Determination of 13-cis-Retinoic Acid and Its Metabolites in Plasma by Micellar Electrokinetic Chromatography Using Cyclodextrin-Assisted Sweeping for Sample Preconcentration.

The online preconcentration technique, cyclodextrin-assisted sweeping (CD-sweeping), coupled with micellar electrokinetic chromatography (MEKC) was established to determine 13-cis-retinoic acid (13-cis-RA), all-trans-retinoic acid (all-trans-RA) and 4-oxo-13-cis-retinoic acid (4-oxo-13-cis-RA) in human plasma. A CD-sweeping buffer (45 mM borate (pH 9.2), containing 80 mM sodium dodecyl sulfate (SDS) and 22 mM hydroxypropyl ß-CD (HP-ß-CD) was introduced into the capillary and, then, the sample dissolved in 70 mM borate (pH 9.2): methanol = 9:1 (v/v) was injected into capillary by pressure. The separation voltage was 23 kV. Compared to the conventional cyclodextrin-micellar electrokinetic chromatography (CD-MEKC) method, the new technique achieved 224-257-fold sensitivity enrichment of analytes. The limits of detection of 13-cis-RA, all-trans-RA were 1 ng/mL, whereas that of 4-oxo-13-cis-RA was 25 ng/mL in plasma. The linear ranges of 13-cis-RA, all-trans-RA were between 15 and 1000 ng/mL, whereas that of 4-oxo-13-cis-RA was between 75 and 1500 ng/mL. The coefficient of correlation between the concentration of analytes and peak area ratio of analytes and internal standard (2, 4-dihydroxy-benzophenone) for intra-day (n = 3) and inter-day (n = 5) analyses were both greater than 0.999. The optimized experimental conditions were successfully applied to determine 13-cis-retinoic acid and its metabolites in plasma samples from a patient during the administration of 13-cis-RA for treating acne.

Effect of fermentation time on the content of bioactive compounds with cosmetic and dermatological properties in Kombucha Yerba Mate extracts.

Kombucha is a beverage made by fermenting sugared tea using a symbiotic culture of bacteria belonging to the genus Acetobacter, Gluconobacter, and the yeasts of the genus Saccharomyces along with glucuronic acid, which has health-promoting properties. The paper presents the evaluation of ferments as a potential cosmetic raw material obtained from Yerba Mate after different fermentation times with the addition of Kombucha. Fermented and unfermented extracts were compared in terms of chemical composition and biological activity. The antioxidant potential of obtained ferments was analyzed by evaluating the scavenging of external and intracellular free radicals. Cytotoxicity was determined on keratinocyte and fibroblast cell lines, resulting in significant increase in cell viability for the ferments. The ferments, especially after 14 and 21 days of fermentation showed strong ability to inhibit (about 40% for F21) the activity of lipoxygenase, collagenase and elastase enzymes and long-lasting hydration after their application on the skin. Moreover, active chemical compounds, including phenolic acids, xanthines and flavonoids were identified by HPLC/ESI-MS. The results showed that both the analyzed Yerba Mate extract and the ferments obtained with Kombucha may be valuable ingredients in cosmetic products.

Green Synthesis of Copper Oxide Nanoparticles using Cucumis Sativus (Cucumber) Extracts and their Bio-Physical and Biochemical Characterization for Cosmetic and Dermatologic Applications.

BACKGROUND & OBJECTIVE: Nanoparticles are used in cosmetic and dermatologic products, due to better skin penetration properties. Incorporation of natural products exhibiting medicinal properties in nano-preparations could significantly improve the efficacy of these products and improve the quality of life without the side effects of synthetic formulations. METHODS: We here report the green synthesis of Copper Oxide nanoparticles, using Cucumber extract, and their detailed bio-physical and bio-chemical characterization. RESULTS: These Copper Oxide-Cucumber nanoparticles exhibit significant anti-bacterial and anti-fungal properties, Ultra Violet-radiation protection ability and reactive-oxygen species inhibition properties. Importantly, these nanoparticles do not exhibit significant cellular toxicity and, when incorporated in skin cream, exhibit skin rejuvenating properties. CONCLUSION: Our findings have implications for nanoparticle-based cosmetics and dermatologic applications.

Dermatological applications of the flavonoid phloretin.

Botanical molecules are known to have the ability to counteract ultraviolet radiation-induced skin damage. The interest in the development of natural compound-based products for the prevention of solar ultraviolet radiation-induced skin photoaging, melasma, and photocarcinogenesis has been increasing. Recently, the flavonoid phloretin has attracted the attention of researchers in the dermatological field for application in cosmetics and therapeutics. In addition to its antioxidant activity, phloretin has been shown to have properties such as anti-aging and depigmenting effects. In this study, we review the dermatological treatments with phloretin for conditions such as melasma, photoaging, acne, and melanoma. Phloretin has been shown to inhibit elastase and matrix metalloproteinase-1 activity, to reduce cellular tyrosinase activity and melanin content, and induce apoptosis in B16 mouse melanoma 4A5 cells. An in vivo study showed that phloretin, applied topically to the dorsal skin of mice, suppressed the 12-O-tetradecanoylphorbol 13-acetate-induced expression of COX-2, a critical molecular target of many chemopreventive, as well as anti-inflammatory agents. Phloretin can penetrate the skin; nevertheless, its penetration profile in different skin layers has not yet been evaluated. Despite its health benefits, phloretin application has been limited because of its photoinstability and poor aqueous solubility, among other limitations. Therefore, we reviewed the recent advances in pharmaceutical applications such as the use of nanotechnology, in order to improve the cutaneous availability of phloretin. In this review, we also focus on the oral application, product development challenges, and recent progress and future research directions on phloretin.

Facilitating Longitudinal Exposure-Response Modeling of a Composite Endpoint Using the Joint Modeling of Sparsely and Frequently Collected Subcomponents.

Longitudinal exposure-response modeling plays an important role in optimizing dose and dosing regimens in clinical drug development. Certain clinical trials contain induction and maintenance phases where the maintenance treatment depends on the subjects' achieving the main endpoint outcome in the induction phase. Due to logistic difficulties and cost considerations, the main endpoint is usually collected more sparsely than a subcomponent (or other related endpoints). The sparse collection of the main endpoint hampers its longitudinal modeling. In principle, the frequent collection of a subcomponent allows its longitudinal modeling. However, the model evaluation via the visual predictive check (VPC) in the maintenance phase is difficult due to the requirement of the main-endpoint model to identify the treatment subgroups. This manuscript proposes a solution to this dilemma via the joint modeling of the main endpoint and the subcomponent. The challenges are illustrated by analyzing the data collected up to 60 weeks from a phase III trial of ustekinumab in patients with moderate-to-severe ulcerative colitis (UC). The main endpoint Mayo score, a commonly used composite endpoint to measure the severity of UC, was collected only at baseline, the end of the induction phase, and the end of the maintenance phase. The partial Mayo score, which is a major subset of the Mayo score, was collected at nearly every 4 weeks. A longitudinal joint exposure-response model, developed under a latent-variable Indirect Response modeling framework, described the Mayo score time course and facilitated the VPC model evaluation under a response-adaptive trial design.

A Chemical Switch for Transforming a Purine Agonist for Toll-like Receptor 7 to a Clinically Relevant Antagonist.

Toll-like receptor 7 (TLR7) is an established therapeutic target in myriad autoimmune disorders, but no TLR7 antagonist is available for clinical use to date. Herein, we report a purine scaffold TLR7 antagonist, first-of-its-kind to our knowledge, which was developed by rationally dissecting the structural requirements for TLR7-targeted activity for a purine scaffold. Specifically, we identified a singular chemical switch at C-2 that could make a potent purine scaffold TLR7 agonist to lose agonism and acquire antagonist activity, which could further be potentiated by the introduction of an additional basic center at C-6. We ended up developing a clinically relevant TLR7 antagonist with favorable pharmacokinetics and 70.8% oral bioavailability in mice. Moreover, the TLR7 antagonists depicted excellent selectivity against TLR8. To further validate the in vivo applicability of this novel TLR7 antagonist, we demonstrated its excellent efficacy in preventing TLR7-induced pathology in a preclinical murine model of psoriasis.

Ex vivo (human skin) and in vivo (minipig) permeation of propylene glycol applied as topical crisaborole ointment, 2.

Crisaborole ointment, 2%, is a non-steroidal phosphodiesterase 4 inhibitor for the treatment of mild-to-moderate atopic dermatitis. It contains 9% w/w propylene glycol (PG). Although PG is generally considered to be safe when used as a pharmaceutical excipient or food additive, the European Medicines Agency has recommended maximum daily limits for PG exposure. To determine the potential skin permeation of PG from crisaborole ointment, ex vivo human skin (normal abdominal skin from healthy volunteers without atopic dermatitis) and in vivo minipig experiments (dermal application on unabraded or abraded skin) were performed. Over a 24-h period, the extent of PG permeation in the ex vivo human skin experiment was 3.7% for crisaborole ointment. In the in vivo minipig study, the bioavailability of PG after dermally applied crisaborole ointment was 3.56% for unabraded skin and 3.65% for abraded skin. Experimental values from this study can serve to provide scientific justification for using a product's specific absorption value, as opposed to a maximum absorption of 100%, when attempting to estimate systemic exposure of PG from a topical product.

Incorporation of benzoyl peroxide nanocrystals into adapalene-loaded solid lipid microparticles: Part II - Solid-in-Oil dispersion of nanoparticulate benzoyl peroxide.

Benzoyl peroxide as a monotherapeutic and in combination with adapalene is a cornerstone of current acne therapy, but its unfavourable side effect profile reduces the therapeutic value of this compound. The incorporation into an adapalene-loaded microparticulate lipid matrix, which - via the principle of targeted erosion - allows the targeted release of active substances in the hair follicles, is a promising approach to reduce side effects such as skin redness, increased scaling and allergic reactions. However, there are challenges to the production of such a vehicle which require a galenic solution. That is in particular the redispersion of nanoparticulate benzoyl peroxide in lipids while maintaining its nanodisperse character. In the present work, the lamellar liquid crystalline phase of a binary water/phospholipid system is used to stabilize a nanosuspension during freeze-drying. Both after redispersing in water and after dispersing in nonpolar fat phases, the initial size of the nanosuspension was recovered with only minor deviations. The found cryoprotective effect of purified phospholipid allows the generation of highly concentrated solid-in-oil systems both in fat phases liquid at room temperature and in lipid melts, which after solidification can serve as starting material for the preparation of lipid microparticles loaded with benzoyl peroxide nanocrystals.

Soft drugs for dermatological applications: recent trends.

A soft drug (SD) displays a metabolically labile spot and, after having exerted its activity in the site of action, undergoes a fast metabolism, leading to inactive metabolites. The SD approach has recently found widespread application in the dermatological field because it provides a means of localising the therapeutic effect in skin, while minimising systemic exposure. The literature is rapidly growing of successful examples of compounds targeting sphingosine-1-phosphate receptor 1 (S1PR1), transient receptor potential vanilloid 1 (TRPV1), Janus kinase (JAK), caspase 1, and histone deacetylase (HDAC), for the treatment of skin inflammatory, autoimmune, and oncological diseases. As a demonstration of the potential of this strategy, the SD approach recently led to the approval of crisaborole, a soft phosphodiesterase 4 (PDE4) inhibitor, for atopic dermatitis, while other agents are in clinical development.

Enhanced skin targeting of retinoic acid spanlastics: in vitro characterization and clinical evaluation in acne patients.

Acne vulgaris is the most common dermatological disorder affecting millions of individuals. Acne therapeutic solutions include topical treatment with retinoic acid (RA) which showed a good efficacy in treatment of mild and moderate cases. However, the high prevalence of adverse events, such as skin dryness, shedding and skin irritation affects the patient convenience and obstruct the acne treatment. Thus, the objective of this paper was to produce Span 60 based elastic vesicles enriched with penetration enhancers, and study their influence on the delivery of RA and its skin irritation. RA-loaded nanovesicles, enriched with Transcutol®/Labrasol®, were made using the thin film hydration technique, and assessed for entrapment efficiency, particle size and zeta potential. The optimized RA-loaded nanovesicles (composed of Span 60-Tween 20, and Transcutol®) were morphologically assessed via transmission electron microscopy. Moreover, RA deposition into newborn mice skin was assessed in vitro under non-occlusive conditions, where the optimized RA-loaded nanovesicles showed 2-fold higher RA deposition in the skin compared to the corresponding one lacking Transcutol. The optimized RA-loaded nanovesicles incorporated into 1% carbopol gel was evaluated for in-vivo clinical performance in acne patients, and showed appreciable advantages over the marketed formulation (Acretin®) in the treatment of acne regarding skin tolerability and patient's compliance.

Topical urea in skincare: A review.

Alterations in barrier function are associated with a number of skin diseases, including xerosis, atopic dermatitis, and psoriasis. Urea, a component of the natural moisturizing factor of the skin, plays an important role in the preservation of skin hydration and integrity. Several studies have investigated the effects of urea in the clinical setting. Here, we summarize the available clinical evidence regarding the effects of urea in the maintenance of healthy skin and management of skin disorders. At lower doses (≤10%), urea-containing topical formulations act as a skin moisturizer, while at higher concentrations (>10% urea), urea-based preparations exert a keratolytic action. Urea is also useful in combination therapies with anti-inflammatory and anti-fungal drugs, due to its activity as a penetration enhancer.

In vitro and ex-vivo evaluation of topical formulations designed to minimize transdermal absorption of Vitamin K1.

Topical application of Vitamin K1 has been demonstrated to effectively treat papulopustular skin rash, a serious and frequently encountered side effect of Epidermal Growth Factor Inhibitors (EGFRIs). Systemic absorption of vitamin K1 from skin and the resultant consequence of antagonizing EGFRIs anticancer effects jeopardizes the clinical acceptability of this rather effective treatment. The purpose of the present study was to rationally formulate and evaluate the release rate and transdermal absorption of a wide range of Vitamin K1 dermal preparations with a variety of physiochemical properties. A library of 33 formulations with were compounded and tested for Vitamin K1 permeation using hydrophobic membranes and porcine skin mounted in a Fran diffusion cells. Our results demonstrate the lowest diffusion for water-in-oil emulsions, which also demonstrated a negligible transdermal absorption. The statistical analysis showed a significant correlation between in vitro and ex vivo results. While viscosity did not have a significant impact on the diffusion or absorption of vitamin K1, an increase in the lipid content was correlated with an increase in transmembrane diffusion (not with transdermal absorption). Overall, formulation design significantly impacts the release rate and transdermal absorption of vitamin K1, and confirms the possibility of minimal systemic distribution of this vitamin for this specific purpose.

Delivery of adapalene using a novel topical gel based on tea tree oil nano-emulsion: Permeation, antibacterial and safety assessments.

The aim of present study was to design and optimize 0.1% adapalene loaded nano-emulsion to improve the drug efficacy and increase its user compliance. Effect of type and concentration of surfactants was studied on size of 0.1% adapalene loaded nano-emulsion. Optimized formulation was then evaluated for particle size, polydispersity index, morphology, viscosity, and pH. Subsequently, 1% carbopol® 934 was incorporated to the optimized formulation for preparation of its gel form. The efficacy and safety of 0.1% adapalene loaded nano-emulsion gel was assessed compared to marketed gel containing 0.1% adapalene. In-vitro studies showed that adapalene permeation through the skin was negligible in both adapalene loaded nano-emulsion gel and adapalene marketed gel. Furthermore, drug distribution studies in skin indicated higher retention of adapalene in the dermis in adapalene loaded nano-emulsion gel compared with adapalene marketed gel. Antibacterial activity against Propionibacterium acnes showed that adapalene loaded nano-emulsion is effective in reducing minimum inhibitory concentration of the formulation in comparison with tea tree oil nano-emulsion, and pure tea tree oil. In vivo skin irritation studies showed absence of irritancy for adapalene loaded nano-emulsion gel. Also, blood and liver absorption of the drug, histological analysis of liver and liver enzyme activity of rats after 90 days' treatment were investigated. No drug was detected in blood/liver which in addition to an absence of any adverse effect on liver and enzymes showed the potential of adapalene loaded nano-emulsion gel as a novel carrier for topical delivery of adapalene.

A review of the mechanisms of action of dimethylfumarate in the treatment of psoriasis.

Fumaric acid esters (FAEs) such as dimethylfumarate (DMF) are used for the treatment of adults with moderate-to-severe psoriasis. The mode of action of FAEs is complex. Here, we provide a comprehensive review of the literature to describe the molecular mechanisms by which DMF and its active metabolite monomethylfumarate (MMF) exert their anti-inflammatory and immune modulatory effects. MMF can bind to the hydroxy-carboxylic acid receptor 2 (HCA2) on the cell surface and both DMF and MMF react with intracellular glutathione following cell penetration. DMF and to some extent also MMF modulate the activity of certain cellular signalling proteins such as the nuclear factor (erythroid-derived 2)-like 2 (Nrf2), nuclear factor kappa B (Nf-κB) and the cellular concentration of cyclic adenosine monophosphate. Some studies show that DMF can also affect the hypoxia-inducible factor 1-alpha (HIF-1α). These actions seem to be responsible for i) the downregulation of inflammatory cytokines and ii) an overall shift from a proinflammatory Th1/Th17 response to an anti-inflammatory/regulatory Th2 response. Both steps are necessary for the amelioration of psoriatic inflammation, although additional mechanisms have been proposed. There is a growing body of evidence to support the notion that DMF/MMF may also exert effects on granulocytes and non-immune cell lineages including keratinocytes and endothelial cells. A better understanding of the multiple molecular mechanisms involved in the cellular action of FAEs will help to adapt and further improve the use of such small molecules for the treatment of psoriasis and other chronic inflammatory diseases.

Application of an Optimized Tape Stripping Method for the Bioequivalence Assessment of Topical Acyclovir Creams.

This study indicates the application of tape stripping (TS) for bioequivalence (BE) assessment of a topical cream product containing 5% acyclovir. A TS method, previously used successfully to assess BE of topical clobetasol propionate and clotrimazole formulations, was used to assess BE of an acyclovir cream (5%) formulation as well as a diluted acyclovir formulation (1.5%) applied to the skin of healthy humans. An appropriate application time was established by conducting a dose duration study using the innovator product, Zovirax® cream. Transepidermal water loss was measured and used to normalize thicknesses between subjects. The area under the curve (AUC) from a plot of amount of acyclovir/strip vs cumulative fraction of stratum corneum (SC) removed was calculated for each application site. BE was assessed using Fieller's theorem in accordance with FDA's guidance for assessment of BE of topical corticosteroids. Adco-acyclovir cream (5%) was found to be BE to Zovirax® cream, where the mean test/reference (T/R) ratio of the AUC's was 0.96 and the bioequivalence interval using a 90% confidence interval was 0.91-1.01 with a statistical power > 95%, whereas the diluted test product fell outside the BE acceptance criteria with T/R ratio of AUC of 0.23 and a 90% CI of 0.20-0.26. This study indicates that the data resulting from the application of this TS procedure has reinforced the potential for its use to assess BE of topical drug products intended for local action, thereby obviating the necessity to undertake clinical trials in patients.

Dermal peptide delivery using enhancer moleculs and colloidal carrier systems. Part II: Tetrapeptide PKEK.

Due to the lipophilic properties of the uppermost skin layer of the stratum corneum (SC) it is highly challenging to reach therapeutic concentrations of cosmetic actives and drugs. Particularly, the hydrophilic ones penetrate poorly across the SC. The purpose of this study was to improve the topical bioavailability of the hydrophilic, polar tetrapeptide PKEK (amino acid sequence in one-letter notation). A nano-sized carrier system (microemulsion, ME) was therefore developed since MEs provide excellent penetration enhancing properties. The penetration of PKEK from the ME was compared to the penetration from a standard formulation. For the two preparations the penetration of the tetrapeptide in ex vivo human skin was investigated. This allows to make statements regarding dermal penetration, localization and distribution of the active substances in each skin layer as well as the influence of vehicle variations, in this case the incorporation of PKEK into a ME system. Relatively high amounts between 40 and 58% of the tetrapeptide PKEK penetrated from the standard cream into the skin. The major proportion of PKEK, which penetrated from the standard cream, remained in the SC and did not reach the target compartment within the skin. Penetration of PKEK from the ME was comparable with the cream for the shortest test time. However, very high PKEK amounts penetrated form the nano-sized carrier system (ME) into the human skin after 100 min (94%) and after 300 min (88%). The largest proportion did not remain in the skin, but permeated into the acceptor compartment. Therefore, the relative peptide content in the viable skin layers was predominantly comparable for the cream and the ME. For some samples a tendency could be observed that slightly higher amounts of PKEK were detected after the application of the standard cream. The absolute peptide concentrations gave a similar conclusion. The results indicate that liquid nano-sized systems are very effective carriers for extremely hydrophilic peptides used in cosmetics and also in therapeutics.

Advances in psoriasis physiopathology and treatments: Up to date of mechanistic insights and perspectives of novel therapies based on innovative skin drug delivery systems (ISDDS).

Psoriasis is a chronic inflammatory disease affecting mainly the skin but which can be complicated by psoriatic arthritis (PsA).This autoimmune skin disorder concerns 2-5% of the world population. To date, the physiopathology of psoriasis is not still completely elucidated but many researches are ongoing which have led for example to the discovery of the Th17/Th22 pathway. The conventional therapeutic approaches (local or systemic route) appeal to various classes of drugs with complex mechanisms of action and non-negligible side effects. Although there is no therapy capable to cure psoriasis, the current goal is to relieve symptoms as longer as possible with a good benefit/risk ratio. That is one of the principal limits of conventional antipsoriatic drugs. New formulations based on nanoencapsulation are a promising opportunity to answer to this limit by offering an optimization of the conventional antipsoriatic drug use (higher activity, lower side effects and frequency of application, etc.). Herein, we tried to put in perspective the mechanistic insights (histological and immunological views) proposed into scientific literature these last years in order to have a better comprehension of psoriasis physiopathology resulting in skin lesions and PsA. The therapeutic armamentarium and the different strategies in the management of psoriasis are discussed in greater details. To finish, the field of encapsulation in nanoparticles is broached in order to put forward recent advances in innovative skin drug delivery systems (ISDDSs) of antipsoriatic active agents for a better efficacy, safety and compliance.

In vitro evaluation of bioactive potential of Bacillus methylotrophicus YML008 against Propionibacterium acnes.

Acne vulgaris is the most common skin diseases that people experience during their lives. Thirteen rhizosphere isolates were screened against Propionibacterium acnes. The bacterium exhibited the highest activity against P. acnes was identified as Bacillus methylotrophicus YML008 by 16S rRNA gene sequencing. Scanning electron microscopy was used to assess the changes in morphology of P. acnes. Preliminary studies on the antimicrobial substance demonstrated the hydrophilic nature of compound with MIC of 0.17mg/ml and MBC of 0.3mg/ml. The cytotoxic effect of the extract was least (80% survival) as compared to benzyperoxide (40% survival). These results suggest YML008 as a promising bioresource and may be useful as a lead bacterium to develop a new type of anti-acne skin care prep to cure or prevent acne. Further, mechanism of action and proper clinical trials may be promising for this research.

Nail disorders in older people, and aspects of their pharmaceutical treatment.

The aim of this paper was to explore how aging influences the nail unit, its disorders and its response to treatment, and to identify some of the age-related gaps in the ungual drug delivery literature. Aging causes obvious changes to the nail, some of which are inherently due to old age, while others are due to diseases/conditions which become more prevalent as we age. Alterations in the nail plate's colour, contour, thickness, fragility, surface features, cell size, chemical composition and growth rate are some of the changes, with toenails and fingernails showing different effects. With respect to disease, the incidence of onychomycosis - the most common nail disorder - is considerably higher in older people. Similarly, brittle nails become more common as we age. In contrast, the literature about aging and the incidence of nail psoriasis is inconclusive, although, it is clear that as one gets older, the negative impact of nail psoriasis on one's quality of life decreases. Pharmaceutical treatment of the diseases comprises local and systemic therapies, sometimes in combination. Systemic therapies have the inherent disadvantages of adverse systemic effects, drug interactions and the need for monitoring, disadvantages which are especially problematic for older people who are more likely to suffer from co-morbidities and be on other medications. Topical therapy avoids such disadvantages. However, the success rates of commercially available preparations are low, and older people may need help with their application. It is also proposed that regular inspection and grooming of nails should become part of routine care of older people, as these would provide opportunities to identify and treat any problems at an earlier stage.

Methylation and Esterification of Magnolol for Ameliorating Cutaneous Targeting and Therapeutic Index by Topical Application.

PURPOSE: As a continuing effort to elucidate the impact of structure modification upon cutaneous absorption behavior, we attempted to assess the skin permeation of magnolol by methylation and acetylation. METHODS: Diacetylmagnolol and 2-O-acetyl-2'-O-methylmagnolol (AMM) were designed and synthesized in this study. The anti-inflammatory activity against stimulated neutrophils and keratinocytes was evaluated to check the bioactivity of the analogues. In vitro skin absorption was investigated using nude mouse and pig skin models at both equimolar and saturated doses. RESULTS: Magnolol generally showed the strongest anti-inflammatory potential, followed by diacetylmagnolol and AMM. The antibacterial activity was observed for magnolol and diacetylmagnolol but not AMM. Diacetylmagnolol and AMM could be partly hydrolyzed to magnolol and 2-O-methylmagnolol after entering the skin. The hydrolysis rate of diacetylmagnolol was faster than that of AMM. The lipophilicity played a crucial role in cutaneous absorption, with AMM exhibiting the highest skin deposition. AMM accumulation within nude mouse skin was about 2.5-fold greater than that of magnolol and diacetylmagnolol. On the other hand, the transdermal penetration across the skin was lessened by methylation and esterification. This led to a superior skin targeting of AMM. Although the pharmacological activity of AMM was low, the high skin uptake and bioconversion into 2-O-methylmagnolol in the skin contributed to a greater therapeutic index (TI, skin deposition x inflammatory inhibition percentage) compared to the others. The accumulation of AMM in the hair follicles was 77.12 nmol/cm(2), which was significantly greater than that with magnolol (44.84 nmol/cm(2)) and diacetylmagnolol (26.96 nmol/cm(2)). The synthetic analogues were tolerable to the nude mouse skin. CONCLUSIONS: Based on the experimental results, we may suggest topically applied AMM as a potent and safe candidate for the treatment of cutaneous inflammation.