized in Western countries. With the recent development of the theory of whole-body systems biology and “-omics”, there is a new opportunity to study TCM and to close the gap between TCM and Western medicine, because of the similarity in the theoretical foundations between TCM and whole-body systems biology. The uniqueness of TCM theory and practice is the approach to maintain and restore the body balance as a whole with no or little unfavourable side effects. Recent studies have also shown that Chinese herbs used as feed additives can modulate nutritional metabolism, immune responses, and intestinal health of food-producing animals, demonstrating good potential as substitutes for dietary antibiotics. Nonetheless, some issues need to be addressed before Chinese herbs can reach their full application. This article has critically reviewed recent progresses in scientific research of Chinese herbs as feed additives and their potential to replace dietary antibiotics. Possible challenges in future application for swine and poultry production are also discussed.

In-Vitro and in-Silico characterization of Sophora interrupta plant extract as an anticancer activity

Sophora interrupta belongs to the family of Fabaceae and the species in this genus have a diverse medicinal importance as a folk medicine for preventing many ailments including cancer. In order to evaluate the anticancer activity of S.interrupta, we have performed in vitro anti-oxidant, anti-inflammatory, anti-proliferative, and cell based anticancer activity in MCF-7 and PC-3 cell lines. Secondary metabolites of S.interrupta were used to identify anticancer compounds using Open Eye software. The antioxidant activity of the S.interrupta root ethylacetate (SEA) extract at 100 µg/ml is equal to that of ascorbic acid at 50 µg/ml. The antiinflammatory activity of SEA is half of that of diclofenac at 50 µg/ml. Anticancer activity was detected by measuring the mitochondrial dehydrogenase activity (MTT assay). The half maximal inhibitory concentrations (IC₅₀) for MCF-7 and PC-3 cell lines are 250 and 700 µg/ml respectively. This was supported by the morphological changes such as membrane blebbing, cell detachment and rounded cell morphology when compared to the parental cells. In addition, we observed few green cells (live) over red cells (dead) based on the uptake of acridine orange and ethidium bromide dyes. Kaempferol-3-O-b-D-glucopyranoside, a Secondary metabolite of S.interrupta form 6 hydrogen bond interactions with Arg 202, Gln 207, Gly 227, Gly 229, Thr 231 and Ala 232 human DEAD box RNA helicase, DDX3 protein and is equivalent to crystal structure of adenosine mono phosphate to DDX3. Overall, it suggests that the SEA extract has anticancer compounds, and it can be used to enhance death receptor mediated cancer cell death.

Total alkaloids from Sophora alopecuroides L. increase susceptibility of extended-spectrum β-lactamases producing Escherichia coli isolates to cefotaxime and ceftazidime

OBJECTIVE

To evaluate the antimicrobial activity of total alkaloids extracted from Sophorea alopecuroides L. (TASA) against clinical isolated extended-spectrum beta-lactamases (ESBLs) producing Escherichia coli (E. coli) strains.

METHODS

The antibacterial activity of TASA either itself or in combination with cefotaxime (CTX) or ceftazidime (CAZ) was investigated by using the microbroth dilution method and phenotypic confirmatory disk diffusion test against three clinical isolated ESBLs-producing E. coli strains; the interactions of TASA and CTX or CAZ were ascertained by evaluating the fractional inhibitory concentration index (FICI).

RESULTS

The antibacterial activity of either TASA itself or in combination with CTX or CAZ was found. The minimum inhibitory concentration (MICs) of TASA against the ESBLs producing isolates was 12.5 mg/mL. In the combinations with a sub-inhibitory concentration of TASA, a synergistic effect on CTX and CAZ against the ESBLs producing isolates was observed. Similarly, the isolates exposed to lower dose of TASA yielded an increased susceptibility to CTX and CAZ by 8-16 folds determined by microdilution assay. Moreover, enzymatic detection of ESBLs demonstrated that TASA induced reversal resistance to CTX and CAZ partially by a mechanism of inhibition of ESBLs activity in these isolates. Additionally, in the tested isolates following the exposure of TASA, molecular analysis verified the SHV-type beta-lactamase encoding ESBL gene in these isolates, and no mutation was introduced into the ESBL gene.

CONCLUSIONS

These results suggest that TASA could be used as a source of natural compound with pharmacological activity of reversal resistance to antimicrobial agent. These findings also indicated that the application of the TASA in combination with antibiotics might prove useful in the control and treatment of infectious diseases caused by the ESBLs producing enterobacteriaceae.

Rapid probing of biological surfaces with a sparse-matrix peptide library

Finding unique peptides to target specific biological surfaces is crucial to basic research and technology development, though methods based on biological arrays or large libraries limit the speed and ease with which these necessary compounds can be found. We reasoned that because biological surfaces, such as cell surfaces, mineralized tissues, and various extracellular matrices have unique molecular compositions, they present unique physicochemical signatures to the surrounding medium which could be probed by peptides with appropriately corresponding physicochemical properties. To test this hypothesis, a naïve pilot library of 36 peptides, varying in their hydrophobicity and charge, was arranged in a two-dimensional matrix and screened against various biological surfaces. While the number of peptides in the matrix library was very small, we obtained “hits” against all biological surfaces probed. Sequence refinement of the “hits” led to peptides with markedly higher specificity and binding activity against screened biological surfaces. Genetic studies revealed that peptide binding to bacteria was mediated, at least in some cases, by specific cell-surface molecules, while examination of human tooth sections showed that this method can be used to derive peptides with highly specific binding to human tissue.

In vitro sortase A inhibitory and antimicrobial activity of flavonoids isolated from the roots of Sophora flavescens

A series of flavonoids (1-14) was isolated from the roots of Sophora flavescens. We evaluated their ability to inhibit both microbial growth and sortase A, an enzyme that plays a key role in cell wall protein anchoring and virulence in Staphylococcus aureus. Most prenylated flavonoids (7-13) displayed potent inhibitory activity against gram-positive and gram-negative bacteria except E. coli, with minimum inhibitory concentrations values ranging from 4.40 to 27.7 μM, and weak or no activity against fungal strains tested. Kurarinol (6) was a potent inhibitor of sortase A, with an IC(50) value of 107.7 ± 6.6 μM. A preliminary structure-activity relationship, including essential structural requirements, is described.

Antibacterial activity of sophoraflavanone G isolated from the roots of Sophora flavescens against methicillin-resistant Staphylococcus aureus

In this study, sophoraflavanone G obtained from Sophora flavescens was evaluated against 10 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), either alone or in combination with ampicillin or oxacillin, via checkerboard assay. At the end point of an optically clear well, the minimum inhibitory concentrations (MICs) ranged from 0.5 to 8 microg/ml for sophoraflavanone G, from 64 to 1024 microg/ml for ampicillin, and from 256 to 1024 microg/ml for oxacillin. The combination of sophoraflavanone G and ampicillin or oxacillin yielded a fractional inhibitory concentration index ranging from 0.188 to 0.375, thereby indicating a principally synergistic effect. The synergistic interaction was verified by time-kill studies using sophoraflavanone G and/or antibiotics. Thirty minutes of treatment with sophoraflavanone G with ampicillin or oxacillin resulted in an increase in the rate of killing in units of CFU/ml to a greater degree than was observed with Sophoraflavanone G alone. These findings indicated that the application of the tested sophoraflavanone G alone or in combination with antibiotics might prove useful in the control and treatment of MRSA infections.

Systematic approach to optimizing specifically targeted antimicrobial peptides against Streptococcus mutans

Previously we reported a novel strategy of "targeted killing" through the design of narrow-spectrum molecules known as specifically targeted antimicrobial peptides (STAMPs) (R. Eckert et al., Antimicrob. Agents Chemother. 50:3651-3657, 2006; R. Eckert et al., Antimicrob. Agents Chemother. 50:1480-1488, 2006). Construction of these molecules requires the identification and the subsequent utilization of two conjoined yet functionally independent peptide components: the targeting and killing regions. In this study, we sought to design and synthesize a large number of STAMPs targeting Streptococcus mutans, the primary etiologic agent of human dental caries, in order to identify candidate peptides with increased killing speed and selectivity compared with their unmodified precursor antimicrobial peptides (AMPs). We hypothesized that a combinatorial approach, utilizing a set number of AMP, targeting, and linker regions, would be an effective method for the identification of STAMPs with the desired level of activity. STAMPs composed of the Sm6 S. mutans binding peptide and the PL-135 AMP displayed selectivity at MICs after incubation for 18 to 24 h. A STAMP where PL-135 was replaced by the B-33 killing domain exhibited both selectivity and rapid killing within 1 min of exposure and displayed activity against multispecies biofilms grown in the presence of saliva. These results suggest that potent and selective STAMP molecules can be designed and improved via a tunable "building-block" approach.

Inhibitory activities of prenylated flavonoids from Sophora flavescens against aldose reductase and generation of advanced glycation endproducts

Important targets for the prevention and treatment of diabetic complications include aldose reductase (AR) inhibitors (ARIs) and inhibitors of advanced glycation endproduct (AGE) formation. Here we evaluate the inhibitory activities of prenylated flavonoids isolated from Sophora flavescens, a traditional herbal medicine, on rat lens AR (RLAR), human recombinant AR (HRAR) and AGE formation. Among the tested compounds, two prenylated chalcones — desmethylanhydroicaritin (1) and 8-lavandulylkaempferol (2) — along with five prenylated flavanones — kurarinol (8), kurarinone (9), (2S)-2′-methoxykurarinone (10), (2S)-3β,7,4′-trihydroxy-5-methoxy-8-(γ,γ-dimethylally)-flavanone (11), and kushenol E (13) were potent inhibitors of RLAR, with IC50 values of 0.95, 3.80, 2.13, 2.99, 3.77, 3.63 and 7.74 μM, respectively, compared with quercetin (IC50 7.73 μM). In the HRAR assay, most of the prenylated flavonoids tested showed marked inhibitory activity compared with quercetin (IC50 2.54 μM). In particular, all tested prenylated flavonols, such as desmethylanhydroicaritin (1, IC50 0.45 μM), 8-lavandulylkaempferol (2, IC50 0.79 μM) and kushenol C (3, IC50 0.85 μM), as well as a prenylated chalcone, kuraridin (5, IC50 0.27 μM), and a prenylated flavanone, (2S)-7,4′-dihydroxy-5-methoxy-8-(γ,γ-dimethylally)-flavanone (12, IC50 0.37 μM), showed significant inhibitory activities compared with the potent AR inhibitor epalrestat (IC50 0.28 μM). Interestingly, prenylated flavonoids 1 (IC50 104.3 μgmL−1), 2 (IC50 132.1 μgmL−1), 3 (IC50 84.6 μgmL−1) and 11 (IC50 261.0 μgmL−1), which harbour a 3-hydroxyl group, also possessed good inhibitory activity toward AGE formation compared with the positive control aminoguanidine (IC50 115.7 μgmL−1). Thus, S. flavescens and its prenylated flavonoids inhibit the processes that underlie diabetic complications and related diseases and may therefore have therapeutic benefit.