Combinatorial activity of flavonoids with antibiotics against drug resistant Staphylococcus aureus

The use of resistance-modifying agents is a potential strategy that is used to prolong the effective life of antibiotics in the face of increasing antibiotic resistance. Since certain flavonoids are potent bacterial efflux pump inhibitors, we assessed morin, rutin, quercetin, hesperidin, and (+)-catechin for their combined activity with the antibiotics ciprofloxacin, tetracycline, erythromycin, oxacillin, and ampicillin against drug-resistant strains of Staphylococcus aureus, including methicillin-resistant S. aureus. Four established methods were used to determine the combined efficacy of each combination: microdilution checkerboard assays, time-kill determinations, the Etest, and dual disc-diffusion methods. The cytotoxicity of the flavonoids was additionally evaluated in a mouse fibroblast cell line. Quercetin and its isomer morin decreased by 3- to 16-fold the minimal inhibitory concentration of ciprofloxacin, tetracycline, and erythromycin against some S. aureus strains. Rutin, hesperidin, and (+)-catechin did not promote any potentiation of antibiotics. Despite the potential cytotoxicity of these phytochemicals at a high concentration (fibroblast IC50 of 41.8 and 67.5mg/L, respectively), quercetin is commonly used as a supplement for several therapeutic purposes. All the methods, with exception of the time-kill assay, presented a high degree of congruence without any apparent strain specificity.This work was supported by Operational Program for Competitiveness Factors—COMPETE, FCT/MEC (PIDDAC), and FEDER through Projects Bioresist—PTDC/EBB-EBI/ 105085/2008; Phytodisinfectants—PTDC/DTP-SAP/1078/ 2012 (COMPETE: FCOMP-01-0124-FEDER-028765) and the PhD grants awarded to Ana Abreu (SFRH/BD/84393/ 2012) and Anabela Borges (SFRH/BD/63398/2009). The authors are very grateful to Professor Simon Gibbons (De- partment of Pharmaceutical and Biological Chemistry, The School of Pharmacy, UCL School of Pharmacy, London) for providing the bacterial strains.info:eu-repo/semantics/publishedVersio

Localization and activity of lipoxygenase in Cd-treated seedlings of Phaseolus coccineus

Lipoxygenase was localized in the primary leaves of Phaseolus coccineus (L.), seedlings treated with 25 µM Cd and in control plants using the immunogold method. The enzyme was localized mainly in the peripheral parts of protoplast of control plant cells. It was found in the cell wall, along the ER elements, at plastid lamellae and inside the mitochondria. In Cd-treated seedlings the elements of parenchyma cells showed an atypical inner structure. The immunolabelling of LOX was less intensive in comparison with control. The enzyme was found in the cytoplasm, at the cell wall area, vacuoles and in the plastid stroma as single gold particles. LOX activity optima were determined at pH 7.0 and 8.0 for both linoleic and linolenic acid used as substrates. After 2 days of seedlings exposure to Cd the activity of LOX decreased at pH 7.0 and 8.0 when linoleic acid was used as substrate, and strongly declined at pH 7.0 after 4 days of the metal treatment. When linolenic acid was the substrate LOX activity slightly increased after 2 days of the plants exposure to Cd, but after 4 days it rapidly decreased at pH 7.0. The changes in LOX activity are discussed

Immunolocalization of lipoxygenase in the microspore of Gagea lutea (L.) Ker.-Gaw.

Localization of lipoxygenase (LOX) in the microspore of Gagea lutea (L.) Ker.-Gaw. was investigated with the immunogold labelling method. The enzyme was found in the cytoplasm, nucleus and sporoderm. The most intensive reaction was observed in the cytoplasm, where the immunogold particles were sometimes grouped into clusters of several or more and showed the highest density. The smallest amount of particles occured in the sporoderm. The role of lipoxygenase in the microspore is discussed.Metodą immunozłotową badano rozmieszczenie lipoksygenazy (LOX) w mi- krosporze Gagea lutea (L.) Ker.-Gaw. Enzym znaleziono w cytoplazmie, jądrze i spo- rodermie mikrospory. Najintenywniejszą reakcję obserwowano w cytoplazmie, gdzie czasteczki immunozłota niekiedy były zgrupowane po kilka lub kilkanaście i wyka- zywały największe zagęszczenie. Najmniej cząsteczek występowało w sporodermie. Dyskutowana jest rola lipoksygenazy w mikrosporze

Structure and bioactive properties of novel textile dyes synthesised by fungal laccase

Novel sustainable processes involving oxidative enzymatic catalysts are considered as an alternative for classical organic chemistry. The unique physicochemical and bioactive properties of novel bio‐products can be obtained using fungal laccase as catalyst. Among them are textile biodyes synthesised during oxidation of substrates belonging to the amine and methoxy organic derivatives. The process of synthesis occurs in mild conditions of pH, temperature, and pressure, and without using harmful oxidants. The effect of fungal laccase activity on the substrates mixture transformation efficiency was analysed in terms of antimicrobial dye synthesis on a large scale. Three new phenazine dyes, obtained in the presence of laccase from Cerrena unicolor, were studied for their structure and properties. The phenazine core structure of the products was a result of tri-molecular transformation of aminomethoxybenzoic acid and aminonaphthalene sulfonic acid isomers. One of the compounds from the synthesised dye, namely 10‐((2‐carboxy‐6‐ methoxyphenyl)amino)‐11‐methoxybenzo[a]phenazine‐8‐carboxylic acid, was able to inhibit the growth of Staphylococcus aureus. The high concentration of substrates (5 g/L) was efficiently transformed during 72 h in the mild conditions of pH 4 with the use of laccase with an activity of 200 U per g of the substrates mixture. The new bioactive dye exhibited excellent dyeing properties with concomitant antibacterial and antioxidative activity. The proposed enzyme‐mediated synthesis represents an alternative eco‐friendly route for the synthesis of novel antimicrobial compounds with high importance for the medical textile industry

Phospholipid bilayer perturbing-properties underlying lysis induced by pH-sensitive cationic lysine-based surfactants in biomembranes

Many strategies for treating diseases require the delivery of drugs into the cell cytoplasm following internalization within endosomal vesicles. Thus, compounds triggered by low pH to disrupt membranes and release endosomal contents into the cytosol are of particular interest. Here, we report novel cationic lysine-based surfactants (hydrochloride salts of Nε- and Nα-acyl lysine methyl ester) that differ in the position of the positive charge and the length of the alkyl chain. Amino acid-based surfactants could be promising novel biomaterials in drug delivery systems, given their biocompatible properties and low cytotoxic potential. We examined their ability to disrupt the cell membrane in a range of pH values, concentrations and incubation times, using a standard hemolysis assay as a model of endosomal membranes. Furthermore, we addressed the mechanism of surfactant-mediated membrane destabilization, including the effects of each surfactant on erythrocyte morphology as a function of pH. We found that only surfactants with the positive charge on the α-amino group of lysine showed pH-sensitive hemolytic activity and improved kinetics within the endosomal pH range, indicating that the positive charge position is critical for pH-responsive behavior. Moreover, our results showed that an increase in the alkyl chain length from 14 to 16 carbon atoms was associated with a lower ability to disrupt cell membranes. Knowledge on modulating surfactant-lipid bilayer interactions may help us to develop more efficient biocompatible amino acid-based drug delivery devices