Effects of cinnamene enhancers on transdermal delivery of ligustrazine hydrochloride

A theoretical investigation on the synergetic effect of hydrogen-bonding interactions and thermodynamic property in the 1: 2 (azacyclopentane-2-one: N-methylolacetamide) ternary complex

CONTEXT

Using chemical penetration enhancers to improve the penetration effect is one kind of important strategies in transdermal drug delivery system. Azone is a widely used transdermal absorption enhancer for transdermal drug delivery. To shed light on the permeation-promoting mechanism of azone, we selected ternary systems formed by azacyclopentane-2-one and N-methylolacetamide (1: 2) and explored the synergetic effect of hydrogen-bonding interactions among them and their thermodynamic properties. The findings indicate that the synergetic effects can enhance the ability of azone to change the original conformation of ceramides and even break the original hydrogen bonds, which is more beneficial for azone to destroy the 3D network structure of ceramides. When azone interacts with ceramide, the order of action tends to interact with one molecule of ceramide first and then with another molecule of ceramide.

METHODS

The synergetic effects of hydrogen-bonding interactions in ternary systems were computed at the B3LYP/6-311 +  + G** and MP2(full)/6-311 +  + G** levels. Thermodynamic parameters for two ternary-complex routes were worked out at the B3LYP/aug-cc-pVDZ level. The shift of the electron density occurring simultaneously with trimer formation was analyzed at the MP2(full)/6-311 +  + G** level. The above calculations were carried out using the Gaussian 03 program packages. Atoms in molecules (AIM) method and the AIMPAC program showed the topological charge density at the MP2(full)/6-311 +  + G** level. The synergetic effects of hydrogen-bonding interactions and thermodynamic property in the 1: 2 (azacyclopentane-2-one: N-methylolacetamide) ternary systems were investigated using the B3LYP and MP2(full) methods.

Hexagonal liquid crystalline system containing Cinnamaldehyde for enhancement of skin permeation of Sinomenine hydrochloride

Sinomenine hydrochloride (SH) is usually applied to treat rheumatoid arthritis (RA) with severe side effect due to oral administration. Cinnamaldehyde (CA) as essential oil possesses anti-RA effect and can facilitate transdermal penetration. Hence, this study developed hexagonal liquid crystalline (HII) gels to deliver two components (SH and CA) across the skins. HII gels were prepared and characterized by polarized light microscopy (PLM), small-angle X-ray scattering (SAXS) and rheology. Moreover, in vitro drug release behavior and ex vivo skin permeation were investigated. Finally, Fourier transform infrared spectral analysis (FTIR) and confocal laser scanning microscopy (CLSM) were used to explore the skin penetration mechanism. PLM and SAXS showed that the inner structure of the gels was HII phase. The addition of lipophilic or hydrophilic molecule slowed down one another's release and the release model was dominated by Fickian diffusion (n< 0.43). Furthermore, in vitro permeation studies indicated that appropriate CA could improve the skin permeability of SH. FTIR and CLSM suggested that infiltration occurred due to disruption of the lipid bilayer structure and increased fluidity of the skin. In conclusion, HII gels and CA exhibited a penetration-promoting effect for transdermal applications in SH.

Mechanisms of Penetration Enhancement and Transport Utilizing Skin Keratine Liposomes for the Topical Delivery of Licochalcone A

Keratin liposomes have emerged as a useful topical drug delivery system given theirenhanced ability to penetrate the skin, making them ideal as topical drug vehicles. However, the mechanisms of the drug penetration enhancement of keratin liposomes have not been clearly elucidated. Therefore, licochalcone A(LA)-loaded skin keratin liposomes (LALs) were prepared to investigate their mechanisms of penetration enhancement on the skin and inB16F10 cells. Skin deposition studies, differential scanning calorimetry (DSC), attenuated total reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR), and skin distribution and intracellular distribution studies were carried out to demonstrate the drug enhancement mechanisms of LALs. We found that the optimal application of LALs enhanced drug permeation via alterations in the components, structure, and thermodynamic properties of the stratum corneum (SC), that is, by enhancing the lipid fluidization, altering the skin keratin, and changing the thermodynamic properties of the SC. Moreover, hair follicles were the main penetration pathways for the LA delivery, which occurred in a time-dependent manner. In the B16F10 cells, the skin keratin liposomes effectively delivered LA into the cytoplasm without cytotoxicity. Thus, LAL nanoparticles are promising topical drug delivery systems for pharmaceutical and cosmetic applications.

Synthesis and biological evaluation of novel ligustrazine-chalcone derivatives as potential anti-triple negative breast cancer agents

A series of novel ligustrazine-chalcone hybrids were synthesized and evaluated for their in vitro and in vivo antitumor activities. The results showed that most of these compounds exhibited significant in vitro cytotoxicity against MDA-MB-231, MCF-7, A549 and HepG2 cell lines with IC₅₀ values as low as sub-micromole. Among them, compounds 6c and 6f possessed better comprehensive characteristics for the antiproliferation effects on both MDA-MB-231 (IC₅₀: 6c, 1.60 ± 0.21 μM; 6f, 1.67 ± 1.25 μM) and MCF-7 (IC₅₀: 6c, 1.41 ± 0.23 μM; 6f, 1.54 ± 0.30 μM). They also exhibited the potent colony-formation inhibitory abilities on above two cell lines in both concentration and time dependent manners, as well as the significantly suppression capabilities against the migration of such cell lines in a concentration dependent manner by wound-healing assay. Of note, compound 6c could significantly induce the apoptosis of MDA-MB-231 cells in a concentration dependent manner and inhibited the transformation of the growth cycle of MDA-MB-231 cells and blocked the cell growth cycle in G0/G1 phase. Moreover, the in vivo antiproliferation assay of compound 6c on TNBC model indicated such compound had a remarkable potency against tumor growth with a widely safety window. Further immunohistochemistry analysis illustrated that compound 6c was provided with a potent capacity to significantly reduce the Ki-67 positive rate in a dose dependent manner. All the results suggested that these hybrids presented both in vitro and in vivo proliferation inhibition potency against breast cancer and further development with good therapeutic potential should be of great interest.

Development of curcumin-loaded composite phospholipid ethosomes for enhanced skin permeability and vesicle stability

Ethosomes are widely applied as the carriers for the transdermal delivery of hydrophobic and hydrophilic drugs. Herein, curcumin-loaded ethosomes (CE) with different phospholipid composition were formulated and thoroughly compared. A significant interaction between the unsaturated phosphatidylcholine (PC) and saturated hydrogenated phosphatidylcholine (HPC) was found by molecular simulation and differential scanning calorimetry (DSC), which led to the reduction of PC peroxidation with the presence of HPC. Subsequently, the composite phospholipid ethosomes containing curcumin were prepared for the first time to evaluate their properties in comparison with the conventional ethosomes composed of PC (CE-P) or HPC (CE-H). CE with PC/HPC ratio of 1:1 (CE-P1H1) with the best vesicle stability and flexibility significantly decreased the uptake by HaCaT cells compared to CE-H and free curcumin, indicating reduced skin cell toxicity. Compared with free curcumin, CE-P1H1 had the highest transdermal efficiency (p < 0.001), followed by CE-P (p < 0.05), partly due to the fact that CE-P1H1 could disturb lipid domain of stratum corneum (SC). Moreover, CE-P1H1 was found to promote curcumin for deep penetration of the skin via the hair follicles route. Our study has shown that using composite phospholipid ethosomes as lipid vesicular carriers could enhance transdermal penetration of drugs and increase in the vesicle stability.

Developments in drug delivery of bioactive alkaloids derived from traditional Chinese medicine

The bioactive alkaloids (e.g. vincristine, hydroxycamptothecin, ligustrazine, and so on) from traditional Chinese medicine (TCM) have exerted potent efficacies (e.g. anti-tumor, anti-inflammation, immunosuppression, etc.). However, a series of undesirable physicochemical properties (like low solubility and weak stability) and baneful pharmacokinetic (PK) profiles (e.g. low bioavailability, short half time, rapid clearance, etc.) have severely restricted their applications in clinic. In addition, some side effects (like cumulative toxicities caused by high-frequency administration and their own toxicities) have recently been reported and also confined their clinical uses. Therefore, developments in drug delivery of such alkaloids are of significance in improving their drug-like properties and, thus, treatment efficiencies in clinic. Strategies, including (i) specific delivery via liposomes; (ii) sustained delivery via nanoparticles, gels, and emulsions; and (iii) transdermal delivery via ethosomes, solid lipid nanoparticles, and penetrating enhancers, have been reported to improve the pharmacokinetic and physicochemical characters of problematic TCM alkaloids, decline their adverse effects, and thus, boost their curative efficacies. In this review, the recent reports in this field were comprehensively summarized with the aim of providing an informative reference for relevant readers.

Lipid nanoparticles loading triptolide for transdermal delivery: mechanisms of penetration enhancement and transport properties

Background

In recent years, nanoparticles (NPs) including nanostructured lipid carries (NLC) and solid lipid nanoparticles (SLN) captured an increasing amount of attention in the field of transdermal drug delivery system. However, the mechanisms of penetration enhancement and transdermal transport properties of NPs are not fully understood. Therefore, this work applied different platforms to evaluate the interactions between skin and NPs loading triptolide (TPL, TPL-NLC and TPL-SLN). Besides, NPs labeled with fluorescence probe were tracked after administration to investigate the dynamic penetration process in skin and skin cells. In addition, ELISA assay was applied to verify the in vitro anti-inflammatory effect of TPL-NPs.

Results

Compared with the control group, TPL-NPs could disorder skin structure, increase keratin enthalpy and reduce the SC infrared absorption peak area. Besides, the work found that NPs labeled with fluorescence probe accumulated in hair follicles and distributed throughout the skin after 1 h of administration and were taken into HaCaT cells cytoplasm by transcytosis. Additionally, TPL-NLC could effectively inhibit the expression of IL-4, IL-6, IL-8, IFN-γ, and MCP-1 in HaCaT cells, while TPL-SLN and TPL solution can only inhibit the expression of IL-6.

Conclusions

TPL-NLC and TPL-SLN could penetrate into skin in a time-dependent manner and the penetration is done by changing the structure, thermodynamic properties and components of the SC. Furthermore, the significant anti-inflammatory effect of TPL-NPs indicated that nanoparticles containing NLC and SLN could serve as safe prospective agents for transdermal drug delivery system.

Monocyclic monoterpenes as penetration enhancers of ligustrazine hydrochloride for dermal delivery

The purpose of this study was to explore the enhancing effects and the mechanism of monocyclic monoterpene penetration enhancers (menthol and menthone) on the transdermal absorption of ligustrazine hydrochloride (LH). Franz-type diffusion cells were used to determine percutaneous parameters of LH in vitro and surface changes of porcine skin were studied by a scanning electron microscope (SEM). The effects of promoters on the biophysical natures of stratum corneum (SC) were researched by Fourier transform-infrared (FT-IR). Penetration parameters of menthol (p < 0.01) and menthone groups (p < 0.05) were greater than those of the control; morphological changes of skin monitored by SEM demonstrated that the menthone group had the most disruption and desquamation of SC flakes, which resulted from extracted lipids. FT-IR measurements showed menthone had the greatest changes in peak shift and peak area, which resulted from C-H stretching vibrations of SC lipids. The results suggest that the penetration mechanism might include disturbing and extracting SC lipids and the hydrogen bond connection.

Novel Application of Natural Anisole Compounds as Enhancers for Transdermal Delivery of Ligustrazine

To improve the transdermal delivery of ligustrazine, Foeniculum vulgare food origin anisole compounds were employed as promoters. Transdermal fluxes of ligustrazine were determined by Franz-type diffusion cells. Fourier transform-infrared (FT-IR) spectra were used to detect the biophysical changes of the stratum corneum and to explore the mechanism of permeation enhancement. A scanning electron microscope (SEM) was used to monitor the morphological changes of the skin. Among the three anisoles, anisic acid increased the penetration flux of ligustrazine significantly. The ligustrazine flux with anisic acid (11.9 μg/cm(2)/h) was higher than that any other group (p < 0.05). Spectra observations revealed that these anisole enhancers were able to disturb and extract the stratum corneum lipids. In addition, apparent density was used to describe the desquamation extent of the scutella. Multiple mechanisms are involved in the permeation enhancement of ligustrazine, including disturbing and extracting stratum corneum lipid, forming a competitive hydrogen bond. All data suggested that anisole compounds could be a group of safe and active penetration enhancers for transdermal delivery of ligustrazine.

Discovery and Current Status of Evaluation System of Bioavailability and Related Pharmaceutical Technologies for Traditional Chinese Medicines--Flos Lonicerae Japonicae--Fructus Forsythiae Herb Couples as an Example

Traditional Chinese medicines (TCMs) have attracted extensive interest throughout the world due to their long history of health protection and disease control, and the internalization of TCM preparations or patented drugs has been considered a wind vane in the process of TCM modernization. However, multi-target effects, caused by multiple components in TCMs, hinder not only the construction of the quality evaluation system (bioavailability), but also the application of pharmaceutical technologies, which results in the poor efficacy in clinical practice. This review describes the methods in the literature as well as in our thoughts about how to identify the marker components, establish the evaluation system of bioavailability, and improve the bioavailability in TCM preparations. We expect that the current study will be positive and informative.

Effect of borneol on the transdermal permeation of drugs with differing lipophilicity and molecular organization of stratum corneum lipids

The aim of the present paper was to investigate the promoting activity of borneol on the transdermal permeation of drugs with differing lipophilicity, and probe its alterations in molecular organization of stratum corneum (SC) lipids. The toxicity of borneol was evaluated in epidermal keratinocyte HaCaT and dermal fibroblast CCC-HSF-1 cell cultures and compared to known enhancers, and its irritant profile was also assessed by transepidermal water loss (TEWL) evaluation. The promoting effect of borneol on the transdermal permeation of five model drugs, namely 5-fluorouracil, antipyrine, aspirin, salicylic acid and ibuprofen, which were selected based on their lipophilicity denoted by logp value, were performed using in vitro skin permeation studies. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) was employed to monitor the borneol-induced alteration in molecular organization of SC lipids. The enhancer borneol displayed lower cytotoxicity or irritation in comparison to the well-established and standard enhancer Azone. Borneol could effectively promote the transdermal permeation of five model drugs, and its enhancement ratios were found to be parabolic curve with the logp values of drugs, which exhibited the optimum permeation activity for relatively hydrophilic drugs (an estimated logp value of -0.5 ∼0.5). The molecular mechanism studies suggested that borneol could perturb the structure of SC lipid alkyl chains, and extract part of SC lipids, resulting in the alteration in the skin permeability barrier.

Potential of Essential Oils as Penetration Enhancers for Transdermal Administration of Ibuprofen to Treat Dysmenorrhoea

The present study was conducted to evaluate and compare five essential oils (EOs) as penetration enhancers (PEs) to improve the transdermal drug delivery (TDD) of ibuprofen to treat dysmenorrhoea. The EOs were prepared using the steam distillation method and their chemical compositions were identified by GC-MS. The corresponding cytotoxicities were evaluated in epidermal keartinocyte HaCaT cell lines by an MTT assay. Furthermore, the percutaneous permeation studies were carried out to compare the permeation enhancement effect of EOs. Then the therapeutic efficacy of ibuprofen with EOs was evaluated using dysmenorrheal model mice. The data supports a decreasing trend of skin cell viability in which Clove oil >Angelica oil > Chuanxiong oil > Cyperus oil > Cinnamon oil >> Azone. Chuanxiong oil and Angelica oil had been proved to possess a significant permeation enhancement for TDD of ibuprofen. More importantly, the pain inhibitory intensity of ibuprofen hydrogel was demonstrated to be greater with Chuanxiong oil when compared to ibuprofen without EOs (p < 0.05). The contents of calcium ion and nitric oxide (NO) were also significantly changed after the addition of Chuanxiong oil (p < 0.05). In summary, we suggest that Chuanxiong oil should be viewed as the best PE for TDD of ibuprofen to treat dysmenorrhea.

Effects and mechanism of action of ligustrazine on isoprenaline-induced cardiomyocyte hypertrophy

The aim of the study is to explore the effects and mechanism of the action of ligustrazine on isoprenaline-induced cardiomyocyte hypertrophy. Primary culture of neonatal rat cardiomyocytes was used as the model, and isoprenaline was used to induce cardiomyocyte hypertrophy. Effects of different dosages of ligustrazine polysaccharide on the cardiomyocyte were observed. RT-PCR was used to detect the expression of atrial natriuretic factor (ANP) mRNA, and Western blot analysis was used to detect the CaN protein level in cardiomyocytes. After treating with ligustrazine, the significant increase of MDA content and decrease of SOD activity were inhibited in supernatant. Compared to the control group, ANP mRNA in isoprenaline-treated cardiomyocytes was significantly increased (P < 0.05); compared to the isoprenaline group, ANP mRNA was significantly decreased in all ligustrazine groups (P < 0.01). In all ligustrazine groups, the CaN expression was inhibited in isoprenaline-treated cardiomyocytes in a dose-dependent manner. In conclusion, ligustrazine has protective effects on isoprenaline-induced neonatal rat cardiomyocyte, which may be related to the decrease of CaN expression.

An explanation for the difference in the percutaneous penetration behavior of tamsulosin induced by two different O-acylmenthol derivatives

Using tamsulosin (TAL) as a model drug, the aim of this study was to investigate and compare the percutaneous permeation behavior of two menthol derivatives, 2-isopropyl-5-methylcyclohexyl heptanoate (M-HEP) and 2-isopropyl-5-methylcyclohexyl decanoate (M-DEC). In vitro transdermal permeation study was carried out using porcine skin. The residual amount of enhancers in the skin after permeation experiment was determined by gas chromatographic (GC) method. The penetration depths of fluorescein were visualized by two-photon confocal laser scanning microscopy (2P-LSM) after the skin being treated with different enhancers. Furthermore, changes in the stretching frequency of functional group of ceramide were investigated by using attenuated total reflectance Fourier transform infrared (ATR-FTIR) technique. After M-HEP addition, the cumulative amount of TAL permeated in 8 h (Q8) reached 20.57±0.54 μg/cm2 and the depth of fluorescein was 40 μm; the CH2 of ceramide symmetric stretching frequency was 4 cm−1 blue shifted. However, M-DEC has an opposite effect on TAL permeation compared with that of M-HEP. TAL is a crucial factor affecting permeation procedure, and microenvironment of lipid region determines promotion capability of the enhancers.

Cytotoxicity and enhancement activity of essential oil from Zanthoxylum bungeanum Maxim. as a natural transdermal penetration enhancer

The aim of this present study is to investigate the effect of Zanthoxylum bungeanum oil (essential oil from Z. bungeanum Maxim.) on cytotoxicity and the transdermal permeation of 5-fluorouracil and indomethacin. The cytotoxicity of Z. bungeanum oil on dermal fibroblasts and epidermal keratinocytes was studied using an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The rat skin was employed to determine the percutaneous penetration enhancement effect of Z. bungeanum oil on hydrophilic and lipophilic model drugs, i.e., 5-fluorouracil and indomethacin. The secondary structure changes of the rat stratum corneum (SC) were determined using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and saturated solubilities and SC/vehicle partition coefficients of two model drugs with and without Z. bungeanum oil were also measured to understand its related mechanisms of action. It was found that the half maximal inhibitory concentration (IC50) values of Z. bungeanum oil were significantly lower in HaCaT and CCC-ESF-1 cell lines compared to the well-established and standard penetration enhancer Azone. The Z. bungeanum oil at various concentrations effectively facilitated the percutaneous penetration of two model drugs across the rat skin. In addition, the mechanisms of permeation enhancement by Z. bungeanum oil could be explained with saturated solubility, SC/vehicle partition coefficient, and secondary structure changes of SC.

Development and characterization of colloidal soft nano-carriers for transdermal delivery and bioavailability enhancement of an angiotensin II receptor blocker

The purpose of this study was to develop and characterize a successful colloidal soft nano-carrier viz. microemulsion system, for the transdermal delivery of an angiotensin II receptor blocker: olmesartan medoxomil. Different microemulsion formulations were prepared. The microemulsions were characterized visually, with the polarizing microscope, and by photon correlation spectroscopy. In addition, the pH and conductivity (σ) of the formulations were measured. The type and structure of microemulsions formed were determined using conductivity measurements analysis, Freezing Differential Scanning Calorimetry (FDSC) and Diffusion-Ordered Spectroscopy (DOSY). Alterations in the molecular conformations of porcine skin were determined using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) biophysical assessment. Olmesartan medoxomil delivery from the investigated formulations was assessed across porcine skin ex-vivo using Franz diffusion cells; the drug was analyzed by liquid chromatography mass spectroscopy (LC/MS/MS). A comparative pharmacokinetic study was done on healthy human subjects between the selected microemulsion and the commercial oral tablets. The physico-chemical and spectroscopic methods revealed the presence of water-in-oil and bicontinuous structures. Biophysical assessment demonstrated various stratum corneum (SC) changes. Olmesartan medoxomil was delivered successfully across the skin with flux achieving 3.65μgcm(-2)h(-1). Higher bioavailability compared to commercial oral tablets with a more sustainment behavior was achieved.

The application and limitations of mathematical modelling in the prediction of permeability across mammalian skin and polydimethylsiloxane membranes

OBJECTIVES

Predicting the rate of percutaneous absorption of a drug is an important issue with the increasing use of the skin as a means of moderating and controlling drug delivery. One key feature of this problem domain is that human skin permeability (as K(p)) has been shown to be inherently non-linear when mathematically related to the physicochemical parameters of penetrants. As such, the aims of this study were to apply and evaluate Gaussian process (GP) regression methods to datasets for membranes other than human skin, and to explore how the nature of the dataset may influence its analysis.

METHODS

Permeability data for absorption across rodent and pig skin, and artificial membranes (polydimethylsiloxane, PDMS, i.e. Silastic) membranes was collected from the literature. Two quantitative structure-permeability relationship (QSPR) models were used to compare with the GP models. Further performance metrics were computed in terms of all predictions, and a range of covariance functions were examined: the squared exponential (SE), neural network (NNone) and rational quadratic (QR) covariance functions, along with two simple cases of Matern covariance function (Matern3 and Matern5) where the polynomial order is set to 1 and 2, respectively. As measures of performance, the correlation coefficient (CORR), negative log estimated predictive density (NLL, or negative log loss) and mean squared error (MSE) were employed.

KEY FINDINGS

The results demonstrated that GP models with different covariance functions outperform QSPR models for human, pig and rodent datasets. For the artificial membranes, GPs perform better in one instance, and give similar results in other experiments (where different covariance parameters produce similar results). In some cases, the GP predictions for some of the artificial membrane dataset are poorly correlated, suggesting that the physicochemical parameters employed in this study might not be appropriate for developing models that represent this membrane.

CONCLUSIONS

While the results of this study indicate that permeation across rodent (mouse and rat) and pig skin is, in a statistical sense, similar, and that the artificial membranes are poor replacements of human or animal skin, the overriding issue raised in this study is the nature of the dataset and how it can influence the results, and subsequent interpretation, of any model produced for particular membranes. The size of the datasets, in both absolute and comparative senses, appears to influence model quality. Ideally, to generate viable cross-comparisons the datasets for different mammalian membranes should, wherever possible, exhibit as much commonality as possible.

Uptake of microemulsion components into the stratum corneum and their molecular effects on skin barrier function

This research determined the uptake of individual components of topically applied microemulsions into the stratum corneum (SC) and assessed their molecular effects on skin barrier function. The microemulsions comprised oleic acid, Tween20, Transcutol and water. The effects of selected formulations, and of the individual components, on the conformational order of the SC intercellular lipids, and on SC hydration, were assessed by infrared spectroscopy. Measurements were made as a function of SC depth by progressively tape-stripping the membrane in the normal way. SC uptake of microemulsion components was quantified via extraction and analysis of the collected tape strips. SC hydration increased in proportion to the water content of the microemulsion. Each of the microemulsion components penetrated into the SC, but to different extents. Oleic acid decreased the conformational order of the SC lipids, and induced some phase separation, as revealed by the frequency shifts and peak areas of the absorbances associated with -CH(2) symmetric and asymmetric stretching vibrations. Tween20 extracted some of the SC intercellular lipids. In summary, SC structure was perturbed by all components of the microemulsions, and the degree of the effects detected was proportional to the level of the respective component present in the skin.

Effect of l-menthol on the thermotropic behavior of ceramide 2/cholesterol mixtures as a model for the intercellular lipids in stratum corneum

The major components of the intercellular lipids in the stratum corneum are ceramides (CERs), cholesterol (CHOL) and free fatty acids. To estimate the effects of l-menthol on the intercellular lipids, we elucidated the thermotropic behavior and lateral structure of a CER2/CHOL mixture. This formed a eutectic mixture at molar fraction of CHOL (Xch) = 0.6, as a lamellar structure with a repeat distance of 3.99 nm, and it showed a hexagonal hydrocarbon chain packing conformation at ambient temperature. In thermograms of the CER2/CHOL mixtures, the addition of l-menthol broadened the transition peaks and reduced the enthalpy of transition. The effect of l-menthol on the change in transition temperature of the eutectic mixture at Xch = 0.6 was weaker than for other molar fractions of CHOL. This suggested that the structure of the eutectic mixture was stable to the effects of l-menthol. Furthermore, l-menthol increased the repeat distance of the lamellar structure and inhibited the formation of hexagonal hydrocarbon chain packing. Therefore, l-menthol induced a disturbance of the lateral structure of the eutectic mixture of CER2/CHOL and the phase transition became unclear. These effects of l-menthol could enhance transdermal drug delivery.