Abstract  We report the use of the ionic liquid tetrabutylphosphonium bromide as a solvent and catalyst for dehydration of diols to conjugated dienes. This system combines stability, high reaction rates, and easy product separation. A reaction mechanism for the model compound 1,2-hexanediol is proposed and experimentally corroborated. This particular mechanism allows for the selective formation of conjugated dienes, in contrast with purely acidic catalysis. Next, the reaction is also performed on various other diols. As a first application, we assessed the biobased production of 1,3-butadiene. With 1,4-butanediol as the starting material, a 94% yield of butadiene was reached at 100% conversion.

Abstract  Sorbitol can be selectively transformed into liquid alkanes over a bifunctional catalytic system Pt/ZrO2 + TiO2-WOx. In this paper, we investigated the reaction mechanism by carefully analyzing the numerous products issued from sorbitol and by studying the reactivity of some identified intermediates (1-hexanol 2-hexanol, 2-hexanone, 2,5-dimethyltetrahydrofuran, 1,2-hexanediol and 1,2,6-hexanetriol). This led us to propose that C-C cleavage reactions occur on terminal C-C bonds and mainly consist of dehydrogenation-decarbonylation reactions. The limiting steps of the sorbitol transformation are the isosorbide and mono-oxygenated intermediate transformations, especially the hydrogenation of ketones. It is also assessed that diols or triols with n carbon atoms are mainly converted in compounds with n - 1 carbon atoms. Short compounds (1 to 3 carbon atoms) are obtained via a dehydrogenation-retro-aldol reaction pathway and not from isosorbide conversion. (C) 2014 Elsevier Inc. All rights reserved.

Abstract  Parabens are used as antimicrobial preservatives in consumer products. Exposure to methylparaben (MP) has been associated with adverse health outcomes, therefore, an alternative compound, 1,2-hexanediol (1,2-H), has been applied for cosmetics. In the present study, the phototoxicity of MP and 1,2-H, as well as the toxic effect caused by chronic exposure, were investigated using Daphnia magna. The 48 h acute toxicity tests with D. magna were conducted under indoor or ultraviolet (UV) light irradiation conditions, i.e., exposure to 4 h/d sunlight. Changes in the transcription of genes related to oxidative stress were determined in D. magna juveniles, to investigate the underlying mechanism of phototoxicity. The 21 d chronic toxicity tests of MP and 1,2-H were performed under indoor light irradiation. Exposure to MP under environmental level of UV light was more detrimental to D. magna. Transcripts of catalase and glutathione-S-transferase genes in D. magna was significantly increased by co-exposure to MP and UV light. After 21 d of chronic exposure to MP and 1,2-H, the reproduction no-observed effect concentrations for D. magna were 1 and >10 mg/L, respectively. The present study showed that exposure to UV could magnify the toxicity of MP on daphnids. Although acute and chronic toxicities of 1,2-H were generally lower than those of MP, its effects on other aquatic organisms should not be ignored. Further studies are needed to identify other mechanisms of MP phototoxicity.

Abstract  Caprylyl glycol and related 1,2-glycols are used mostly as skin and hair conditioning agents and viscosity agents in cosmetic products, and caprylyl glycol and pentylene glycol also function as cosmetic preservatives. The Cosmetic Ingredient Review (CIR) Expert Panel noted that, while these ingredients are dermally absorbed, modeling data predicted decreased skin penetration of longer chain 1,2-glycols. Because the negative oral toxicity data on shorter chain 1,2-glycols and genotoxicity data support the safety of the 1,2-glycols reviewed in this safety assessment, the Panel concluded that these ingredients are safe in the present practices of use and concentration described in this safety assessment.

Abstract  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.

Abstract  The ruthenium aqua complexes [cp*Ru(OH2)(N-N)](OTf) (cp* = [small eta]5-pentamethylcyclopentadienyl, N-N = 2,2[prime or minute]-bipyridine, phen = 1,10-phenanthroline, OTf- = trifluoromethanesulfonate) and the acetonitrile complex [cpRu(CH3CN)(bipy)](OTf) (cp = [small eta]5-cyclopentadienyl) are water-, acid-, and thermally stable (200 [degree]C) catalysts for the hydrogenation of aldehydes and ketones in sulfolane solution. In the presence of HOTf as a co-catalyst, they effect the deoxygenation of 1,2-hexanediol to 1-hexanol and hexane. Glycerol is deoxygenated to 1-propanol in up to 18% yield and under more forcing conditions completely deoxygenated to propene. The structure of the acetonitrile pro-catalyst [cpRu(CH3CN)(bipy)](OTf) has been determined by X-ray crystallography (space group P[1 with combining macron] (a = 9.3778(10) A; b = 10.7852(10) A; c = 11.1818(13) A; [small alpha] = 101.718(5)[degree]; [small beta] = 114.717(4)[degree]; [gamma] = 102.712(5)[degree]; R = 3.95%).

Abstract  1,2-Hexanediol (1,2-HD) and 1,2,3-octanetriol (1,2,3-OT) are known to self-associate in a manner very similar to that of conventional surfactants to give rise to micellelike aggregates (Hajii, S.; et al. J. Phys. Chem. 1989, 93, 4819). This paper reports on fluorescence probing, with pyrene as a probe, of these aggregates and on a study of the kinetics of monomer exchange between aggregates and bulk phase by means of the ultrasonic relaxation method in the frequency range 0.5-100 MHz. Thus the polarity sensed by pyrene solubilized in the aggregates is lower than for conventional nonionic surfactants of the C(n)E(m) type. The critical micellization concentrations determined by fluorescence probing are in agreement with the reported values. The ultrasonic relaxation amplitude A and frequency f(R) have been found to vary with concentration as expected from the expressions derived for conventional surfactants on the basis of the Aniansson and Wall treatment for the kinetics of surfactant exchange. The full use of these expressions permitted us to obtain the values of the rate constants kappa+ kappa-for the incorporation of a surfactant monomer into, and the dissociation of a monomer from, a micelle, respectively, as well as the standard deviation characterizing the distribution of micelle aggregation numbers (polydispersity) and the volume change upon incorporation. These results are discussed and compared to those obtained for conventional surfactants.

Abstract  A series of ruthenium complexes of the general composition [(eta(6) -arene)(N boolean AND N)Ru(X)] (Y)(n), (arene = p-Me-Pr-i-C6H4, C6Me6; N boolean AND N = bipy, phen, 6,6'-diamino-2,2'-bipyridine, 2,9-diamino-1,10-phenanthroline; X=Cl, H, H2O; Y=Cl, OTf) was synthesized and the new compounds exhaustively structurally characterized by standard techniques (NMR, IR, elemental analysis, single-crystal X-ray crystallography). The single-crystal X-ray structures of [(p-Me-Pr-i-C6H4)Ru(dabipy)Cl][CI] (3CI[CI]), [(p-Me-Pr-i-C6H4)Ru(daphen)CI][CI] (4CI[CI]), [(C6Me6)Ru(dabipy)CI][CI] (7CI[CI]), [(C6Me6)Ru(daphen)CI][CI] (8CI[OTf]), [(p-Me-Pr-i-C6H4)Ru(bipy)(H2O)][OTf](2) (1O[OTf](2)), [(p-Me-Pr-i-C6H4)Ru(dabipy)(H2O)][OTf](2) (3O[OTf](2)), [(p-Me-Pr-i-C6H4)Ru(dabipy)(H2O)][SO4] (3O[SO4]), [(P-Me-(PrC6H4)-Pr-i)-Ru(daphen)(H2O)][OTf](2) (4O[OTf](2)), [(C6Me6)Ru(daphen)(MeOH)][OTf](2) (8(MeOH)[OTf](2)), [(p-Me-Pr-i-C6H4)Ru(dabipy)(H)][OTf] (3H[OTf]), [(p-Me-Pr-i-C6H4)Ru(daphen)(H)][OTf] (4H[OTf]), [(C6Me6)Ru(dabipy-BH2-OTf)(H)] (7H[-NH2-BH2-OTf]) have been determined. Under 750-1100 psi (5-7.5 MPa) of hydrogen pressure at 110 degrees C in the presence of acid and water in sulfolane solvent the aquo complexes form active catalysts for the selective deoxygenation of terminal diols, notably 1,2-hexanediol, to the corresponding primary alcohol, i.e., 1-hexanol in up to 60% yield. The presence of amino functions on the ortho-positions of the chelating ligands results in lower catalyst activity. Under the same reaction conditions the catalysts fail to convert glycerol to GC-detectable products. At the higher temperatures (T> 150 degrees C) possibly required for glycerol activation the catalysts show increasing decomposition with increasing temperature. (C) 2007 Elsevier B.V. All rights reserved.

Abstract  The inhibition effect of the surfactants 1,2-hexanediol (HD), 1,2,3-octanetriol (OT); 1,2,3-nonanetriol (NT); and 3,7-dimethyl-1,2,3,6,7-octanepentol (DOP) on the corrosion of iron in 1 M hydrochloric acid (HCl) was studied, Results obtained from gravimetric methods showed inhibition efficiencies increased with increasing surfactant concentrations and attained a maximum around their critical micellar concentration (cmc). A comparative study of corrosion inhibition of surfactants indicated DOP was the best inhibitor, Polarization measurements showed DOP was a cathodic type-inhibitor and acted on the cathodic reaction without modifying the mechanism of the hydrogen evolution reaction. DOP appeared to function through a general adsorption mode following the Langmuir adsorption isotherm The effect of temperature on the corrosion behavior of iron in both 1 M HCl and 1 M HCl with addition of various concentrations of DOP was studied in the temperature range from 18 degrees C to 48 degrees C, The associated activation corrosion and free adsorption energies were determined.

Abstract  BACKGROUND/AIMS: The research on the treatment of "dry skin syndrome" is hampered by the lack of a suitable animal model. Formerly, we developed a validated guinea pig in vivo model in which the dry skin syndrome persists at least for 1 week. We can, therefore, compare the pharmacological effectiveness of known and potential moisturizers for the treatment of dry skin syndrome. Our aim is to study whether the moisturizing efficiency of humectants depends on the solvents in which they are dissolved.

METHODS: "Dry skin syndrome" was induced on the shaved skin on one side of guinea pigs by daily application of 2% sodium lauryl sulphate in deionized water (SLS) for 3 days. The other shaved side was used as control. After ascertaining skin dryness, that side was treated for 6 days with glycerol or 1,2-hexanediol in different solvents: water, or medium chain triglycerides (MCT) or mixtures of MCT with isopropyl alcohol in different proportions. Measurement of the in vivo moisturizing effect was carried out by a Comeometer CM 825; erythema was measured by a Mexameter MX 16.

RESULTS: Treatments with glycerol (1M) in water reversed the skin dryness shown by both instruments. When dissolving glycerol in MCT, no moisturizing effect was found, probably because glycerol does not dissolve in the oil. No moisturizing effect was found with different combinations of glycerol in the mixtures of MCT and isopropyl alcohol. No moisturizing effect was found using another polyol moisturizer: 1,2 hexanediol (1M) dissolved in MCT oil. Glycerol or 1,2-hexanediol abolished the erythema only when they were dissolved in water alone.

CONCLUSION: Polyol moisturizers such as glycerol or 1,2-hexanediol do not act in the presence of oils against the sodium lauryl sulphate-induced dry skin in our guinea pig model. Since in an oil-in-water (O/W) emulsion, the water evaporates within several minutes, one has to question the ability of moisturizing emulsions to treat dry skin. In such instances, one cannot draw conclusions about the moisturizing efficiency of the preparation merely from the presence of the humectant. One has to study the effect of the finished preparation.

Abstract  A series of novel pentacoordinated germanium(IV) complexes (I) has been prepared by the reaction of germanium dioxide with diols, such as 1,2-propanediol, 1,2-butanediol, 2,3-dimethyl-2,3-butanediol ,1-phenyl-1,2-ethanediol, 1,2-hexanediol, 3,3-dimethyl-1,2-butanediol in an aqueous sodium hydroxide medium. The general molecular formula can be represented as NaGe(OH)L2 where L is the deprotonated diol The reaction of germanium dioxide with catechol in distilled water gives Ge(C6H4O2)2.2H2O (II). Further treatment of this complex (II) with methanol, ethanol or 2-propanol gives hexacoordinated germanium (IV) complexes (III), Ge(C6H4O2)2.2ROH (where R = CH3, C2H5, (CH3)2CH, respectively). These complexes, which have been characterized by elemental analyses, thermogravimetric analyses, infrared, H-1 and C-13 NMR spectral studies, reveal that the pentacoordinated germanium(IV) complexes (I) have a slightly distorted trigonal-bipyramidal geometry. However, the suitable structure of the hexacoordinated complexes (II-III) are octahedral.

Abstract  Strontium phenylphosphonate intercalates with 1,2-diols (from 1,2-ethanediol to 1,2-hexanediol) were synthesized and characterized by X-ray diffraction, thermogravimetry, chemical analysis, and molecular simulation methods. Prepared samples exhibit a very good stability at ambient conditions. Structural arrangement calculated by simulation methods suggested formation of cavities surrounded by six benzene rings. Each cavity contained one molecule of diol and one molecule of water for the 1,2-ethanediol to 1,2-butanediol intercalates. In the case of 1,2-pentanediol two types of cavities alternated: one with diol molecules and another one with two water molecules. In the 1,2-hexanediol intercalate the benzene rings created two types of cavities containing one or two diol molecules, respectively, and this conformational variability led to a more disordered arrangement with respect to the models with shorter alkyl chains. Coordination of the oxygen atoms of the diols to the strontium atoms of the host follows the same pattern for all 1,2-diol intercalates except the 1,2-hexanediol intercalate, where these oxygen atoms can be mutually exchanged at their positions. The calculated basal spacings and structural models are in good agreement with experimental basal spacings obtained from X-ray powder diffraction and with other experimental results.

Abstract  Diols with short aliphatic chains were known to exhibit antimicrobial activities, which were found to depend on the chain length and the position of the hydroxyl groups. We carried out the conformational preferences of 1,n-hexanediols (n = 2-6) and (S)-3-alkoxypropane-1,2-diols in the gas phase and in water using density functional methods and explored the factors important to exhibit antimicrobial activities. In the case of 1,2-, 1,3-, and 1,4-hexanediols, intramolecular H-bonds played a role in stabilizing their preferred conformers in the gas phase, whereas they were remarkably depopulated in water. For 1,5-, and 1,6-hexanediols, no H-bonded conformers were favored both in the gas phase and in water. The C-H center dot center dot center dot O interactions appeared to be of consequence in determining the preferred structures of 1,n-hexanediols (n = 3-6) in water. The stabilization of the preferred conformers of (S)-3-alkoxyprop ane-1,2-diols could be ascribed to the bifurcated H-bonds both in the gas phase and in water. However, their populations were decreased and the -CH2-O-(CH2)(m)-CH3 chain became more extended in water. In the optimized structures of dimers and trimers of 1,2-hexanediol and (S)-3-(hexyloxy)propane-1,2-diol in water, the head OH groups are oriented to each other to form intermolecular H-bonds and the aliphatic tails are stretched out away from the head groups, which are likely to form micelle-like structures in water. When two hydroxyl groups become closer and the aliphatic chain becomes longer, the amphipathicity of alkanediol is increased and thus, it is likely to penetrate more easily into membrane bilayers of the microbial cell and may disrupt the membrane structure. (C) 2015 Elsevier B.V. All rights reserved.

Abstract  The ceria-supported rhenium catalyst modified with palladium (ReOx-Pd/CeO2 (Re = 2 wt %, Pd/Re = 0.25)) is still the best catalyst for simultaneous hydrodeoxygenation. Higher Re loading amount decreased the activity. The simultaneous hydrodeoxygenation of cyclic vicinal diols occurs with high cis-stereoselectivity. ReOx-Pd/CeO2 catalysts were characterized by means of XRD, TEM, H-2-TPR, XAFS, XPS, Raman, and DFT calculations. The Re species on ReOx-Pd/CeO2 (Re = 2 wt %, Pd/Re = 0.25) catalyst after reduction and after stoichiometric reaction of 1,2-hexanediol to 1-hexene were Re-IV and Re-VI, and the Re-IV species were converted to Re-VI through the stoichiometric reaction. The Re species on ReOx-Pd/CeO2 are proposed to be randomly located on the CeO2 surface, and probably only monomeric Re species have catalytic activity for simultaneous hydrodeoxygenation. This model can explain the higher activity of Re = 2 wt % catalyst than those of higher Re loading catalysts. The reaction is proposed to proceed by the tetra/hexavalent redox cycle of the Re center in the catalysis followed by hydrogenation.

Abstract  Surface tension of aqueous solutions of 1,2-hexanediol (1,2HD), 1,5-hexanediol (1,5HD), 1,6-hexanediol (1,6HD), and 2,5-hexanediol (2,5HD) was measured as a function of composition using the method of capillary rise at 283.15, 288.15, 293.15, 298.15, 303.15 and 308.15 K with emphasis in the very dilute region.

The experimental data were used according to the model proposed by Connors for liquid solutes. Binding constants were determined for 1,2-hexanediol (1,2HD), 1,5-hexanediol (1,5HD) and 2,5-hexanediol (2,5HD). Infinite dilution activity coefficients were evaluated using the procedure suggested by Gracia-Fadrique and the results are discussed in terms of temperature and the size of the alkyl chain exposed to the solvent.

Pure 1,6-hexanediol (1,6HD) is a solid at the selected temperatures so the models mentioned before were not used with this solute.

The surface tension data, the binding constants and the infinite dilution activity coefficients were correlated with the position of hydroxyl groups in the solute and the results were used to evaluate the effect of hexanediols on the water structure. (c) 2007 Elsevier B.V. All rights reserved.

Abstract  Enantiospecific syntheses of methyl 2,3,4-trideoxy-alpha-D- and -beta-D-glycero-hexopyranoside (10 and 11), methyl-alpha-D- and beta-D-amicetopyranoside (24 and 25), (2S)-1,2-hexanediol (36), (2S)-1,2,6-hexanetriol (37), and some derivatives thereof from D-glucono-1,5-lactone are described.

Abstract  A green synthesis of silver nanoparticles was developed, using a low-toxic system of microemulsion and nano emulsion with castor oil as the oily phase, Brij 96 V and 1,2-hexanediol as the surfactant and co-surfactant respectively. Geranium (P. hortorum) leaf aqueous extract was employed as a reducing agent. The content and concentration of a metallic precursor and geranium leaf extract (GLE) in the systems used makes it possible to obtain different sizes of silver nanoparticles from 25 to 150 nm. The characterization by FTIR and Z potential shows that the biomolecules of the plant extract act as a reducing and capping agent, giving negative charges to the nanoparticle surface. The present study represents a contribution to the green synthesis of silver nano particles that can be extended to other metals.

Abstract  The purpose of this study was to develop tretinoin-loaded phospholipid vesicles, namely conventional liposomes, hexosomes, glycerosomes and ethosomes, and to investigate their efficacy on croton oil induced rosacea. Vesicles were prepared with soy phospholipid, sodium deoxycholate and tretinoin; 1,2-hexanediol, glycerol and ethanol were added to obtain hexosomes, glycerosomes and ethosomes, respectively. The prepared formulations were characterized in terms of size distribution, morphology, zeta potential and entrapment efficiency. All vesicles were spherical in shape with a mean diameter ranging between 60 and 132 nm and a fairly narrow distribution (0.23-0.29), negative zeta potential values (from -19 to -29 mV) and entrapment efficiency between 32 and 63%. Furthermore, vesicles were evaluated for an in vitro model of dermal delivery, and their mode of action was studied by performing confocal laser scanning microscopy (CLSM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analyses. In addition, in vivo skin penetration was also investigated. The results of in vitro and in vivo studies showed that vesicular formulations, especially hexosomes, promoted the drug deposition into the skin stratums and reduced the permeation into the blood. Finally, administration of vesicular tretinoin on croton oil-induced skin resulted in marked attenuation of oedema and inflammatory cells, especially using hexosomes. The proposed approach based on tretinoin vesicular formulations may be of value in the treatment of rosacea.

Abstract  The present study was aimed at the encapsulation of ketoconazole (KCZ) in the novel modified nanovesicles for dermal targeting delivery. To this purpose, innovative modified vesicles were prepared with soy phospholipid and aqueous solutions containing different concentrations of two targeting modifiers, 1,2-hexanediol and 1,4-cyclohexanediol. Conventional liposomes, with soy phospholipid and cholesterol, were used as control. The prepared formulations were characterized in terms of entrapment efficiency, size distribution, morphology, and stability. Dermal KCZ targeting delivery from modified vesicles was investigated in vitro and in vivo through newborn pig and rat skin, respectively. All vesicles showed a mean size ranging from 58 to 147 nm with fairly narrow size distribution and drug entrapment efficiency between 20 and 75 %. Results of in vitro and in vivo studies indicated that modified vesicles provided an improved KCZ targeting delivery into skin layers. Images of the confocal laser scanning microscopy analyses supported the conclusion that modified vesicles could enhance the drug deposition into the skin strata and reduce the drug permeation into the blood, due to a synergic effect of phospholipid and modifiers. Finally, histological evaluation showed that KCZ-loaded modified vesicles caused no irritation to the skin. The results obtained encouraged the use of the KCZ-loaded modified vesicles as the formulation for the potential topical treatment of fungal infections.

Abstract  This article describes the formation of microemulsions by utilising fatty acid methyl esters (FAME) and a surfactant or mixed surfactant system derived from palm oil-based oleochemicals. The effects of 1,2 hexanediol as a conventional non-toxic co-surfactant were investigated by observing the ternary phase behaviour of palm oil-based microemulsions for three types of surfactant systems, i.e., fatty alcohol ethoxylates 7EO (FAE 7); mixed surfactants FAE 7 and fatty alcohol ethoxylates 2EO (FAE 2) in a 75:25 ratio; and mixed surfactants FAE 7, FAE 2 and methyl ester sulphonate (MES) in a 60:20:20 ratio. The microemulsion (mu E) solutions formed were characterised by conductivity, viscosity and droplet-size measurements. The cleaning performance of selected palm oil-based microemulsions as all-purpose spray liquid cleaners for hard surfaces is also reported.

Abstract  Experimental data are presented for liquid-liquid equilibria of mixtures of the room-temperature ionic liquid 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ([C2MIM][NTf2]) with the three alcohols propan-1-ol, butan-1-ol, and pentan-1-ol and for the 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ([C4MIM] [NTf2]) with cyclohexanol and 1,2-hexanediol in the temperature range of 275 K to 345 K at ambient pressure. The synthetic method has been used. Cloud points at a given composition were observed by varying the temperature and using light scattering to detect the phase splitting. In addition, the influence of small amounts of water on the demixing temperatures of binary mixtures of [C2MIM][NTf2] and propan-1-ol, butan-1-ol, and pentan-1-ol was investigated.

Abstract  We present small-angle neutron scattered intensity measurements in heavy water binary solutions of some short-chain glycols (diols and triols) at room temperature. The spectra were analyzed in terms of a model which takes into account the simultaneous presence of spherical aggregates and concentration fluctuations. We found that hydrated micelle-like aggregates are present in some bi- and trivalent alcohols (e.g., 1,2-hexanediol, 1,2,3-octanetriol) and are absent in others (e.g., 2,5-hexanediol, 1,2,3-hexanetriol). Results are discussed in terms of location of the polar hydroxyl groups in the short hydrocarbon chain. The size and aggregation numbers of the found aggregates are compared with those of other short-chain nonionic surfactants.

Abstract  The objective of this study was to investigate the percutaneous absorption of metronidazole (MTZ) in the topical formulations containing a combination of 1,4-cyclohexanediol and 1,2-hexanediol. Six formulations were studied in an in vitro hairless mouse skin model using Franz Diffusion Cell. MTZ was applied at infinite doses (50mg and 100mg of the formulations, which correspond to 375 and 750 μg of MTZ, respectively). Based on the flux values and retardation ratio (RR), a synergistic retardation effect on percutaneous absorption of MTZ was observed for the formulations containing a combination of 1,4-cyclohexanediol and 1,2-hexanediol (RRs are 0.40 for 375 μg dose and 0.69 for 750 μg dose, respectively). Interestingly, retention of MTZ in epidermis and dermis layer showed no significant differences (p>0.05) between the formulations containing the retardant combination and control formulations. In other words, the retardant combination in the formulation decreases MTZ fluxes while maintaining similar level of retention in epidermis and dermis layer when compared to the control formulations. These observations provide insight in formulating superior topical formulations with minimized potential systematic toxicity while maintaining therapeutic efficiency. A mechanistic explanation of the observed synergistic effect is proposed.

Abstract  Several studies have reported that 1,2-alkanediols show increasing anti-microbial activity as their alkane chain length increases. However, there are no reports on the influence of alkane chain length on the skin irritation potential of 1,2-alkanediols. To investigate the influence of alkane chain length on the skin irritation potential of 1,2-alkanediols. The objective and subjective (sensory) skin irritation potentials of five 1,2-alkanediols - 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol and 1,2-decanediol - were evaluated. We also estimated percutaneous absorption by measuring in vitro skin penetration using a Franz diffusion cell system. Like anti-microbial activity, sensory irritation potential increased as alkane chain length increased, most likely due to increasing membrane interference and/or intrinsic toxicity of 1,2-alkanediols. 1,2-Hexanediol showed the lowest objective skin irritation potential, which increased when the alkane chain length decreased or increased. Furthermore, percutaneous absorption negatively correlated with the alkane chain length of 1,2-alkanediols. These results show that a lower skin absorption potential is not indicative of a low skin irritation potential. Our results suggest that the factors and processes involved in skin irritation potential are complex and that skin irritation potential is influenced by intrinsic toxicity and the potential for penetration or integration in the lipid bilayer.