Crystal structures and thermal analyses of alkyl 2-deoxy-α-d-arabino-hexopyranosides

The crystal structures of alkyl 2-deoxy-α-d-arabino-hexopyranosides, with the alkyl chain lengths from C₈ to C₁₈, are established by the single crystal X-ray structural determination. The even-alkyl chain length derivatives crystallized orthorhombic, with space group P2₁2₁2₁, whereas the odd-alkyl chain length derivatives crystallized monoclinic, with space group P2₁. The sugar moieties retained a ⁴C₁ chair conformation and the conformation of the alkyl chains was all-trans. The molecules formed a bilayer structure, in which alkyl chains were interdigitated. The hydrogen bonds, originating from the sugar moieties, were observed in adjacent layers and also within the same layer, resulting in the formation of infinite chains. The alkyl chains arranged parallel to each other and formed planar structures. The thermal properties of the alkyl 2-deoxy glucosides were analyzed further. It was observed that none of the derivatives exhibited mesomorphism. This study establishes that the absence of the hydroxyl group at C-2 of the sugar moiety results in a non-mesogenic nature of the alkyl 2-deoxy-α-d-glycosides, as opposed to the profound mesogenic nature of the normal alkyl glycosides.     

Biological activity of new N-oxides of tertiary amines

Potential biological properties of newly synthesized single and double alkyl chain N-oxides of tertiary amines (NTA) were studied. Individual compounds in each of the series had alkyl chains of different length. Various experiments were performed to determine a mechanism of the interaction between NTA and model and biological membranes. These were measurements of hemolytic efficiencies of NTA (pig erythrocytes), their influence on the transition temperatures (DPPC liposomes), on potassium leakage from cucumber, its growth and chlorophyll content (Cucumis sativus cv. Krak F1), and on the resting membrane potential in alga cells (Nitellopsis obtusa). Also, prevention of erythrocyte membrane lipid oxidation induced by UV irradiation was studied. Potential antioxidative properties of NTA were additionally tested in radical chromogen (ABTS) experiments in which antioxidative efficiencies of NTA were compared to that of the standard antioxidant Trolox. It was found that NTA readily interacted with erythrocyte membranes. Their hemolyzing efficiency increased with the alkyl chain length. Slightly more intensive interaction was found for double alkyl chain compounds. Similar results were obtained in DSC experiments, where incorporation of NTA into liposomal membranes shifted the main transition temperatures and caused a broadening of the main transition peaks depending on the alkyl chain length. Double alkyl chain compounds were also found more efficiently influencing the growth of cucumber. Influence of NTA on the resting membrane potential of algae cells was not quite following the alkyl chain length rule found in erythrocyte and liposome experiments. Also potassium leakage and chlorophyll content determined in physiological experiments were not following the increase of lipophilicity of compounds. Most efficiently influencing those parameters were NTA having shorter alkyl chains, and efficiencies of single alkyl chain compounds were evidently stronger. Both methods used to test the antioxidative properties of NTA showed that they depended on the alkyl chain lengths of compounds within each series, but double alkyl chain ones exhibited markedly greater efficiency.     

The modulation of thermal properties of vinblastine by cholesterol in membrane bilayers

It has been shown that the partitioning of vinblastine in 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) single and multiple bilayer dispersions induces partial interdigitation of the lipid alkyl chains. Similar behavior has been observed for abietic and ursodeoxycholic acids and may well be generalized for the partitioning of bulky amphoteric molecules, which tend to localize in the vicinity of the polar heads. For the present study, differential scanning calorimetry (DSC) has been employed to investigate the role of lipid molecular characteristics such as the alkyl chain length and the polarity of the head-group, as well as the impact of cholesterol upon vinblastine-induced interdigitation. It is found that vinblastine does not induce interdigitation in lipids with either shorter or longer alkyl chains than DPPC, or having head-groups of different polarity. In addition, it is shown that the presence of cholesterol in the lipid bilayer tends to modulate the phase behavior of the lipid/vinblastine bilayer system. Preliminary studies show that such properties directly affect the encapsulation efficiency and the pharmacokinetics of liposomes.     

The modulation of thermal properties of vinblastine by cholesterol in membrane bilayers

It has been shown that the partitioning of vinblastine in 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) single and multiple bilayer dispersions induces partial interdigitation of the lipid alkyl chains. Similar behavior has been observed for abietic and ursodeoxycholic acids and may well be generalized for the partitioning of bulky amphoteric molecules, which tend to localize in the vicinity of the polar heads. For the present study, differential scanning calorimetry (DSC) has been employed to investigate the role of lipid molecular characteristics such as the alkyl chain length and the polarity of the head-group, as well as the impact of cholesterol upon vinblastine-induced interdigitation. It is found that vinblastine does not induce interdigitation in lipids with either shorter or longer alkyl chains than DPPC, or having head-groups of different polarity. In addition, it is shown that the presence of cholesterol in the lipid bilayer tends to modulate the phase behavior of the lipid/vinblastine bilayer system. Preliminary studies show that such properties directly affect the encapsulation efficiency and the pharmacokinetics of liposomes.     

Effect of Hydrocarbon Chain Length in 1,2-Alkanediols on Percutaneous Absorption of Metronidazole: Toward Development of a General Vehicle for Controlled Release

The objective of the present study is to investigate the effect of hydrocarbon chain length in 1,2-alkanediols on percutaneous absorption of metronidazole (MTZ). Twelve formulations (1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol in 4% concentration, 1,2-hexanediol, and 1,2-heptanediol in 1% concentration, in the absence and presence of 1,4-cyclohexanediol, respectively) were studied in an in vitro hairless mouse skin model using Franz diffusion cell. Based on the flux values and retardation ratios (RR), a penetration retardation effect on percutaneous absorption of MTZ was observed for the formulations containing 1,2-diols having six- to seven-carbon chain in the presence of 1,4-cyclohexanediol (1,2-hexanediol with chain length of six hydrocarbons, RRs are 0.69 and 0.76 in the concentration of 4% and 1%, respectively; 1,2-heptanediol with chain length of seven hydrocarbons, RR is 0.78 in the concentration of 1%). On the other hand, no retardation effect was observed in formulations containing short alkyl chains (RRs of 1,2-propanediol, 1,2-butanediol, and 1,2-pentanediol are 0.99, 1.61, and 0.96, respectively). Instead, a penetration enhancement effect was observed for 1,2-diols having four and five carbons. In other words, effect of 1,2-alkanediols on percutaneous absorption of MTZ can be systematically modulated by simply varying number of –CH₂ groups in the hydrocarbon chain—from being a penetration enhancer to retardant. These observations shed light on mechanism of the penetration enhancement and retardation effect and provide insight into rational design of penetration enhancers and retardants. Furthermore, the combination of 1,2-alkanediols and 1,4-cyclohexanediol could become a general vehicle for controlled release of pharmaceutical and cosmetic active ingredients.

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Open in a separate windowᅟKEY WORDS: 1,2-alkanediols; controlled release; hydrocarbon chain length; skin penetration     

Structural requirements of alkyl acyldithiocarbazates for the uncoupling of oxidative phosphorylation in mitochondria

A structure-activity relationship study on the uncoupling of alkyl acyldithiocarbazates was carried out. Greater activity was observed with increasing alkyl chain length, the optimum being C₉. A further increase in alkyl chain length caused a decrease in the activity. Thione-thiol tautomeric forms with a dissociable proton were found to be of primary importance for the uncoupling and the role of the acyl group was auxiliary.The reactivity of the SH group of alkyl acyldithiocarbazates with an SH-reagent was very low. These compounds facilitated the valinomycin-induced swelling of non-respiring mitochondria and non-sonicated lecithin liposomes in isotonic potassium acetate solution.     

Synergistic effects of anacardic acids and methicillin against methicillin resistant Staphylococcus aureus

The synergistic effects of 6-alk(en)ylsalcylic acids, also known as anacardic acids, in combination with methicillin against Staphylococcus aureus ATCC 33591 (MRSA) was investigated. The double bond in C15-anacardic acids is not essential in eliciting the antibacterial activity but is associated with increasing the activity. The synergistic effects decreased with increasing the number of double bonds in the alkyl chain. On the other hand, the antibacterial activity of anacardic acids possessing different alkyl chain lengths against the same MRSA strain was found to be a parabolic function of their lipophilicity and maximized with the alkyl chain length of C10 and C12. Notably, the synergistic effects were noted to increase with increasing the alkyl chain length.     

Study of interaction of long-chain n-alcohols with fluid DOPC bilayers by a lateral pressure sensitive fluorescence probe

The excimer 1,2-dipyrenedecanoyl-sn-glycero-3-phosphatidylcholine (dipy10PC) fluorescence probe was used to determine effects of aliphatic alcohols (CnH2n+1OH, n = 12-18 is the even number of carbons in alkyl chain) on fluid dioleoylphosphatidylcholine (DOPC) +dioleoylphosphatidylserine (DOPS) bilayers in multilamellar vesicles at molar ratio DOPC/DOPS = 24.7. The excimer to monomer fluorescence intensity ratio increases with the increase of CnH2n+1OH/DOPC molar ratio and decreases with the CnH2n+1OH alkyl chain length n at a constant CnH2n+1OH/DOPC = 0.4 molar ratio. These effects indicate changes in the bilayer lateral pressure on the level of pyrenyl moieties location.     

Effects of alkyl chain length of gallate on self-association and membrane binding

Alkyl gallates are anticipated for their use as anti-bacterial and anti-viral agents. Although their pharmacological activities depend on their alkyl chain length, no mechanism has yet been clarified. As described herein, we investigated the membrane binding properties of a series of alkyl gallates using fluorescence measurement to elucidate their different pharmacological activities. Membrane binding of the alkyl gallates increased concomitantly with increasing alkyl chain length, except for cetyl gallate and stearyl gallate. Dynamic light scattering revealed that alkyl gallates with a long alkyl chain are prone to self-association in the solution. Membrane binding abilities of the alkyl gallates are correlated with anti-bacterial and anti-virus activities, as described in previous reports. The partition constants of the alkyl gallates to lipid membranes depend on the membrane components and the membrane phase. Self-association and lipid binding of the alkyl gallates might be primary biophysical factors associated with their pharmacological activities.     

The effects of a series of capsaicin analogues on nociception and body temperature in the rat

A series of capsaicin analogues have been synthesized in an attempt to try to separate the antinociceptive properties of capsaicin from its hypothermic effects. In capsaicin analogues with an unbranched alkyl side-chain of varying length, maximum antinociceptive and hypothermic activity was achieved with a chain length of 8–9 C atoms. Decreasing the chain length decreased both parameters equally. Substitution in the aromatic ring abolished activity. Several compounds related to homovanilloyl dodecylamide, an analogue of capsaicin in which the acylamide linkage is reversed, produced some antinociceptive activity without concomitant hypothermia, but the maximum antinociceptive effect achieved was very small. In the present series of capsaicin analogues good antinociception without hypothermia was not found.     

Effects of pentanol isomers on the phase behavior of phospholipid bilayer membranes

Differential scanning calorimetry (DSC) was used to analyze the thermotropic phase behavior of dipalmitoylphosphatidylcholine (DPPC) bilayers in the presence of pentanol isomers. The concentration of each pentanol isomer needed to induce the interdigitated phase was determined by the appearance of a biphasic effect in the main transition temperatures, the onset of a hysteresis associated with the main transition from the gel-to-liquid crystalline phase, and the disappearance of the pretransition. Lower threshold concentrations were found to correlate with isomers of greater alkyl chain length while branching of the alkyl chain was found to increase biphasic behavior. The addition of a methyl group to butanol systems drastically decreased threshold concentrations. However, as demonstrated in the DPPC/neopentanol system, branching of the alkyl chain away from the -OH group lowers the threshold concentration while maintaining a biphasic effect.     

Antibacterial cellulose fiber via RAFT surface graft polymerization

2-(dimethylamino)ethyl methacrylate (DMAEMA) was polymerized from cellulosic filter paper via reversible addition-fragmentation chain transfer (RAFT) polymerization. The tertiary amino groups of the grafted PDMAEMA chains were subsequently quaternized with alkyl bromides of different chain lengths (C8-C16) to provide a large concentration of quaternary ammonium groups on the cellulose surface. The antibacterial activity of the quaternized and nonquaternized PDMAEMA-grafted cellulosic fibers was tested against Escherichia coli. The antibacterial activity was found to depend on the alkyl chain length and on the degree of quaternization, i.e., the amount of quaternary amino groups present in the cellulose graft copolymers. The PDMAEMA-grafted cellulose fiber with the highest degree of quaternization and quaternized with the shortest alkyl chains was found to exhibit particularly high activity against E. coli.     

Requirements for mammalian carboxylesterase inhibition by substituted ethane-1,2-diones

Carboxylesterases (CE) are ubiquitous enzymes found in both human and animal tissues and are responsible for the metabolism of xenobiotics. This includes numerous natural products, as well as a many clinically used drugs. Hence, the activity of these agents is likely dependent upon the levels and location of CE expression. We have recently identified benzil is a potent inhibitor of mammalian CEs, and in this study, we have assessed the ability of analogues of this compound to inhibit these enzymes. Three different classes of molecules were assayed: one containing different atoms vicinal to the carbonyl carbon atom and the benzene ring [PhXC(O)C(O)XPh, where X=CH?, CHBr, N, S, or O]; a second containing a panel of alkyl 1,2-diones demonstrating increasing alkyl chain length; and a third consisting of a series of 1-phenyl-2-alkyl-1,2-diones. In general, with the former series of molecules, heteroatoms resulted in either loss of inhibitory potency (when X=N), or conversion of the compounds into substrates for the enzymes (when X=S or O). However, the inclusion of a brominated methylene atom resulted in potent CE inhibition. Subsequent analysis with the alkyl diones [RC(O)C(O)R, where R ranged from CH? to C?H??] and 1-phenyl-2-alkyl-1,2-diones [PhC(O)C(O)R where R ranged from CH? to C?H??], demonstrated that the potency of enzyme inhibition directly correlated with the hydrophobicity (clogP) of the molecules. We conclude from these studies that that the inhibitory power of these 1,2-dione derivatives depends primarily upon the hydrophobicity of the R group, but also on the electrophilicity of the carbonyl group.     

Trifluoromethylated carboline compounds targeting DNA: Synthesis,binding and anti-proliferative effects on human cancer cell lines

Three sets of carboline derived compounds were prepared by Pictet-Spengler cyclization. These tetrahydro β- and γ-carbolines have CF₃ group with an additional amino alkyl chains (α- or δ-position) and guanidine alkyl chains (α-position), of varying length. Structure–activity relationship of these molecules with calf thymus DNA was emphasized by fluorescence, ITC, FTIR and viscosity. Binding with DNA resulted in dramatic enhancement and quenching in the fluorescence emission. Gamma-carboline analogs showed maximum DNA binding followed by beta-carboline compounds with amino alkyl chain and least with guanidine alkyl chain compounds. It decreased with increasing chain length. The bindings were entropically driven being more with guanidine alkyl chain analogs. Site preference and mode of binding with partial intercalation and external binding was supported by FTIR and viscosity. Cytotoxic potencies of the compounds were tested on seven different cancer cell lines. The smallest alkyl chain analog attached to gamma position, Comp3, showed maximum cytotoxicity with GI₅₀ 6.2 µM, against HCT-116 causing apoptosis, followed by the guanidine alkyl chain compounds, but amino alkyl chain compounds to beta position showed poor cytotoxicity.These results may be of prospective use in a framework to design novel carboline derivatives as antitumor drugs for improved therapeutic applications in future.     

Improved method for removal of albumin from serum by affinity chromatography

Ges prepared from alkyl succinic anhydride coupled to agarose beads by diaminoalkane spacers have been studied to evaluate the influence of the chain length of both the alkyl succinic anhydride and the spacer on the gel's quantitative capacity and specificity to absorb albumin. The maximum absorptive eapacity for albumin of these gels varied from 13 to 30 mg of albumin/ml of gel and was related to the chain length of the alkyl succinic anhydride and the spacer. Before gel capacities were reached, eluates were albumin free when examined by electroimmunoassay (sensitivity, 1 μg/ml). The gels were not completely specific for albumin. However, pretreatment of the gels with gelatin decreased their nonspecific binding.     

Rosmarinic acid and its esters inhibit membrane cholesterol domain formation through an antioxidant mechanism based,in nonlinear fashion,on alkyl chain length

BackgroundUnder conditions of oxidative stress, cholesterol aggregates into discrete membrane bilayer domains that precipitate the formation of extracellular crystals, a feature of advanced atheroma in cardiovascular disease. Therapeutic interventions using membrane-directed antioxidants, such as polyphenolic esters, may reduce cholesterol domains and crystal formation. In this study, the effects of rosmarinic acid (RC0) and rosmarinic esters, with alkyl chain lengths ranging from 4 to 16?carbons (RC4-RC16), on membrane lipid oxidation and cholesterol domain formation were investigated.MethodsModel membranes were prepared with 1,2-dilinoleoyl-sn-glycero-3-phosphocholine and cholesterol at different cholesterol-to-phospholipid mole ratios (0.3:1, 0.9:1, and 1.2:1), in the absence or presence of each molecule and exposed to 72 h of oxidation. Changes in lipid hydroperoxide (LOOH) and cholesterol domain formation were measured using iodometric and small angle x-ray diffraction approaches, respectively.ResultsRosmarinic acid and its esters had differential effects on LOOH formation based on alkyl chain length. RC8 exhibited the greatest antioxidant effect, reducing LOOH levels by 82%, and inhibited cholesterol domain formation. By contrast, RC0 and RC16 failed to inhibit either LOOH formation or cholesterol domain formation.ConclusionThese data indicate that the membrane antioxidant and cholesterol domain inhibition activities of rosmarinic acid esters are dependent, nonlinearly, on alkyl chain length. The mechanism for this effect is attributed to the influence of alkyl chain length on the optimal depth of the polyphenols into the lipid bilayer for trapping free radicals.General significanceThese findings provide insight into novel atheroprotective benefits of polyphenol esters that are dependent on their membrane location.     

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.     

Role of hydrophobic and polar interactions for BSA-amphiphile composites

To evaluate the role of hydrophobic and electrostatic or other polar interactions for protein–ligand binding, we have studied the interactions of bovine serum albumin (BSA) with 2-alkylmalonic acid and 2-alkylbenzimidazole amphiphiles having different head group and alkyl chain length. The binding affinity for the protein–amphiphile interactions is found to depend predominantly on the length of hydrocarbon chain, suggesting the crucial role of hydrophobic forces, supported by polar interactions at the protein surface. The BSA fluorescence exhibits appreciable hypsochromic shift along with a reduction in fluorescence intensity and mean lifetime upon binding with 2-alkylmalonic acid. UV–visible, steady state and time-resolved fluorescence measurements were performed to compare the effects of amphiphiles on BSA as a function of the amphiphiles head group and alkyl chain length.     

Rat butyrylcholinesterase-catalysed hydrolysis of N-alkyl homologues of benzoylcholine

The purpose of this work was to study the catalytic properties of rat butyrylcholinesterase with benzoylcholine (BzCh) and N-alkyl derivatives of BzCh (BCHn) as substrates. Complex hysteretic behaviour was observed in the approach to steady-state kinetics for each ester. Hysteresis consisted of a long lag phase with damped oscillation. The presence of a long lag phase, with no oscillations, in substrate hydrolysis by rat butyrylcholinesterase was also observed with N-methylindoxyl acetate as substrate. Hysteretic behaviour was explained by the existence of two interconvertible butyrylcholinesterase forms in slow equilibrium, while just one of them is catalytically active. The damped oscillations were explained by the existence of different substrate conformational states and/or aggregates (micelles) in slow equilibrium. Different substrate conformational states were confirmed by 1H-NMR. The K(m) values for substrates decreased as the length of the alkyl chain increased. High affinity of the enzyme for the longest alkyl chain length substrates was explained by multiple hydrophobic interactions of the alkyl chain with amino acid residues lining the active site gorge. Molecular modelling studies supported this interpretation; docking energy decreased as the length of the alkyl chain increased. The long-chain substrates had reduced k(cat) values. Docking studies showed that long-chain substrates were not optimally oriented in the active site for catalysis, thus explaining the slow rate of hydrolysis. The hydrolytic rate of BCH12 and longer alkyl chain esters vs. substrate concentration showed a premature plateau far below V(max). This was due to the loss of substrate availability. The best substrates for rat butyrylcholinesterase were short alkyl homologues, BzCh - BCH4.     

Biosynthesis and utilization of long-chain alcohols in rat brain: aspects of chain length specificity

Chain Length specificity in alkyl glycerolipid biosynthesis was studied with microsomal preparations from 19-day-old rat brain. Saturated alcohols ranging from 12 to 22 carbon atoms were incorporated at different rates into alkyl dihydroxyacetone phosphate, the first intermediate in ether lipid biosynthesis. The rate of alkyl dihydroxyacetone phosphate formation was highest with hexadecanol and alcohols of either longer or shorter chain length were utilized much less efficiently. The monounsaturated octadecenol was incorporated more readily than any of the saturated alcohols. Rat brain microsomes were also found to reduce saturated fatty acids ranging from 12 to 22 carbon atoms, and oleic acid to the corresponding alcohols in the presence of ATP, coenzyme A, Mg²⁺, and NADPH. Chain length selectivity in the reduction was less pronounced than that in alkyl DHAP synthesis. The data indicate that the alkyl and alk-1-enyl composition of rat brain ether lipids is controlled by substrate specificity in the formation of both fatty alcohol and alkyl dihydroxyacetone phosphate.