Effects of tail alkyl chain length (n), head group structure and junction (Z) on amphiphilic properties of 1-Z-R-D,L-xylitol compounds (R = CnH2n+1)

Sugar-Based Surfactants: Effects of Structural Features on the Physicochemical Properties of Sugar Esters and Their Comparison to Commercial Octyl Glycosides

Two series of sugar esters with alkyl chain lengths varying from 5 to 12 carbon atoms, and with a head group consisting of glucose or galactose moieties, were synthesized. Equilibrium surface tension isotherms were measured, yielding critical micellar concentration (CMC) surface tensions at CMC (γcmc) and minimum areas at the air-water interface (Amin). In addition, Krafft temperatures (Tks) were measured to characterize the ability of molecules to dissolve in water, which is essential in numerous applications. As a comparison to widely used commercial sugar-based surfactants, those measurements were also carried out for four octyl d-glycosides. Impacts of the linkages between polar and lipophilic moieties, alkyl chain lengths, and the nature of the sugar head group on the measured properties were highlighted. Higher Tk and, thus, lower dissolution ability, were found for methyl 6-O-acyl-d-glucopyranosides. CMC and γcmc decreased with the alkyl chain lengths in both cases, but Amin did not appear to be influenced. Both γcmc and Amin appeared independent of the ester group orientation. Notably, alkyl (methyl α-d-glucopyranosid)uronates were found to result in noticeably lower CMC, possibly due to a closer distance between the carbonyl function and the head group.

Disulfide-incorporated lipid prodrugs of cidofovir: Synthesis, antiviral activity, and release mechanism

The double-stranded DNA (dsDNA) viruses represented by adenovirus and monkeypox virus, have attracted widespread attention due to their high infectivity. In 2022, the global outbreak of mpox (or monkeypox) has led to the declaration of a Public Health Emergency of International Concern. However, to date therapeutics approved for dsDNA virus infections remain limited and there are still no available treatments for some of these diseases. The development of new therapies for treating dsDNA infection is in urgent need. In this study, we designed and synthesized a series of novel disulfide-incorporated lipid conjugates of cidofovir (CDV) as potential candidates against dsDNA viruses including vaccinia virus (VACV) and adenovirus (AdV) 5. The structure-activity relationship analyses revealed that the optimum linker moiety was C₂H₄ and the optimum aliphatic chain length was 18 or 20 atoms. Among the synthesized conjugates, 1c exhibited more potency against VACV (IC₅₀ = 0.0960 μM in Vero cells; IC₅₀ = 0.0790 μM in A549 cells) and AdV5 (IC₅₀ = 0.1572 μM in A549 cells) than brincidofovir (BCV). The transmission electron microscopy (TEM) images revealed that the conjugates could form micelles in phosphate buffer. The stability studies in the GSH environment demonstrated that the formation of micelles in phosphate buffer might protect the disulfide bond from glutathione (GSH) reduction. The dominant means of the synthetic conjugates to liberate the parent drug CDV was by enzymatic hydrolysis. Furthermore, the synthetic conjugates remained sufficiently stable in simulated gastric fluid (SGF), simulated intestinal fluid (SIF), and pooled human plasma, which indicated the possibility for oral administration. These results indicated 1c may be a broad-spectrum antiviral candidate against dsDNA viruses with potential oral administration. Moreover, modification of the aliphatic chain attached to the nucleoside phosphonate group was involved as an efficient prodrug strategy for the development of potent antiviral candidates.

Impact of the chemical structure on amphiphilic properties of sugar-based surfactants: A literature overview

In this review, structure-property trends are systematically analyzed for four amphiphilic properties of sugar-based surfactants: critical micelle concentration (CMC), its associated surface tension (γ_CMC), efficiency (pC₂₀) and Krafft temperature (T_K). First, the impact on amphiphilic properties of the alkyl chain size and the presence of branching and/or unsaturation is investigated. Then, various polar head parameters are explored, such as the degree of polymerization of the sugar unit (mono- or oligosaccharides), the chemical nature of the linker and the sugar configuration. Some systematic comparisons between ethoxylated surfactants and sugar-based surfactants are also carried out. While some structural trends with the impact of alkyl chain length or the polar head size are now well understood, this analysis points out that systematic studies of more specific effects of alkyl chain (e.g. branching, unsaturation, presence of rings, position on the polar head) and polar head (e.g. linker, anomeric configuration, internal stereochemistry, cyclic vs. acyclic sugar residues) were scarcer or not available to date. This work encourages the use of these structural trends in the perspective of developing new bio-based surfactants and their consideration in predictive models. It also highlights the need of further experimental tests to fill remaining gaps notably to explore some specific structural features (such as the introduction of rings in the alkyl chain or the position of the alkyl chain on the polar head) and towards applicative properties (like foaming capacity or wettability).

Catalytic Synthesis of a New Series of Alkyl Uronates and Evaluation of Their Physicochemical Properties

Large quantities (>3 g) of a new series of alkyl uronates were synthesized in two steps from commercial methyl hexopyranosides. Firstly, several tens of grams of free methyl α-d-glucopyranoside were selectively and quantitatively oxidized into corresponding sodium uronate using 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO)-catalyzed oxidation. Hydrophobic chains of different length were then introduced by acid-mediated esterification with fatty alcohols (ethyl to lauryl alcohol) leading to the desired alkyl glucuronates with moderate to good yields (49%–72%). The methodology was successfully applied to methyl α-d-mannopyranoside and methyl β-d-galactopyranoside. Physicochemical properties, such as critical micelle concentration (CMC), equilibrium surface tension at CMC (γ_cmc), solubility, and Krafft temperature were measured, and the effect of structural modifications on surface active properties and micelle formation was discussed.

Micellar aggregation and membrane partitioning of bile salts, fatty acids, sodium dodecyl sulfate, and sugar-conjugated fatty acids: correlation with hemolytic potency and implications for drug delivery

The co-administration of a drug with a penetration enhancer (PE) is one method by which the membrane permeability of a drug can be improved. To facilitate PE design, it is important that the molecular basis of PE toxicity and efficacy be examined, so we investigated the membrane affinity and micellar aggregation of a series of synthetic liposaccharide PEs and correlated these properties with hemolytic potency. The influence of liposaccharide alkyl chain length (nc) on the system was studied, and comparisons were made with conventional PEs such as bile salts, fatty acids, and surfactants. The liposaccharides were each synthesized in eight steps in good overall yield. Their critical micelle concentrations (CMCs) in phosphate-buffered saline ranged from 0.207 to 20.2 mM, and it was found that increasing nc by 2 afforded a 1 order of magnitude decrease in the CMC. Immobilized artificial membrane (IAM) chromatography was used to determine each PE's affinity for biological membranes, and an increase in nc caused a significant increase in the extent of membrane binding. A study of hemolytic activity revealed that liposaccharides with an nc of < or = 12 are the most likely to be biocompatible. The CMC values for all PEs showed a negative correlation with hemolytic potency; however, it was PE monomers, not micelles, that were responsible for the onset of hemolysis. The affinity of all enhancers for the IAM displayed a positive correlation with hemolytic potency, and therefore, IAM chromatography can be used to predict PE hemolytic activity. It was concluded that the biocompatibility of liposaccharides can be modulated by minor alterations in nc.

Relating surfactant properties to activity and solubilization of the human adenosine a3 receptor

The effects of various surfactants on the activity and stability of the human adenosine A3 receptor (A3) were investigated. The receptor was expressed using stably transfected HEK293 cells at a concentration of 44 pmol functional receptor per milligram membrane protein and purified using over 50 different nonionic surfactants. A strong correlation was observed between a surfactant's ability to remove A3 from the membrane and the ability of the surfactant to remove A3 selectively relative to other membrane proteins. The activity of A3 once purified also correlates well with the selectivity of the surfactant used. The effects of varying the surfactant were much stronger than those achieved by including A3 ligands in the purification scheme. Notably, all surfactants that gave high efficiency, selectivity and activity fall within a narrow range of hydrophile-lipophile balance values. This effect may reflect the ability of the surfactant to pack effectively at the hydrophobic transmembrane interface. These findings emphasize the importance of identifying appropriate surfactants for a particular membrane protein, and offer promise for the development of rapid, efficient, and systematic methods to facilitate membrane protein purification.

Direct syntheses of S-alkylthio-d-galactono-, d-mannono-1,4-lactones, S-alkylthio-l-galactitols and d-mannitols displaying amphiphilic and mesophasic properties

Alkylthio-L-galactitols and D-mannitols were obtained in good yields (70-81%) by reduction, with NaBH4, of the corresponding 6-S-alkyl-6-thio-D-hexono-1,4-lactones.

Synthesis and amphiphilic properties of S-alkylthiopentonolactones and their pentitol derivatives

The amphiphilic properties of S-alkylthiopentono-1,4-lactones (D-ribono-, D-arabinono-, D-xylono-) and corresponding pentitol derivatives with the general formula Su-SR (R=CnH2n+1) are studied. It was shown that CMC, surface area, CPP, and pC20 are influenced by the following structural parameters: alkyl chain length, the number of free hydroxyls, cyclic or acyclic Su structure, and alditol configuration.