Search Results (90)

Hop (Humulus lupulus L.) is recognized as a valuable source of bioactive compounds; however, the phytochemical composition and biological potential of wild Romanian hops remain insufficiently characterized. In this study, the bioactive profile of wild hop cones was evaluated using an integrated phytochemical, biological, and in silico approach. The hydroethanolic extract was characterized by a total phenolic content of 25.61 mg GAE/g DW and a total flavonoid content of 3.20 mg RE/g DW, with α-acids predominating (8.77%) and β-acids detected only at trace levels (0.15%). Hydrodistillation yielded 0.613 ± 0.11% essential oil, which was rich in sesquiterpene hydrocarbons (64.61%), mainly α-humulene, β-caryophyllene oxide, selina-3,7-diene, and germacrene B. The hydroethanolic extract exhibited strong antioxidant activity (IC₅₀ = 5.03 µg GAE/mL), whereas the essential oil showed a moderate but dose-dependent radical-scavenging capacity (IC₅₀ = 0.44% v/v). In addition, the essential oil displayed pronounced antibacterial and antibiofilm activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, at 25 mg/mL, with the highest antibiofilm inhibition observed for Pseudomonas aeruginosa (96.44%). Molecular docking analysis suggested that the major volatile constituents may interact with Staphylococcus aureus Sortase A, providing a plausible mechanistic basis for the observed antibiofilm effects. Overall, these findings indicate that wild Romanian hop cones represent a promising source of antioxidant and antimicrobial bioactive compounds, supporting their potential applications in pharmaceutical, food, and cosmetic formulations, as well as in natural-product-based drug discovery. Full article

Listeria monocytogenes (LM) is a lethal foodborne intracellular pathogen. Internalins A and B (inlA and inlB) are critical virulence factors that promote LM’s adhesion and invasion into host cells. InlA is covalently anchored to the cell wall by LM SortaseA (SrtA), while inlB is anchored to the cell wall via non-covalent bonds. Therefore, inhibiting SrtA and inlB is expected to suppress LM’s adhesion and invasion of host cells, enabling the prevention and control of infections. This study demonstrated that Luteolin inhibited the activity of purified LM SrtA protein in vitro. Interactive mechanism analysis indicated that Luteolin generates interaction with the critical active sites of SrtA, which may affect its binding to its natural substrates, thereby reducing the anchoring of inlA on the cell wall and achieving the inhibition of bacterial adhesion and invasion. In addition, Luteolin binds to the groove at the binding interface between inlB and its host receptor. The key residues in inlB that interact with the host receptor form weak interactions (Hydrogen bonds and van der Waals interactions) with Luteolin, this binding may inhibit their binding, suppressing LM’s adhesion and invasion of host cells. At the tested concentrations, Luteolin did not affect the growth of LM, but remarkably reduced the mortality and alleviated the infection symptoms of LM-infected Galleria mellonella. These results provide additional theoretical evidence for the application of Luteolin in the prevention and control of LM infections, which is expected to accelerate its application progress. Full article

Listeria monocytogenes is a foodborne pathogen of significant public health concern due to its high environmental resilience and ability to cause severe infections in vulnerable populations. The objective of the present study is to characterize foodborne strains of Listeria monocytogenes isolated between 2020 and 2024 in northwestern Italy. Lm was detected through isolation, biochemical confirmation and molecular serogrouping. Next generation sequencing (NGS) analysis was used to characterize the strains in terms of virulence and antibiotic resistance. A total of 39 positive samples were identified from various food matrices, including meat products, fish, cheeses and ready-to-eat foods. The most frequently detected serogroups were IIc and IIa, with a notable presence of the highly virulent IVb group. Next-generation sequencing (NGS) was applied to all isolates, revealing the presence of virulence genes associated with the LIPI-1 island and internalins. In addition to pathogenicity islands, genes related to stress resistance (clpCEP, Gad A, GadB, GadC), biofilm production (agrA, flaA, degU, hfq) and sortase-mediated anchoring of surface protein (strA, strB) have been identified. The presence of antibiotic resistance genes was confirmed, with all isolates harboring the fosX gene. Moreover, four isolates exhibited resistance determinants against antibiotics belonging to two different classes: tetracyclines (tetM) and lincosamides (lsa(A)). Multilocus sequence typing (MLST) showed that clonal complex CC9 was the most prevalent among the isolates. Further, cgMLST and SNP analyses identified a principal cluster of closely related strains, which were isolated from meat products. These findings highlight the need for continuous surveillance of L. monocytogenes. Full article

Streptococcus pneumoniae (S. pneumoniae) Sortase A (SrtA) anchors virulence proteins to the surface of the cell wall by recognizing and cleaving the LPXTG motif. These toxins help bacteria adhere to and colonize host cells, promote biofilm formation, and trigger host inflammatory responses. Therefore, SrtA is an ideal target for the development of new preparations for S. pneumoniae. In this study, we found that phloretin (pht) and phlorizin (phz) exhibited excellent affinities for SrtA based on virtual screening experiments. We analyzed the interactive mechanism between pht, phz, and alnusone (aln, a reported S. pneumoniae SrtA inhibitor) and SrtA based on molecular dynamics simulation experiments. The results showed that these inhibitors bound to the active pocket of SrtA, and the root mean square deviation (RMSD) and distance analyses showed that these compounds and SrtA maintained stable configuration and binding during the assay. The binding free energy analysis showed that both electrostatic forces (ele), van der Waals forces (vdw), and hydrogen bonds (Hbonds) promoted the binding between pht, phz, and SrtA; however, for the binding of aln and SrtA, the vdw force was much stronger than ele, and Hbonds were not found. The binding free energy decomposition showed that HIS141, ILE143, and PHE119 contributed more energy to promote pht and SrtA binding; ARG215, ASP188, and LEU210 contributed more energy to promote phz and SrtA binding; and HIS141, ASP209, and ARG215 contributed more energy to promote aln and SrtA binding. Finally, the transpeptidase activity of SrtA decreased significantly when treated with different concentrations of pht, phz, or aln, which inhibited S. pneumoniae biofilm formation and adhesion to A549 cells without affecting normal bacterial growth. These results suggest that pht, phtz, and aln are potential materials for the development of novel inhibitors against S. pneumoniae infection. Full article

Most studies on the Arthrosphaera genus, or giant pill millipedes, focus on its taxonomy, distribution, and ecology. Therefore, this investigation aimed to explore the chemical composition and bioactive properties of the hemolymph of the giant pill millipede Arthrosphaera lutescens (Butler, 1872). Chemical characterization of hemolymph was performed using gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–quadrupole time-of-flight mass spectrometry (LC-MS Q-TOF), revealing a complex array of over 200 compounds. The bioactive properties of hemolymph were determined by using radical scavenging capacity (DPPH assay); antibacterial activity against human pathogens like Escherichia coli (Migula, 1895) Castellani and Chalmers 1919, Klebsiella pneumonia (Schroeter, 1886) Trevisan 1887, and Staphylococcus aureus (Rosenbach, 1884); and cytotoxicity against Dalton’s lymphoma ascites (DLA) cells using the trypan blue assay. The hemolymph showed radical scavenging properties and antibacterial and cytotoxic activity. Among the identified metabolites, 1,2-dimethoxy-13-methyl-[1,3]benzodioxolo[5,6-c]phenanthridine (DMBP) emerged as a promising candidate due to its high abundance and bioactivity profile, showcasing therapeutic potential against both lymphoma and S. aureus in further docking studies. Computational analysis identified key T-cell lymphoma targets, with molecular docking suggesting DMBP’s anticancer properties through interactions with proteins like AKT1 and mTOR. Additionally, docking revealed DMBP’s antibacterial effects via interactions with proteins such as Sortase-A and DNA gyrase. This research underscores the potential pharmaceutical applications of metabolites from giant pill millipedes. Full article

Background: This study evaluated the polyphenolic composition, antibacterial activity, molecular docking interactions, and pharmacokinetic properties of Romanian oak and fir honeydew honeys. Methods: Spectrophotometric methods quantified total phenolic, flavonoid contents and antioxidant activity, and individual polyphenols were identified via HPLC-MS. Antibacterial efficacy against Gram-positive and Gram-negative bacteria was evaluated by determining the bacterial inhibition percentage and minimum inhibitory concentrations. The bioactive compounds identified via LC-MS analysis were used to further delineate the possible antibacterial activities in silico. Molecular docking was carried out to predict the binding interactions and complex formation of the identified compounds against protein crystal structures of the bacteria used in this study. Additionally, the pharmacokinetic profile of compounds with high inhibitory potential was assessed via ADMET (absorption, Distribution, Metabolism, Excretion, toxicity) predictors to ascertain their value. Results: Fir honeydew honey showed higher total phenolic (844.5 mg GAE/kg) and flavonoid contents (489.01 mg QUE/kg) compared to oak honeydew honey, correlating with more potent antioxidant activity (IC50 = 5.16 mg/mL). In vitro antimicrobial tests indicated a stronger inhibitory effect of fir honeydew honey, especially against Gram-positive strains like S. aureus, S. pyogenes, and L. monocytogenes, alongside certain Gram-negative strains such as E. coli and H. influenzae. Oak honeydew honey displayed selective antimicrobial action, particularly against P. aeruginosa and S. typhimurium. The docking outcomes showed rutin, rosmarinic acid, beta resorcylic acid, quercetin, ferulic acid, and p-coumaric acid have high inhibitory activities characterised by binding affinities and binding interactions against shiga toxin, riboflavin synthase, ATP-binding sugar transporter-like protein, undecaprenyl diphosphate synthase, putative lipoprotein, sortase A, and immunity protein, making them key contributors to the honey’s antimicrobial activity. Moreover, beta-resorcylic acid, quercetin, ferulic acid, and p-coumaric acid revealed interesting ADMET scores that qualify honey to serve as a good antimicrobial agent. Conclusions: These findings support their potential use as natural antibacterial agents and emphasise the value of integrating chemical, biological, and computational approaches for multidisciplinary characterisations. Full article

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a major human opportunistic pathogen that causes a wide range of infections. The vast arsenal of virulence factors expressed remains the biggest challenge in treating MRSA with conventional antibiotic therapy. Methods: We investigated the effects of Kuraridin at subinhibitory minimum inhibition concentrations (MICs) of 1/8, 1/16, and 1/32 (concentrations that did not inhibit bacterial growth) on adhesion to fibrinogen, adhesion, internalization into HaCaT cells, and biofilm production in three MRSA strains representing the clonal types USA300, ST30, and ST239. Results: All three MRSA strains exhibited a significant decrease (p < 0.001) in adhesion to fibrinogen upon treatment with 1/8 and 1/16 MICs of Kuraridin. The adhesion and internalization of all the MRSA strains to HaCaT cells were decreased significantly (p < 0.001) upon treatment with the three subinhibitory concentrations of Kuraridin. The biofilm formation of USA300 (p < 0.001), ST30 (p < 0.001), and ST239 (p < 0.01) was significantly reduced at a 1/8 MIC. A significant decrease in biofilm formation at a 1/16 MIC was observed for USA300 (p < 0.001) and ST30 (p < 0.05). Confocal laser scanning microscopy (CSLM) analysis of the biofilms revealed a reduction in biofilm formation in the MRSA strain when treated with Kuraridin. In the in vivo Caenorhabditis elegans model, Kuraridin offered a sizable degree of protection against MRSA infection without being toxic to the nematode. Conclusions: Our findings reveal that Kuraridin has the potential to be an alternative antivirulence option for reducing MRSA pathogenicity. Full article

The arid mountainous region of Hail in Saudi Arabia has a variety of desert vegetation, some of which are conventionally used in Bedouin traditional medicine. These plants need scientific examination. This research seeks to examine Blepharis ciliaris using a thorough multi-analytical methodology that includes antibacterial and antioxidant assessments as well as computational modeling. GC–MS analysis of the methanolic extract revealed 17 organic compounds, including pentadecanoic acid, ethyl methyl ester (2.63%); hexadecanoic acid, methyl ester (1.00%); 9,12-octadecadienoic acid (Z,Z)-, methyl ester (2.74%); 9-octadecenoic acid, methyl ester (E) (2.78%); octadecanoic acid (5.88%); 9-tetradecenoic acid (Z) (3.22%); and undec-10-enoic acid, undec-2-n-1-yl ester (5.67%). The DPPH test evaluated antioxidant activity, revealing a notable increase with higher concentrations of the methanolic extract, achieving maximum inhibition of 81.54% at 1000 µg/mL. The methanolic extract exhibited moderate antibacterial activity, with average inhibition zones of 10.33 ± 1.53 mm, 13.33 ± 1.53 mm, 10.67 ± 1.53 mm, and 10.00 ± 2.00 mm against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Serratia marcescens, respectively, as determined by the disk diffusion method. The minimum inhibitory concentration (MIC) values were 500 µg/mL for S. aureus and B. subtilis, whereas E. coli and S. marcescens showed susceptibility at 1000 µg/mL. Computational simulations were employed to assess the toxicity, drug-likeness, and ADMET profiles of compounds derived from Blepharis ciliaris. Thirteen bioactive compounds were assessed in silico against Staphylococcus aureus sortase A (PDB: 1T2O), Bacillus subtilis BsFabHb (PDB: 8VDB), Escherichia coli LPS assembly protein (LptD) (PDB: 4RHB), and a modeled Serratia marcescens outer-membrane protein TolC, focusing on cell wall and membrane structures. Compound 3, (+)-Ascorbic acid 2,6-dihexadecanoate, shown significant binding affinities to B. subtilis BsFabHb, E. coli LPS assembly protein, and S. marcescens TolC. Full article

Targeting virulence determinants is a promising approach to controlling S. aureus infections in the face of the global spread of antibiotic resistance. S. aureus-induced peritonitis often occurs in dialysis, implant and trauma patients. To develop novel prevention and treatment options for peritoneal infection, we investigated the oligopeptide sortase A inhibitor LPRDA as a non-conventional antibacterial that does not affect staphylococcal survival. Administration of LPRDA prior to S. aureus challenge reduced the bacterial load of internal organs and bacterial colonization of the abdominal cavity in animals. In addition, LPRDA inhibited α-hemolysin production in 80% of the 35 reference and clinical S. aureus strains tested. Consequent research of LPRDA interactions with cefazolin and vancomycin has demonstrated the potential for combined application of the antivirulent and antibiotic agents under study. Full article

Sortase A (SrtA) of Staphylococcus aureus has long been shown to be a relevant molecular target for antibacterial development. Moreover, the designed SrtA inhibitors act via the antivirulence mechanism, potentially causing less evolutional pressure and reduced antimicrobial resistance. However, no marketed drugs or even drug candidates have been reported until recently, despite numerous efforts in the field. SrtA has been shown to be a tough target for rational structure-based drug design (SBDD), which hampers the regular development of small-molecule inhibitors using the available arsenal of drug discovery tools. Recently, several oligopeptides resembling the sorting sequence LPxTG (Leu-Pro-Any-Thr-Gly) of the native substrates of SrtA were reported to be active in the micromolar range. Despite the good experimental design of those works, their molecular modeling parts are still not convincing enough to be used as a basis for a rational modification of peptidic inhibitors. In this work, we propose to use the ensemble docking approach, in which the relevant SrtA conformations are extracted from the molecular dynamics simulation of the LPRDA (Leu-Pro-Arg-Asp-Ala)-SrtA complex, to effectively represent the most significant and diverse target conformations. The developed protocol is shown to describe the known experimental data well and then is applied to a series of new peptidomimetic molecules resembling the active oligopeptide structures reported previously in order to prioritize structures from this work for further synthesis and activity testing. The proposed approach is compared to existing alternatives, and further directions for its development are outlined. Full article

Stonikacidin A (1), the first representative of a new class of 4-bromopyrrole alkaloids containing an aldonic acid core, was isolated from the marine sponge Lissodendoryx papillosa. The compound is named in honor of Prof. Valentin A. Stonik, who is one of the outstanding investigators in the field of marine natural chemistry. The structure of 1 was determined using NMR, MS analysis, and chemical correlations. The L-idonic acid core was established by the comparison of GC, NMR, MS, and optical rotation data of methyl-pentaacetyl-aldonates obtained from the hydrolysis products of 1 and standard hexoses. The L-form of the idonic acid residue in 1 was confirmed by GC analysis of pentaacetate of (S)-2-butyl ester of the hydrolysis product from 1 and compared with corresponding derivatives of L- and D-idonic acids. The biosynthetic pathway for stonikacidin A (1) was proposed. The alkaloid 1 inhibited the growth of Staphylococcus aureus and Escherichia coli test strains, as well as affected the formation of S. aureus and E. coli biofilms. Compound 1 inhibited the activity of sortase A. Molecular docking data showed that stonikacidin A (1) can bind with sortase A due to the interactions between its bromine atoms and some amino acid residues of the enzyme. Full article

Affinity chromatography is a widely used technique for antibody isolation. This article presents the successful synthesis of a novel affinity resin with a mutant form of protein A (BsrtA) immobilized on it as a ligand. The key aspect of the described process is the biocatalytic immobilization of the ligand onto the matrix using the sortase A enzyme. Moreover, we used a matrix with primary amino groups without modification, which greatly simplifies the synthesis process. The resulting resin shows a high dynamic binding capacity (up to 50 mg IgG per 1 mL of sorbent). It also demonstrates high tolerance to 0.1 M NaOH treatment and maintains its effectiveness even after 100 binding, elution, and sanitization cycles. Full article

Sortase A (SrtA) is a cysteine transpeptidase that binds to the periplasmic membrane and plays a crucial role in attaching surface proteins, including staphylococcal protein A (SpA), to the peptidoglycan cell wall. Six pentacyclic polyketides (1–6) were isolated from the marine sponge Xestospongia sp., and their structures were elucidated using spectroscopic techniques and by comparing them to previously reported data. Among them, halenaquinol (2) was found to be the most potent SrtA inhibitor, with an IC₅₀ of 13.94 μM (4.66 μg/mL). Semi-quantitative reverse transcription PCR data suggest that halenaquinol does not inhibit the transcription of srtA and spA, while Western blot analysis and immunofluorescence microscopy images suggest that it blocks the cell wall surface anchoring of SpA by inhibiting the activity of SrtA. The onset and magnitude of the inhibition of SpA anchoring on the cell wall surface in S. aureus that has been treated with halenaquinol at a value 8× that of the IC₅₀ of SrtA are comparable to those for an srtA-deletion mutant. These findings contribute to the understanding of the mechanism by which marine-derived pentacyclic polyketides inhibit SrtA, highlighting their potential as anti-infective agents targeting S. aureus virulence. Full article

Listeria monocytogenes is a ubiquitous bacterial pathogen that threatens the food chain and human health. In this study, whole-genome sequencing (WGS) was used for the genomic characterization of L. monocytogenes (n = 24) from beef and beef-based products. Multilocus Sequence Type (MLST) analysis revealed that ST204 of CC204 was the most common sequence type (ST). Other sequence types detected included ST1 and ST876 of CC1, ST5 of CC5, ST9 of CC9, ST88 of CC88, ST2 and ST1430 of CC2, and ST321 of CC321. Genes encoding for virulence factors included complete LIPI-1 (pfrA-hly-plcA-plcB-mpl-actA) from 54% (13/24) of the isolates of ST204, ST321, ST1430, and ST9 and internalin genes inlABC that were present in all the STs. All the L. monocytogenes STs carried four intrinsic/natural resistance genes, fosX, lin, norB, and mprF, conferring resistance to fosfomycin, lincosamide, quinolones, and cationic peptides, respectively. Plasmids pLGUG1 and J1776 were the most detected (54% each), followed by pLI100 (13%) and pLM5578 (7%). The prophage profile, vB_LmoS_188, was overrepresented amongst the isolates, followed by LP_101, LmoS_293_028989, LP_030_2_021539, A006, and LP_HM00113468. Listeria genomic island 2 (LGI-2) was found to be present in all the isolates, while Listeria genomic island 3 (LGI-3) was present in a subset of isolates (25%). The type VII secretion system was found in 42% of the isolates, and sortase A was present in all L. monocytogenes genomes. Mobile genetic elements and genomic islands did not harbor any virulence, resistance, or environmental adaptation genes that may benefit L. monocytogenes. All the STs did not carry genes that confer resistance to first-line antibiotics used for the treatment of listeriosis. The characterization of L. monocytogenes in our study highlighted the environmental resistance and virulence potential of L. monocytogenes and the risk posed to the public, as this bacterium is frequently found in food and food processing environments. Full article

A promising strategy for combating bacterial infections involves the development of agents that disarm the virulence factors of pathogenic bacteria, thereby reducing their pathogenicity without inducing direct lethality. Sortase A, a crucial enzyme responsible for anchoring virulence factors to the cell surface of several pathogenic bacteria, has emerged as a possible target for antivirulence strategies. A series of hippocastanum species (Aesculus pavia, A. parviflora, Aesculus x carnea, and A. hippocastanum) were used to prepare ethanol- and water-based extracts for assessing their effect on Staphylococcus aureus sortase A. The extracts were characterized through HPLC analysis, and their polyphenols content was determined using the Folin–Ciocalteu method. The specific toxicity profile was evaluated in Daphnia magna using the median lethal concentration (LC₅₀) and against the fibroblast MRHF cell line. The half maximal inhibitory concentration (IC₅₀) values on sortase A, determined after 30 min of incubation, ranged from 82.70 to 304.31 µg/mL, with the A. pavia water extract exhibiting the highest inhibitory effect. The assessment of the A. pavia water extract on human fibroblasts revealed no significant signs of toxicity, even at a concentration of 500 µg/mL. This reduced toxicity was further validated through the Daphnia assay. These findings highlight the low toxicity and the potential of this extract as a promising source of future development of bacteria antivirulence solutions. Full article