Arkadiusz Kozubek

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.

Cereal grain resorcinolic lipids: mono and dienoic homologues are present in rye grains

Abstract Analyses (UV, IR, 1H-NMR, MS) of the main phenolic fractions isolated by sequential separation on normal-phase and by argentation chromatography on silica gel confirmed the presence of monoenoic and dienoic homologues of 1,3-dihydroxy-5-n-alkylbenzene in acetone extracts from rye grains. Conversion of mono and dienoic homologue dimethyl ethers to the cis-diols with osmium tetroxide, transformation of the diol to the acetonide with acetone and subsequent MS analysis of resulting derivatives showed that the breakdown pattern for the monoenoic homologues was consistent with a double bond in all the homologous chain length at the 8-position. For dienes, the results were not so conclusive, although the 8- and 11-positions appear to be the favoured ones. It has been also shown that rye 5-n-ketoalkylresorcinols contain a previously unobserved C17 homologue. All identifications were confirmed by comparison with synthetically obtained C19:0 and C21:0 5-n-alkylresorcinols and a 5-n-(2-keto-heptadecyl)resorcinol. Other minor phenolic components present in the acetone extract were identified as homologous 5-n-(2-hydroxyalkyl)resorcinols.

Antimutagenic activity of alkylresorcinols from cereal grains

Alkylresorcinols, natural amphiphilic compounds commonly found in cereal grains, markedly decreased mutagenic activity of four standard mutagens examined in the Ames test. The effect was the strongest in the case of indirect-acting mutagens, benzo[a]pyrene and 2-aminofluorene. In the case of direct-acting mutagens, daunorubicin and methyl methanesulfonate, the diminution of the mutagenic activity by the alkylresorcinols was smaller but still noticeable. In the Sister Chromatid Exchanges test (SCEs) with cultured in vitro human blood-derived lymphocytes, a significant decrease of SCEs frequency induced by benzo[a]pyrene was observed in the presence of alkylresorcinols. These preliminary results seem to be important in the aspect of possible antimutagenic and anticarcinogenic potency of alkylresorcinols found in cereal grains.

Alkylresorcinols in Selected Polish Rye and Wheat Cereals and Whole-Grain Cereal Products

The alkylresorcinol content and homologue composition in selected Polish rye and wheat cultivars and selected whole-grain cereal products were determined in this study. Cereal grains and whole-grain cereal products were extracted with acetone, whereas bread types were extracted with hot 1-propanol. The average alkylresorcinol content in tested rye (approximately 1100 mg/kg DM) and wheat (approximately 800 mg/kg DM) grains harvested in Poland was within the range previously reported in Swedish and Finnish samples. The total alkylresorcinol content in tested cereal products available on the Polish market varied from very low levels in barley grain-based foods up to 3000 mg/kg DM in wheat bran. The total alkylresorcinol content in 14 bread samples extracted with hot 1-propanol varied from approximately 100 mg/kg DM in whole bread made with honey up to approximately 650 mg/kg DM in whole-rye bread. Calculated ratios of C17:0 to C21:0 homologues, a useful parameter previously used to distinguish between rye and wheat cereals and their derived products, was about 1.2-1.4 in rye products, about 0.2 in wheat products, and varied between 0.2 and 0.6 in cereal-derived products containing a mixture of whole rye and/or wheat. The data set obtained were subsequently compared using cluster and principal component analysis, which allowed the tested cereal products to be classified into two major groups consisting of whole-rye or whole-wheat products, respectively. On the basis of that approach, mixed cereal products containing rye and wheat bran or whole rye and wheat flour were grouped between those two well-defined clusters. Our work not only provides a detailed examination of alkylresorcinols in selected Polish rye and wheat cultivars and selected whole-grain cereal products, but also demonstrates that this type of analysis accompanied by the use of proper statistical algorithms offers an objective way to evaluate the quality of whole-grain rye and/or wheat and their derived products.

Permeability changes of erythrocytes and liposomes by 5-(n-alk(en)yl) resorcinols from rye

5-(n-Alk(en)yl) resorcinols can induce potassium release from liposomes and erythrocytes. The results suggest that 5-(n-pentyl)resorcinol can induce a specific permeability to protons as well as to potassium and other small molecules. The highest permeability changes were found in the presence of 5-(n-pentadecyl)resorcinol and alkenyl resorcinols. Orcin and resorcin were without effect. The size of permeant as investigated by turbidity measurements indicated that Ca2+ and Mg2+ cannot pass through the alkyl resorcinol-modified membrane but can pass through the alkenyl resorcinol-modified membrane. It was observed that alkenyl resorcinol at a concentration of 15 microM induced not only potassium release but also lysis of erythrocytes.

The encapsulation of idarubicin within liposomes using the novel EDTA ion gradient method ensures improved drug retention in vitro and in vivo

The purpose of this study was to design a new stable liposomal formulation for the anticancer drug idarubicin. Idarubicin is a relatively hydrophobic member of the anthracycline family. It exhibits pronounced bilayer interactions leading to rapid in vivo drug release from liposomes. This rapid drug leakage is due to the presence of cholesterol and charged lipids in the liposomal bilayer. Therefore, a novel method of remote drug loading was developed to prevent rapid drug release from PEGylated cholesterol-containing liposomes. This method uses EDTA disodium or diammonium salt as an agent to form low solubility complexes between the drug and EDTA molecules inside the liposomes, thus yielding improved drug retention. The efficiency of idarubicin encapsulation is close to 98% at a drug to lipid molar ratio of 1:5. An in vitro long-term storage experiment confirmed the high stability of the liposomes. The in vivo studies also showed the superiority of the new idarubicin formulation over the recently used remote loading methods. The plasma level of idarubicin was much higher when EDTA liposomes were used. The presented results fully demonstrate the superiority of the proposed method of idarubicin encapsulation over existing methods. The method offers the possibility of encapsulating not only all the anthracyclines, but also other weakly amphiphilic bases within the liposomes.

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.

Inhibitory effect of some natural and semisynthetic phenolic lipids upon acetylcholinesterase activity

The effect of phenolic lipids isolated from rye grains and cashew nut shell liquid (CNSL) from Anacardium occidentale and their semisynthetic derivatives on erythrocyte ghosts acetylcholinesterase activity was studied. It has been shown that all tested compounds decreased the enzymatic activity of acetylcholinesterase. This effect depends on the type of studied compounds. Three of them completely inhibit acetylcholinesterase activity at the micromolar concentration.

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

The effect of alk(en)ylresorcinol homologs (5-(n-nonadecyl)- and 5-(n-nonadecenyl)resorcinol) on the mobility of 5-doxyl- and 12-doxylstearate spin probes incorporated into DMPC, DMPC-cholesterol and erythrocyte membranes was studied. It was found that both homologs affect the properties of hydrophobic environment of the membranes: (1) In DMPC vesicles both homologs induce an increase in the order parameter of 5-doxylstearate at temperatures of Tc and above. (2) At higher concentrations of both homologs a decrease in mobility of the 12-doxylstearate was also observed. (3) In the presence of cholesterol in the liposome membrane the influence of alk(en)ylresorcinols on the mobility of spin probes was much greater, depending on the cholesterol content and the position of the probe in the bilayer. (4) In natural membranes (erythrocyte ghosts) both alkyl- and alkenylresorcinols induced a decrease of mobility in the region of 12-doxylstearate as well as in the region closer to the polar head groups of lipids (5-doxylstearate).

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.