Malvidin and Its Mono- and Di-Glucosides Forms: A Study of Combining Both In Vitro and Molecular Docking Studies Focused on Cholinesterase, Butyrylcholinesterase, COX-1 and COX-2 Activities.

Malvidin, one of the six most prominent anthocyanins found in various fruits and vegetables, may possess a wide range of health-promoting properties. The biological activity of malvidin and its glycosides is not entirely clear and has been relatively less frequently studied compared to other anthocyanins. Therefore, this study aimed to determine the relationship between the structural derivatives of malvidin and their anti-cholinergic and anti-inflammatory activity. The study selected malvidin (Mv) and its two sugar derivatives: malvidin 3-O-glucoside (Mv 3-glc) and malvidin 3,5-O-diglucoside (Mv 3,5-diglc). The anti-inflammatory activity was assessed by inhibiting the enzymes, specifically COX-1 and COX-2. Additionally, the inhibitory effects on cholinesterase activity, particularly acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), were evaluated. Molecular modeling was also employed to examine and visualize the interactions between enzymes and anthocyanins. The results revealed that the highest inhibitory capacity at concentration 100 µM was demonstrated by Mv 3-glc in relation to AChE (26.3 ± 3.1%) and BChE (22.1 ± 3.0%), highlighting the crucial role of the glycoside substituent at the C3 position of the C ring in determining the inhibitory efficiency of these enzymes. In addition, the glycosylation of malvidin significantly reduced the anti-inflammatory activity of these derivatives compared to the aglycone form. The IC50 parameter demonstrates the following relationship for the COX-1 enzyme: Mv (12.45 ± 0.70 µM) < Mv 3-glc (74.78 ± 0.06 µM) < Mv 3,5-diglc (90.36 ± 1.92 µM). Similarly, for the COX-2 enzyme, we have: Mv (2.76 ± 0.16 µM) < Mv 3-glc (39.92 ± 3.02 µM) < Mv 3.5-diglc (66.45 ± 1.93 µM). All tested forms of malvidin exhibited higher activity towards COX-2 compared to COX-1, indicating their selectivity as inhibitors of COX-2. Theoretical calculations were capable of qualitatively replicating most of the noted patterns in the experimental data, explaining the impact of deprotonation and glycosylation on inhibitory activity. It can be suggested that anthocyanins, such as malvidins, could be valuable in the development of treatments for inflammatory conditions and Alzheimer's disease and deserve further study.

Analytical and Theoretical Studies of Antioxidant Properties of Chosen Anthocyanins; A Structure-Dependent Relationships.

The relationship between the structure and the antiradical and antioxidant activities of three anthocyanidins, namely peonidin, petunidin, and delphinidin, and their glucosides was investigated in this study. The ability of anthocyanins to scavenge free radicals was determined using DPPH● assay, whereas the inhibition of peroxidation in liposomes in relation to a model membrane that imitated the composition of a lipid membrane in tumor cells was specified using the fluorimetric method. To explore this issue at the atomistic level, density functional theory studies were applied. It was shown that glycosides performed better than anthocyanidins in protecting membranes against oxidation. The highest redox potential was demonstrated by anthocyanidins with the highest number of hydroxyl groups in the B ring in the order as follows: (Dp > Pt > Pn), and the same relationship was proven for their glucosides. The majority of the compounds studied here proved to be better antioxidants than ascorbic acid. They showed consistent electrodonating properties and though the f-HAT mechanism became more feasible with each consecutive deprotonation. Glycosylation did not have a direct impact on reactivity, apart from peonidin and petunidin in the study of which it was found that this process was responsible for lifting off steric hindrance between B and C rings and rendering certain pathways more feasible. Kinetic and molecular dynamics are essential to properly describe the membrane's lipid oxidation.

Biological Activity of Extracts of Red and Yellow Fruits of Cornus mas L.-An In Vitro Evaluation of Antioxidant Activity, Inhibitory Activity against α-Glucosidase, Acetylcholinesterase, and Binding Capacity to Human Serum Albumin.

Although extracts are broadly used in order to support the treatment of numerous diseases, only in a limited number of cases is the process of applying and establishing their mechanisms of action scientifically analyzed. Fruits of Cornelian cherry are an abundant source of iridoids, anthocyanins, flavonols and phenolic acids. The aim of the present study was to evaluate the in vitro bioactivity of red and yellow Cornelian cherry fruits' extracts. The biological potential of extracts, in a broad sense, involved antioxidant activity in relation to phosphatidylcholine liposomes, inhibitory ability against α-glucosidase and acetylcholinesterase enzymes, as well as interactions with human serum albumin. Studies showed that both extracts were more effective in protecting liposome membranes against free radicals produced by AAPH in an aqueous environment due to the fact that they can be better eliminated by the hydrophilic components of the extracts than those produced by UVB radiation. Extracts exhibited inhibitory activity against acetylcholinesterase and α-glucosidase, wherein loganic acid extract showed noncompetitive inhibition of the enzyme. Moreover, extracts binded to albumin mainly through hydrogen bonds and van der Waals forces. Taken together, red and yellow cherry fruits' extracts exhibit diverse biological properties and can be exploited as a source of natural therapeutic agents.

Antitumor and antioxidant activities of purple potato ethanolic extract and its interaction with liposomes, albumin and plasmid DNA.

The aim of the study was to broadly determine the biological activities of purple potato ethanolic extract of the Blue Congo variety (BCE). The antioxidant activity of BCE was determined in relation to liposome membranes, and peroxidation was induced by UVB and AAPH. To clarify the antioxidant activity of BCE, we investigated its interactions with hydrophilic and hydrophobic regions of a membrane using fluorimetric and FTIR methods. Next, we investigated the cytotoxicity and pro-apoptotic activities of BCE in two human colon cancer cell lines (HT-29 and Caco-2) and in normal cells (IPEC-J2). In addition, the ability to inhibit enzymes that are involved in pro-inflammatory reactions was examined. Furthermore, BCE interactions with serum albumin and plasmid DNA were investigated using steady state fluorescence spectroscopy and a single molecule fluorescence technique (TCSPC-FCS). We proved that BCE effectively protects lipid membranes against the process of peroxidation and successfully inhibits the cyclooxygenase and lipoxygenase enzymes. Furthermore, it interacts with the hydrophilic and hydrophobic parts of lipid membranes as well as with albumin and plasmid DNA. It was observed that BCE is more cytotoxic against colon cancer cell lines than normal IPEC-J2 cells; it also induces apoptosis in cancer cell lines, but does not induce cell death in normal cells.

Microbiological, antioxidant and lipoxygenase-1 inhibitory activities of fruit extracts of chosen Rosaceae family species.

BACKGROUND: Extracts from the Rosaceae family fruits are rich in natural, biologically active polyphenols, but their antibacterial properties are still poorly understood. Therefore, we focused our research on their activity against uropathogenic Escherichia coli strains. This research also concerned the proof of their ability to reduce oxidative stress and modulate the activity of lipoxygenase-1 (LOX-1). It is well-known that plants represent a source of bioactive compounds whose antioxidant activity may be useful in protecting against oxidative damage in cells, which have been linked to the pathogenesis of many oxidative diseases. OBJECTIVES: The study determined the biological activity of methanol (ME) and water (WE) extracts rich in polyphenols from the hawthorn (Crataegus monogyna Jacq.), dog rose (Rosa canina L.), quince (Cydonia oblonga Mill.), and Japanese quince (Chaenomeles speciosa (Sweet) Nakai). MATERIAL AND METHODS: The antioxidant capacity was evaluated using 1,1diphenyl-2-picrylhydrazyl (DPPH▪) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS+▪) radical scavenging methods. The inhibition of liposome membrane oxidation was studied using the thiobarbituric acid reactive substances assay. Lipoxygenase-1 inhibitory activity was measured using the spectrophotometric method. Bacterial growth was determined by evaluating the number of colony forming units per milliliter (CFU/mL). Hydrophobicity was established with salt aggregation hydrophobicity test (SAT). Swimming and swarming motilities were evaluated using soft-agar plates. Production of curli fimbriae was estimated on CFA agar. The P fimbriae were detected using the hemagglutination of erythrocytes. Adhesion of bacteria to human uroepithelial cells was assessed. The amount of biofilm was determined spectrophotometrically. RESULTS: We showed that most of these extracts are effective antioxidants and free radical scavengers, possess reasonable potential anti-inflammatory activity, reduce the adhesion of E. coli to uroepithelial cells, and reduce the ability of these bacteria to form biofilm. CONCLUSIONS: The extracts examined, showing very promising biological properties, seem to be able to join the list of substances that can be used as dietary supplements aimed at preventing, for example, urinary tract infections, or as support of drug treatment in many diseases.

Antidiabetic and Antioxidative Potential of the Blue Congo Variety of Purple Potato Extract in Streptozotocin-Induced Diabetic Rats.

This study was designed to evaluate the effects of purple potato extract of the Blue Congo variety (PP) on diabetes and its antioxidant activities after two-week administration tostreptozotocin (STZ)-induced diabetic rats. The activities of PP were evaluated at a dose of 165 mg/kg body weight (b.w.) by estimating biochemical changes in blood plasma and through a histopathological study of kidney, muscles, and liver tissue. We evaluated the effect of treatment with extract on glucose level, glycated hemoglobin, activities of enzymatic antioxidants (including superoxide dismutase, glutathione peroxidase, and catalase), and lipid peroxidation. Moreover, we determined advanced glycation end-products (AGEs), advanced oxidation protein products (AOPPs), and the level of oxidative modified proteins (OMPs) as markers of carbonyl-oxidative stress in rats with diabetes. Using high-performance liquid chromatography, we identified five anthocyanins and six phenolic acids in the extract from Blue Congo with the dominant acylated anthocyanin as petunidin-3-p-coumaroyl-rutinoside-5-glucoside. The administration of Blue Congo extract lowered blood glucose, improved glucose tolerance, and decreased the amount of glycated hemoglobin. Furthermore, PP demonstrated an antioxidative effect, suppressed malondialdehyde levels, and restored antioxidant enzyme activities in diabetic rats. After administration of PP, we also noticed inhibition of OMP, AGE, and AOPP formation in the rats' blood plasma.

A Comprehensive Study on the Biological Activity of Elderberry Extract and Cyanidin 3-O-Glucoside and Their Interactions with Membranes and Human Serum Albumin.

In our research we used the extract from dietary supplement of elderberry (EE) and its dominant anthocyanin-cyanidin 3-O-glucoside (Cy 3-gluc). By interacting with a model membrane that reflects the main lipid composition of tumor membranes, the extract components, including Cy 3-gluc, caused an increase in packing order, mainly in the hydrophilic region of the membrane. It can thus be stated that EE caused a rigidifying effect, which is fundamental for understanding its anticancer and antioxidant activity. This study represents the first attempt to unravel the mechanism of interaction of elderberry extract with membranes. The results of the interaction with human serum albumin (HSA) proved that the studied substance quenches the fluorescence of HSA through a static mechanism in which the main interaction forces are Van der Waals and hydrogen bonding. The antioxidant activity of EE and Cy 3-gluc on liposomal membranes, antiradical properties and ability to inhibited the activity of the enzymes cyclooxygenase-1 and cyclooxygenase-2 were also demonstrated. Moreover, the anticancer activity of EE and Cy 3-gluc on human breast adenocarcinoma cell line were investigated. In addition, EE also exhibited the ability to form lipid aggregates in the form of liposomal capsules that can be applied as carriers of active biological substances, and the highest efficacy of EE encapsulation was obtained for multilayered liposome formulations.

Bioactivity In Vitro of Quercetin Glycoside Obtained in Beauveria bassiana Culture and Its Interaction with Liposome Membranes.

Quercetin (Q) was used as substrate for regioselective glycosylation at the C-7 position catalyzed by Beauveria bassiana AM278 strain. As a result the glycoside quercetin 7-O-ß-d-(4″-O-methyl)glucopyranoside (Q 7-MeGlu) was formed. The goal of the studies was to determine the anti-oxidative (liposome membrane protection against free radicals IC50Q 7-MeGlu = 5.47 and IC50Q = 4.49 µM) and anti-inflammatory (COX-1 and COX-2 enzymes activity inhibition) properties of Q 7-MeGlu as compared to Q. Every attempt was made to clarify the antioxidant activity of these molecules, which are able to interact with egg phosphatidylcholine liposomes, using a fluorometric method (by applying the probes MC540, TMA-DPH and DPH). The results indicated that Q 7-MeGlu and Q are responsible for increasing the packing order, mainly in the hydrophilic but also in hydrophobic regions of the membrane (Q > Q 7-MeGlu). These observations, confirmed by a ¹H-NMR method, are key to understanding their antioxidant activity which is probably caused by the stabilizing effect on the lipid membranes. The results showed that Q 7-MeGlu and Q have ability to quench the human serum albumin (HSA) intrinsic fluorescence through a static quenching mechanism. The results of thermodynamic parameters indicated that the process of formation complexes between studied molecules and HSA was spontaneous and caused through Van der Waals interactions and hydrogen bonding.

ACTIVITY OF BLACKCURRANT AND CHOKEBERRY EXTRACTS AND TWO MAJOR CYANIDIN GLYCOSIDES AGAINST LIPID MEMBRANE OXIDATION AND THEIR BINDING PROPERTIES TO ALBUMIN.

The purpose of this study was to explain how extracts from chokeberry and blackcurrant interact with the lipid phase of biological membrane and with human albumin - the main protein of blood. Aiming at better understanding of the observed biological activity of the extracts, we also conducted experiments with their main components: cyanidin-3-0-galactoside and cyanidin-3-0-ruthinoside. Antioxidant activities of extracts and cyanidin derivatives were investigated with phosphatidy1choline liposomes and AAPH as oxidation inducing factor. Fluorescent probes (merocyanin and N-phenyl-1-naphthylamine) that were located at different depths within the membrane lipid bilayer were also used. The interaction between the compounds and human serum albumin was investigated using natural fluorescence quenching. According to our study it is highly likely that the significant antioxidant activity of chokeberry and blackcurrant extracts (IC50chokeberry = 4.92 pg/mL; IC50blackbcurrant = 7.04 µg/mL) is probably due to cyjanidin's main derivatives, which protect the lipid membrane more than the extracts. In addition, it has been suggested that the compounds are anchored mainly on the membrane surface and rigidify/order the lipids in the membrane. That rigidifying effect is the key factor for understanding their antioxidant properties. Experimental results have proved that all the study compounds quench the fluorescence of HSA through a static mechanism and the main interaction forces are the Van der Waals and hydrogen bonding interactions. The results of the study have improved our knowledge on how to protect membranes against lipid peroxidation using extracts rich in anthocyanins. The results can be relevant to pharmacists and nutritionists.

Interaction between Mimic Lipid Membranes and Acylated and Nonacylated Cyanidin and Its Bioactivity.

We investigated the effects of acylated cyanidin-3-O-ß-(6″-O-E-p-coumaroyl-sambubioside)-5-O-ß-glucoside (C3-cs-5G) and nonacylated cyanidin, cyanidin-3,5-di-O-ß-glucoside (C3,5G) and cyanidin-3-O-ß-glucoside (C3G), on cell-mimic membranes (MM) that reflected the membrane lipid composition of tumor cells. The relationship between structural derivatives of cyanidin (Cy-d), membrane interactivity, their antioxidant activity, and interaction with albumin were characterized. Studies showed that Cy-d caused an increase in packing order mainly in the hydrophilic region of the membranes. Cy-d have shown high antioxidant activity against liposome oxidation induced by AAPH and ability to bind to albumin through a static quenching mechanism. The results showed that glycosylation number and the presence of aromatic acid attached to sugars affected the membrane properties, according to the sequence C3-cs-5G > C3,5G > C3G. It can be stated that Cy-d in the process of interaction with MM caused a rigidifying effect, which is fundamental for understanding their anticancer and antioxidant activity and is one of the possible pharmaceutical mechanisms.

Biological Activity of Japanese Quince Extract and Its Interactions with Lipids, Erythrocyte Membrane, and Human Albumin.

The aim of the study was to determine in vitro biological activity of fruit ethanol extract from Chaenomeles speciosa (Sweet) Nakai (Japanese quince, JQ) and its important constituents (-)-epicatechin (EC) and chlorogenic acid (CA). The study also investigated the structural changes in phosphatidylcholine (PC) liposomes, dipalmitoylphosphatidylcholine liposomes, and erythrocyte membranes (RBC) induced by the extract. It was found that the extract effectively inhibits oxidation of RBC, induced by 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH), and PC liposomes, induced by UVB radiation and AAPH. Furthermore, JQ extract to a significant degree inhibited the activity of the enzymes COX-1 and COX-2, involved in inflammatory reactions. The extract has more than 2 times greater activity in relation to COX-2 than COX-1 (selectivity ratio 0.48). JQ extract stimulated growth of the beneficial intestinal bacteria Lactobacillus casei and Lactobacillus plantarum. In the fluorimetric method by means of the probes Laurdan, DPH and TMA-DPH, and (1)H-NMR, we examined the structural changes induced by JQ and its EC and CA components. The results show that JQ and its components induce a considerable increase of the packing order of the polar heads of lipids with a slight decrease in mobility of the acyl chains. Lipid membrane rigidification could hinder the diffusion of free radicals, resulting in inhibition of oxidative damage induced by physicochemical agents. JQ extract has the ability to quench the intrinsic fluorescence of human serum albumin through static quenching. This report thus could be of huge significance in the food industry, pharmacology, and clinical medicine.

Biological activity of the methanol and water extracts of the fruits of anthocyanin-rich plants grown in south-west Poland.

In this study we focused on the chemical composition, antioxidant, anti-inflammatory and antibacterial properties of methanol and water extracts of fruits of six species grown in south-west Poland: blackberry, blackcurrant, chokeberry, cherry, gooseberry and raspberry. No general correlation could be drawn between extract chemical properties (i.e. antioxidant and free radical scavenging) and observed biological effects. However, blackcurrant and blackberry extracts (both methanol and water) appeared to be good antioxidants and free radical scavengers, as well as effective inhibitors of E. coli adhesion to the uroepithelial cells. On the other hand, the poorest antioxidants and free radical scavengers, cherry and gooseberry extracts, also poorly affected bacterial growth, swimming ability and adhesion to epithelial cells. Surprisingly, gooseberry extracts, which showed generally weak effects, appearedto be the most effective inhibitor of bacterial biofilm formation. Additionally, most of the studied extracts showed reasonably strong anti-inflammatory properties.

Biological activity and stability in vitro of polyphenolic extracts as potential dietary supplements.

INTRODUCTION: In times of worsening civilization diseases the interest in natural healing substances is on the increase. To reduce unwanted side effects of many synthetic drugs, it is reasonable to introduce to the daily diet foods rich in natural compounds of plant origin that are beneficial for health. The purpose of the study was to determine the biological activity and stability of selected ethanol extracts of the fruit of chokeberry, blackcurrant, hawthorn, rosehip, quince and Japanese quince as potential nutraceuticals. MATERIALS AND METHODS: Antioxidant activity of the extracts was determined in relation to model phospholipid membranes (IC50(PC)). Antiradical activity was determined in a test with the DPPH• radical (IC50(DPPH)). Also the inhibition of enzymatic (1-LOX) oxidation of linoleic acid was determined at the beginning of the period of storage of the extracts at room temperature and after 12 months. RESULTS: After 12 months of storage the highest antioxidant stability was shown by blackcurrant extract (1.5% increase in IC50(PC)), the highest antiradical stability by quince extract (1.0% reduction in IC50(DPPH)), and the highest stability of 1-LOX enzyme inhibition by chokeberry extract (6.3% reduction in inhibition at a concentration of 8 µg∙(-1)). Japanese quince extract showed the strongest regenerating properties with respect to oxidized phospholipid membranes and the highest ability to eliminate the free radical DPPH•. CONCLUSION: It can be concluded that the ethanol extracts of the fruits (in particular blackcurrant, chokeberry and Japanese quince) are a potential source of dietary supplements of expected effectiveness in preventive treatment.

The modified action of triphenyllead chloride on UVB-induced effects in albumin and lipids.

Previously we have shown a toxic effect of the organometallic compound triphenyllead (TPhPb) on cells. In the present study we evaluated the destructive effect of TPhPb on model systems--serum albumin and liposome membranes--alone and under UVB irradiation. UVB irradiation of bovine serum albumin results in protein S-S bond reduction, free SH- and CO- group formation and decrease in fluorescence intensity of tryptophans. Triphenyllead chloride alone and under UVB irradiation did not induce protein oxidation, measured as formation of carbonyl groups, in serum albumin; however, it decreased the content of SH- groups in both cases (alone and under UVB radiation) in a dose-dependent manner. It was found that triphenyllead chloride alone did not induce lipid peroxidation of liposomes but increased their fluidity. However, under UVB irradiation TPhPb dramatically enhances the pro-oxidant action of UVB in a manner dependent on concentration and intensity of radiation, and these effects were suppressed by Trolox. These results suggest that the toxicity of TPhPb under UVB irradiation is due to formation of radical forms of the compound and its disordered effects on the membrane structure.

Study on the influence of cranberry extract Zuravit S·O·S(®) on the properties of uropathogenic Escherichia coli strains, their ability to form biofilm and its antioxidant properties.

Consumption of cranberries is known to exert positive health effects, especially against urinary tract infections. For this reason, presumably, they are widely used in folk medicine. Different aspects of cranberry phenolics activity were studied in individual papers but complex study in this matter is missing. The aim of the present study is to provide complex data concerning various aspects of cranberry extract activity. We studied the effects of subinhibitory concentrations of commercially available extract (Zuravit S·O·S(®)) against two Escherichia coli strains isolated from urine of patients with pyelonephritis. Additionally the main extract anthocyanins were characterized. The activity of extract against lipid peroxidation and its radical scavenging ability were also assessed. Zuravit S·O·S(®) decreased the hydrophobicity of one of the studied E. coli strains, reduced swimming motility and adhesion to epithelial cells of both studied strains, it also limited the ability of bacteria to form biofilm. Expression of curli was not affected by cranberry extract, the assessment of P fimbriae expression was not reliable due to extract-induced agglutination of erythrocytes. Cranberry extract caused filamentation in both studied E. coli strains. It also showed pronounced antioxidant and radical scavenging properties. The properties of the studied cranberry extract show that it could be effectively used in prevention and/or elimination of urinary tract infections, specially the recurrent ones.

Antioxidative effect of quercetin and its equimolar mixtures with phenyltin compounds on liposome membranes.

Our earlier studies have shown that the compounds diphenyltin dichloride (DPhT) and triphenyltin chloride (TPhT) in the presence of UVC radiation enhanced the degree of phosphatidylcholine liposome membrane oxidation (J. Agric. Food Chem. 2005, 53, 76-83). The prooxidative behavior of the compounds has now been confirmed with the electron paramagnetic resonance method, which proved the possibility that the studied compounds can exist in free radical forms. The present work investigates the possibility of the protective action of quercetin on phosphatidylcholine liposome membranes exposed to the prooxidative action of DPhT and TPhT induced by UV radiation (lambda = 253.7 nm). The concentrations of quercetin and its equimolar mixtures with DPhT and TPhT were determined (and compared with well-known antioxidants as standards-trolox and butylated hydroxytoluene, also in the presence of phenyltins) as those that induce 50% inhibition in oxidation of liposomes radiated with UV. They are 5.1 +/- 0.10, 2.9 +/- 0.12, and 1.9 +/- 0.08 microM (differences between the values are statistically significant), constituting the following sequence of antioxidative activity: quercetin:TPhT > quercetin:DPhT > quercetin. This relation is confirmed by the results on the antiradical ability of quercetin and its mixtures with DPhT and TPhT toward the free radical 1,1-diphenyl-2-pricrylhydrazil. Similar sequences obtained in both studies suggest a possible mechanism of the antiradical action of the mixtures as free radical scavengers. We suggested that (i) quercetin's ability, documented by spectrophotometric, infrared attenuated total reflectance spectroscopy, (1)H NMR, and molecular modeling methods, to form complexes with phenyltins indicates a possible way of protection against the peroxidation caused by the free radical forms of phenyltins and (ii) the differentiation in the action of the quercetin/TPhT and quercetin/DPhT associates (statisticaly significant) may result from a different localization in the liposome membrane, which is indicated by the results of the fluorimetric studies.

Binding of antibiotic amphotericin B to lipid membranes: a 1H NMR study.

The (1)H NMR technique was applied to study binding of AmB, an antifungal drug, to lipid membranes formed with egg yolk phosphatidylcholine. The analysis of (1)H NMR spectra of liposomes, containing also cholesterol and ergosterol (at 40 mol%), shows that AmB binds preferentially to the polar headgroups. Such a binding restricts molecular motion of the choline fragment in the hydrophilic region at the surface of liposomes but increases the segmental motional freedom in the hydrophobic core. The same effects are also observed in the sterol-containing membranes, except that the effect on the hydrophobic core was exclusively observed in the membranes containing ergosterol.

Binding of antibiotic amphotericin B to lipid membranes: monomolecular layer technique and linear dichroism-FTIR studies.

Amphotericin B (AmB) is one of the main antibiotics applied in treatment of deep-seated mycotic infections. Tensiometric technique has been applied to monitor binding of AmB, from the water subphase, to the lipid monomolecular layers, formed with dipalmitoylphosphatidylcholine at the air-water interface. Time dependencies of surface pressure in the monolayers demonstrate strong enhancement of AmB binding to monolayers brought about by sterols present in the membranes. The monolayers have been deposited to a solid support and examined by means of FTIR spectroscopy. FTIR measurements show that majority of the AmB molecules which bind to the membranes are localized in the polar headgroup region. The results of the linear dichroism-FTIR measurements are consistent with the microscopic picture according to which the molecules of the membrane-bound AmB are distributed among two orientational fractions: one horizontal and one vertical with respect to the plane of the membrane (59% versus 41% respectively, in the case of the membrane formed with the pure lipid without sterols). The presence of cholesterol in the membranes (50 mol% with respect to lipid) slightly affects such a distribution (53% horizontal versus 47% vertical) but the presence of ergosterol has a pronounced effect in the increase in population of the fraction of horizontally bound AmB (85% horizontal vs. 15% vertical). The results of the measurements indicate that mode of action of the AmB consists in disruption of the polar headgroup region of biomembranes, brought about by the AmB molecules bound horizontally with respect to the plane of the membrane.

Antioxidant activity of anthocyanin glycoside derivatives evaluated by the inhibition of liposome oxidation.

Cyanidin-3-glycosides (arabinoside, rutinoside, galactoside and glucoside) and delphinidin-3-rutinoside were examined for their ability to inhibit lipid peroxidation induced either by Fe(II) ions, UV irradiation or 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) peroxyl radicals in a liposomal membrane system. The antioxidant abilities of anthocyanins were compared with a water-soluble tocopherol derivative, trolox. The antioxidant efficacies of these compounds were evaluated by their ability to inhibit the fluorescence intensity decay of the extrinsic probe 3-[p-(6-phenyl)-1,3,5,-hexatrienyl] phenylpropionic acid, caused by the free radicals generated during peroxidation. All the anthocyanins tested (at concentrations of 15-20 microM) exhibited higher antioxidant activities against Fe(II)-induced peroxidation than UV- and AAPH-induced peroxidation, suggesting that metal chelation may play an important role in determining the antioxidant potency of these compounds. It was also found that delphinidin-3-rutinoside had a higher antioxidant activity against Fe(II)-induced liposome oxidation than cyanidin-3-rutinoside, which indicates an important role of the OH group in the B ring of delphinidin-3-rutinoside in its antioxidant action. The antioxidant activity of all the anthocyanins studied was higher than that of trolox in the case of Fe(II)-induced liposome oxidation and was comparable with the action of trolox in the case of UV- and AAPH-induced liposome membrane oxidation.

Studies on canthaxanthin in lipid membranes.

Polar carotenoid pigment - canthaxanthin - has been found to interfere with the organization of biological membranes, in particular of the retina membranes of an eye of primates. The organization of lipid membranes formed with dipalmitoylphosphatidylcholine (DPPC) and egg yolk phosphatidylcholine containing canthaxanthin was studied by means of several techniques including: electronic absorption spectroscopy, linear dichroism, X-ray diffractometry, (1)H-NMR spectroscopy and FTIR spectroscopy. It appears that canthaxanthin present in the lipid membranes at relatively low concentration (below 1 mol% with respect to lipid) modifies significantly physical properties of the membranes. In particular, canthaxanthin (i) exerts restrictions to the segmental molecular motion of lipid molecules both in the headgroup region and in the hydrophobic core of the bilayer, (ii) promotes extended conformation of alkyl lipid chains, (iii) modifies the surface of the lipid membranes (in particular in the gel state, L(beta )) and promotes the aggregation of lipid vesicles. It is concluded that canthaxanthin incorporated into lipid membranes is distributed among two pools: one spanning the lipid bilayer roughly perpendicularly to the surface of the membrane and one parallel to the membrane, localized in the headgroup region. The population of the horizontal fraction increases with the increase in the concentration of the pigment in the lipid phase. Such a conclusion is supported by the linear dichroism analysis of the oriented lipid multibilayers containing canthaxanthin: The mean angle between the dipole transition moment and the axis normal to the plane of the membrane was determined as 20+/-3 degrees at 0.5 mol% and 47+/-3 degrees at 2 mol% canthaxanthin. The analysis of the absorption spectra of canthaxanthin in the lipid phase and (1)H-NMR spectra of lipids point to the exceptionally low aggregation threshold of the pigment in the membrane environment (approximately 1 mol%). All results demonstrate a very strong modifying effect of canthaxanthin with respect to the dynamic and structural properties of lipid membranes.