The influence of alkane chain length on the skin irritation potential of 1,2-alkanediols

A Novel Machine Learning Model and a Web Portal for Predicting the Human Skin Sensitization Effects of Chemical Agents

Skin sensitization is a significant concern for chemical safety assessments. Traditional animal assays often fail to predict human responses accurately, and ethical constraints limit the collection of human data, necessitating a need for reliable in silico models of skin sensitization prediction. This study introduces HuSSPred, an in silico tool based on the Human Predictive Patch Test (HPPT). HuSSPred aims to enhance the reliability of predicting human skin sensitization effects for chemical agents to support their regulatory assessment. We have curated an extensive HPPT database and performed chemical space analysis and grouping. Binary and multiclass QSAR models were developed with Bayesian hyperparameter optimization. Model performance was evaluated via five-fold cross-validation. We performed model validation with reference data from the Defined Approaches for Skin Sensitization (DASS) app. HuSSPred models demonstrated strong predictive performance with CCR ranging from 55 to 88%, sensitivity between 48 and 89%, and specificity between 37 and 92%. The positive predictive value (PPV) ranged from 84 to 97%, versus negative predictive value (NPV) from 22 to 65%, and coverage was between 75 and 93%. Our models exhibited comparable or improved performance compared to existing tools, and the external validation showed the high accuracy and sensitivity of the developed models. HuSSPred provides a reliable, open-access, and ethical alternative to traditional testing for skin sensitization. Its high accuracy and reasonable coverage make it a valuable resource for regulatory assessments, aligning with the 3Rs principles. The publicly accessible HuSSPred web tool offers a user-friendly interface for predicting skin sensitization based on chemical structure.

Acid-Catalyzed Solvolysis of Softwood in Caprylyl Glycol to Produce Lignin Derivatives

Glycol lignin (GL) is produced via the acid-catalyzed solvolysis of softwood meal using glycols such as polyethylene glycol. The physicochemical and thermal properties of GL are expected to be controllable by varying the glycol type. In this study, caprylyl glycol (CG), which is a biobased glycol derived from the caprylic acid component of coconut and palm oils, was used to investigate the effects on the acid-catalyzed solvolysis of softwood. The reactions were performed at 140, 150, and 160 °C for 30-120 min to obtain lignin derivatives (CG-lignin: CGL). The chemical and physical properties of CGLs were investigated. Two-dimensional heteronuclear single-quantum coherence nuclear magnetic resonance analysis suggested that CGL possesses an α-CG-β-O-4 structure as CG is grafted onto the lignin structure. CGLs prepared at higher reaction temperatures exhibited lower molecular weights. The thermomechanical analysis of CGL revealed a glass transition temperature of 89-96 °C and a viscous thermal flow temperature of 134-155 °C.

Synergistic/antagonistic antimicrobial effects of cosmetic ingredients in combination with 1,2-hexanediol

With the rise of the clean beauty trend in the cosmetics and personal care industry, consumers' interest in cosmetic ingredients, especially preservatives, continues to grow. Paraben, previously the most used preservative in cosmetics, has been excluded from many products owing to its potential risks. Therefore, a movement to lower the content of various preservatives is ongoing. One approach to achieve a suitable level of preservation is to use multifunctional ingredients as preservative boosters. In this study, we aimed to confirm the synergistic antimicrobial interactions between various cosmetic ingredients and 1,2-hexanediol, a preservative introduced as a substitute for paraben, using the checkerboard assay. We also measured the antagonistic effect by measuring the fold changes in the minimum inhibitory concentration of 1,2-hexanediol. Niacinamide, a form of vitamin B3, showed synergistic antifungal activity with 1,2-hexanediol, which lowered the content of 1,2-hexanediol in the oil-solubilized toner formulation. Among the substances, 50000 ppm of methyl methacrylate crosspolymer elevated the minimum inhibitory concentration of 1,2-hexanediol against bacteria and fungi by 2‒8 times. Through this study, we suggest applying the synergistic effects of various cosmetic ingredients in the formulation as a method to effectively reduce the content of preservatives.

Solvent-free enzymatic synthesis and evaluation of vanillyl propionate as an effective and biocompatible preservative

Preservatives are chemicals added to protect products against microbial spoilage, and thus are indispensable for pharmaceuticals, cosmetics, and foods. Due to growing concerns about human health and environments in conventional chemical preservatives, many companies have been seeking safe and effective alternatives that can be produced through environment-friendly processes. In this work, in order to develop effective and safe preservatives from plants, we attempt solvent-free lipase-catalyzed transesterification of vanillyl alcohol with ethyl propionate for the first time. The reaction product, vanillyl propionate was efficiently obtained in a high yield. Unlike vanillyl alcohol and ethyl propionate, vanillyl propionate showed antimicrobial activity. The minimal inhibitory concentration test showed that it exhibited high and broad antimicrobial activity against all the tested microorganisms (Gram-negative and Gram-positive bacteria, yeasts, and molds), which was overall comparable to that of propyl paraben, which is one of the most effective preservatives. It was also found to have even higher antioxidant capacity and biocompatibility with human cells than propyl paraben. Vanillyl propionate, which is a plant-based preservative produced through a green bioprocess, is expected to be successfully applied to various industries thanks to its high antimicrobial and antioxidant effect, and high biocompatibility.

A Randomized, Double-Blind, Placebo-Controlled, Multicentric Study to Evaluate the Efficacy and the Tolerability of a Class II Medical Device in the Treatment of Mild and Moderate Acne

INTRODUCTION

Several options are available to treat acne lesions, including topical benzoyl peroxide, topical retinoids, topical antibiotics, oral antibiotics, hormonal therapy, isotretinoin, and procedural therapies, such as light and laser therapies, although these cause side effects. This study aimed to establish the efficacy and tolerability of a class IIa medical device containing lactic acid, azelaic acid/polyglyceryl-3 copolymer, azelamidopropyl dimethyl amine, and bifida ferment lysate for the treatment of mild and moderate acne lesions.

METHODS

A randomized, double-blind, placebo-controlled, multicentric study was carried out in which 60 persons of both genders aged ≥ 16 years affected by mild or moderate acne were enrolled. Each person used the product twice daily for 2 months. The clinical score (classified as absent, mild, moderate, and severe) of lesions such as blackheads, whiteheads, papules and pustules, erythema, desquamation, sebum secretion, and porphyrins production by a wood lamp was evaluated on the basis of a dermatologist's visual assessment at baseline (t0) and after 2 months of treatment (t1), and the results were compared between groups. Digital photographic images were also taken.

RESULTS

Sixty subjects concluded the trial. It was observed that subjects treated with the medical device (group I) showed overall improvement in the analyzed acne lesions compared with placebo (group II) after 2 months of treatment. The efficacy of the treatment was also expressed as partial and total clearance. The medical device produced higher percentages of both partial and total clearance in all analyzed parameters, compared with the placebo group. The study was safe and well tolerated.

CONCLUSIONS

It was observed that the participants showed an overall improvement of the analyzed lesions in comparison with the placebo group, without adverse events during the trial. Hence, the medical device was found to be safe and effective in the treatment of mild or moderate acne.

Impact of Alkanediols on Stratum Corneum Lipids and Triamcinolone Acetonide Skin Penetration

Alkanediols are widely used as multifunctional ingredients in dermal formulations. In addition to their preservative effect, considering their possible impact on drug penetration is also essential for their use. In the present study, the influence of 2-methyl-2,4-pentanediol, 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol on the skin penetration of triamcinolone acetonide from four different semisolid formulations was investigated. Furthermore, confocal Raman spectroscopy measurements were performed to examine the influence of the alkanediols on stratum corneum lipid content and order. Alkanediols were found to increase the penetration of triamcinolone acetonide. However, the extent depends strongly on the formulation used. In certain formulations, 1,2-pentanediol showed the highest effect, while in others the penetration-enhancing effect increased with the alkyl chain length of the alkanediol used. None of the tested alkanediols extracted lipids from the stratum corneum nor reduced its thickness. Notwithstanding the above, the longer-chained alkanediols cause the lipids to be converted to a more disordered state, which favors drug penetration. This behavior could not be detected for the shorter-chained alkanediols. Therefore, their penetration-enhancing effect is supposed to be related to an interaction with the hydrophilic regions of the stratum corneum.

Antibacterial Activity of the Mixed Systems Containing 1,2-Dodecanediol against Staphylococcus aureus and Staphylococcus epidermidis

1,2-Alkanediols are characteristic cosmetic ingredients because these moisturizers exhibit the antibacterial activity against Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). However, the antimicrobial behavior in mixed systems containing several active ingredients is unclear because previous reports focus on an antibacterial system containing only 1,2-alkanediol. In this study, the minimal inhibitory concentration (MIC) and the fractional inhibitory concentration (FIC) were evaluated for 1,2-dodecanediol/lactic acid, 1,2-dodecanediol/myristic acid, 1,2-dodecanediol/methylparaben, and 1,2-dodecanediol/isopropyl methylphenol mixed systems to show the effect of the addition of other antimicrobial components to 1,2-dodecanediol. The antibacterial property of 1,2-dodecanediol/lactic acid mixed system was almost similar compared to 1,2-dodecanediol monomeric system. On the other hand, the antimicrobial activity of 1,2-dodecanediol against S. epidermidis was inhibited in the 1,2-dodecanediol/myristic acid mixed system. Because the selective antimicrobial activity of myristic acid against S. aureus was demonstrated in the mixed system. The present findings are useful for designing formulations of cosmetics and body cleansers containing 1,2-dodecanediol.

Dermatologic reactions to disinfectant use during the COVID-19 pandemic

Infection preventive practice of using disinfectants against SARS-CoV-2 has become the new normal due to the COVID-19 pandemic. Although disinfectants may not be applied directly to the human body, it remains at high risk of exposure including close skin contact on disinfected surfaces or during handling. This dermal contact, on a regular basis, can induce hazardous skin reactions like irritation, inflammation, and burning in severe conditions. Disinfectants are germicide chemicals that can penetrate the skin and create skin reactions that are usually regarded as irritant and allergic contact dermatitis. More importantly, disinfectants can react with skin components (proteins and lipids) to facilitate their skin penetration and disrupt the skin barrier function. Whereas the antimicrobial actions of disinfectants are well understood, much less is known regarding their dermatologic reactions, including but not limited to irritation and hypersensitivity. We reviewed the skin reactions created by those disinfectants against SARS-CoV-2 approved by the European Chemical Agency and the US Environmental Protection Agency.

Hydrophilic and organophilic pervaporation of industrially important α,β and α,ω-diols

The distillation-based purification of α,β and α,ω-diols is energy and resource intensive, as well as time consuming. Pervaporation separation is considered to be a remarkable energy efficient membrane technology for purification of diols. Thus, as a core pervaporation process, hydrophilic polyvinyl alcohol (PVA) membranes for the removal of water from 1,2-hexanediol (1,2-HDO) and organophilic polydimethylsiloxane-polysulfone (PDMS-PSF) membranes for the removal of isopropanol from 1,5 pentanediol (1,5-PDO) were employed. For 1,2-HDO/water separation using a feed having a 1 : 4 weight ratio of 1,2-HDO/water, the membrane prepared using 4 vol% glutaraldehyde (GA4) showed the best performance, yielding a flux of 0.59 kg m-2 h-1 and a separation factor of 175 at 40 °C. In the organophilic pervaporation separation of the 1,5-PDO/IPA feed having a 9 : 1 weight ratio of components, the PDMS membrane prepared with a molar ratio of TEOS alkoxy groups to PDMS hydroxyl groups of 70 yielded a flux of 0.12 kg m-2 h-1 and separation factor of 17 638 at 40 °C. Long term stability analysis found that both hydrophilic (PVA) and organophilic (PDMS) membranes retained excellent pervaporation output over 18 days' continuous exposure to the feed. Both the hydrophilic and organophilic membranes exhibited promising separation performance at elevated operating conditions, showing their great potential for purification of α,β and α,ω-diols.

Investigation of partially myristoylated carboxymethyl chitosan, an amphoteric-amphiphilic chitosan derivative, as a new material for cosmetic and dermal application

Background

Cationic amphiphilic chitosan derivatives can form polymeric micelles, which are useful cosmetic materials, but they form polyion complexes with anionic polymers, which can cause formulation difficulties.

Aims

This study aimed to evaluate the usefulness of partially myristoylated carboxymethyl chitosan, an amphoteric‐amphiphilic chitosan derivative, as a new material for cosmetics in the absence of a surfactant comprising an anionic polymer.

Methods

An anionic polymer and 1,2‐decanediol (an antimicrobial agent)‐containing partially myristoylated carboxymethyl chitosan nanoemulsified lotion and glabridin (an antimelanogenic agent)‐containing partially myristoylated carboxymethyl chitosan polymeric micelle were prepared using a pressure homogenization method. The release of interleukin‐1α, cell viability, and melanogenesis inhibition was evaluated on a human skin model. Antimicrobial activity was evaluated using agar dilution method.

Results

A mixture of partially myristoylated carboxymethyl chitosan and carboxyvinyl polymer did not form a polyion complex, but it formed a hydrophilic gel. The anionic polymer‐containing partially myristoylated carboxymethyl chitosan nanoemulsified formulation was stable, with no decrease in cell viability and horny layer exfoliation, which are typically observed with Tween 60. Compared with the formulation with methyl paraben (0.2%), the formulation to which 1,2‐decanediol (0.05%) was added improved the antibacterial activity against methicillin‐resistant Staphylococcus aureus and Propionibacterium acnes; however, no interleukin‐1α upregulation was observed. The glabridin‐containing partially myristoylated carboxymethyl chitosan polymeric micelles enhanced melanogenesis inhibition and percutaneous glabridin delivery to the epidermis compared with conventional emulsified micelles.

Conclusions

These results suggest that partially myristoylated carboxymethyl chitosan‐forming polymeric micelles, in combination with 1,2‐decanediol and glabridin, may be useful for surfactant‐free cosmetic emulsions.

Investigations on Alkanediols as Alternative Preservatives in a Nonionic Hydrophilic Cream

Alkanediols are often used as alternative antimicrobial preservatives for dermal formulations, e.g., hydrophilic creams. These substances show an antimicrobial effect due to their amphiphilic structure. At the same time, their amphiphilic behavior enables various interactions with the cream base itself. Therefore, the effect of four different alkanediols, namely 1,2-pentanediol, 2-methyl-2,4-pentanediol (hexylene glycol), 1,2-hexanediol, and 1,2-octanediol on the physical stability of a nonionic hydrophilic cream was investigated. Further, the incorporation of the alkanediols into lamellar structures of the cream was evaluated using differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) measurements. The interaction with the mixed crystals of the cream was found to increase with raising alkyl chain length of the added alkanediol. As a result, consistency and stability of the cream are slightly impaired. A test for efficacy of antimicrobial preservation according to the European Pharmacopoeia (Ph.Eur.) revealed that the antimicrobial activity is directly linked to the length of the alkyl chain of the alkanediols. 2-Methyl-2,4-pentanediol differs from both findings. This compound has non-vicinal hydroxy groups which result in a reduced amphiphilicity compared to the others. Consequently, it has a smaller impact on the colloidal structure of the cream and shows a comparatively low antimicrobial activity.

Sensitive Skin Syndrome: An Update

Sensitive skin syndrome is a widely reported complaint but a diagnostic challenge because of its subjective symptoms and lack of clearly visible manifestations. Epidemiological studies have shown the prevalence of sensitive skin to be as high as 60-70% among women and 50-60% among men. Patients with this syndrome usually have unpleasant sensations when exposed to physical, thermal, or chemical stimuli that normally cause no provocation on healthy skin. Recent studies and newly accepted position papers have provided a more in-depth understanding and consensus of its underlying pathophysiology, associations, diagnosis, and treatment. Since no clinical studies have been conducted about specific treatment protocols, patients with this condition should be provided with personalized skin management. Given this updated knowledge, our review offers an approach to sensitive skin syndrome, with differential diagnoses, and interventions targeting its pathophysiology.

Pleiotropic Effects of White Willow Bark and 1,2-Decanediol on Human Adult Keratinocytes

BACKGROUND

Acne vulgaris is a common skin defect, usually occurring during adolescence, but often it can persist in adults leaving permanent face scarring. Acne is usually treated with topical drugs, oral antibiotics, retinoids, and hormonal therapies, but medicinal plants are increasingly employed.

OBJECTIVE

To investigate the protective role of white willow bark (WWB) and 1,2-decanediol (DD) on the damage caused by lipopolysaccharides (LPS) on human adult keratinocytes (HaCaT).

METHODS

HaCaT were exposed to LPS alone or in association with WWB and DD. Epidermal viability, metabolic modulation, inflammatory activity, and cell migration were assessed with both common standardized protocols or high-throughput screening systems.

RESULTS

The preincubation of HaCaT with WWB and DD (used separately or in combination) differently prevented the alterations induced by LPS on HaCaT in terms of growth factor release (IGF, EGF, VEGF), cytokine production (IL-1α, IL-6, IL-8), or expression of the transcription factor FOXO-I. Moreover, they partially restore wound repair lowered by LPS.

CONCLUSIONS

These results suggest that both natural compounds were able to differently affect several functions of LPS-stressed keratinocytes suggesting their potential role for the prevention of acne vulgaris, without adverse effects.

The anti-inflammatory and antioxidant properties of 1,2-decanediol and willow bark extract in lipopolysaccharide-stimulated keratinocytes

BACKGROUND

1,2-Decanediol (S-Mal) is an organic compound belonging to the 1,2-alkanediol family, with two hydroxyl groups located on the first and second carbon of the alkane chain, probably responsible for the enhanced anti-bacterial efficacy. The willow bark total extract (W-Mal) has been used since thousands of years as an herbal remedy for its antipyretic, analgesic, anti-inflammatory and anti-microbial activities. S-Mal is used in cosmetic preparations, whether W-Mal can be topically or systemically administered. Aim of our study was to evaluate in vitro the anti-inflammatory and antioxidant properties of S-Mal and W-Mal, singularly or in combination, in LPS-stimulated keratinocytes.

METHODS

The possible toxic effect of S-Mal and W-Mal was assessed through analysis of cell viability 24 hours after treatment. The anti-inflammatory and antioxidant activities were evaluated by measuring IL-8, TNF-α and IL-1β production as well as cellular antioxidants (GSH and NADPH) consumption, 24 and 48 hours, respectively, after LPS stimulation.

RESULTS

Both substances resulted able to: 1) increase cell viability (P<0.05); 2) decrease the release of inflammatory mediators (IL-8, TNF-α and IL-1β) (P<0.05 - P<0.001); and 3) limit the depletion of cellular antioxidants (GSH and NADPH) (P<0.001).

CONCLUSIONS

S-Mal and W-Mal have shown a potential cytoprotective activity when used together, and good anti-inflammatory and antioxidant effects when used either singularly or in combination. In light of our results, S-Mal and W-Mal could represent effective and safe options in the management of bacterial-induced or aggravated skin conditions.

Margin of safety of pentylene glycol derived using measurements of cutaneous absorption and volatility

The safety assessment of pentylene glycol (PG) has been based on a bioavailability extrapolated from those of other 1,2-glycols or an assumed 100% absorption. To make a better safety assessment and an accurate calculation of the margin of safety (MoS), the skin penetration of PG present in a commercially available sunscreen was measured in pig skin at different exposure durations. The mass balance of PG decreased with increasing exposure durations, from 98% (1 h) to 29% (24 h) and the amount of PG detected in the skin wash decreased over time from 93% to 3%. The decrease in mass balance was attributed to an unexpected volatility of PG, which was confirmed in additional experiments. The maximum bioavailable amount of PG was 123 μg/cm2 after 24 h and was considered to be worst case scenario (10 mg/cm² i.e. 5-fold the recommended application standard dose, 2 mg/cm²). MoS values for the application of a standard dose of sunscreen after 1-24 h exposure were 140-671 in adults and, if calculated for children ratios, 87-217 Based on the available toxicological data for PG in comparison to the amounts determined to be potentially bioavailable, PG in the test sun protection product SPF 50 + does not show any safety concerns for daily usage at the recommended dosage of 2 mg/cm² or lower.

A randomized, investigator-blinded efficacy assessment study of stand-alone emollient use in mild to moderately severe atopic dermatitis flares

BACKGROUND

Whereas emollients are integral to the long-term management of atopic dermatitis (AD), the evidence for their efficacy in disease flares is limited.

OBJECTIVE

We aimed to investigate the stand-alone efficacy of an emollient formulation with regard to improvement of the clinical symptoms, skin barrier function and reduction of pathogenic bacterial colonization in acute stage of AD.

MATERIALS AND METHODS

Twenty AD volunteers aged 12-65 years with symmetric, mild to moderately severe inflammatory lesions on the forearms/arms were recruited for the study. At inclusion, the forearms/arms of each volunteer were randomized to receive for 1 week either an o/w formulation containing licochalcone A (Glycyrrhiza Inflata root extract), decanediol, menthoxypropanediol and ω-6-fatty acids (emollient arm) or 1% hydrocortisone (HC arm); after 1 week, the application of the emollient and HC were discontinued and the volunteers applied a w/o emollient containing licochalcone A and ω-6-fatty acids on both arms for further 3 weeks. The outcomes included reduction of the clinical and itch severity, decrease in S.aureus colonization, improvement of the barrier function, skin hydration and skin tolerability assessed after 1 week (D7) and after 4 weeks (D28) respectively.

RESULTS

In both arms, there was a significant decrease in the severity score, itch intensity, erythema and TEWL on D7 and D28 compared to baseline. In addition, emollient use resulted in pronounced decrease in S.aureus colonization and significant increase of skin hydration on D7. The comparison of the outcomes, based on percentage change from baseline, showed no significant differences between the emollient and HC arm at any time point.

CONCLUSIONS

The results of the study indicate that the 1-week stand-alone application of an emollient, tailored to target inflammation, pruritus, compromised barrier function and pathogenic bacterial colonization may offer benefit for the improvement of mild to moderately severe localized flares of AD.