The effect of nonadec(en)ylresorcinol on the fluidity of liposome and erythrocyte membranes

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.

Inhibition of development, swarming differentiation and virulence factors in Proteus mirabilis by an extract of Lithrea molleoides and its active principle (Z,Z)-5-(trideca-4',7'-dienyl)-resorcinol

Antibacterial activity of Lithrea molleoides extract against Proteus mirabilis has been previously reported by our group. In the present study, the compound (Z,Z)-5-(trideca-4',7'-dienyl)-resorcinol (1) was isolated as its responsible active principle. The effects of the compound obtained and of L. molleoides extract on P. mirabilis growth and virulence factors were evaluated. Compound 1 showed MIC and MBC values of 4000 μg/ml. It was found that the extract, at four times the MIC, produced complete killing of the uropathogen at 2h from the beginning of the experiment, while the alkylresorcinol, at four times the MIC, produced the same effect after 24 h. Hemolysis was adversely affected in treatments with both products at 8 μg/ml, while hemagglutination was not altered. The whole extract induced complete autoaggregation of P. mirabilis at 2000 μg/ml, while compound 1 at the same concentration did not show this property. Swarming motility was delayed in treatments with the extract and with 1 at 1000 and 8 μg/ml, respectively, at 8h from the beginning of the assay. Complete inhibition of the phenomenon was still observed after 24 h when compound 1 was added at 125 μg/ml. These findings offer the possibility of new classes of antimicrobial medicines to tackle infections caused by P. mirabilis.

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.

An expedient synthesis of 5-n-alkylresorcinols and novel 5-n-alkylresorcinol haptens

The first synthesis of bioactive long alkyl chain 5-n-alkylresorcinols, present in whole grain products, by a novel modification of the Wittig reaction is described. All the main long chain 5-n-alkylresorcinols present in rye and wheat, including C(23) and C(25) analogues and haptens, which have not been previously prepared, were synthesised. Microwave-promoted reactions of a semi-stabilized ylid and alkanals in water gave good yields in both pressurized and open systems. An alternative microwave-promoted synthesis starting from non-stabilized alkyltriphenylphosphonium salts and 3,5-dimethoxybenzaldehyde worked as well. Aqueous media were suitable for the reactions even if the starting materials were not soluble in water. The 5-n-alkylresorcinols are potential biomarkers of whole grain intake, and the new hapten derivatives of 5-n-alkylresorcinols will open the way for the immunochemical detection techniques of alkylresorcinols.

In vitro antioxidant activity and antigenotoxicity of 5-n-alkylresorcinols

Incubation with 5-n-alkylresorcinols (chain lengths C15:0, C17:0, C19:0, C21:0, and C23:0) increased the self-protection capacity of HT29 human colon cancer cells against DNA damage induced by hydrogen peroxide and genotoxic fecal water samples using comet assay (single-cell gel electrophoresis assay). The alkylresorcinols did not exert potent antioxidant activity in the FRAP (ferric reduction ability of plasma) and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical assays. However they were able to significantly inhibit copper-mediated oxidation of human LDL (low-density lipoprotein) in vitro, and pentadecylresorcinol at 25 micromol/L increased lag time by 65 min. The results show that alkylresorcinols have antigenotoxic and antioxidant activity under in vitro conditions.

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.

Higher cardol homologs (5-alkylresorcinols) in rye seedlings

The occurrence of alkylresorcinols, polyketide compounds that in the same homologous series as cardol isolated from Anacardium occidentale (cashew) or bilobol from Ginkgo biloba which are derivatives of 1,3-dihydroxy-5-alk(en)ylbenzene, have been demonstrated in developing rye (Secale cereale L.) kernels. The 3-day-old seedlings grown in sterile conditions already contain detectable amounts of phenolic compounds that were identified as alkylresorcinols. This fraction is the mixture of saturated and enoic homologs of various lengths of the aliphatic side chain. The composition of homologs is similar to that determined in mature grains. The relatively high level of alkylresorcinols in mitochondria and plastids (enhanced approximately twice in the absence of light) suggests that their synthetic pathway and/or biological function may be related to these cellular compartments. Resorcinolic lipids, when present in the external medium, are taken up by seedlings in the energy-dependent manner.

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

The effect of 5-n-alkylresorcinols, natural amphiphilic compounds, upon properties of phospholipid vesicles depends on their localization asymmetry. A significant increase of the bilayer permeability is observed when the title compounds are present only in the external medium. When these amphiphiles are preincorporated into the bilayer during its formation, the resulting liposomes effectively encapsulate water-soluble solutes which still remain in liposomes after 25 h. Additionally, the size of liposomes made of alkylresorcinol-phosphatidylcholine mixtures after eight cycles of freezing and thawing only (180-200 nm) is severalfold smaller than the size of vesicles prepared in a similar way from phospholipids only and the resulting liposomes are more homogeneous. These liposomes modified with alkylresorcinols are also stable during 40 day storage at both 4 degrees C and 20 degrees C, in contrast to control liposomes that already strongly aggregate after 10 days.

Chemical basis of the resistance of barley seeds to pathogenic fungi

The 5-(n)-alkylresorcinol fraction of the epicuticular waxes of Hordeum vulgare seeds appeared to be responsible for their in-born resistance to pathogenic fungi such as Aspergillus niger and Penicillium crysogenum. The antifungal properties of this fraction were evaluated qualitatively and quantitatively with a novel bioassay where the extreme lipophilicity of these compounds was taken into account. The minimum inhibitory concentration in the fungi tested ranged from 5.6 to 10 micrograms cm-2 for the alkyresorcinols. The behaviour of the different cultivars against these fungi could be predicted by measuring the natural amount of resorcinols of each variety by TLC-scanning densitometry. The ranking of cultivars thus established correlated well with the field behaviour of each cultivar, providing a useful and rapid method for predicting the behaviour against fungi of new varieties being developed.

The effect of annexin IV and VI on the fluidity of phosphatidylserine/phosphatidylcholine bilayers studied with the use of 5-deoxylstearate spin label

An effect of annexin IV and VI on the fluidity of phosphatidylserine/phosphatidylcholine (PS/PC) membranes was studied by spin labeling technique with the use of 5-doxylstearic acid. It was found that calcium ions at micromolar concentrations induced a marked decrease in the order parameter of PS/PC membranes. This effect was completely abolished by both annexins. The influence of annexins on the mobility of fatty acid chains in the studied region in PE/PC membranes was insignificant.

Membrane-structuring properties of bacterial long-chain alkylresorcinols

To investigate the mechanism by which 5-n-alkyl(C19-C25)-resorcinols synthesized by certain bacteria of the Azotobacter genus affect the lipid bilayers of cellular membranes, planar bimolecular membranes were formed from these alkyl-resorcinols and from mixtures of those and typical bacterial phospholipids such as phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol. The electrical properties and, in some instances, the stability of the prepared membranes have been studied. The alkylresorcinols have been found to associate with phospholipids to form oligomeric and polymeric complexes, thereby giving rise to modifications in the bilayer structure and properties. It has been shown that the same compounds suppress the mitochondrial respiration in the presence of NAD-dependent substrates, but they activate it if succinate is used as substrate. This fact is explained in terms of the interaction between the alkylresorcinols and membrane phospholipids.