Dual effect of alkylresorcinols, natural amphiphilic compounds, upon liposomal permeability

The Role of Resorcinolic Lipids of Caryopsis Surface in the Process of Cereal Infection by Rhizoctonia solani and Fusarium culmorum

Cereal caryopses are rich in 5-n-alk(en)ylresorcinols, antimicrobial compounds. In this paper, the correlation between the presence of resorcinolic lipids on the surface of cereal grains and the susceptibility of their seedlings to infection by Rhizoctonia solani or Fusarium culmorum was evaluated. The declines in length of both the roots and coleoptiles were observed in barley seedlings of Scarlett and Rabel cultivars grown from the wax-impoverished seeds infected with F92 and F93 strains of Rhizoctonia solani, respectively. Regarding wheat, R. solani F93 significantly reduced only the coleoptile growth. Resorcinolic lipids, being the mixture of homologues with C17–C25 carbon chains, were the only compounds washed off wheat caryopses by chloroform. Moreover, the better anti-Rhizoctonia solani F93 activity of 5-n-alk(en)ylresorcinols of wheat grains than that of rye caryopsis lipids was proven by the poisoned medium technique. Two saturated homologues (C21:0 and C23:0) were the most effective inhibitors of the mycelial growth of this fungus. Thus, the susceptibilities of barley and wheat seedlings to some fungal pathogens have been found to be related to the content and composition of 5-n-alk(en)ylresorcinols in the waxy layer of cereal grains, confirming the protective role of these compounds, during the early stages of cereal development.

Alkyl-Resorcinol Derivatives as Inhibitors of GDP-Mannose Pyrophosphorylase with Antileishmanial Activities

Leishmaniasis is a vector-borne disease caused by the protozoan parasite Leishmania found in tropical and sub-tropical areas, affecting 12 million people around the world. Only few treatments are available against this disease and all of them present issues of toxicity and/or resistance. In this context, the development of new antileishmanial drugs specifically directed against a therapeutic target appears to be a promising strategy. The GDP-Mannose Pyrophosphorylase (GDP-MP) has been previously shown to be an attractive therapeutic target in Leishmania. In this study, a chemical library of 5000 compounds was screened on both L. infantum (LiGDP-MP) and human (hGDP-MP) GDP-MPs. From this screening, oncostemonol D was found to be active on both GDP-MPs at the micromolar level. Ten alkyl-resorcinol derivatives, of which oncostemonols E and J (2 and 3) were described for the first time from nature, were then evaluated on both enzymes as well as on L. infantum axenic and intramacrophage amastigotes. From this evaluation, compounds 1 and 3 inhibited both GDP-MPs at the micromolar level, and compound 9 displayed a three-times lower IC₅₀ on LiGDP-MP, at 11 µM, than on hGDP-MP. As they displayed mild activities on the parasite, these compounds need to be further pharmacomodulated in order to improve their affinity and specificity to the target as well as their antileishmanial activity.

A novel cytosporone 3-Heptyl-4,6-dihydroxy-3H-isobenzofuran-1-one: synthesis; toxicological, apoptotic and immunomodulatory properties; and potentiation of mutagenic damage

BACKGROUND

A large number of studies are attempting to identify alternative products from natural sources or synthesized compounds that effectively interact with cancer cells without causing adverse effects on healthy cells. Resorcinolic lipids are a class of bioactive compounds that possess anticancer activity and are able to interact with the lipid bilayer. Therefore, the objective of this study was to synthesize a novel resorcinolic lipid and test its biological proprieties.

METHODS

We aimed to synthesize a novel resorcinolic lipid belonging to the class of cytosporones, AMS049 (3-Heptyl-4,6-dihydroxy-3H-isobenzofuran-1-one) and to evaluate the toxicity of two concentrations of this lipid (7.5 and 10 mg/kg) by determining its genotoxic, mutagenic, immunomodulatory, and apoptotic effects, as well as any biochemical and histopathological alterations in mice treated with cyclophosphamide. The results were analyzed by ANOVA followed by the Tukey test A . level of significance of p < 0.05 was adopted.

RESULTS

The new cytosporone AMS049 was synthesized in only three steps and in satisfactory yields. The results indicate that the compound is neither genotoxic nor mutagenic and does not alter biochemical parameters. The histological alterations observed in the liver and kidneys did not compromise the function of these organs. Histology of the spleen suggested immunomodulation, although no changes were observed in splenic phagocytosis or differential blood cell count. The results also show that AMS049 potentiates the mutagenic effect of the chemotherapy drug cyclophosphamide and that the combination induces apoptosis.

CONCLUSION

These facts indicate a potential therapeutic application of this novel cytosporone as an important chemotherapeutic adjuvant.

Kinetic and equilibrium studies of bile salt-liposome interactions

Research has suggested that exposure to sub-micellar concentrations of bile salts (BS) increases the permeability of lipid bilayers in a time-dependent manner. In this study, incubation of soy phosphatidylcholine small unilamellar vesicles (liposomes) with sub-micellar concentrations of cholate (C), deoxycholate (DC), 12-monoketocholate (MKC) or taurocholate (TC) in pH 7.2 buffer increased membrane fluidity and negative zeta potential in the order of increasing BS liposome-pH 7.2 buffer distribution coefficients (MKC < C ≈ TC < DC). In liposomes labeled with the dithionite-sensitive fluorescent lipid N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)phosphatidylethanolamine (NBD-PE) in both leaflets and equilibrated with sub-micellar concentrations of BS, fluorescence decline during continuous exposure to dithionite was biphasic involving a rapid initial phase followed by a slower second phase. Membrane permeability to dithionite as measured by the rate of the second phase increased in the order control < MKC < TC ∼ C < DC. In liposomes labeled with NBD-PE in the inner leaflet only and incubated with the same concentrations of C, DC and MKC, membrane permeability to dithionite initially increased very rapidly in the order MKC < C < DC before impermeability to dithionite was restored after which fluorescence decline was consistent with NBD-PE flip-flop. For liposomes incubated with TC, membrane permeability to dithionite was only slightly increased and the decline in fluorescence was mainly the result of NBD-PE flip-flop. These results provide evidence that BS interact with lipid bilayers in a time-dependent manner that is different for conjugated and unconjugated BS. MKC appears to cause least disturbance to liposomal membranes but, when the actual MKC concentration in liposomes is taken into account, MKC is actually the most disruptive.

Topical delivery of Avastin to the posterior segment of the eye in vivo using annexin A5-associated liposomes

Effective delivery to the retina is presently one of the most challenging areas in drug development in ophthalmology, due to anatomical barriers preventing entry of therapeutic substances. Intraocular injection is presently the only route of administration for large protein therapeutics, including the anti-Vascular Endothelial Growth Factors Lucentis (ranibizumab) and Avastin (bevacizumab). Anti-VEGFs have revolutionised the management of age-related macular degeneration and have increasing indications for use as sight-saving therapies in diabetes and retinal vascular disease. Considerable resources have been allocated to develop non-invasive ocular drug delivery systems. It has been suggested that the anionic phospholipid binding protein annexin A5, may have a role in drug delivery. In the present study we demonstrate, using a combination of in vitro and in vivo assays, that the presence of annexin A5 can significantly enhance uptake and transcytosis of liposomal drug carrier systems across corneal epithelial barriers. This system is employed to deliver physiologically significant concentrations of Avastin to the posterior of the rat eye (127 ng/g) and rabbit retina (18 ng/g) after topical application. Our observations provide evidence to suggest annexin A5 mediated endocytosis can enhance the delivery of associated lipidic drug delivery vehicles across biological barriers, which may have therapeutic implications.

Sirolimus encapsulated liposomes for cancer therapy: physicochemical and mechanical characterization of sirolimus distribution within liposome bilayers

Sirolimus has recently been introduced as a therapeutic agent for breast and prostate cancer. In the current study, conventional and Stealth liposomes were used as carriers for the encapsulation of sirolimus. The physicochemical characteristics of the sirolimus liposome nanoparticles were investigated including the particle size, zeta potential, stability and membrane integrity. In addition atomic force microscopy was used to study the morphology, surface roughness and mechanical properties such as elastic modulus deformation and deformation. Sirolimus encapsulation in Stealth liposomes showed a high degree of deformation and lower packing density especially for dipalmitoyl-phosphatidylcholine (DPPC) Stealth liposomes compared to unloaded. Similar results were obtained by differential scanning calorimetry (DSC) studies; sirolimus loaded liposomes were found to result in a distorted state of the bilayer. X-ray photon electron (XPS) analysis revealed a uniform distribution of sirolimus in multilamellar DPPC Stealth liposomes compared to a nonuniform, greater outer layer lamellar distribution in distearoylphosphatidylcholine (DSPC) Stealth liposomes.

N-octyl-O-sulfate chitosan-modified liposomes for delivery of docetaxel: preparation, characterization, and pharmacokinetics

A N-octyl-O-sulfate chitosan (NOSC) anchored liposome system was developed as the carrier for antitumor drug, docetaxel (DTX). The physicochemical and pharmacokinetic properties of NOSC-modified DTX liposomes (NDLs) were evaluated compared with the conventional DTX liposomes (DLs) and commercial dosage form of DTX, Taxotere(®). The results showed that NDLs had DTX-loading rate of 3.41%, entrapment efficiency of 61.73%, narrow distributed particle size of 147.6±1.9nm, and high zata potential of -44.2±3.9mV. The decreased permeability of the liposome bilayer was evaluated by release behavior of calcein (CAL) from the internal phase of NOSC-modified CAL liposomes (NCLs) and enhanced stability of NDLs owed to shielding effect of sulfonic shell from adsorption by BSA. After i.v. administration at the dose of 12mg/kg, a significant increase in the AUC, MRT, and T(1/2β) (P<0.05) was observed in NDLs group compared with DLs and Taxotere(®) group. AUC(0-∞) of NDLs was 6.14 and 1.55 times higher than Taxotere(®) and DLs, respectively, and MRT(0-∞) of NDLs was 5.77 and 1.37 times higher than Taxotere(®) and DLs, respectively. All these results suggested that anchored liposomes could increase the stability of DTX in vitro and in vivo, as compared with conventional liposomes and Taxotere(®). Therefore, NOSC as a polymeric shell to liposomes was effective to enhance the stability of liposomes containing DTX.

Cell ATP level of Saccharomyces cerevisiae sensitively responds to culture growth and drug-inflicted variations in membrane integrity and PDR pump activity

Cellular ATP level in Saccharomyces cerevisiae was measured during culture growth of strain US50-18C overproducing all major PDR pumps and its isogenic mutants variously deleted in these pumps. It was found to be inversely proportional to the intensity of cell metabolism during different growth phases and to the activity of PDR pumps, which are thus among major ATP consumers in the cells. The ATP level was increased when membrane integrity was affected by 0.5% butanol, and further increased by compound 23.1, a semisynthetic phenol lipid derivative that acts as inhibitor of Pdr5p and Snq2p pumps. The magnitude of increase in cell ATP caused by inhibition of Pdr5p pump by compound 23.1 and the Pdr5p pump inhibitor FK506 used for comparison reflects the activity and hence the energy demand of the pump. The rise in cell ATP caused by different PDR pump inhibitors can be thus used as an indicator of pump activity and the potency of the inhibitor.

Biological activity of phenolic lipids

Phenolic lipids are a very diversified group of compounds derived from mono and dihydroxyphenols, i.e., phenol, catechol, resorcinol, and hydroquinone. Due to their strong amphiphilic character, these compounds can incorporate into erythrocytes and liposomal membranes. In this review, the antioxidant, antigenotoxic, and cytostatic activities of resorcinolic and other phenolic lipids are described. The ability of these compounds to inhibit bacterial, fungal, protozoan and parasite growth seems to depend on their interaction with proteins and/or on their membrane-disturbing properties.

Disturb or stabilize? A molecular dynamics study of the effects of resorcinolic lipids on phospholipid bilayers

Resorcinolic lipids, or resorcinols, are commonly found in plant membranes. They consist of a substituted benzene ring forming the hydrophilic lipid head, attached to an alkyl chain forming the hydrophobic tail. Experimental results show alternative effects of resorcinols on lipid membranes. Depending on whether they are added to lipid solutions before or after the formation of the liposomes, they either stabilize or destabilize these liposomes. Here we use atomistic molecular dynamics simulations to elucidate the molecular nature of this dual effect. Systems composed of either one of three resorcinol homologs, differing in the alkyl tail length, interacting with dimyristoylphosphatidylcholine lipid bilayers were studied. It is shown that resorcinols preincorporated into bilayers induce order within the lipid acyl chains, decrease the hydration of the lipid headgroups, and make the bilayers less permeable to water. In contrast, simulations in which the resorcinols are incorporated from the aqueous solution into a preformed phospholipid bilayer induce local disruption, leading to either transient pore formation or even complete rupture of the membrane. In line with the experimental data, our simulations thus demonstrate that resorcinols can either disturb or stabilize the membrane structure, and offer a detailed view of the underlying molecular mechanism.

Modeling leakage kinetics from multilamellar vesicles for membrane permeability determination: application to glucose

The glucose permeability of bilayers formed from phosphatidylcholine, Brij30, and sodium octadecyl sulfate has been determined via an enzymatic reaction. Glucose is encapsulated in either uni- or multilamellar vesicles (MLV) and its concentration in the dispersion medium is monitored by spectrophotometry analysis through the rate of glucose oxidase-catalyzed reaction of glucose oxidation. A kinetic model of leakage, taking explicitly into account one, two, or n(w)-walls (n(w) >> 1) for the vesicles and assuming an enzymatic Michaelis-Menten behavior, is proposed and used to fit the experimental data. The two-wall model was chosen to fit experimental data obtained on MLV since an average value of 1.7 bilayers was estimated for MLV by cryo-TEM imaging. A permeability value of 5.8 +/- 4.4 10(-9) cm/s was found. The proposed model is validated by the measurement of the bilayer permeability deduced from the modeling of glucose leakage from unilamellar vesicles with the same composition. In this latter case, a value of 8.3 +/- 0.7 10(-9) cm/s is found for the permeability, which is within the error bar of the value found with MLV.

Dietary alkylresorcinols: absorption, bioactivities, and possible use as biomarkers of whole-grain wheat- and rye-rich foods

The biologic and chemical properties of alkylresorcinols (ARs) have been reviewed previously, but there has been relatively little research or focus on the importance of ARs in food and diet. ARs represent a significant proportion of the phytochemicals present in wheat and rye, in which they normally exist in concentrations between 300 and 1500 microg/g. ARs are concentrated in the bran fraction of these cereals, and are therefore a significant component of food products rich in whole grain wheat and rye but not in products containing only refined cereal flour. In this review, we discuss the presence of ARs in food, methods of analysis, their absorption and role in the diet in light of their in vitro bioactivities, and their possible use as biomarkers of whole-grain wheat and rye intake.

Gas chromatographic-mass spectrometric method for the determination of alkylresorcinols in human plasma

Alkylresorcinols can be found in high amounts in whole grain cereals, especially in rye. Previously it has not been possible to measure alkylresorcinols in plasma. In this paper a validated gas chromatographic-mass spectrometric method for the quantitative determination of alkylresorcinols with chain lengths of C15:0, C17:0, C19:0, C21:0, and C23:0 in human plasma samples is presented. Other alkylresorcinols may be measured with the method as well, but their assay was not validated in this work. In this work also the amount of alkylresorcinol C25:0 was measured. The pretreatment of plasma samples consists of a simple incubation, an extraction with diethyl ether and a chromatographic purification before the GC-MS analysis. As internal standard an alkylresorcinol C20:0 was used. The validation of the method showed that it fulfilled the reliability criteria. Calibration graphs were linear over the range of 4.1-660pg per injection. The mean recovery percentage was 112+/-10.8%. Our results show that the alkylresorcinols are found in plasma in the same ratio, as found in rye grains, according to literature. The alkylresorcinols were in the unconjugated form. The total amounts of alkylresorcinols in two plasma samples analyzed here were 333 and 381nmol/L.

Formation of liposomes by resorcinolic lipids, single-chain phenolic amphiphiles from Anacardium occidentale L

Resorcinolic lipids isolated from Anacardium occidentale nut oil extract (CNSL), unsaturated congeners of those isolated from bacterial and graminaceous sources, form at alkaline conditions liposomal structures alone as well as in the mixtures with cholesterol, fatty acids or phosphatidylethanolamine. Those vesicular structures show relatively high entrapment of the marker and stability of their size. The retention of the captured solute depends upon the type of resorcinolic lipid and on the temperature, but in general, is lower than control phospholipid liposomes.