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 micelle formation process for a typical anionic surfactant. sodium dodecyl sulfate, and a typical cationic surfactant, dodecyltrimethylammonium bromide, has been investigated in a series of mixed solvents consisting of different concentrations of isomeric hexanediols (1,2-hexanediol and 1,6-hexanediol) in water. The critical micelle concentrations and the degrees of counterion dissociation of the mixed micelles were obtained from conductance experiments. Luminescence probing experiments have been used to determine the concentration of micelles in solution and, hence, the micellar aggregation numbers of the surfactants in the mixed solvent systems. The alcohol aggregation numbers were determined by combining the partition coefficients (obtained using NMR paramagnetic relaxation enhancement experiments) with the micellar concentrations from the luminescence probing experiments. All these results are interpreted in terms of the difference in the interaction of the isomeric hexanediols with the surfactant as a function of the position of the hydroxyl groups on the six-carbon chain of the alcohol.

Abstract  Long chain aliphatic 1,2-diols like 1,2-hexanediol and 1,2-octanediol can be converted to the corresponding alpha-hydroxy-alkanoates with total chemoselectivity, in an oxidation catalyzed by an aqueous gold sol under O-2 atmosphere. The sol is stabilized with poly(vinylalcohol), and the reaction is performed in alcohol solvents. Two methods are proposed for the efficient recycling of the colloidal Au catalyst. Firstly a solvent-resistant membrane filtration can be applied. As the membrane material, poly(dimethylsiloxane) is chosen. Secondly, in appropriate conditions, the reaction proceeds in the liquid biphasic mode, and the aqueous Au sol can be recycled by phase separation. Using either of both approaches, the colloidal stability and catalytic activity can be preserved over several recycles.

Abstract  Background: Traditional preservation systems currently used in cosmetic and skin care products are safe and effective. New ingredients with similar efficacy are continually being introduced to fulfill this function. Objective: To study the potential for delayed type IV allergic hypersensitivity and irritation of a new preservative system containing 1,2-hexanediol and caprylyl glycol. Methods: A 200-subject repeat insult patch test (RIPT) was performed. A 15% mixture of 1,2-hexanediol and caprylyl glycol (equal parts of the two ingredients) in carbomer gel was placed under a series of 9 continuous occlusive induction patches, each 48 hours in duration. Three induction patches were applied each week, for a total of 3 weeks. Following a 10-day rest period during which no patches were applied, a single challenge application using the same mixture was applied and left on for 48 hours and read at 48 and 72 hours postapplication. A cosmetic formulation containing this same preservation system at an actual use concentration was tested by the same RIPT protocol. Results: Two hundred and twelve subjects completed the study. One hundred and sixty-eight were female and 44 were male ranging in age from 18 to 70 years. No reactions were seen during the induction or challenge phases. An additional 212 subjects were enrolled in a separate RIPT that evaluated the cosmetic formulation containing the same preservation system. No delayed type IV allergic hypersensitivity or irritation reactions were observed. Conclusion: A new preservative system utilizing 1,2-hexanediol and caprylyl glycol did not induce delayed type IV allergic hypersensitivity or irritation in human subjects.

Abstract  A study has been made of the acetoxylation of 1-hexene and cyclohexene in the presence of PdCl42- and a nitrate-iodate reoxidative system ensuring high yields of the corresponding acetoxyalkanes. It has been established that a binuclear pi-olefinic bridge-type palladium complex is a catalytically active particle. It is assumed that the mechanisms of formation of 1,2-hexanediol monoacetate and diacetoxycyclohexane differ at the final stage of transformation of the acetoxonium ion. Acetoxylation is retarded by the reaction products, which screen the coordination sphere of palladium.

Abstract  Aqueous dilute solutions of 2-butoxyethanol, 1,2-hexanediol, tert-butanol, 1-pentylamine and 1-butylamine are analized through the dynamic light scattering technique. The mutual diffusion coefficient is determined against amphiphile composition, showing, in all cases, clear minima in the dilute region. Using the Stokes-Einstein relation, the mean size of the aggregates is also obtained as a function of mole fraction. For enough concentrated solutions, structures in the range 2-20 angstrom are observed. It is found that both their size and the minimum amphiphile mole fraction for which aggregation is observed are strongly correlated with the hydrophobic character of the amphiphile. (C) 2017 Elsevier B.V. All rights reserved.

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  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  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 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.

Abstract  Optically active alcohol is an important building block as a versatile chiral synthon for the asymmetric synthesis of pharmaceuticals and agrochemicals. We purified and characterized glycerol dehydrogenase from Hansenula ofunaensis and prepared optically active 1,2-octanediol using a recombinant Escherichia coli harboring the glycerol dehydrogenase gene. The deduced amino acid sequence was investigated for identities with those of other alcohol dehydrogenases in the NCBI databank. The identification of the unknown product of a resting-cell reaction was performed by GC-MS. In the deduced amino acid sequence composed of 376 residues, the NAD(H) binding pattern and cysteine residues that correspond to the cysteine ligands at the zinc atom were conserved as they are in alcohol dehydrogenases from other origins. Glycerol dehydrogenase from Hansenula polymorpha DL-1 (Pichia angusta, DDBJ/EMBL/GenBank accession no. BAD32688) had the highest identity to our enzyme, showing 73% identity. Our glycerol dehydrogenase catalyzed the NAD(+)-dependent oxidation of long-chain secondary alcohols such as 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, and 1,2-octanediol. Activities toward 2,4-pentanediol and 2,5-hexanediol were hardly detected. From these results, it was confirmed that our enzyme requires two hydroxyl groups on adjacent carbon atoms for oxidation. 2,3-Pentanedione, 2,3-hexanedione, and 3,4-hexanedione were significantly reduced. The transformants oxidized only (R)-1,2-octanediol in 50 mM racemate (R:S=52:48), and produced (S)-1,2-octanediol (24 mM, <99.9% e.e.) after 24 h of incubation. The reaction product was suggested to be 1-hydroxy-2-octanone by GC-MS, which showed secondary hydroxyl groups oxidized. Glycerol dehydrogenase from H. ofunaensis could be useful for the production of long-chain optically active secondary alcohols.

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 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.