Robust antimicrobial compounds and polymers derived from natural resin acids

We report novel robust resin acid-derived antimicrobial agents that exhibit excellent antimicrobial activities against a broad spectrum of bacteria (6 Gram-positive and 7 Gram-negative) with selective lysis of microbial membranes over mammalian membranes. Our results indicate that hydrophobicity and unique structures of resin acids can be determining factors in dictating the antimicrobial activity.     

Cage-like monoterpenoid indole alkaloids with antimicrobial activity from Alstonia scholaris

Three new cage-like monoterpenoid indole alkaloids, scholarisines T–V (1–3), together with three known analogues 4–6 were isolated from the leaves of Alstonia scholaris. Among them, 2 represents a unique degraded derivative, whereas 3 shares a rare 5,16-seco lactone scaffold. The structures were mainly established by extensive spectroscopic data analyses, and their plausible biosynthesis pathway from picrinine were proposed. Compared with positive control cefotaxime, alkaloid 2 showed remarkable antibacterial activity against Bacillus subtilis with an MIC value of 3.12?μg/mL, whereas 1–3 exhibited significant antibacterial effects on Escherichia coli with an MIC value of 0.78?μg/mL.     

A synthetic alternative to natural lecithins with antimicrobial properties

Two soft biocompatible cationic surfactants from the amino acid arginine, 1,2-dilauroyl-3-acetylarginyl-rac-glycerol (1212RAc) and 1,2-dimirystoyl-3-acetylarginyl-rac-glycerol (1414RAc), were prepared. Their physicochemical properties show that they can be classified as multifunctional surfactants with self-aggregation behaviour comparable to that of short-chain lecithins. The two surfactants can simultaneously stabilise water-in-oil (W/O) droplets and oil-in-water (O/W) droplets, forming multiple emulsions. They have antimicrobial activity similar to that of conventional cationic surfactants and are as harmless as amphoteric betaines. These surfactants constitute an interesting alternative to the diglycerides and lecithins in formulations that require antimicrobial properties.     

A prenylated xanthone with antimicrobial activity from the seeds of Symphonia globulifera

A prenylated xanthone has been isolated from the seeds of Symphonia globulifera together with the known compounds sitosterol and oleanolic acid. The structure of the new compound was elucidated by spectroscopic methods.     

Important insights from the antimicrobial activity of Calotropis procera

Calotropis procera (family Apocynaceae) is a valuable medicinal plant as it contains many valuable phytochemicals such as glycosides (mostly cardenolides), flavonoids, triterpenes, alkaloids, steroids, saponins, proteins and enzymes. Multiparous biological activities such as anti-inflammatory, antioxidant, anticancer, wound healing and wideranging antimicrobial activities of C. procera have been well investigated and reported. The main aim of this review was to present the encompassing information regarding antimicrobial activities of C. procera latex, different crude extracts and some isolated compounds which have been tested for antimicrobial property. Comprehensive data extracted from earlier as well as recently published original articles regarding antibacterial, antifungal, anti-protozoal and antiviral properties of C. procera were discussed and summarised in tabular forms. The compiled data comprised of plant parts, geographical origin, type of tested extracts/fractions, test model, used doses, tested microorganisms, obtained results and relevant references. In addition, the isolated antimicrobial pure compounds of C. procera are also discussed in a separate section. The analysis and information presented in this review identified the existing critical knowledge gaps in the research and also explored the future perspectives and further research opportunities of C. procera.     

Synthesis and antimicrobial activity of novel oxysterols from lanosterol

Chemically diverse oxysterols and their synthetic manipulations were carried out from variety of Δ⁸⁽⁹⁾-lanosterol derivatives and evaluated for their in vitro antimicrobial activities. Most of the synthesized oxysterols exhibited significant antifungal activity against the tested strains.     

Physicochemical signatures of natural sea films from Middle Adriatic stations

Monolayer studies and a force-area quantification approach, in combination with electrochemical methods, are applied for physicochemical characterization of surface active substances (SAS) of the sea surface microlayers (MLs) from Middle Adriatic stations. Higher primary production during late spring-early autumn was reflected in the presence of MLs of higher surfactant activity containing on average molecules of lower molecular masses (M(w) = 0.65 ± 0.27 kDa) and higher miscibility (y = 6.46 ± 1.33) and elasticity (E(isoth) = 18.33 ± 2.02 mN m(-1)) modulus in comparison to structural parameters (average M(w) = 2.15 ± 1.58 kDa; y = 3.51 ± 1.46; E(isoth) = 6.41 ± 1.97 mN m(-1)) obtained for MLs from a period of lower production. A higher inhibition effect on the reduction process of Cd(2+) was observed for SAS abundant MLs from a more productive period. This kind of distribution is explained as the consequence of competitive adsorption of hydrophobic lipid-like substances of lower M(w) that act as end-members, highly influencing the surface structural properties of the natural air-water interface forming there segregated surface films during more productive period.     

Environmentally-safe bimetallic Ag@Co magnetic nanocomposites with antimicrobial activity

In this communication we describe the synthesis, characterization and evaluation of the bactericide activity of a superparamagnetic bimetallic Ag/Co polymeric nanocomposite material for the treatment of bacteria contaminated aqueous solutions.     

Pyridazine and phthalazine derivatives with potential antimicrobial activity

Fifteen new pyridazine and phthalazine derivatives were prepared (in good to excellent yields) and tested in vitro as antimicrobial compounds. All the compounds have proved to have a remarkable activity against Gram positive germs, the results on Sarciria Luteea being spectacular. Correlation structure ‐ biological activity have been done. Stereo‐ and region‐ chemistry involved in these reactions are discussed.     

The chemical constituents from the active fractions of Eleutherine bulbosa with their antimicrobial activity

Abstract

Six compounds including three new polyketide ones named eleubosas A-C (1–3) were isolated from the active frations of Eleutherine bulbosa. Their structures were elucidated by extensive spectroscopic methods, including NMR, MS and IR spectroscopic analyses data. All the isolates were evaluated against three pathogenic bacteria, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, and the results showed that compounds 1 and 2 displayed moderate inhibitory activities against E. coli with MIC values both 12.5?μg/mL, which are consistent with the clinical applications and need further studies.     

An antimicrobial compound isolated from Cinnamomum iners leaves with activity against methicillin-resistant Staphylococcus aureus

This study was designed to investigate the antimicrobial activity of Cinnamomum iners standardized leave methanolic extract (CSLE), its fractions and isolated compounds. CSLE and fractions were subjected to disc diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests using different Gram positive and Gram negative bacteria and yeast. Within the series of fractions tested, the ethyl acetate fraction was the most active, particularly against methicillin resistant Staphylococcus aureus (MRSA) and Escherichia coli, with MIC values of 100 and 200 μg/mL, respectively. The active compound in this fraction was isolated and identified as xanthorrhizol [5-(1, 5-dimethyl-4-hexenyl)-2-methylphenol] by various spectroscopic techniques. The overall results of this study provide evidence that Cinnamomum iners leaves extract as well as the isolated compound xanthorrhizol exhibit antimicrobial activity for both Gram negative and Gram positive pathogens, especially against MRSA strains.     

Novel illudalane sesquiterpenes from Encephalartos villosus Lehm. antimicrobial activity

Phytochemical investigation of Encephalartos villosus Lehm. leaves afford two new illudalane sesquiterpenes namely Encephaldiene 1 and Encephaldiene 2 together with four known flavone glycosides, Luteolin-7-rutinoside, Luteolin-7-glucoside, Luteolin-7-rhamnoside and Apigenin-7-glucoside. The structures of the isolated compounds were elucidated by means of spectroscopic methods including 1D and 2D NMR experiments along with HRESIMS spectrometry. Antimicrobial activity of CHCl₃ and MeOH extracts was investigated. Both extracts showed antibacterial activity against Gram-positive bacteria Streptococcus pneumonia and Bacillus subtilis, and antifungal activity against Aspergillus fumigatus. While CHCl₃ extract showed additional activity against Gram-negative bacteria Escherichia coli.     

The intrinsic GTPase activity of the Gtr1 protein from Saccharomyces cerevisiae

ABSTRACT: BACKGROUND: The Gtr1protein of Saccharomyces cerevisiae is a member of the RagA subfamily of the Ras-like small GTPase superfamily. Gtr1 has been implicated in various cellular processes. The Switch regions in Gtr1 mediate activation of the TORC1 complex [R. Gong, L. Li, Y. Liu, P. Wang, H. Yang, L. Wang, J. Cheng, K.L. Guan, Y. Xu, Genes Dev. 25 (2011) 1668-1673]. Therefore, knowledge about the biochemical activity is required to understand its mode of action and regulation. RESULTS: Here we employ tryptophan fluorescence analysis and radioactive GTPase assays to demonstrate that Gtr1 can adopt two distinct GDP- and GTP-bound conformations, and that it hydrolyses GTP much slower than Ras proteins. Using cysteine mutagenesis of Arginine-37 and Valine-67, residues at the Switch I and II regions, respectively, we show altered GTPase activity and associated conformational changes as compared to the wild type protein and the cysteine-less mutant. CONCLUSIONS: The extremely low intrinsic GTPase activity and distinct conformations upon nucleotide binding imply a strict regulation of Gtr1. These findings as well as the altered properties obtained by mutagenesis in the Switch regions provide insights into the function of Gtr1 and its homologues in yeast and mammals.     

Synthesis and antimicrobial activity of tryptanthrin adducts with ketones

Reactions of tryptanthrin with acetone, cyclopentanone, hexan-2-one, 4-methylpentan-2-one, 4-hydroxy-4-methylpentan-2-one, cyclohexanone, and butan-2-one in the presence of potassium carbonate afforded racemic phaitanthrin A and other addition products to the ketone group of tryptanthrin with high yields. Thermal dissociation, some chemical transformations, and antimicrobial activity of some adducts were studied, and inhibitory effect against gram-positive bacteria was found for particular derivatives.     

New hemisynthetic manoyl oxide derivatives with antimicrobial activity.

The synthesis and antimicrobial activity of ten labdane-type diterpenes derived from ent-3-beta-hydroxy-13-epi-manoyl oxide (ribenol) is reported. The chloroethyl carbamidic ester 9 showed the strongest antimicrobial activity against all the tested gram (+), gram (-) bacteria and pathogenic fungi. Moreover, the glycoside 11 exhibited an interesting activity against the three tested fungi.     

Strontium-doped hardystonite plasma sprayed coatings with robust antimicrobial activity

A strontium-doped hardystonite (Sr-HT) bioceramic, in bulk form, demonstrates excellent bioactivity for bone regeneration with high fracture toughness and compressive strength. This work examines the antibacterial and mechanical properties of Sr-HT coatings on an alpha-beta titanium alloy with a high specific strength and excellent corrosion resistance (Ti-6Al-4V) produced by atmospheric plasma spray (APS) as the deposition coating technique. A hydroxyapatite (HAp) APS coating, a commercial bioceramic coating, is chosen as the control. The in-situ observation showed that Sr-HT powders experience temperatures during plasma processing that exceeded their melting point to form a coating well adhered to the substrate. It was demonstrated that the Sr-HT coating possessed superior antibacterial properties against Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) and Gram-negative Pseudomonas aeruginosa. In addition, the Sr-HT coating exhibits a uniform distribution of hardness and elastic moduli, higher nanohardness and elastic moduli compared to the equivalent properties of the HAp coating. Moreover, the Sr-HT coating outperforms the HAp coating regarding scratch and wear resistance. The bonding and shear strength of the Sr-HT coating are higher than the values required for orthopedic implant coatings. The Sr-HT coating also allows efficient zinc, silicon and strontium ions release when immersed in cell culture media. In summary, the antibacterial capabilities and the mechanical properties of the Sr-HT APS coating exceed those of the commercial HAp APS coating. Therefore, Sr-HT APS coatings are candidates for bioceramic coating applications in orthopedic implants.     

Synthesis of novel heterocycles with antimicrobial and surface activity

A new series of anionic surfactants with dual type of activity antimicrobial and surface activity have been synthesized by reaction of 4H‐3,1‐benzoxazinone 3 and quinazolinethione 10 with nitrogen nucleophiles and activated olefinic compounds. The compounds were evaluated for their surface activity as well as their antimicrobial and biodegradability properties.     

Amphiphilic block and statistical siloxane copolymers with antimicrobial activity

Statistical and block all‐siloxane copolymers containing quaternary ammonium salt (QAS) groups with biocidal activity as lateral substituents were synthesized as models for the study of the effect of the arrangement of the QAS groups in the copolymer chain on their antimicrobial activity. The bioactive siloxane unit was [3‐n‐octyldimethylammoniopropyl]methylsiloxane, and the neutral unit was dimethylsiloxane. The copolymers also contained siloxane units with unreacted precursor 3‐chloropropyl or 3‐bromopropyl groups. A small number of units containing highly hydrophilic 3‐(3‐hydroxypropyl‐dimethylammonio)propyl groups were introduced to increase the solubility of the copolymers in water. The bioactive and bioneutral units were arranged in the polymer chain either in blocks or in statistical order. The block copolymers differed in the number and length of segments. The copolymers were obtained by the quaternization of tertiary amines by chloropropyl or bromopropyl groups attached to polysiloxane chains. The arrangement of the bioactive groups was controlled by the arrangement of the halogenopropyl groups in the bioactive copolymer precursor. All model siloxane copolymers showed high bactericidal activity in a water solution toward the gram‐negative bacteria Escherichia coli and the gram‐positive bacteria Staphylococcus aureus. However, no essential differences in the activities of the copolymers with block and statistical arrangements of units were detected. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2939–2948, 2003