Antioxidative activity of new N-oxides of tertiary amines: membrane model and chromogen studies.

Potential antioxidative activities of three series of newly synthesized N-oxides were studied. Individual components in each of the series differed in the lipophilicities and number of free radical scavenging groups. Various methods were used to determine their antioxidative efficiencies: Prevention of erythrocyte membrane lipid oxidation induced by UV irradiation and chromogen experiments in which antioxidative efficiencies of compounds were compared to that of the standard antioxidant Trolox (a water-soluble vitamin E analogue). Additionally, some hemolytic (pig erythrocytes) and differential scanning calorimetry (DSC) measurements were performed to determine a mechanism of the interaction between membranes and N-oxides. It was found that N-oxides, especially those of long alkyl chains (> C12H25), readily interacted with both, erythrocyte and liposomal membranes. No marked differences were found in their protection of erythrocytes against oxidation. In most cases inhibition of oxidation changed between 15% and 25%. Still, it was far better than in chromogen experiments where suppression of free radicals reached 20% in the best case. It may be concluded that antioxidative capabilities of N-oxides are moderate. Studies on the interaction mechanism showed that incorporation of particular compounds into model membranes varied. Hemolysing activities of compounds increased with the elongation of the alkyl chain but differed for corresponding compounds of particular series indicating that lipophilicity of compounds is not the only factor determing their interaction with erythrocyte membranes. DSC experiments showed that N-oxides, upon incorporation into 1,2-dipalmitoyl-3-sn-phosphatidylcholine liposomes, shifted the subtransition (Tp) and the main transition (Tm). The shifts observed depended on the alkyl chain length. The effects differed for each series. It seems that in the case of long alkyl chain compounds the domain formation may take place. Generally, the decrease of Tm was greatest for the same compounds that exhibited the best hemolytic efficacy. The same conclusion concerns the decrease of cooperativity of the main transition and the observed changes suggest an increase in membrane fluidity. Both, erythrocyte and DSC experiments seem to indicate that compounds of particular series incorporate in a somewhat different way into membranes.

Assessment of potential application of binary mixtures of 2,4-d with novel aminophosphonates.

A series of new aminoalkane- and aminofluorenephosphonates was synthesized for agrochemical application. The particular compounds had different alkyl substituents at the carbon, nitrogen and phosphorus atoms. Their pesticidal activity was checked by applying various experimental methods. These included the measurements of compounds' potency: to inhibit growth of cucumber and germination of white mustard seeds, to influence on the membrane potential of algae and to damage human erythrocyte membranes resulting in hemolysis. All the aminophosphonates were also used in equimolar binary mixtures with the well-known herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), to check, if using such mixtures, the biological efficiencies found for particular compounds could be enhanced due to interactions between aminophosphonates and 2,4-D. The results demonstrated, that depending on the structural features of the compounds, the final effects differed from antagonistic, through additive to the most promising synergistic ones. However, the type of interaction between 2,4-D and the compounds studied found in different experiments was somewhat different. In order to estimate those effects various statistical methods were used (toxic unit method, isobole method).

Hemolysis of erythrocytes and erythrocyte membrane fluidity changes by new lysosomotropic compounds.

This work contains the results of studies on the influence of newly synthesized lysosomotropic substances (lysosomotropes) on human erythrocytes. Six homologous series of the compounds differing in the alkyl chain length and counterions were studied. They were found to hemolyse erythrocytes and to change their osmotic resistance. The observed hemolytic effects were dependent both on the compound's structure (polar head dimension and alkyl chain length of compound) and its form (the kind of the counterion). In parallel, the influence of lysosomotropes on fluidity of the erythrocyte membrane was studied. Three different fluorescent probes were used; 1,6-diphenyl-1,3,5-hexatriene (DPH), 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene, p-toluenesulfonate (TMA-DPH) and 6-dodecanoyl-2-dimethylaminonaphthalene (laurdan). Their anisotropy (DPH and TMA-DPH) or general polarization (laurdan) values after incorporation into ghost erythrocyte membranes were measured. The results obtained show that fluidity changes accompanied the effects observed in hemolytic experiments both quantitatively and qualitatively.

Protection of erythrocytes against organometals-induced hemolysis.

The hemolytic toxicity of tributyllead (TBL) and triphenyllead (TPhL) chlorides and its prevention by dithiotreitol (DTT), diethylenetriaminepentamethylenephosphonic acid pentasodium (PMP) and sodium disulfide (Na2S) was studied. It was found that both TBL and TPhL efficiently hemolyzed pig erythrocytes when used in micromolar concentrations; tributyllead chloride being about twice more efficient than triphenyllead chloride. The hemolytic efficiency of these compounds was blocked by PMP, DTT and Na2S in a concentration-dependent manner. However, significant differences in anti-hemolytic efficiency of these compounds were found. Namely, DTT and Na2S were very efficiently protecting erythrocytes against the action of organoleads, while the PMP protection was weak. Also, differences between DTT and Na2S protective efficiency were found. They more efficiently prevented erythrocyte hemolysis by TPhL than by TBL. Moreover, erythrocytes were better protected against the action of TBL by Na2S than by DTT. Such differentiation may be connected with possible differences in localization of the organolead compounds and protective agents in the erythrocyte membrane. To check these possibilities a series of experiments was performed using the fluorescence technique and various fluorimetric probes. These measurements enabled to determine fluidity changes induced in erythrocyte membranes by the organoleads and the protective compounds and to formulate some remarks concerning the differences in the mechanism of interaction of the organoleads with these membranes.

The hemolytic and physiological activities of mixtures of some phenoxy and organophosphorous herbicides.

Experiments were performed investigating the potential to improve the biological activity of some phenoxy and organophosphorous compounds by using them in binary mixtures. The compounds were: 2,4-dichlorophenoxyacetic acid (1) and its sodium salt (2), dibutyl 1-butylamino-1-cyclohexanephosphonate (3) and diethyl 9-butylamino-9-fluorenephosphonate (4), all widely used as herbicides. There were two test methods: the inhibition of cucumber (Cucumis sativus) growth induced by one single herbicide or by equimolar binary mixtures of herbicides; and, in parallel, the hemolytic efficiency of separate compounds or their mixtures. The hemolytic properties of the compounds were studied as hemolysis is generally a good measure of their toxicity, especially in the case of lipophilic compounds. Pig erythrocytes were used as good models for the determination of toxicity and the kinetics of red blood cell hemolysis. In the plant-based experiments, binary mixtures were found to display additive type toxicity. The compounds' hemolytic activities were of additive or antagonistic types. In some combinations, the addition of a second component did not change the hemolytic efficiency of the first component, and vice versa.

Antioxidative activity of some phenoxy and organophosphorous compounds.

Experiments were performed in order to check whether biological activity of some organophosphorous compounds widely applied as herbicides: 2,4-dichlorophenoxyacetic acid (1) and its sodium salt (2), N-phosphonomethylglycine acid (3) and its sodium salt (4), diethyl 1-butylamino-1-cyclohexanephosphonate (5) and diethyl 9-butylamino-9-fluorenephosphonate (6) followed from their oxidative activity. The compounds studied differed in their polarity and hydrophobicity. On the contrary, it was found that all herbicides protected erythrocyte membranes against partial peroxidation induced by UV irradiation. The effect was somewhat differentiated and followed the sequence: 5 >1 >2 >6 >3 >4. The observed differences between the antioxidative activities of the compounds are probably related to differences in their ability to incorporate into the lipid phase of the erythrocyte membrane. Once incorporated, they change fluidity of the membranes. The extent of the changes was determined in fluorescence measurements. Polarization and anisotropy coefficients of erythrocyte membranes modified by micromolar concentrations of herbicides at different temperatures were measured for that purpose. Generally, they followed the sequence found for antioxidative activity of the herbicides studied, which confirms the assumption of close correlation between the depth of incorporation of a herbicide into the erythrocyte membrane and its protective efficiency.

Antioxidative properties of pyrrolidinium and piperidinium salts.

Two series of pyrrolidinium (PYA-n) and piperidinium (PPPA-n) bromides with incorporated antioxidant function were synthesized. Both have hydrocarbon chains with odd number of the carbon atoms (n) ranging between 7 and 15. Pig erythrocytes (RBC) were used to study antioxidant activity of these compounds. They were incorporated into RBC membranes in sublytic (micromolar) concentrations and RBC were then subjected to UV radiation. It was found that all the salts used protected erythrocyte membranes against oxidation of membrane lipids. This protection increased with hydrocarbon chain length. Such effect may be the result of an incorporation of particular compounds to different depths into the lipid phase of RBC membrane depending on their chain length. Such possibility was checked by studies on fluidity changes induced by the compounds studied in ghost membranes by fluorimetric measurements. The measurements showed that pyrrolidinium bromides were slightly more effective in a protection of erythrocytes than the corresponding piperidinium ones. The possible reason of such behaviour may be the difference in lipophilicity between piperidine and pyrrolidine rings.