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Hydroxybenzylidene hydrazines exhibit a wide spectrum of biological activities. Here, we report synthesis and free radical scavenging activity of nine new N-(hydroxybenzylidene)-N'-[2,6-dinitro-4-(trifluoromethyl)]phenylhydrazines. The chemical structures of these compounds were confirmed by 1H-NMR, 13C-NMR, 19F-NMR, IR spectroscopy, LC-MS, and elemental analysis. The prepared compounds were tested for their activity to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH), galvinoxyl radical (GOR), and 2,2'-azino-bis(3-ethylbenzothiazoline)-6-sulphonic acid (ABTS) radicals. The free radical scavenging activity expressed as SC50 values of these compounds varied in a wide range, from a strong to no radical scavenging effect. The most effective radical scavengers were hydroxybenzylidene hydrazines containing three hydroxyl groups in the benzylidene part of their molecules. The prepared compounds were also tested for their activity to inhibit photosynthetic electron transport in spinach chloroplasts. IC50 values of these compounds varied in wide range, from an intermediate to no inhibitory effect., Competing Interests: The authors declare no conflict of interest.

In this study, a series of twelve ring-substituted salicylanilides and carbamoylphenylcarbamates were prepared and characterized. The compounds were analyzed using RP-HPLC to determine lipophilicity. They were tested for their activity related to the inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. Moreover, their site of action in the photosynthetic apparatus was determined. Primary in vitro screening of the synthesized compounds was also performed against mycobacterial, bacterial and fungal strains. Several compounds showed biological activity comparable with or higher than the standards 3-(3,4-dichlorophenyl)-1,1-dimethylurea, isoniazid, penicillin G, ciprofloxacin or fluconazole. The most active compounds showed minimal anti-proliferative activity against human cells in culture, indicating they would have low cytotoxicity. For all compounds, the relationships between lipophilicity and the chemical structure are discussed.

There is a strong demand to identify new strategies for disinfection and treatment of human, animal, and plant pathogens. The presented work shows the potential of clay minerals to contribute to the development of novel disinfection materials. Enhanced antimicrobial effect of a photoactive organic dye, methylene blue (MB), in the colloids of clay mineral was observed. Singlet oxygen (1O2) formed upon visible light irradiation was detected directly using luminescence measurements atthe near-infrared region and by spin-trapping method. While MB adsorbed on clay colloid particles lost the ability to produce 1O2 due to molecular aggregation, surprisingly, the antimicrobial activity was significantly enhanced. Under visible light irradiation, MB/clay minerals dispersions prevented the sporulation of A. niger and Penicillium sp. and inhibited the growth of C. albicans by an additional 6-15% when compared with MB solution. In the experiments with E. coli, the efficiency of MB was increased by the reduction of surviving cells by 27 and 33%. S. aureus proved to be the most susceptible to MB/clay dispersions. Only less than 20% cells survived with respect to the control experiment at the low MB concentration (1.1 x 10(-6) mol dm(-3)). The contradiction between the significant antimicrobial properties of MB in clay colloidal systems and low 1O2 formation can be explained in terms of the photosensitization mechanism. The role of clay particles is most likely to promote the contact between microorganism cells and photoactive MB. Although the dye directly bound to the clay surface exhibits significantly reduced photoactivity, the presence of clay mediates the delivery of dye molecules on the surface or inside cells. The results indicate new perspectives of potential implementations of clay minerals as parts of complex disinfection materials for industrial applications or in understanding similar processes in nature.

The paper deals with the separation and identification of a flavonoid glycoside from the petals of Lilium candidum L. and the antioxidative properties of the ethanolic extract of the flowers and selected compounds isolated from this species. The isolated flavonoid glycoside was identified as isorhamnetin-3-O-rutinoside by acid hydrolysis, TLC comparison with authentic samples, and UV and mass spectra. Isorhamnetin rutinoside was isolated from Lilium candidum L. for the first time. The antioxidative activity of the ethanolic extract of the flowers and some isolated compounds were determined using DPPH assays.

A new heterogeneous photocatalyst was prepared by oxidative polymerization of the thiophene with ferric chloride in the ZSM-5 zeolite type. The synthesized polythiophene absorbs radiation in the visible range of the electromagnetic spectrum and by illumination with visible light generates reactive oxygen species (ROS) in water medium. During illumination reactive hydroxyl radical was detected by the spin trapping EPR method. Efficiency of the photocatalyst was tested on the killing of Gram-positive bacteria Staphylococcus aureus and Gram negative bacteria Escherichia coli.

The antioxidant properties of melatonin were tested in this work by EPR technique. It was found that melatonin scavenges phenylglyoxylic ketyl radicals. Its effectiveness was 10-times lower than that of vitamin C. A new method of generation of phenylglyoxylic ketyl radicals by spontaneous decomposition of D,L-2,3-diphenyltartaric acid in propan-2-ol was used.

The paper describes spontaneous decomposition of D,L-2,3-diphenyltartaric acid in propane-2-ol, which takes place via radicals at ambient temperature. The primary product of the decomposition is short-living ketyl radicals of phenylglyoxalic acid, which are captured and stabilized by means of the spin trap of N-terc-butyl-alpha-phenylnitrone. The spontaneous decomposition of D,L-2,3-diphenyltartaric acid in propane-2-ol served as the source of radicals for the determination of the antioxidative effect of known antioxidants: C-vitamin, E-vitamin, and selenomethionine. It was found that the above-mentioned antioxidants are effective scavengers of radicals of phenylglyoxalic acid. On the basis of these data, the method can be recommended for testing the antioxidative properties of other substances as potential antioxidants.

Photoinhibition of photosystem II was studied in vivo with bean (Phaseolus vulgaris) plants grown in the presence of 0.3 (control), 4, or 15 microM Cu(2+). Although photoinhibition, measured in the presence of lincomycin to block concurrent recovery, is faster in leaves of Cu(2+)-treated plants than in control leaves, thylakoids isolated from Cu-treated plants did not show high sensitivity to photoinhibition. Direct effects of excess Cu(2+) on chloroplast metabolism are actually unlikely, because the Cu concentration of chloroplasts of Cu-treated plants was lower than that of their leaves. Excess Cu in the growth medium did not cause severe oxidative stress, collapse of antioxidative defenses, or loss of photoprotection. Thus, these hypothetical effects can be eliminated as causes for Cu-enhanced photoinhibition in intact leaves. However, Cu treatment lowered the leaf chlorophyll (Chl) concentration and reduced the thylakoid membrane network. The loss of Chl and sensitivity to photoinhibition could be overcome by adding excess Fe together with excess Cu to the growth medium. The addition of Fe lowered the Cu(2+) concentration of the leaves, suggesting that Cu outcompetes Fe in Fe uptake. We suggest that the reduction of leaf Chl concentration, caused by the Cu-induced iron deficiency, causes the high photosensitivity of photosystem II in Cu(2+)-treated plants. A causal relationship between the susceptibility to photoinhibition and the leaf optical density was established in several plant species. Plant species adapted to high-light habitats apparently benefit from thick leaves because the rate of photoinhibition is directly proportional to light intensity, but photosynthesis becomes saturated by moderate light.

The influence of the Cu(II)-complexes of thiophene oligomers synthesized by oxidative polymerization of thiophene with Cu2+ ions in ZSM-5 zeolite channels on fungicidal and antimicrobial properties was studied. It has been found that the heterogeneous system culture medium-modified zeolite increases sporulation of the tested fungus (Aspergillus niger) and concurrently kills yeast (Candida albicans). These effects are attributed to a slow release of Cu2+ ions and thiophene oligomers into the culture medium. As for the tested bacteria (G+ Staphylococcus aureus, G- Escherichia coli), the percentage of the killed cells increases due to light activation of the system. The light effect is assigned to photogeneration of the reactive oxygen species (ROS), mainly *OH radicals, which were registered in the water solution by EPR spectroscopy. It has been confirmed that the thiophene oligomers present in the Cu-ZSM-5 microstructure slow down the release of copper into the medium.

The effect of 18 compounds of the aryloxyaminopropanol type--potential beta-adrenolytics (differing each from other by modifications in the hydrophilic and lipophilic part of the molecule) on the inhibition of oxygen evolution rate in spinach chloroplasts has been investigated. The compounds with n-octyloxymethyl and n-nonyloxymethyl group in position 3 of aromatic ring were found to exhibit the highest inhibitory activity (IC50 = 67, resp. 120 mumol dm-3). The compounds containing a heterocycle or the dimethylamino group in the hydrophilic part of the molecule and with propoxymethyl group on the aromatic ring were not active. Using EPR spectroscopy it was found that the studied compounds interact with Z+/D+ intermediates, i.e. tyrosine radicals TyrZ and TyrD situated in D1 and D2 proteins on the donor side of photosystem 2. Higher concentrations of the studied inhibitors cause release of Mn2+ ions from the oxygen evolving complex which is situated in photosystem 2. The interaction of the tested compounds with chlorophyll occurring in the photosynthetic centres has been confirmed by fluorescence measurements as well.

The effects of piperidinopropylesters of 2-, 3- and 4-alkoxy substituted phenylcarbamic acids (PPACs) on oxygen evolution rate (OER) in spinach chloroplasts were investigated. PPAGs show concentration-dependent effects, namely OER inhibition at higher effector concentrations and OER stimulation at lower concentrations, i.e. below the inhibitory concentration range. The inhibitory efficiency of PPACs showed dependence on the alkyl chain length of the alkoxy substituent as well as on the position of this substituent on the benzene ring. Using EPR spectroscopy and fluorescence measurements it was confirmed that the site of PPAC inhibitory action is the donor side of photosystem 2, where D1 and D2 proteins are situated, namely the intermediates Z+/Y+, and the manganese cluster containing protein as well. The stimulating effects of PPACs on OER in spinach chloroplasts at relatively low effector concentrations are caused by photophosphorylation uncoupling due to protonophore properties of the effectors.

A simple method is presented for the determination of partition coefficient of an effector between water environment and biological material, based on concentration-dependent effects. The method allows the determination of partition coefficients for biological objects such as algae, bacteria and other microorganisms.

The inhibitory effect of 14 aqua(aryloxyacetato) copper(II) complexes on oxygen evolution rate in spinach chloroplasts has been investigated. The inhibitory effect of these effectors on photosynthesis was confirmed by Hill reaction as well as by EPR and fluorescence spectroscopies. The results of the EPR study showed that the sites of action of the studied effectors are Z+ and Y+ intermediates at the donor side of the photosystem (PS) 2. The EPR study also showed that another site of action is the oxygen evolving complex, namely its manganese cluster. The above suggestions were supported by the results of the fluorescence study as well. Based on the restoring of the photosynthetic electron transport to 2,6-dichlorophenol-indophenol in chloroplasts inhibited by the studied Cu(II) complexes using sym-diphenylcarbazide it can be assumed that the own core of PS2 (P680) and a part of the electron transport chain-at least up to plastoquinone-remain intact.

Using the model compound trimecaine, it was found that algicidal effects exhibited by the local anaesthetics of the acetanilide type were caused by two different mechanisms. The first inhibitory mechanism occurring at low concentrations of the anaesthetic is connected with the uncoupling of the photophosphorylations in algal chloroplasts and is accompanied by the enhancement of the oxygen evolving rate in algal photosynthesis. The second mechanism of inhibition of the photosynthesis in algae, taking place at higher concentrations of the anaesthetic, is connected with the damaging of the manganese containing protein on the donor side of photosystem 2 and is accompanied by a decrease of the oxygen evolving rate in algal photosynthesis.

2-Alkylthio-6-aminobenzothiazoles and their 6-N-substituted derivatives 3-(2-alkylthio-6-benzothiazolylaminomethyl)-2-benzothiazolineth iones and 3-(2-alkylthio-6-benzothiazolylaminomethyl)-6-bromo-2-benzothia zolinones inhibit photosynthetic processes in spinach chloroplasts and the chlorophyll production in Chlorella vulgaris. The inhibitory activity depends on the alkyl chain length of the thioalkyl substituent. The site of action of the effectors studied is on the donor side of photosystem 2 before the site of action of diphenylcarbazide. The highest antialgal effects were exhibited by compounds containing bromine.

The inhibitory activity of 22 substituted aryloxyaminopropanols having beta-lytic and local anaesthetic properties was studied from the view-point of their influences on photosynthesis in plant chloroplasts as well as growth and synthesis of chlorophyll in algae and wheat plants. The inhibitory activity increased significantly with the increasing length of alkyl-substituents of the aryloxyaminopropanol molecule. Less pronounced dependences were found with respect to the position of the substituent chain on benzene ring. The inhibitory activity was found to correlate well with the lipophilicity of the compounds studied.

Electron spin resonance spectroscopy (ESR) was used to study the effects of amphiphilic amines of the carbamate, amide, and ester type and amine oxide on the photosynthetic system of spinach chloroplasts. The ESR signal II connected to the photosynthetic center PS II donor side was observed to diminish in the presence of amines, whereas that of PS I remained unchanged. The inhibition of PS II increased with the increasing of amine concentration. In the presence of amines, the light: dark chloroplast ESR signals ratio as well as the intensity of the ESR signal of unbound Mn2+ increased. It is suggested that the amphiphilic amines affect the structure of PS II and the electron transfer to PS I. The effects of the amines tested on the photosynthetic system correlate with their potency to perturb the lipid membrane structure.

The antimicrobial activity of the homologous series of N,N-dimethylalkylamine oxides (DMAO) was found to be quasi parabolically dependent on alkyl chain length with a maximum at n approximately 15 and n approximately 12 for Staphylococcus aureus and Escherichia coli, respectively. The physiochemical properties of DMAOs as characterized by critical micelle concentrations, retention times of 1-alkenes generated from DMAOs by gas-liquid chromatography, Rm values in reversed phase chromatography, and bacterial lipid/aqueous phase partition coefficients were found to correlate with the alkyl chain length. The effect of DMAOs on the structure of the model membrane prepared from isolated lipids from Escherichia coli as detected by a spin probe method was maximal for the alkyl chain length n approximately 10-12 coinciding with the maximum in the antimicrobial activity observed with Escherichia coli. It is suggested that the cut-off in the DMAO antimicrobial activity is caused by the cut-off in the DMAO perturbing effect on the membrane structure.

Interaction of bactericidal surfactants N-(1-methyldodecyl)-N, N, N-trimethylammonium bromide (2-ATDBr) and N-(1-methyldodecyl)-N, N-dimethylamine oxide (2-ATDNO) with phospholipid membranes prepared from Escherichia coli -- isolated lipids was studied by ESR spectroscopy using m-doxyl stearic acid (m-DSA, m = 5, 12, 16) and N-cetyl-N, N-dimethyl-N-tempoylammonium bromide spin labels located in different membrane depths. 2-ATDBr was found to be a more potent membrane perturbant than 2-ATDNO both at equal membrane and sample concentrations; this is in compliance with the respective antimicrobial activities of these agents. Using the statistical model of hydrocarbon chains in lipid bilayers, the probabilities of the formation of gauche conformations and the effective energy differences between the trans and gauche conformations were calculated from m-DSA order parameters for two different bilayer regions. Based on these parameters, a molecular model of the location of surfactant molecules in bilayer has been formulated. It has been suggested that at low concentrations the surfactant molecules are located in structural defects between lipid clusters in the bilayer. After filling up these defects, the surfactant molecules penetrate into the clusters between lipid molecules, expand the bilayer laterally and increase the amount of gauche conformations in the hydrocarbon chains in the hydrophobic core of the bilayer.