Antibacterial activity of flavanostilbenes against methicillin-resistant Staphylococcus aureus

Assembly of the Tricyclic Core of Alopecurone C by Asymmetric Donor/Donor Carbene C-H Insertion

Two routes to assemble the complete tricyclic core of alopecurone C are described. In the first-generation route, an efficient synthesis of the "eastern" half of the target, including a decagram-scale rhodium-catalyzed C-H insertion reaction, was developed. When this route proved intractable for assembling the final flavanone ring, a successful second-generation route was developed from a flavanone precursor (naringenin) employing a later stage C-H insertion. Although the second route was ultimately unsuccessful for preparation of the final target, it does provide the basis for the efficient assembly of the complete tricyclic core of alopecurone C and related flavonostilbenoid natural products.

Antimicrobial potentials of natural products against multidrug resistance pathogens: a comprehensive review

Antibiotic resistance is one of the critical issues, describing a significant social health complication globally. Hence, the discovery of novel antibiotics has acquired an increased attention particularly against drug-resistant pathogens. Natural products have served as potent therapeutics against pathogenic bacteria since the glorious age of antibiotics of the mid 20th century. This review outlines the various mechanistic candidates for dealing with multi-drug resistant pathogens and explores the terrestrial phytochemicals isolated from plants, lichens, insects, animals, fungi, bacteria, mushrooms, and minerals with reported antimicrobial activity, either alone or in combination with conventional antibiotics. Moreover, newly established tools are presented, including prebiotics, probiotics, synbiotics, bacteriophages, nanoparticles, and bacteriocins, supporting the progress of effective antibiotics to address the emergence of antibiotic-resistant infectious bacteria. Therefore, the current article may uncover promising drug candidates that can be used in drug discovery in the future.

Sophoraflavanone G Resensitizes ABCG2-Overexpressing Multidrug-Resistant Non-Small-Cell Lung Cancer Cells to Chemotherapeutic Drugs

Elevated expression of the ATP-binding cassette (ABC) drug transporter ABCG2 in cancer cells contributes to the development of the multidrug resistance phenotype in patients with advanced non-small-cell lung cancer (NSCLC). Due to the lack of U.S. Food and Drug Administration (FDA)-approved synthetic inhibitors of ABCG2, significant efforts have been invested in discovering bioactive compounds of plant origin that are capable of reversing ABCG2-mediated multidrug resistance in cancer cells. Sophoraflavanone G (SFG), a phytoncide isolated from the plant species Sophora flavescens, is known to possess a wide spectrum of pharmacological activities, including antibacterial, anti-inflammatory, antimalarial, and antiproliferative effects. In the present study, the chemosensitizing effect of SFG in ABCG2-overexpressing NSCLC cells was investigated. Experimental results demonstrate that at subtoxic concentrations SFG significantly reversed ABCG2-mediated multidrug resistance in a concentration-dependent manner. Additional biochemical data and in silico docking analysis of SFG to the inward-open conformation of human ABCG2 indicate that SFG inhibited the drug transport function of ABCG2 by interacting with residues within the transmembrane substrate-binding pocket of ABCG2. Collectively, these findings provide evidence that SFG has the potential to be further tested as an effective inhibitor of ABCG2 to improve the efficacy of therapeutic drugs in patients with advanced NSCLC.

Phytoextracts as Antibacterials: A Review

Botanicals have been cultured to flavour food, to treat health disorders and to put a stop to diseases caused by various microorganisms. The awareness of curative features of different medicinal plants has been spread among human communities. The application of herbal products as antimicrobial agents may be a better choice for the extensive and imprudent use of synthetic antibiotics. World Health Organization recommended traditional medicines as the safest remedies for the treatment of diseases of microbial origin. The plant extracts are generally nonhazardous, available in plenty at reasonable prices, biodegradable, eco-friendly and sometimes show broad-spectrum activities against different microorganisms. The current knowledge on plant extracts, phytochemicals and their antibacterial activity, target specific mechanism of action, solvents deployed during extraction, properties of an active ingredient isolated may help in biological control of bacteria. Antimicrobial properties of different plant parts, which act in a low dose, have been organised separately for easy understanding.

Sophora alopecuroides L.: An ethnopharmacological, phytochemical, and pharmacological review

ETHNOPHARMACOLOGICAL RELEVANCE

Sophora alopecuroides L., which is called Kudouzi in China, is a medicinal plant distributed in Western and Central Asia, especially in China, and has been used for decades to treat fever, bacterial infection, heart disease, rheumatism, and gastrointestinal diseases.

AIM OF THE REVIEW

This review aims to provide up-to-date information on S. alopecuroides, including its botanical characterization, medicinal resources, traditional uses, phytochemistry, pharmacological research, and toxicology, in exploring future therapeutic and scientific potentials.

MATERIALS AND METHODS

The information related to this article was systematically collected from the scientific literature databases including PubMed, Google Scholar, Web of Science, Science Direct, Springer, China National Knowledge Infrastructure, published books, PhD and MS dissertations, and other web sources, such as the official website of Flora of China and Yao Zhi website (https://db.yaozh.com/).

RESULTS

A total of 128 compounds, such as alkaloids, flavonoids, steroids, and polysaccharides, were isolated from S. alopecuroides. Among these compounds, the effects of alkaloids, such as matrine and oxymatrine, were extensively studied and developed into new drugs. S. alopecuroides and its active components had a wide range of pharmacological activities, such as anticancer, antiviral, anti-inflammatory, antimicrobial, analgesic, and neuroprotective functions, as well as protective properties against pulmonary fibrosis and cardiac fibroblast proliferation.

CONCLUSIONS

As an important traditional Chinese medicine, modern pharmacological studies have demonstrated that S. alopecuroides has prominent bioactivities, especially on gynecological inflammation and hepatitis B, and anticancer activities. These activities provide prospects for novel drug development for cancer and some chronic diseases. Nevertheless, the comprehensive evaluation, quality control, understanding of the multitarget network pharmacology, long-term in vivo toxicity, and clinical efficacy of S. alopecuroides require further detailed research.

C-H Insertion Reactions of Donor/Donor Carbenes: Inception, Investigation, and Insights

Insertion reactions of donor/donor carbenes have emerged from obscurity to become a versatile method for the synthesis of a variety of cyclic structures with excellent control of diastereo- and enantioselectivity. This Account describes the origin of this project as part of a natural product synthesis and the ensuing decade of reaction development that has resulted in new asymmetric methods as well as intriguing tangential observations.

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.

Chemical constituents isolated from the Mongolian medicinal plant Sophora alopecuroides L. and their inhibitory effects on LPS-induced nitric oxide production in RAW 264.7 macrophages

Three new flavonostilbenes, alopecurones M-O (1-3), were isolated from the root bark of Sophora alopecuroides L. together with 21 known compounds. The structures of the isolated compounds were elucidated by using NMR, MS, and CD spectroscopic data. All isolates were evaluated for their potential to inhibit LPS-induced nitric oxide production in RAW 264.7 cells.

Flavonostilbenes from Sophora alopecuroides L. as multidrug resistance associated protein 1 (MRP1) inhibitors

Flavonoids have always attracted much attention due to their reversal activity on multidrug resistance (MDR). Eight flavonoids isolated from traditional Chinese medicine Sophora alopecuroides L. were applied to test their effect on MDR associated protein 1 (MRP1) through the established predicting assay. Three flavonostilbenes (alopecurone A, B and D) were first found exhibiting potent inhibitory activity on MRP1. All of them dramatically increased 6-carboxyfluorescein diacetate and doxorubicin accumulation in MRP1-transfected U-2 OS cells. The compounds significantly increased the cytotoxicity and decreased the IC₅₀ value of doxorubicin on the MDR cells (12-, 5- and 8-fold, respectively) at a non-toxic concentration (20 μM). Besides, Q-PCR analysis reveals that the MRP1 mRNA level in U-2 OS/MRP1 was also markedly decreased by the three compounds. These findings indicate a new therapeutic role of the herb. The three flavonostilbenes may have the possibility for further development as novel therapeutic reversal agents against MDR.

Synthesis of stilbene-fused 2'-hydroxychalcones and flavanones

Synthesis of stilbene-fused chalcones and flavanones were successfully completed. Molecules were designed in a way to mimic the structural features of both "stilbene and chalcones" or "stilbene and flavanones" at the same time, and synthesized by three steps. Heck reactions of 3-bromobenzaldehyde with styrene derivatives gave corresponding (E)-stilbenes, which were reacted with acetophenones to furnish stilbene-fused 2'-hydroxychalcones under basic conditions. Finally, intramolecular cyclization reactions were performed to produce stilbene-fused flavanones.

Antibacterial activity of phytochemicals isolated fromErythrina zeyheri against vancomycin-resistant enterococci and their combinations with vancomycin

Six phytochemicals were isolated from the roots of Erythrina zeyheri (Leguminosae) by repeated silica gel column chromatography using various eluting solvents. Extensive spectroscopic studies revealed that all were isoflavonoids. The antibacterial activity of the six compounds against vancomycin-resistant enterococci (VRE) was estimated by determining the minimum inhibitory concentration (MIC). Of the six isoflavonoids, erybraedin A ((6aR, 11aR)-3,9-dihydroxy-4,10-di(gamma,gamma-dimethylallyl)pterocarpan) exhibited the highest growth inhibitory potency against VRE with an MIC value of 1.56-3.13 microg/mL, followed by eryzerin C ((3R)-7,2',4'-trihydroxy-6,8-di(gamma,gamma-dimethylallyl)isoflavan) (MIC 6.25 microg/mL). These compounds also inhibited the growth of methicillin-resistant Staphylococcus aureus (MRSA) at 3.13-6.25 microg/mL. The antibacterial effects of the two compounds against VRE and MRSA were based on bacteriostatic action. When erybraedin A or eryzerin C was combined with vancomycin, the fractional inhibitory concentration (FIC) index against VRE ranged from 0.5306 to 1.0 and from 0.5153 to 0.75, respectively. The combinations also showed FIC indices of 0.6125-1.0 against MRSA. The results indicate that, depending on the case, both compounds act either synergistically or additively with vancomycin against VRE and MRSA. Erybraedin A and eryzerin C show evidence of being potent phytotherapeutic agents against infections caused by VRE and MRSA.

Antibacterial properties of a new isoflavonoid from Erythrina poeppigiana against methicillin-resistant Staphylococcus aureus

A new isoflavonoid, together with four known isoflavonoids, was isolated from the roots of Erythrina poeppigiana. The chemical structure was determined by extensive spectroscopic studies, and then its antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) was investigated. The new isoflavonoid was identified as 3,9-dihyroxy-10-gamma,gamma-dimethylallyl-6a,11a-dehydropterocarpan (compound 1). Compound 1 inhibited bacterial growth most potently of the five isolates, and had a minimum inhibitory concentration (MIC) of 125 microg/ml against thirteen MRSA strains. Inhibitory activity was based on bactericidal action and viable cell number reduced by approximately 1/10,000 after 4 h incubation with compound 1. Despite intense bactericidal action against MRSA, compound 1 never resulted in leakage of 260 nm-absorbing substances from bacterial cells. Compound 1 (12.5 microg/ml) completely inhibited incorporation of radio-labeled thymidine, uridine and leucine into MRSA cells. Although glucose incorporation was also markedly inhibited by the compound, the amount of glucose incorporated by bacterial cells increased gradually with incubation time. These findings suggest that compound 1 exhibits anti-MRSA activity by interfering with incorporation of metabolites and nutrients into bacterial cells or by affecting the nucleic acids of MRSA cells. Furthermore, this new compound could be a potent phytotherapeutic agent for treating MRSA infections.

Antibacterial activity of isoflavonoids isolated from Erythrina variegata against methicillin-resistant Staphylococcus aureus

AIMS

To screen 16 isoflavonoids isolated from Erythrina variegata (Leguminosae) for their antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA).

METHODS AND RESULTS

The roots of E. variegata were macerated with acetone. The chloroform-soluble fraction of the residue was subjected to repeated silica gel column chromatography followed by elution with various solvents. Structures of the isolated compounds were determined by extensive spectroscopic studies. Each compound was dissolved in dimethyl sulphoxide and added to agar plates (final concentration 1.56-100 microg ml(-1) and suspensions of MRSA spotted onto the agar plates to determine the minimum inhibitory concentration (MIC). Repeated silica gel chromatography yielded 16 compounds and spectroscopic studies revealed that all were isoflavonoids. Whilst 14 compounds showed antibacterial activity in this concentration range, the MIC values varied significantly among them. Of the active compounds, 3,9-dihydroxy-2,10-di(gamma,gamma-dimethylallyl)-6a,11a-dehydropterocarpan (erycristagallin) and 9-hydroxy-3-methoxy-2-gamma,gamma-dimethylallylpterocarpan (orientanol B) exhibited the highest activity with MIC values of 3.13-6.25 microg ml(-1).

CONCLUSIONS

Erycristagallin and orientanol B showed the highest anti-MRSA activity (3.13-6.25 microg ml(-1).

SIGNIFICANCE AND IMPACT OF THE STUDY

Erycristagallin and orientanol B could be leading compounds for phytotherapeutic agents against MRSA infections.

The pathogenesis of Staphylococcus aureus in the trauma patient and potential future therapies

BACKGROUND

Staphylococcus aureus is the most frequently isolated pathogen in the trauma patient and uses multiple virulent factors to cause infection. At the cellular level, infection begins with the prokaryotic bacterial cell manipulating the eukaryotic host cell through its virulent factors. Researching this cellular interaction by describing the mechanisms of actions of various virulent factors may lead to new preventive therapies which will make the trauma patient less susceptible to S aureus infections.

METHODS

Surgical, medical, and microbial literature was reviewed to provide an update on S aureus pathogenesis.

RESULTS

Novel future therapies, in addition to antibiotics, are being devised based on understanding the molecular nature of S aureus pathogenesis.

CONCLUSION

The impact of S aureus on trauma will increase as S aureus develops more antibiotic resistance and as the trauma population becomes older and includes an increasing proportion of immunocompromised patients. To meet the challenge of increased virulence, trauma surgeons should be directly involved in the research of microbial pathogenesis.

Comparative study on the antibacterial activity of phytochemical flavanones against methicillin-resistant Staphylococcus aureus

Differently substituted flavanones were isolated from Leguminosae and their antibacterial activity was comparatively studied against methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentrations (MICs) of phytochemical flavanones to clinical isolates of MRSA were determined by a serial agar dilution method. The structure-activity relationship has indicated that 2',4'- or 2',6'-dihydroxylation of the B ring and 5,7-dihydroxylation of the A ring in the flavanone structure are important for significant anti-MRSA activity and that substitution with a certain aliphatic group at the 6- or 8-position also enhances the activity. Among the thirteen flavanones tested, tetrahydroxyflavanones with these structural characteristics isolated from Sophora exigua and Echinosophora koreensis showed intensive activity to inhibit the growth of all MRSA strains at 3.13-6.25 micrograms/ml. The present hydroxyflavanones would be useful in the phytotherapeutic strategy against MRSA infections.