Deciphering the Antibacterial Mode of Action of Alpha-Mangostin on Staphylococcus epidermidis RP62A Through an Integrated Transcriptomic and Proteomic Approach

Staphylococcus epidermidis uses the SrrAB regulatory system to modulate oxidative stress and intracellular survival in mouse macrophage cell line Ana-1

The two-component system (TCS) SrrAB responds to oxidative stress in Staphylococcus epidermidis. A srrAB deletion mutant (∆srrAB) was constructed using S. epidermidis strain 1457 (SE1457) as the parent strain to study its regulatory function in oxidative stress. Compared to SE1457, the viable cell counts of the ∆srrAB mutant significantly decreased in the post-stationary phase culture, coinciding with a sharp increase in reactive oxidative species (ROS) accumulation. The impaired growth of the ∆srrAB mutant was partially restored by shifting the culture from oxic to microaerobic conditions. Consistently, growth of the ∆srrAB mutant in tryptone soy broth (TSB) medium containing H2O2 was notably inhibited compared to parent strain SE1457, and the mutant showed significantly decreased resistance (100- to 1,000-fold) to H2O2 and cumene hydroperoxide in both oxic and microaerobic conditions, which was fully rescued by the addition of ROS inhibitor 2,2-dipyridyl. Furthermore, the deletion of srrAB resulted in decreased intracellular survival in the Ana-1 macrophages, likely due to intracellular ROS accumulation. The complementation of srrAB in the ∆srrAB mutant restored ROS resistance and intracellular survival to wild-type levels. RNA-seq analysis revealed that srrAB deletion affected the transcription levels of 610 genes, including those involved in oxidative stress, respiratory and energy metabolism, and transition ion homeostasis. These findings were corroborated by quantitative real-time reverse transcription-PCR. In the ∆srrAB mutant, expressions of ROS-scavenging genes katA, ahpC, scdA, serp1797, and serp0483 were downregulated compared to SE1457. Electrophoretic mobility shift assay further demonstrated phosphorylated SrrA bound to the promoter regions of srrAB, katA, ahpC, scdA, serp1797, and serp0483 genes. This study elucidates that in S. epidermidis, SrrAB is the critical TCS to sense and respond to the oxidants, directly regulating transcription levels of the genes involved in ROS scavenging and ion homeostasis, thereby facilitating S. epidermidis detoxification of ROS and adaptation to the commensal environment.

IMPORTANCE

Staphylococcus epidermidis in the human skin and mucous microbiome is a leading cause of hospital-acquired infection, whereas the mechanism by which it inhabits, adapts, and further results in infection is not well known. In this study, we found that the two-component regulatory system SrrAB directly regulates transcription levels of the genes involved in reactive oxidative species (ROS) scavenging and ion homeostasis in S. epidermidis, influencing ROS accumulation during growth, thereby facilitating detoxification of ROS and adaptation to the commensal environment. This work provides new molecular insight into the mechanisms of SrrAB in regulating resistance and intracellular viability against oxidative stress in S. epidermidis.

Sample Preparation and Processing for Quick, Universal, and Insightful Microbial Proteomics

Next-generation shotgun proteomics is one of the most valuable tools for gaining insight into the function of organisms. By providing a list of peptides and abundance information, proteomics enables the identification of proteins, their quantities, posttranslational modifications, and localization. The most refined shotgun proteomics workflow involves protein extraction, trypsin digestion, ultrahigh-performance liquid chromatography coupled to high-resolution tandem mass spectrometry, and confident assignment of resulting spectra to peptide sequences. In this study, we present a versatile, time- and cost-efficient experimental workflow for protein extraction, digestion, and analysis that can be applied to any type of microorganism. Our experimental procedure exhibits superior sensitivity compared to gel-based protocols and can be used for comparative microbial proteomics to highlight key players that explain phenotypic differences between conditions or for proteotyping new microbial isolates for taxonomic purposes.

Can α-Mangostin and Photodynamic Therapy Support Ciprofloxacin in the Inactivation of Uropathogenic Escherichia coli and Staphylococcus aureus Strains?

Multidrug-resistant bacteria represent a significant challenge in the treatment of bacterial infections, often leading to therapeutic failures. This issue underlines the need to develop strategies that improve the efficacy of conventional antibiotic therapies. In this study, we aimed to assess whether a plant-derived compound, α-mangostin, and photodynamic therapy (PDT) could enhance the antibacterial activity of ciprofloxacin against uropathogenic strains of Escherichia coli and Staphylococcus aureus. Using nanopore sequencing technology, we confirmed that the clinical strains tested were classified as multidrug-resistant. Digital holotomography (DHT) was used to examine α-mangostin-induced changes in the bacterial cells' penetration by a photosensitizer. A scanning confocal fluorescence microscope was used to visualize photosensitizer penetration into bacterial cells and validate DHT results. A synergistic effect between α-mangostin and ciprofloxacin was observed exclusively in S. aureus strains, while no enhancement of ciprofloxacin's antibacterial activity was detected in E. coli strains when combined with α-mangostin. Notably, photodynamic therapy significantly potentiated the antibacterial effects of ciprofloxacin and its combination with α-mangostin compared to untreated controls. In addition, morphological changes were observed in bacterial cells exposed to these antimicrobials. In conclusion, our findings suggest that α-mangostin and PDT may serve as valuable adjuncts to ciprofloxacin, improving the eradication of uropathogens.

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.

Mangostanin hyaluronic acid hydrogel as an effective biocompatible alternative to chlorhexidine

Periodontal disease (PD) prevention and treatment products typically demonstrate excellent antibacterial activity, but recent studies have raised concerns about their toxicity on oral tissues. Therefore, finding a biocompatible alternative that retains antimicrobial properties is imperative. In this study, a chemically modified hyaluronic acid (HA) hydrogel containing mangostanin (MGTN) was developed. Native HA was chemically modified, incorporating amino and aldehyde groups in different batches of HA, allowing spontaneous crosslinking and gelation when combined at room temperature. MGTN at different concentrations was incorporated before gelation. The structure, swelling characteristics MGTN release, rheological parameters, and in vitro degradation performance of the loaded hydrogel were first evaluated in the study. Then, antimicrobial properties were tested on Porphyromonas gingivalis and its biocompatibility in 3D-engineered human gingiva. HA hydrogel was very stable and showed a sustained release for MGTN for at least 7 days. MGTN-loaded HA hydrogel showed equivalent antimicrobial activity compared to a commercial gel of HA containing 0.2 % chlorhexidine (CHX). In contrast, while MGTN HA hydrogel was biocompatible, CHX gel showed high cytotoxicity, causing cell death and tissue damage. Modified HA hydrogel allows controlled release of MGTN, resulting in a highly biocompatible hydrogel with antibacterial properties. This hydrogel is a suitable alternative therapy to prevent and treat PD.

Hypoglycemic activity of Garcinia mangostana L. extracts on diabetes rodent models: A systematic review and network meta-analysis

Background

Diabetes mellitus is a significant global health issue, and alternative treatments from natural products like Garcinia mangostana L. [Clusiaceae] or GM are being explored for their potential benefits. This study focused on evaluating the hypoglycemic effects of GM on diabetic rodent models.

Methods

A comprehensive search was conducted in PubMed, Scopus, and Embase for studies reporting blood glucose levels within 2 weeks as the primary outcome and changes in total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) as secondary outcomes. A network meta-analysis (NMA) was performed to determine the pooled effectiveness of each intervention, estimating the weighted mean difference (WMD) and 95% confidence interval (CI) from both direct and indirect evidence. The surface under the cumulative ranking curve (SURCA) was used to rank the interventions.

Results

Ten articles were identified, with nine included for quantitative analysis. All GM extracts showed greater effectiveness than the control in decreasing blood glucose levels within 2 weeks. GM at 200 mg/kg (GM200) was the top-ranked extract for reducing glucose levels beyond 2 weeks and increasing HDL-C levels. The ethanol extract of GM at 200 mg/kg (GME200) was the most effective for blood glucose reduction within 2 weeks and for TC and TG reductions. The methanol extract of GM at 200 mg/kg (GMM200) was the top-ranked extract for LDL-C reductions.

Conclusion

GM and its extracts demonstrated significant hypoglycemic activity and improvements in lipid profiles in diabetic rodent models, highlighting their potential as therapeutic agents for the prevention and treatment of diabetes mellitus. Further research in human trials is warranted to confirm these findings and establish clinical applications.

Clinical trial registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023426254.

In vitro and in vivo evaluation of the anti-infective potential of the essential oil extracted from the leaves of Plectranthus amboinicus (lour.) spreng against Klebsiella pneumoniae and elucidation of its mechanism of action through proteomics approach

ETHNOPHARMACOLOGICAL RELEVANCE

Members of Plectranthus genus such as Plectranthus amboinicus (Lour.) Spreng is a well-known folkloric medicine around the globe in treating several human ailments such as cardiovascular, respiratory, digestive, urinary tract, skin and infective diseases. Its therapeutic value is primarily attributed to its essential oil. Although several properties of Plectranthus amboinicus essential oil have been documented, its mechanism of action and safety has not been completely elucidated.

AIM OF THE STUDY

To investigate the anti-infective potential of Plectranthus amboinicus essential oil against Klebsiella pneumoniae using in vitro and in vivo bioassays and identify its mode of action. The study was conducted to scientifically validate the traditional usage of Plectranthus amboinicus oil and propose it as a complementary and alternative medication to combat Klebsiella pneumoniae infections due to emerging antibiotic resistance problem.

MATERIALS AND METHODS

Plectranthus amboinicus essential oil was extracted through steam distillation and was chemically characterized using Gas Chromatography Mass Spectrometry (GC-MS). The antibacterial activity was assessed using microbroth dilution assay, metabolic viability assay and growth curve analysis. The mode of action was elucidated by the proteomics approach using Nano-LC-MS/MS followed by in silico analysis. The results of proteomic analysis were further validated through several in vitro assays. The cytotoxic nature of the essential oil was also confirmed using adenocarcinomic human alveolar basal epithelial (A549) cells. Furthermore, the safety and in vivo anti-infective efficacy of Plectranthus amboinicus essential oil was evaluated through survival assay, CFU assay and histopathological analysis of vital organs using zebrafish as a model organism.

RESULTS

The chemical characterization of Plectranthus amboinicus essential oil revealed that it is predominantly composed of thymol. Thymol rich P. amboinicus essential oil demonstrated potent inhibitory effects on Klebsiella pneumoniae growth, achieving a significant reduction at a concentration of 400 μg/mL within 4 h of treatment The nano-LC-MS/MS approach unveiled that the essential oil exerted its impact by disrupting the antioxidant defense system and efflux pump system of the bacterium, resulting in elevated cellular oxidative stress and affect the biosynthesis of biofilm. The same was validated through several in vitro assays. Furthermore, the toxicity of Plectranthus amboinicus essential oil determined using A549 cells and zebrafish survival assay established a non-toxic concentration of 400 μg/mL and 12.5 μg/mL respectively. The results of anti-infective potential of the essential oil using Zebrafish as a model organism demonstrated significantly improved survival rates, reduced bacterial load, alleviated visible signs of inflammation and mitigated the adverse effects of infection on various organs, as evidenced by histopathological analysis ensuring its safety for potential therapeutic application.

CONCLUSION

The executed in vitro and in vivo assays established the effectiveness of essential oil in inhibiting bacterial growth by targeting key proteins associated with the bacterial antioxidant defense system and disrupted the integrity of the cell membrane, highlighting its critical role in addressing the challenge posed by antibiotic-resistant Klebsiella pneumoniae.

In Vitro Evaluation of Mangostanin as an Antimicrobial and Biocompatible Topical Antiseptic for Skin and Oral Tissues

Skin and oral tissue infections pose significant health challenges worldwide, necessitating the exploration of new antiseptic agents that are both effective and biocompatible. This study evaluated the antibacterial efficacy and biocompatibility of mangostanin (MGTN), a xanthone derived from Garcinia mangostana L., against commercial antiseptics across various bacterial strains (Porphyromonas gingivalis, Streptococcus mutans, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, and Cutibacterium acnes) and in vitro models of skin and oral tissues. MGTN demonstrated significant antimicrobial activity against all tested pathogens concurrently exhibiting negligible cytotoxic effects on human gingival fibroblasts as well as on three-dimensional (3D) models of human epidermis and oral epithelium. Furthermore, using pooled human saliva, MGTN effectively inhibited plaque biofilm formation, suggesting its potential as a natural, biocompatible antiseptic for skin and oral health applications. These findings position MGTN as a promising candidate for further development into antiseptic formulations, offering a natural alternative to current synthetic options.

Effects of the antimicrobial glabridin on membrane integrity and stress response activation in Listeria monocytogenes

Glabridin is a prenylated isoflavan which can be extracted from liquorice roots and has shown antimicrobial activity against foodborne pathogens and spoilage microorganisms. However, its application may be hindered due to limited information about its mode of action. In this study, we aimed to investigate the mode of action of glabridin using a combined phenotypic and proteomic approach on Listeria monocytogenes. Fluorescence and transmission electron microscopy of cells exposed to glabridin showed membrane permeabilization upon treatment with lethal concentrations of glabridin. Comparative proteomics analysis of control cells and cells exposed to sub-lethal concentrations of glabridin showed upregulation of proteins related to the two-component systems LiaSR and VirRS, confirming cell envelope damage during glabridin treatment. Additional upregulation of SigmaB regulon members signified activation of the general stress response in L. monocytogenes during this treatment. In line with the observed upregulation of cell envelope and general stress response proteins, sub-lethal treatment of glabridin induced (cross)protection against lethal heat and low pH stress and against antimicrobials such as nisin and glabridin itself. Overall, this study sheds light on the mode of action of glabridin and activation of the main stress responses to this antimicrobial isoflavan and highlights possible implications of its use as a naturally derived antimicrobial compound.

Antimicrobial activity of α-mangostin against Staphylococcus species from companion animals in vitro and therapeutic potential of α-mangostin in skin diseases caused by S. pseudintermedius

Antimicrobial resistance in Staphylococcus species from companion animals is becoming increasingly prevalent worldwide. S. pseudintermedius is a leading cause of skin infections in companion animals. α-mangostin (α-MG) exhibits various pharmacological activities, including antimicrobial activity against G (+) bacteria. This study investigated the antimicrobial activity of α-MG against clinical isolates of Staphylococcus species from companion animals and assessed the therapeutic potential of α-MG in skin diseases induced by S. pseudintermedius in a murine model. Furthermore, the action mechanisms of α-MG against S. pseudintermedius were investigated. α-MG exhibited antimicrobial activity against clinical isolates of five different Staphylococcus species from skin diseases of companion animals in vitro, but not G (-) bacteria. α-MG specifically interacted with the major histocompatibility complex II analogous protein (MAP) domain-containing protein located in the cytoplasmic membrane of S. pseudintermedius via hydroxyl groups at C-3 and C-6. Pretreatment of S. pseudintermedius with anti-MAP domain-containing protein polyclonal serum significantly reduced the antimicrobial activity of α-MG. The sub-minimum inhibitory concentration of α-MG differentially regulated 194 genes, especially metabolic pathway and virulence determinants, in S. pseudintermedius. α-MG in pluronic lecithin organogel significantly reduced the bacterial number, partially restored the epidermal barrier, and suppressed the expression of cytokine genes associated with pro-inflammatory, Th1, Th2, and Th17 in skin lesions induced by S. pseudintermedius in a murine model. Thus, α-MG is a potential therapeutic candidate for treating skin diseases caused by Staphylococcus species in companion animals.

General toxicity studies of alpha mangostin from Garcinia mangostana: A systematic review

Alpha mangostin (AM), the main xanthone derivative contained in mangosteen pericarp (Garcinia mangostana/GM), has many pharmacological activities such as antioxidant, antiproliferation, antiinflammatory, and anticancer. Several general toxicity studies of AM have been previously reported to assess the safety profile of AM. Toxicity studies were carried out by various methods such as on test animals, interventions, and various routes of administration, but the test results have not been well documented. Our study aimed to systematically summarizes research on the safety profile of GM containing AM through general toxicity tests to get the LD₅₀ and NOAEL values, and so, can be used as a database related to AM toxicity profiles. This could facilitate other researchers in determining further development of GM-or-AM-based products. Pubmed, Google scholar, ScienceDirect, and EBSCO were chosen to collect the articles while ARRIVE 2.0 was used to evaluate the quality and risk-of-bias of the in vivo toxicity studies included in this systematic review. A total of 20 articles met the eligibility criteria and were reviewed to predict the LD₅₀ and NOAEL of AM. The results showed that the LD₅₀ of AM is between >15.480 mg/kgBW to ≤6000 mg/kgBW while the NOAEL value is between <100 and ≤2000 mg/kgBW.

Characterization of Lemon Pepper and Black Ginger Extracts and Macroemulsions as Natural Pain Relievers for Spice Stick Balsam Formulation

Lemon pepper or andaliman (Zanthoxylum acanthopodium) and black ginger (Kaempferia parviflora) are rich in bioactive compounds that possess antioxidant and anti-inflammatory activities. Our recent study demonstrated that andaliman ethanolic extract also exerted anti-arthritic and anti-inflammatory effects in arthritic mice in vivo. Therefore, natural anti-inflammatory and anti-arthritic compounds for alternative natural pain relievers in balsam formulation are needed. This study aimed to produce and characterize lemon pepper and black ginger extracts and their macroemulsion products, followed by formulation, characterization, and stability of spice stick balsam products containing lemon pepper and black ginger macroemulsions. The extraction yields obtained were 24% w/w for lemon pepper and 59% w/w for black ginger. GC/MS results showed that the lemon pepper extract contained limonene and geraniol compounds, and black ginger extract contained gingerol, shogaol, and tetramethoxyflavone compounds. Spice extracts were successfully made in the form of a stable emulsion. The antioxidant activity in both spice extracts and emulsions was relatively high (>50%). The five stick balsam formulas obtained had a pH of 5, 4.5–4.8 cm spread ability, and 30–50 s of adhesion. The stability of products showed no microbial contamination. Based on the organoleptic results, the stick balsam formula of black ginger and black ginger: lemon pepper (1:3) was the most preferred by the panelists. In conclusion, lemon pepper and black ginger extracts and macroemulsions could be used as natural pain relievers in stick balsam products to promote health protection.

Efflux pump inhibitor combined with ofloxacin decreases MRSA biofilm formation by regulating the gene expression of NorA and quorum sensing

Carbonyl cyanide p-nitrophenylhydrazone (2e) displayed a lone or synergistic efficacy against MRSA (RSC Adv., 2020, 10, 17854). In this work, the synergistic mechanism of 2e with ofloxacin was studied. MRSA2858 had potential for biofilm formation, and the value of MBEC of 2e alone was 0.78-1.56 μM, while that of 2e + ofloxacin was 0.39-0.78 μM. 2e combined with ofloxacin showed a synergistic anti-biofilm effect against MRSA. Efflux pump inhibitor 2e can better bind to NorA protein. After MRSA2858 was treated with 2e of 1/2MIC (0.78 μM) and ofloxacin of 1/8MIC (0.097 μM), the transcript levels of efflux genes (norA) and quorum-sensing (QS) regulatory genes (agrA, sarA, icaA, hla) were substantially down-regulated, and alpha-hemolysin (Hla) was inhibited by 99.15%. 2e combined with ofloxacin was more effective than 2e alone in reducing bacterial load in vivo. All in all, efflux pump inhibitor 2e enhanced the bactericidal activities of antibiotics through regulating the gene expression of NorA and QS system.

A review of stingless bees' bioactivity in different parts of the world

Stingless bees, also known as meliponines, live in beehives. However, reports on the distribution of stingless bees are scattered, resulting in a lack of precision. Honey and propolis are the main components that can be harvested from their beehive, with a great commercial value of up to 610 million USD. Despite the enormous potential profits, discrepancies in their bioactivities have been observed worldwide, leading to a lack of confidence. Therefore, this review provided oversight on the potential of stingless bee products and highlighted the differences between stingless bees in Asia, Australia, Africa, and America. The bioactivity of stingless bee products is diverse and exhibits great potential as an antimicrobial agent or in various diseases such as diabetes, cardiovascular disease, cancers, and oral problems.

The utilization of mangosteen pericarp extract for anticoccidial drug replacement in broiler feed

The use of anticoccidial drugs in broilers has led to concerns, especially the drug residues in meat and the occurrence of drug resistance. This study aimed to extract, standardize, quantify and utilize mangosteen pericarp extract (MPE) containing α-mangostin as a replacement for anticoccidial drugs in broiler feed. The pericarp was acquired from different areas of Thailand and used for extraction and standardization. The antioxidant activity of the extract was evaluated. The extract was formulated into granules, and the flowability and stability of the granules were assessed. The MPE formulation was added to the broiler feed and then fed to the broilers that were infected with Eimeria tenella. The growth rate and intestinal lesion score (post-mortem) of the broilers were assessed. The pericarp obtained passed the identification test and phytochemical analyses. The active compound, α-mangostin, was best extracted using 95% ethanol. The MPE had superior antioxidant activity compared to standard antioxidants. Granules of the extract formulated with Avicel® PH102 provided desirable flowability and stability. The broilers fed with the feed containing 500 mg/kg α-mangostin showed a similar growth rate and post-mortem lesion score compared with the control group and those that received feed containing 60 mg/kg salinomycin. Our findings demonstrated that MPE with a high content of the active compound could be developed and used in place of anticoccidial drugs in the broiler feed.

Alpha-mangostin Protects PC12 Cells Against Neurotoxicity Induced by Cadmium and Arsenic

Arsenic and cadmium are nonessential elements that are of importance in public health due to their high toxicity. Contact with these toxic elements, even in very small amounts, can induce various side effects, including neurotoxicity. Oxidative stress and apoptosis are part of the main mechanisms of arsenic- and cadmium-induced toxicity. Alpha-mangostin is the main xanthone derived from mangosteen, Garcinia mangostana, with anti-oxidative properties.In this study, PC12 cells were selected as a nerve cell model, and the protective effects of alpha-mangostin against neurotoxicity induced by arsenic and cadmium were investigated. PC12 cells were exposed to cadmium (5-80 µM) and arsenic (2.5-180 µM) for 24 h. Cytotoxicity, reactive oxygen species (ROS) production, and the protein expression of Bax, Bcl2, and cleaved caspase 3 were determined using MTT assay, fluorimetry, and western blot, respectively.Arsenic (10-180 µM) and cadmium (50-80 µM) significantly reduced cell viability. IC₅₀ values were 10.3 ± 1.09 and 45 ± 4.63 µM, respectively. Significant increases in ROS, Bax/Bcl-2 ratio, and cleaved caspase-3 were observed after arsenic and cadmium exposures. Cell viability increased and ROS production decreased when cells were pretreated with alpha-mangostin for 2 h. Alpha-mangostin reduced the increased level of cleaved caspase-3 induced by cadmium and decreased the elevated level of the Bax/Bcl-2 ratio after arsenic exposure.Alpha-mangostin significantly increased cell viability and reduced oxidative stress caused by cadmium and arsenic in PC12 cells. Moreover, alpha-mangostin reduced cadmium-induced apoptosis through the reduction in the level of cleaved caspase 3. Further studies are required to determine the different mechanisms of alpha-mangostin against neurotoxicity induced by these elements.

Novel FabI inhibitor disrupts the biofilm formation of MRSA through down-regulating the expression of quorum-sensing regulatory genes

OBJECTIVES

The aim of this study was to explore the antibiofilm and antivirulence efficacy of benzylaniline 4k against MRSA.

METHODS

The clinical MRSA strains were identified and used to evaluate their potential to form biofilm using crystal violet assay. The minimal inhibitory concentration (MIC) was determined using broth microdilution method. The expression of genes was detected using quantitative real-time PCR (qRT-PCR). Rabbit blood hemolytic assay was used to observe the inhibitory ability of alpha-hemolysin (Hla).

RESULTS

Compound 4k showed potent antibacterial activity against 16 clinical MRSA with an MIC₅₀ of 1.25 mg/L and MIC₉₀ of 2.25 mg/L. The value of minimum biofilm eradication concentration (MBEC) against MRSA2858 biofilm was of 1.5 mg/L, close to its MIC, superior to those of vancomycin and erythromycin. Compound 4k eradicated the formation of biofilm through inhibiting the gene expression of branched-chain fatty acid synthesis, down-regulating the expression of quorum-sensing (QS) regulatory genes (norA, agrA, icaA, hla), decreasing the level of hemolysis in a dose-dependent manner, and inhibiting rabbit blood hemolysis by 86.9% at a concentration of 1.25 mg/L. In a mouse model of abdominal infection, compound 4k was more effective than vancomycin in reducing bacterial load.

CONCLUSIONS

These results suggested that compound 4k could be developed as promising an anti-MRSA agent through affecting quorum-sensing system.

Biotin Transport-Targeting Polysaccharide-Modified PAMAM G3 Dendrimer as System Delivering α-Mangostin into Cancer Cells and C. elegans Worms

The natural xanthone α-mangostin (αM) exhibits a wide range of pharmacological activities, including antineoplastic and anti-nematode properties, but low water solubility and poor selectivity of the drug prevent its potential clinical use. Therefore, the targeted third-generation poly(amidoamine) dendrimer (PAMAM G3) delivery system was proposed, based on hyperbranched polymer showing good solubility, high biocompatibility and low immunogenicity. A multifunctional nanocarrier was prepared by attaching αM to the surface amine groups of dendrimer via amide bond in the ratio 5 (G3^2B12gh5M) or 17 (G3^2B10gh17M) residues per one dendrimer molecule. Twelve or ten remaining amine groups were modified by conjugation with D-glucoheptono-1,4-lactone (gh) to block the amine groups, and two biotin (B) residues as targeting moieties. The biological activity of the obtained conjugates was studied in vitro on glioma U-118 MG and squamous cell carcinoma SCC-15 cancer cells compared to normal fibroblasts (BJ), and in vivo on a model organism Caenorhabditis elegans. Dendrimer vehicle G3^2B12gh at concentrations up to 20 µM showed no anti-proliferative effect against tested cell lines, with a feeble cytotoxicity of the highest concentration seen only with SCC-15 cells. The attachment of αM to the vehicle significantly increased cytotoxic effect of the drug, even by 4- and 25-fold for G3^2B12gh5M and G3^2B10gh17M, respectively. A stronger inhibition of cells viability and influence on other metabolic parameters (proliferation, adhesion, ATP level and Caspase-3/7 activity) was observed for G3^2B10gh17M than for G3^2B12gh5M. Both bioconjugates were internalized efficiently into the cells. Similarly, the attachment of αM to the dendrimer vehicle increased its toxicity for C. elegans. Thus, the proposed α-mangostin delivery system allowed the drug to be more effective in the dendrimer-bound as compared to free state against both cultured the cancer cells and model organism, suggesting that this treatment is promising for anticancer as well as anti-nematode chemotherapy.

Nanoformulations of α-Mangostin for Cancer Drug Delivery System

Natural compounds are emerging as effective agents for the treatment of malignant diseases. The active constituent of α-mangostin from the pericarp of Garcinia mangostana L. has earned significant interest as a plant base compound with anticancer properties. Despite α-mangostin's superior properties as an anticancer agent, its applications are limited due to its poor solubility and physicochemical stability, rapid systemic clearance, and low cellular uptake. Our review aimed to summarize and discuss the nanoparticle formulations of α-mangostin for cancer drug delivery systems from published papers recorded in Scopus, PubMed, and Google Scholar. We investigated various types of α-mangostin nanoformulations to improve its anticancer efficacy by improving bioavailability, cellular uptake, and localization to specific areas These nanoformulations include nanofibers, lipid carrier nanostructures, solid lipid nanoparticles, polymeric nanoparticles, nanomicelles, liposomes, and gold nanoparticles. Notably, polymeric nanoparticles and nanomicelles can increase the accumulation of α-mangostin into tumors and inhibit tumor growth in vivo. In addition, polymeric nanoparticles with the addition of target ligands can increase the cellular uptake of α-mangostin. In conclusion, nanoformulations of α-mangostin are a promising tool to enhance the cellular uptake, accumulation in cancer cells, and the efficacy of α-mangostin as a candidate for anticancer drugs.

LsrB, the hub of ABC transporters involved in the membrane damage mechanisms of heavy ion irradiation in Escherichia coli

BACKGROUND

Ionizing radiation, especially heavy ion (HI) beams, has been widely used in biology and medicine. However, the mechanism of membrane damage by such radiation remains primarily uncharacterized.

PURPOSE

Transcriptomic profiles of Escherichia coli (E. coli) treated with HI illustrated the response mechanisms of the membrane, mainly ABC transporters, related genes regulated by antibiotics treatment through enrichment analyses of GO and KEGG. The networks of protein-protein interactions indicated that LsrB was the crucial one among the ABC transporters specially regulated by HI through the calculation of plugins MCODE and cytoHubba of Cytoscape. Finally, the expression pattern, GO/KEGG enrichment terms, and the interaction between nine LuxS/AI-2 quorum sensing system members were investigated.

CONCLUSIONS

Above all, results suggested that HI might perform membrane damage through regulated material transport, inhibited LuxS/AI-2 system, finally impeded biofilm formation. This work provides further evidence for the role of ABC transporters, especially LsrB, in membrane damage of E. coli to HI. It will provide new strategies for improving the precise application of HI.

The diverse bioactivity of α-mangostin and its therapeutic implications

α-Mangostin is a xanthone natural product isolated as a secondary metabolite from the mangosteen tree. It has attracted a great deal of attention due to its wide-ranging effects on certain biological activity, such as apoptosis, tumorigenesis, proliferation, metastasis, inflammation, oxidation, bacterial growth and metabolism. This review focuses on the key pathways directly affected by α-mangostin and how this varies between disease states. Insight is also provided, where investigated, into the key structural features of α-mangostin that produce these biological effects. The review then sheds light on the utility of α-mangostin as a investigational tool for certain diseases and demonstrate how future derivatives may increase selectivity and potency for specific disease states.

Ethnobotany and the Role of Plant Natural Products in Antibiotic Drug Discovery

The crisis of antibiotic resistance necessitates creative and innovative approaches, from chemical identification and analysis to the assessment of bioactivity. Plant natural products (NPs) represent a promising source of antibacterial lead compounds that could help fill the drug discovery pipeline in response to the growing antibiotic resistance crisis. The major strength of plant NPs lies in their rich and unique chemodiversity, their worldwide distribution and ease of access, their various antibacterial modes of action, and the proven clinical effectiveness of plant extracts from which they are isolated. While many studies have tried to summarize NPs with antibacterial activities, a comprehensive review with rigorous selection criteria has never been performed. In this work, the literature from 2012 to 2019 was systematically reviewed to highlight plant-derived compounds with antibacterial activity by focusing on their growth inhibitory activity. A total of 459 compounds are included in this Review, of which 50.8% are phenolic derivatives, 26.6% are terpenoids, 5.7% are alkaloids, and 17% are classified as other metabolites. A selection of 183 compounds is further discussed regarding their antibacterial activity, biosynthesis, structure-activity relationship, mechanism of action, and potential as antibiotics. Emerging trends in the field of antibacterial drug discovery from plants are also discussed. This Review brings to the forefront key findings on the antibacterial potential of plant NPs for consideration in future antibiotic discovery and development efforts.

A review on α-mangostin as a potential multi-target-directed ligand for Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by progressive memory loss, declining language skills and other cognitive disorders. AD has brought great mental and economic burden to patients, families and society. However due to the complexity of AD's pathology, drugs developed for the treatment of AD often fail in clinical or experimental trials. The main problems of current anti-AD drugs are low efficacy due to mono-target method or side effects, especially high hepatotoxicity. To tackle these two main problems, multi-target-directed ligand (MTDL) based on "one molecule, multiple targets" has been studied. MTDLs can regulate multiple biological targets at the same time, so it has shown higher efficacy, better safety. As a natural active small molecule, α-mangostin (α-M) has shown potential multi-factor anti-AD activities in a series of studies, furthermore it also has a certain hepatoprotective effect. The good availability of α-M also provides support for its application in clinical research. In this work, multiple activities of α-M related to AD therapy were reviewed, which included anti-cholinesterase, anti-amyloid-cascade, anti-inflammation, anti-oxidative stress, low toxicity, hepatoprotective effects and drug formulation. It shows that α-M is a promising candidate for the treatment of AD.

New dihydrochromene and xanthone derivatives from Lisotrigona furva propolis

A new dihydrochromene derivative, named lisofurvin (1) and a xanthone, named dihydrobrasixanthone B (2) together with twenty one known compounds (3-23) were isolated from propolis of the stingless bee Lisotrigona furva. Their chemical structures were determined by means of spectroscopic methods including 1D and 2D NMR, and MS. The chemical constituents are predominantly geranyl(oxy) xanthones and Cratoxylum cochinchinense was suggested as a resin source, besides two other plants Mangifera indica and dammar trees (Dipterocarpaceae). Compound 1 showed significant cytotoxic activity against KB, HepG-2, and Lu-1 cancer cell lines with IC₅₀ values range from 12.63 to 15.17 μg/mL. Several isolated compounds were active against one to four tested cancer cell lines. In addition, among the isolated compounds, α-mangostin (15) displayed the strongest antimicrobial activity against three Gram (+) strains, P. aeruginosa, and C. albicans with MIC values ranging between 1 and 2 μg/mL. Compound 22 showed good activity against three Gram (+) strains and C. albicans.

Natural Xanthones and Skin Inflammatory Diseases: Multitargeting Mechanisms of Action and Potential Application

The pathogenesis of skin inflammatory diseases such as atopic dermatitis, acne, psoriasis, and skin cancers generally involve the generation of oxidative stress and chronic inflammation. Exposure of the skin to external aggressors such as ultraviolet (UV) radiation and xenobiotics induces the generation of reactive oxygen species (ROS) which subsequently activates immune responses and causes immunological aberrations. Hence, antioxidant and anti-inflammatory agents were considered to be potential compounds to treat skin inflammatory diseases. A prime example of such compounds is xanthone (xanthene-9-one), a class of natural compounds that possess a wide range of biological activities including antioxidant, anti-inflammatory, antimicrobial, cytotoxic, and chemotherapeutic effects. Many studies reported various mechanisms of action by xanthones for the treatment of skin inflammatory diseases. These mechanisms of action commonly involve the modulation of various pro-inflammatory cytokines such as interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor α (TNF-α), as well as anti-inflammatory cytokines such as IL-10. Other mechanisms of action include the regulation of NF-κB and MAPK signaling pathways, besides immune cell recruitment via modulation of chemokines, activation, and infiltration. Moreover, disease-specific activity contributed by xanthones, such as antibacterial action against Propionibacterium acnes and Staphylococcus epidermidis for acne treatment, and numerous cytotoxic mechanisms involving pro-apoptotic and anti-metastatic effects for skin cancer treatment have been extensively elucidated. Furthermore, xanthones have been reported to modulate pathways responsible for mediating oxidative stress and inflammation such as PPAR, nuclear factor erythroid 2-related factor and prostaglandin cascades. These pathways were also implicated in skin inflammatory diseases. Xanthones including the prenylated α-mangostin (2) and γ-mangostin (3), glucosylated mangiferin (4) and the caged xanthone gambogic acid (8) are potential lead compounds to be further developed into pharmaceutical agents for the treatment of skin inflammatory diseases. Future studies on the structure-activity relationships, molecular mechanisms, and applications of xanthones for the treatment of skin inflammatory diseases are thus highly recommended.

Molecular evaluation of quorum quenching potential of vanillic acid against Yersinia enterocolitica through transcriptomic and in silico analysis

Introduction. Yersinia enterocolitica is one of the leading food-borne entero-pathogens causing various illnesses ranging from gastroenteritis to systemic infections. Quorum sensing (QS) is one of the prime mechanisms that control the virulence in Y. enterocolitica .

Hypothesis/Gap Statement. Vanillic acid inhibits the quorum sensing and other virulence factors related to Y. enterocolitica . It has been evaluated by transcriptomic and Insilico analysis. Therefore, it can be a prospective agent to develop a therapeutic combination against Y. enterocolitica .

Aim. The present study is focused on screening natural anti-quorum-sensing agents against Y. enterocolitica . The effect of selected active principle on various virulence factors was evaluated.

Methodology. In total, 12 phytochemicals were screened by swarming assay. MATH assay, EPS and surfactant production assay, SEM analysis, antibiotic and blood sensitivity assay were performed to demonstrate the anti-virulence activity. Further, RNA sequencing and molecular docking studies were carried out to substantiate the anti-QS activity.

Results. Vanillic acid (VA) has exhibited significant motility inhibition, thus indicating the anti-QS activity with MQIC of 400 µg ml−1 without altering the cell viability. It has also inhibited the violacein production in Chromobacterium violaceum ATCC 12472, which further confirms the anti-QS activity. VA has inhibited 16 % of cell-surface hydrophobicity (CSH), 52 % of EPS production and 60 % of surfactant production. Moreover, it has increased the sensitivity of Y. enterocolitica towards antibiotics. It has also made the cells upto 91 % more vulnerable towards human immune cells. The transcriptomic analysis by RNA sequencing revealed the down regulation of genes related to motility, virulence, chemotaxis, siderophores and drug resistance. VA treatment has also positively regulated the expression of several stress response genes. In furtherance, the anti-QS potential of VA has been validated with QS regulatory protein YenR by in silico molecular simulation and docking study.

Conclusion. The present study is possibly the first attempt to demonstrate the anti-QS and anti-pathogenic potential of VA against Y. enterocolitica by transcriptomic and in silico analysis. It also deciphers that VA can be a promising lead to develop biopreservative and therapeutic regimens to treat Y. enterocolitica infections.

Design, synthesis and activity against Staphylococcus epidermidis of 5-chloro-2- or 5-chloro-4-methyl-9H-xanthen-9-one and some of its derivatives

Ten new xanthone derivatives have been designed and synthesized for their potential antibacterial activity. All compounds have been screened against Staphylococcus epidermidis strains ATCC 12228 and clinical K/12/8915. The highest antibacterial activity was observed for compound 3: 5-chloro-2-((4-(2-hydroxyethyl)piperazin-1-yl)methyl)-9H-xanthen-9-one dihydrochloride, exhibiting MIC of 0.8 µg/ml against ATCC 12228 strain, compared to linezolid (0.8 µg/ml), ciprofloxacin (0.2 µg/ml) or trimethoprim and sulfamethoxazole (0.8 µg/ml). For the most active compound 3, genotoxicity assay with use of Salmonella enterica serovar Typhimurium revealed safety in terms of genotoxicity at concentration 75 µg/ml and antibacterial activity against Salmonella at all higher concentrations. A final in silico prediction of skin metabolism of compound 3 seems promising, indicating stability of the xanthone moiety in the metabolism process.

Transcriptomic and proteomic profiling response of methicillin-resistant Staphylococcus aureus (MRSA) to a novel bacteriocin, plantaricin GZ1-27 and its inhibition of biofilm formation

Methicillin-resistant Staphylococcus aureus (MRSA) has become a worrisome superbug, due to its wide distribution and multidrug resistance. To characterize effects of a newly identified plantaricin GZ1-27 on MRSA, transcriptomic and proteomic profiling of MRSA strain ATCC43300 was performed in response to sub-MIC (16 μg/mL) plantaricin GZ1-27 stress. In total, 1090 differentially expressed genes (padj < 0.05) and 418 differentially expressed proteins (fold change > 1.2, p < 0.05) were identified. Centralized protein expression clusters were predicted in biological functions (biofilm formation, DNA replication and repair, and heat-shock) and metabolic pathways (purine metabolism, amino acid metabolism, and biosynthesis of secondary metabolites). Moreover, a capacity of inhibition MRSA biofilm formation and killing biofilm cells were verified using crystal violet staining, scanning electron microscopy, and confocal laser-scanning microscopy. These findings yielded comprehensive new data regarding responses induced by plantaricin and could inform evidence-based methods to mitigate MRSA biofilm formation.

Nanoparticle Drug Delivery Systems for α-Mangostin

α-Mangostin, a xanthone derivative from the pericarp of Garcinia mangostana L., has numerous bioactivities and pharmacological properties. However, α-mangostin has low aqueous solubility and poor target selectivity in the human body. Recently, nanoparticle drug delivery systems have become an excellent technique to improve the physicochemical properties and effectiveness of drugs. Therefore, many efforts have been made to overcome the limitations of α-mangostin through nanoparticle formulations. Our review aimed to summarise and discuss the nanoparticle drug delivery systems for α-mangostin from published papers recorded in Scopus, PubMed and Google Scholar. We examined various types of nanoparticles for α-mangostin to enhance water solubility, provide controlled release and create targeted delivery systems. These forms include polymeric nanoparticles, nanomicelles, liposomes, solid lipid nanoparticles, nanofibers and nanoemulsions. Notably, nanomicelle modification increased α-mangostin solubility increased more than 10,000 fold. Additionally, polymeric nanoparticles provided targeted delivery and significantly enhanced the biodistribution of α-mangostin into specific organs. In conclusion, the nanoparticle drug delivery system could be a promising technique to increase the solubility, selectivity and efficacy of α-mangostin as a new drug candidate in clinical therapy.

Transporters and Efflux Pumps Are the Main Mechanisms Involved in Staphylococcus epidermidis Adaptation and Tolerance to Didecyldimethylammonium Chloride

Staphylococcus epidermidis cleanroom strains are often exposed to sub-inhibitory concentrations of disinfectants, including didecyldimethylammonium chloride (DDAC). Consequently, they can adapt or even become tolerant to them. RNA-sequencing was used to investigate adaptation and tolerance mechanisms of S. epidermidis cleanroom strains (SE11, SE18), with S. epidermidis SE11Ad adapted and S. epidermidis SE18To tolerant to DDAC. Adaptation to DDAC was identified with up-regulation of genes mainly involved in transport (thioredoxin reductase [pstS], the arsenic efflux pump [gene ID, SE0334], sugar phosphate antiporter [uhpT]), while down-regulation was seen for the Agr system (agrA, arC, agrD, psm, SE1543), for enhanced biofilm formation. Tolerance to DDAC revealed the up-regulation of genes associated with transporters (L-cysteine transport [tcyB]; uracil permease [SE0875]; multidrug transporter [lmrP]; arsenic efflux pump [arsB]); the down-regulation of genes involved in amino-acid biosynthesis (lysine [dapE]; histidine [hisA]; methionine [metC]), and an enzyme involved in peptidoglycan, and therefore cell wall modifications (alanine racemase [SE1079]). We show for the first time the differentially expressed genes in DDAC-adapted and DDAC-tolerant S. epidermidis strains, which highlight the complexity of the responses through the involvement of different mechanisms.

Umbelliferone Impedes Biofilm Formation and Virulence of Methicillin-Resistant Staphylococcus epidermidis via Impairment of Initial Attachment and Intercellular Adhesion

Staphylococcus epidermidis is an opportunistic human pathogen, which is involved in numerous nosocomial and implant associated infections. Biofilm formation is one of the prime virulence factors of S. epidermidis that supports its colonization on biotic and abiotic surfaces. The global dissemination of three lineages of S. epidermidis superbugs highlights its clinical significance and the imperative need to combat its pathogenicity. Thus, in the current study, the antibiofilm activity of umbelliferone (UMB), a natural product of the coumarin family, was assessed against methicillin-resistant S. epidermidis (MRSE). UMB exhibited significant antibiofilm activity (83%) at 500 μg/ml concentration without growth alteration. Microscopic analysis corroborated the antibiofilm potential of UMB and unveiled its potential to impair intercellular adhesion, which was reflected in auto-aggregation and solid phase adherence assays. Furthermore, real time PCR analysis revealed the reduced expression of adhesion encoding genes (icaD, atlE, aap, bhp, ebh, sdrG, and sdrF). Down regulation of agrA and reduced production of secreted hydrolases upon UMB treatment were speculated to hinder invasive lifestyle of MRSE. Additionally, UMB hindered slime synthesis and biofilm matrix components, which were believed to augment antibiotic susceptibility. In vivo assays using Caenorhabditis elegans divulged the non-toxic nature of UMB and validated the antibiofilm, antivirulence, and antiadherence properties of UMB observed in in vitro assays. Thus, UMB impairs MRSE biofilm by turning down the initial attachment and intercellular adhesion. Altogether, the obtained results suggest the potent antibiofilm activity of UMB and the feasibility of using it in clinical settings for combating S. epidermidis infections.