Transferosomes stabilized hydrogel incorporated rhodomyrtone-rich extract from Rhodomyrtus tomentosa leaf fortified with phosphatidylcholine for the management of skin and soft-tissue infections.

Rhodomyrtus tomentosa leaf (RT)-incorporated transferosomes were developed with lecithin and cholesterol blends with edge activators at different ratios. RT-transferosomes were characterized and employed in transferosomal gel formulations for the management of skin and soft-tissue infections. The optimized formulation entrapped up to 81.90 ± 0.31% of RT with spherical vesicles (405.3 ± 2.0 nm), polydispersity index value of 0.16 ± 0.08, and zeta potential of - 61.62 ± 0.86 mV. Total phenolic and flavonoid contents of RT-transferosomes were 15.65 ± 0.04 µg GAE/g extract and 43.13 ± 0.91 µg QE/g extract, respectively. RT-transferosomes demonstrated minimum inhibitory and minimum bactericidal concentrations at 8-256 and 64-1024 µg/mL, respectively. Free radical scavenging assay showed RT-transferosomes with high scavenging activity against DPPH and ABTS radicals. Moreover, RT-transferosomes demonstrated moderate activity against mushroom tyrosinase, with IC50 values of 245.32 ± 1.32 µg/mL. The biocompatibility results against L929 fibroblast and Vero cells demonstrated IC50 at 7.05 ± 0.17 and 4.73 ± 0.13 µg/mL, respectively. In addition, nitric oxide production significantly decreased by 6.78-88.25% following the treatment with 31.2-500 ng/mL RT-transferosomes (p < 0.001). Furthermore, the freeze-thaw stability study displayed no significant change in stability in the sedimentation and pH of gel fortified with RT-transferosomes. The results suggested that RT-transferosome formulation can be effectively employed as natural biomedicines for scar prevention and the management of skin soft-tissue infections.

Camaldulensals A-C, the First Meroterpenoids Possessing Two Spatially Separated Formyl Phloroglucinols Conjugated to a Terpene Core from the Leaves of Eucalyptus camaldulensis Dehnh.

Three new bis-formyl phloroglucinol-meroterpenoids (1-3), three new euglobal type formyl phloroglucinol-meroterpenoids (4-6), and one new dimeric formyl phloroglucinol (7) were isolated from the leaves of Eucalyptus camaldulensis. Camaldulensal A (1) is the first bis-isovaleryl-formyl-phloroglucinol-sesquiterpenoid. It features a novel 6/6/10/3/6/6 fused ring system and contains six stereogenic centers. Camaldulensals B (2) and C (3) are the first bis-isovaleryl-formyl-phloroglucinols, each conjugated to a monoterpene. Formyl phloroglucinol compounds (FPCs) containing two spatially separated formyl phloroglucinols conjugated to a terpene core such as 1-3 have not been reported previously. The structures of these compounds were elucidated by spectroscopic methods and computational analysis. Camaldulensals B (2) and C (3) exhibited significant antibacterial activity against methicillin-susceptible and methicillin-resistant Staphylococcus aureus. Structure activity relationships are discussed in relation to previously reported antibacterial activities of other molecules from the FPC structure class.

Biogenic nanosilver-fabricated endotracheal tube to prevent microbial colonization in a veterinary hospital.

COVID-19 patients have often required prolonged endotracheal intubation, increasing the risk of developing ventilator-associated pneumonia (VAP). A preventive strategy is proposed based on an endotracheal tube (ETT) modified by the in situ deposition of eucalyptus-mediated synthesized silver nanoparticles (AgNPs). The surfaces of the modified ETT were embedded with AgNPs of approximately 28 nm and presented a nanoscale roughness. Energy dispersive X-ray spectroscopy confirmed the presence of silver on and inside the coated ETT, which exhibited excellent antimicrobial activity against Gram-positive and Gram-negative bacteria, and fungi, including multidrug-resistant clinical isolates. Inhibition of planktonic growth and microbial adhesion ranged from 99 to 99.999% without cytotoxic effects on mammalian cells. Kinetic studies showed that microbial adhesion to the coated surface was inhibited within 2 h. Cell viability in biofilms supplemented with human tracheal mucus was reduced by up to 95%. In a porcine VAP model, the AgNPs-coated ETT prevented adhesion of Pseudomonas aeruginosa and completely inhibited bacterial invasion of lung tissue. The potential antimicrobial efficacy and safety of the coated ETT were established in a randomized control trial involving 47 veterinary patients. The microbial burden was significantly lower on the surface of the AgNPs-coated ETT than on the uncoated ETT (p < 0.05). KEY POINTS: • Endotracheal tube surfaces were modified by coating with green-synthesized AgNPs • P. aeruginosa burden of endotracheal tube and lung was reduced in a porcine model • Effective antimicrobial activity and safety was demonstrated in a clinical trial.

Nationwide Surveillance and Molecular Characterization of Critically Drug-Resistant Gram-Negative Bacteria: Results of the Research University Network Thailand Study.

A large-scale surveillance is an important measure to monitor the regional spread of antimicrobial resistance. We prospectively studied the prevalence and molecular characteristics of clinically important Gram-negative bacilli, including Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii complex (ABC), and Pseudomonas aeruginosa, from blood, respiratory tract, urine, and sterile sites at 47 hospitals across Thailand. Among 187,619 isolates, 93,810 isolates (50.0%) were critically drug resistant, of which 12,915 isolates (13.8%) were randomly selected for molecular characterization. E. coli was most commonly isolated from all specimens, except the respiratory tract, in which ABC was predominant. Prevalence of extended-spectrum cephalosporin resistance (ESCR) was higher in E. coli (42.5%) than K. pneumoniae (32.0%), but carbapenem-resistant (CR)-K. pneumoniae (17.2%) was 4.5-fold higher than CR-E. coli (3.8%). The majority of ESCR/CR-E. coli and K. pneumoniae isolates carried blaCTX-M (64.6% to 82.1%). blaNDM and blaOXA-48-like were the most prevalent carbapenemase genes in CR-E. coli/CR-K. pneumoniae (74.9%/52.9% and 22.4%/54.1%, respectively). In addition, 12.9%/23.0% of CR-E. coli/CR-K. pneumoniae cocarried blaNDM and blaOXA-48-like. Among ABC isolates, 41.9% were extensively drug resistant (XDR) and 35.7% were multidrug resistant (MDR), while P. aeruginosa showed XDR/MDR at 6.3%/16.5%. A. baumannii was the most common species among ABC isolates. The major carbapenemase gene in MDR-A. baumannii/XDR-A. baumannii was blaOXA-23-like (85.8%/93.0%), which had much higher rates than other ABC species. blaIMP, blaVIM, blaOXA-40-like, and blaOXA-58-like were also detected in ABC at lower rates. The most common carbapenemase gene in MDR/XDR-P. aeruginosa was blaIMP (29.0%/30.6%), followed by blaVIM (9.5%/25.3%). The findings reiterate an alarming situation of drug resistance that requires serious control measures.

Biologically rapid synthesized silver nanoparticles from aqueous Eucalyptus camaldulensis leaf extract: Effects on hyphal growth, hydrolytic enzymes, and biofilm formation in Candida albicans.

Bionanotechnology has increasingly gained attention in biomedical fields as antifungal and antibiofilm agents. In this study, biosynthesized silver nanoparticles (bio-AgNPs) using aqueous Eucalyptus camaldulensis leaf extract were successfully performed by a one-step green approach. Spherical-shaped nanoparticles, approximately 8.65 nm, exhibited noncytotoxicity to erythrocytes, HeLa, and HaCaT cells. The synthesized nanoparticles showed strong fungicidal activity ranging from 0.5 to 1 µg/ml. The nanoparticles affected Candida adhesion and invasion into host cells by reduced germ tube formation and hydrolytic enzyme secretion. Inhibitory effects of bio-AgNPs on Candida biofilms were evaluated by the prevention of yeast-to-hyphal transition. A decrease in cell viability within mature biofilm demonstrated the ability of bio-AgNPs to penetrate into the extracellular matrix and destroy yeast cell morphology, leading to cell death. Molecular biology study on biofilms confirmed downregulation in the expression of genes ALS3, HWP1, ECE1, EFG1, TEC1, ZAP1, encoding hyphal growth and biofilm development and PLB2, LIP9, SAP4, involved in hydrolytic enzymes. In addition to candida treatment, the bio-AgNPs could be applied as an antioxidant to protect against oxidative stress-related human diseases. The findings concluded that bio-AgNPs could be used as an antifungal agent for candida treatment, as well as be incorporated in medical devices to prevent biofilm formation.

The novel antibiotic rhodomyrtone traps membrane proteins in vesicles with increased fluidity.

The acylphloroglucinol rhodomyrtone is a promising new antibiotic isolated from the rose myrtle Rhodomyrtus tomentosa, a plant used in Asian traditional medicine. While many studies have demonstrated its antibacterial potential in a variety of clinical applications, very little is known about the mechanism of action of rhodomyrtone. Preceding studies have been focused on intracellular targets, but no specific intracellular protein could be confirmed as main target. Using live cell, high-resolution, and electron microscopy we demonstrate that rhodomyrtone causes large membrane invaginations with a dramatic increase in fluidity, which attract a broad range of membrane proteins. Invaginations then form intracellular vesicles, thereby trapping these proteins. Aberrant protein localization impairs several cellular functions, including the respiratory chain and the ATP synthase complex. Being uncharged and devoid of a particular amphipathic structure, rhodomyrtone did not seem to be a typical membrane-inserting molecule. In fact, molecular dynamics simulations showed that instead of inserting into the bilayer, rhodomyrtone transiently binds to phospholipid head groups and causes distortion of lipid packing, providing explanations for membrane fluidization and induction of membrane curvature. Both its transient binding mode and its ability to form protein-trapping membrane vesicles are unique, making it an attractive new antibiotic candidate with a novel mechanism of action.

Prolonged inhibitory effects against planktonic growth, adherence, and biofilm formation of pathogens causing ventilator-associated pneumonia using a novel polyamide/silver nanoparticle composite-coated endotracheal tube.

Microbial cells can rapidly form biofilm on endotracheal tubes (ETT) causing ventilator-associated pneumonia, a serious complication in patients receiving mechanical ventilation. A novel polyamide with a good balance of hydrophilic/hydrophobic moieties was used for the embedment of green-reduction silver nanoparticles (AgNPs) for the composite-coated ETT. The films were conformal with a thickness of ∼ 17 ± 3 µm accommodating high loading of 60 ± 35 nm spherical-shaped AgNPs. The coated ETT resulted in a significant difference in reducing both planktonic growth and microbial adhesion of single and mixed-species cultures, compared with uncoated ETT (p < 0.05). A time-kill assay demonstrated rapid bactericidal effects of the coating on bacterial growth and cell adhesion to ETT surface. Biofilm formation by Pseudomonas aeruginosa and Staphylococcus aureus, commonly encountered pathogens, was inhibited by > 96% after incubation for 72 h. Polyamide/AgNP composite-coated ETT provided a broad-spectrum activity against both Gram-positive and Gram-negative bacteria as well as Candida albicans and prolonged antimicrobial activity.

Rhodomyrtus tomentosa Leaf Extract and Rhodomyrtone Combat Streptococcus pneumoniae Biofilm and Inhibit Invasiveness to Human Lung Epithelial and Enhance Pneumococcal Phagocytosis by Macrophage.

Rhodomyrtus tomentosa leaf has been traditionally used to treat many infections. This plant species has been documented to possess a wide spectrum of pharmacological effects. This study aimed to determine the effects of Rhodomyrtus tomentosa leaf extract and its potent purified compound, rhodomyrtone, on Streptococcus pneumoniae virulence factors including biofilms, capsule formation, and invasiveness which play important roles in infections. Ethanol leaf extract and rhodomyrtone demonstrated excellent antibacterial activity against S. pneumoniae with minimal inhibitory concentration (MIC) ranging from 16-32 µg/ml and 0.125-1 µg/ml, respectively. The ability of the extract and rhodomyrtone to prevent biofilm formation and eradicate mature biofilms was assessed. The extract and rhodomyrtone at 1/8 × MIC significantly inhibited biofilm formation in all clinical isolates (P < 0.05). The viability of 8-day biofilm-grown cells significantly decreased following the treatment with the extract and rhodomyrtone at 16 × MIC. 40-90% reduction in the bacterial adhesion and invasion to A549 human alveolar epithelial cells was observed after challenging with the extract and rhodomyrtone, compared with the control within 60 min. Increase in 90-99% phagocytosis of the bacterial cells by RAW264.7 macrophage cell line was detected following the treatment with the extract and rhodomyrtone at 1/2 × MIC, compared with the control. The results suggested potential medicinal benefits of the extract and rhodomyrtone for the treatment of pneumococcal infections.

Potential of antimicrobial topical gel with synthesized biogenic silver nanoparticle using Rhodomyrtus tomentosa leaf extract and silk sericin.

OBJECTIVE: Silver nanoparticles synthesized using Rhodomyrtus tomentosa leaf extract and silk sericin were used to functionalize carbopol 940 gel for topical applications. RESULTS: UV-vis spectra presented surface plasmon resonance at 426 nm, transmission electron microscopy revealed that nanoparticles were spherical with an average size of 25-50 nm. X-ray diffraction presented crystalline silver nanoparticles with zeta potential of ≈ - 30 mV. FTIR spectra showed a reduction of silver nitrate indicated by the shift in -OH at 2958 cm-1. The silver nanoparticle demonstrated broad-spectrum antimicrobial activity against Gram-positive, Gram-negative and fungi with MIC ranging between 0.26 and 2.10 µg mL-1, respectively. MIC of hydrogel ranged between 1.05-2.10 µg mL-1 with cell viability of 89%. Spreadability and extrudability of gel were 9.3 ± 0.85 s and 19.85 ± 0.03%, respectively with first order of fickian diffusion. CONCLUSIONS: The silver nanoparticle gel exhibited an effective antimicrobial property, hence can be exploited for topical applications.

Rhodomyrtone decreases Staphylococcus aureus SigB activity during exponentially growing phase and inhibits haemolytic activity within membrane vesicles.

Sigma factor B (SigB) controls the expression of Staphylococcus aureus genes including virulence factors and plays a role in the bacterial secretion system through membrane vesicle production. Inhibition of SigB could attenuate SigB dependent virulence and secretion system. The objective of this study was to determine the effects of rhodomyrtone on SigB and virulence factors related to SigB. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of rhodomyrtone against 67 clinical methicillin-resistant S. aureus isolates were 0.25-8 µg/ml, which were similar to those of vancomycin. Using luciferase gene fused to SigB dependent promoters of asp23, five time reduction in SigB activity was observed when the bacteria were treated with rhodomyrtone for 3 h. Rhodomyrtone significantly reduced SigB activity in a concentration dependent manner in exponentially growing cells (P < 0.05). In addition, sigB mutant was more sensitive towards increasing concentrations of rhodomyrtone than the wild type and yabJ-spoVG mutant. Rhodomyrtone at 0.625 µg/ml reduced the growth of sigB mutant by approximately 99%, compared with the yabJ-spoVG mutant and the wild type. Membrane vesicles were significantly reduced in the bacterial cells when treated with 0.5 × MIC rhodomyrtone (P < 0.05). Decreased haemolytic activity was detected within rhodomyrtone-treated membrane vesicles. The results indicated that rhodomyrtone inhibited S. aureus SigB activity during exponentially growing phase and inhibited haemolytic activity within membrane vesicles.

Rhodomyrtone (Rom) is a membrane-active compound.

Particularly in Asia medicinal plants with antimicrobial activity are used for therapeutic purpose. One such plant-derived antibiotic is rhodomyrtone (Rom) isolated from Rhodomyrtus tomentosa leaves. Rom shows high antibacterial activity against a wide range of Gram-positive bacteria, however, its mode of action is still unclear. Reporter gene assays and proteomic profiling experiments in Bacillus subtilis indicate that Rom does not address classical antibiotic targets like translation, transcription or DNA replication, but acts at the cytoplasmic membrane. In Staphylococcus aureus, Rom decreases the membrane potential within seconds and at low doses, causes release of ATP and even the excretion of cytoplasmic proteins (ECP), but does not induce pore-formation as for example nisin. Lipid staining revealed that Rom induces local membrane damage. Rom's antimicrobial activity can be antagonized in the presence of a very narrow spectrum of saturated fatty acids (C15:0, C16:0, or C18:0) that most likely contribute to counteract the membrane damage. Gram-negative bacteria are resistant to Rom, presumably due to reduced penetration through the outer membrane and its neutralization by LPS. Rom is cytotoxic for many eukaryotic cells and studies with human erythrocytes showed that Rom induces eryptosis accompanied by erythrocyte shrinkage, cell membrane blebbing, and membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Rom's distinctive interaction with the cytoplasmic membrane reminds on the amphipathic, alpha-helical peptides, the phenol-soluble modulins (PSMs), and renders Rom an important tool for the investigation of membrane physiology.

Quercus infectoria inhibits Set7/NF-κB inflammatory pathway in macrophages exposed to a diabetic environment.

Chronic inflammation plays a key role in the pathogenesis of myriad complications associated with diabetes and thus anti-inflammatory therapies may ameliorate these complications. Quercus infectoria (Qi) extract has been shown to downregulate inflammatory processes; however, the molecular mechanisms of this anti-inflammatory activity remain unclear. The hypothesis of our study was that Qi extract exerts its anti-inflammatory effect by downregulating the Set7/NF-κB pathway. Bone marrow-derived macrophages (BMM) were treated with high glucose plus palmitate medium (HG/Pa) to simulate the diabetic environment. Compared with control conditions, HG/Pa elevated expression Set7, expression and activity of NF-κB along with expression of several inflammatory cytokines. These changes were associated with increased levels of intracellular reactive oxygen species (ROS). Moreover, similar alterations were demonstrated in BMM derived from mice fed a high fat diet (HFD) compared to those from lean mice, suggesting that HFD-induced changes in BM progenitors persist throughout differentiation and culture. Importantly, Qi extract dose-dependently reduced Set7, p65 and inflammatory cytokine expression relative to vehicle controls in both HG/Pa-and HFD-treated BMM. Finally, macrophages/monocytes isolated from wounds of diabetic mice that were treated with Qi solution exhibited lower expression of the inflammatory cytokines, IL-1ß and TNF-α, compared with vehicle treated wounds, demonstrating translation to the in vivo diabetic environment. Taken together, data from this study suggests that Qi downregulates diabetes-induced activity of the Set7/NF-kB pathway.

In vitro and in vivo comparative analysis of antibacterial activity of green-synthesized silver nanoparticles.

This study aims to compare antibacterial effects of green-synthesized silver nanoparticles (AgNPs) with silver nitrate (AgNO3 ). AgNPs were successfully synthesized using Eucalyptus camaldulensis leaf extract as a reducing and stabilizing agent. Minimum inhibitory concentrations (MIC) of AgNPs and AgNO3 against Staphylococcus aureus and Pseudomonas aeruginosa ranged between 4.8 and 6.75 µg mL-1 . Growth curves demonstrated that inhibition of P. aeruginosa occurred right after AgNPs were added and throughout the period of the study (72 h). Antibacterial effects of both AgNPs and AgNO3 could be abrogated by cysteine and 2-mercaptoethanol, thiol-containing compounds. Galleria mellonella model revealed relatively low toxic effects of both AgNPs and AgNO3 . At 20MIC of AgNPs (≈137.8 mg kg-1 ), more than 80% survival of G. mellonella was observed. Unexpectedly, silver-containing agents could not rescue larvae after S. aureus infection. Further ex vivo experiments in the presence of coelomic larval fluid demonstrated the reduction of antibacterial activity of both AgNPs and AgNO3 . It was speculated that anionic molecules present in the coelomic fluid might neutralize the action of Ag ions. Binding of AgNPs or AgNO3 to albumin, a major protein in human blood which transport several endogenous compounds was not detected, indicating that the silver-containing agents could be applied as an antimicrobial agent.

Advanced biomaterial agent from chitosan/poloxamer 407-based thermosensitive hydrogen containing biosynthesized silver nanoparticles using Eucalyptus camaldulensis leaf extract.

CONTEXT: The emergence of multidrug-resistant (MDR) pathogens poses a significant challenge for global public health systems, increasing hospital morbidity and mortality and prolonged hospitalization. OBJECTIVE: We evaluated the antimicrobial activity of a thermosensitive hydrogel containing bio-synthesized silver nanoparticles (bio-AgNPs) based on chitosan/poloxamer 407 using a leaf extract of Eucalyptus calmadulensis. RESULTS: The thermosensitive hydrogel was prepared by a cold method after mixing the ingredients and left at 4°C overnight to ensure the complete solubilization of poloxamer 407. The stability of the hydrogel formulation was evaluated at room temperature for 3 months, and the absorption peak (420 nm) of the NPs remained unchanged. The hydrogel formulation demonstrated rapid gelation under physiological conditions, excellent water retention (85%), and broad-spectrum antimicrobial activity against MDR clinical isolates and ATCC strains. In this regard, minimum inhibitory concentration and minimum microbial concentration values of the bio-AgNPs ranged from 2-8 µg/mL to 8-128 µg/mL, respectively. Formulation at concentrations <64 µg/mL showed no cytotoxic effect on human-derived macrophages (THP-1 cells) with no induction of inflammation. CONCLUSIONS: The formulated hydrogel could be used in biomedical applications as it possesses a broad antimicrobial spectrum and anti-inflammatory properties without toxic effects on human cells.

Rifampicin Enhanced Carbapenem Activity with Improved Antibacterial Effects and Eradicates Established Acinetobacter baumannii Biofilms.

Biofilm-mediated infections are critical to public health and a leading cause of resistance among pathogens, amounting to a prolonged hospital stay and increased mortality rate in the intensive care unit. In this study, the antibacterial and antibiofilm activities of rifampicin or carbapenem monotherapies were compared with rifampicin and carbapenem combination therapies against rifampicin-resistant and carbapenem-resistant Acinetobacter baumannii isolates. Among 29 CRAB isolates, 24/29 (83%) were resistant to rifampicin, with MIC values between 2-256 µg/mL. Checkerboard assays disclosed that combination therapies at FICIs between 1/8 and 1/4 improved the activity of carbapenems at subinhibitory concentrations. Time-kill kinetics indicated a 2- to 4-log reduction at 1/2 MIC rifampicin + 1/4 MIC carbapenem and 1/4 MIC rifampicin + 1/4 MIC carbapenem against the isolates, with the MIC values ranging from 2-8 µg/mL. The MTT assay revealed a dose-dependent decrease of the cell viability of established bacterial biofilm at 4 MIC rifampicin + 2 MIC carbapenems, with a percentage reduction of 44-75%, compared with monotherapies at 16 MIC. Scanning electron microscopy further confirmed bacterial cell membrane disruption, suggesting a synergism between carbapenem and rifampicin against a representative isolate. The findings demonstrated that the combination of rifampicin with carbapenems could improve antibacterial activities and eradicate established Acinetobacter baumannii biofilm.

Thai ethnomedicinal plants as resistant modifying agents for combating Acinetobacter baumannii infections.

BACKGROUND: Acinetobacter baumannii is well-recognized as an important nosocomial pathogen, however, due to their intrinsic resistance to several antibiotics, treatment options are limited. Synergistic effects between antibiotics and medicinal plants, particularly their active components, have intensively been studied as alternative approaches. METHODS: Fifty-one ethanol extracts obtained from 44 different selected medicinal plant species were tested for resistance modifying agents (RMAs) of novobiocin against A. baumannii using growth inhibition assay. RESULTS: At 250 µg/ml, Holarrhena antidysenterica, Punica granatum, Quisqualis indica, Terminalia bellirica, Terminalia chebula, and Terminalia sp. that possessed low intrinsic antibacterial activity significantly enhanced the activity of novobiocin at 1 µg/ml (1/8xminimum inhibitory concentration) against this pathogen. Holarrhena antidysenterica at 7.8 µg/ml demonstrated remarkable resistant modifying ability against A. baumannii in combination with novobiocin. The phytochemical study revealed that constituents of this medicinal plant contain alkaloids, condensed tannins, and triterpenoids. CONCLUSION: The use of Holarrhena antidysenterica in combination with novobiocin provides an effective alternative treatment for multidrug resistant A. baumannii infections.

A new alkaloid and a new benzaldehyde derivative from the twig of Zanthoxylum rhetsa (Roxb.) DC.

A new alkaloid, 2-acetyl-4-methoxyfuro[2,3-b]quinoline (1), and a new benzaldehyde derivative, (2'S)-4-(2'-hydroxy-3'-methyl-3'-butenoxy)benzaldehyde (2), were isolated from the twig of Zanthoxylum rhetsa (Roxb.) DC. along with twenty-six known compounds (3-28). Their structures were determined by spectroscopic analysis (1D and 2D NMR spectroscopy and HRMS analysis) and comparison with data reported in the literature. Thirteen of the known compounds were evaluated for their cytotoxic activities against human cancer cell lines that included MDA-MB-231, SW1353, A549, and HCT116. (±)-8-Acetonyldihydronitidine (15) showed moderate cytotoxicity toward the SW1353 cancer cell line with an IC50 value of 18.90±0.39 µg/mL, and exhibited weak cytotoxic activity against MDA-MB-231, A549 and HCT116 cell lines with IC50 values of 49.86-71.32 µg/mL.

Isolation and Characterisation of Bacteriophage Selective for Key Acinetobacter baumannii Capsule Chemotypes.

Nineteen bacteriophages against five main capsular types of multidrug-resistant Acinetobacter baumannii were isolated from tertiary care hospital sewage. Eight representative phages from each capsular type were characterized and tested for their biological properties. The biological features revealed that phages T1245, T444, and T515 had a large burst size of more than 420 pfu/mL, together with a short latent period lasting less than 6 min, and were readily adsorbed to a bacterial host within 10 min. Moreover, these phages demonstrated host specificity and stability over a broad range of temperatures (-20 to 60 °C) and pH (5.0-9.0). A whole-genome analysis of six lytic and two temperate phages revealed high genomic similarity with double-stranded DNA between 40 and 50 kb and G + C content of 38-39%. The protein compositions disclosed the absence of toxin-coding genes. The phylogenic results, together with morphological micrographs, confirmed that three selected phages (T1245, T444, and T515) belong to the Podoviridae family within the order Caudovirales. The biological data and bioinformatics analysis indicated that these novel A. baumannii phages possess important enzymes, including depolymerase and endolysin, which could be further developed as promising alternative antibacterial agents to control A. baumannii infections.

Phloroglucinol-meroterpenoids from the leaves of Eucalyptus camaldulensis Dehnh.

Fourteen undescribed phloroglucinol-meroterpenoids, namely eucalypcamals A-N, were isolated from a CH2Cl2 extract of the leaves of Eucalyptus camaldulensis Dehnh. In addition, from the same extract, twelve known phloroglucinols, three known flavonoids, and four known phenolic compounds were also isolated. The structures of the undescribed compounds were analyzed by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, and high resolution electrospray ionization mass spectrometry (HRESIMS). The assignments of the absolute configurations were performed by comparing the experimental electronic circular dichroism (ECD) data with the calculated values. Eucalyprobusal E was found to be cytotoxic against HCT116, Jurkat, and MDA-MB-231 cell lines with IC50 values of 17.6, 9.44, and 17.9 µM, respectively. Eucalrobusone F exhibited antibacterial activity against methicillin-resistant S. aureus (MRSA) and S. aureus with minimum inhibitory concentration/minimum bactericidal concentration (MIC/MBC) values of 4/4 µg/mL while euglobal Ia1 showed antifungal activity with MIC/MFC values of 16/16 µg/mL.

Eucalyptus-Mediated Synthesized Silver Nanoparticles-Coated Urinary Catheter Inhibits Microbial Migration and Biofilm Formation.

Catheter-associated urinary tract infections (CAUTIs) are significant complications among catheterized patients, resulting in increased morbidity, mortality rates, and healthcare costs. Foley urinary catheters coated with synthesized silver nanoparticles (AgNPs) using Eucalyptus camaldulensis leaf extract were developed using a green chemistry principle. In situ-deposited AgNPs with particle size ranging between 20 and 120 nm on the catheter surface were illustrated by scanning electron microscopy. Atomic force microscopy revealed the changes in surface roughness after coating with nanoparticles. The coated catheter could significantly inhibit microbial adhesion and biofilm formation performed in pooled human urine-supplemented media to mimic a microenvironment during infections (p 0.05). AgNPs-coated catheter exhibited broad-spectrum antimicrobial activity against important pathogens, causing CAUTIs with no cytotoxic effects on HeLa cells. A reduction in microbial viability in biofilms was observed under confocal laser scanning microscopy. A catheter bridge model demonstrated complete prevention of Proteus mirabilis migration by the coated catheter. Significant inhibition of ascending motility of Escherichia coli and P. mirabilis along the AgNPs-coated catheter was demonstrated in an in vitro bladder model (p 0.05). The results suggested that the AgNPs-coated urinary catheter could be applied as an alternative strategy to minimize the risk of CAUTIs by preventing bacterial colonization and biofilm formation.