Delivery of oat-derived phytoceramides into the stratum corneum of the skin using nanocarriers: Formulation, characterization and in vitro and ex-vivo penetration studies.

Deficiency or altered composition of stratum corneum (SC) lipids such as ceramides (CERs), causing skin barrier dysfunction and skin dryness, have been associated with skin diseases such as atopic dermatitis and psoriasis, and ageing. Replenishing the depleted native CERs with exogenous CERs has also been shown to have beneficial effects in restoring the skin barrier. Phyto-derived CERs such as oat CERs were shown to be potential for skin barrier reinforcement. To effect this, however, the oat CERs should overcome the SC barrier and delivered deep into the lipid matrix using the various novel formulations. In an attempt to demonstrate the potential use of oat CERs, lecithin-based microemulsions (MEs) and starch-based nanoparticles (NPs) were formulated and characterized. Besides, ME gel and NP gel were also prepared using Carbopol®980 as a gelling agent. The in vitro release and penetration (using artificial four-layer membrane system) and ex vivo permeation (using excised human skin) of oat CERs from the various formulations were investigated. The results revealed ME enhanced the in vitro release and penetration oat CERs compared to the other formulations. On the other hand, the NPs retarded the release of oat CERs and small quantities of oat CERs incorporated into NP gel penetrated into the deeper layers of the multilayer membranes. The penetration-enhancing effect of ME was also observed in the ex vivo permeation studies where significant quantities of oat CERs were found in the acceptor compartment. Compared to the ME, the ME gel exhibited reduced depth and extent of oat CERs permeation. As compared to NP gel, ME gel enhanced the degree of permeation of oat CERs into the deeper layer of the skin. Generally the gel formulations were effective in concentrating oat CERs in the SC where they are needed to be.

Potential application of oat-derived ceramides in improving skin barrier function: Part 1. Isolation and structural characterization.

The impaired epidermal barrier and skin dryness in chronic skin conditions such as atopic dermatitis, psoriasis and aged skin are associated with the depletion of ceramides (CERs) in the stratum corneum. Previously, the beneficial effects of phyto-CERs, mainly from wheat and rice, in replenishing the depleted epidermal CERs and restoring the skin barrier have been shown. However, very few efforts have been made to exploit CERs from other plants for dermal applications. In an attempt to explore alternative plant source of CERs, glucosylceramides (GlcCERs) were isolated from the lipid extract of Ethiopian oat grain (Avena abyssinica). The GlcCER species were separated on a reversed phase HPLC and the structure of individual GlcCERs were identified by tandem MS with atmospheric pressure chemical ionization interface. The glycosidic linkage of the GlcCERs was cleaved by acid treatment and the predominant CERs species were isolated using column chromatography and preparative LC-MS. Further structural characterization of the CERs was made by HR/ESI-MS and NMR analyses. All the detected oat-derived GlcCER species consisted of C18 dihydroxy sphingoid bases amide-linked with α-hydroxylated saturated fatty acids (C16-C24). The two predominant GlcCER species consisted of sphingenine (d18:1) amide-linked to hydroxypalmitic acid (h16:0) and hydroxyarachidic acid (h20:0). The molecular formulae of the two major CERs assigned by HR/ESI-MS were identical to the ones identified by LC/APCI-MS/MS. The structural information was also supported by 1H, 13C, 1H COSY NMR and HMBC spectral analyses. The amount of GlcCERs in oat grain, quantified by HPTLC, was found to be 193.5mg/kg. The results indicated the similarity of oat CERs with commercial plant CERs (with comparable GlcCER content) suggesting its potential as source of CERs for oral (as dietary supplements) as well as topical applications.

Potential Applications of Phyto-Derived Ceramides in Improving Epidermal Barrier Function.

The outer most layer of the skin, the stratum corneum, consists of corneocytes which are coated by a cornified envelope and embedded in a lipid matrix of ordered lamellar structure. It is responsible for the skin barrier function. Ceramides (CERs) are the backbone of the intercellular lipid membranes. Skin diseases such as atopic dermatitis and psoriasis and aged skin are characterized by dysfunctional skin barrier and dryness which are associated with reduced levels of CERs. Previously, the effectiveness of supplementation of synthetic and animal-based CERs in replenishing the depleted natural skin CERs and restoring the skin barrier function have been investigated. Recently, however, the barrier function improving effect of plant-derived CERs has attracted much attention. Phyto-derived CERs (phytoCERs) are preferable due to their assumed higher safety as they are mostly isolated from dietary sources. The beneficial effects of phytoCER-based oral dietary supplements for skin hydration and skin barrier reinforcement have been indicated in several studies involving animal models as well as human subjects. Ingestible dietary supplements containing phytoCERs are also widely available on the market. Nonetheless, little effort has been made to investigate the potential cosmetic applications of topically administered phytoCERs. Therefore, summarizing the foregoing investigations and identifying the gap in the scientific data on plant-derived CERs intended for skin-health benefits are of paramount importance. In this review, an attempt is made to synthesize the information available in the literature regarding the effects of phytoCER-based oral dietary supplements on skin hydration and barrier function with the underlying mechanisms.

Production of Rare Phyto-Ceramides from Abundant Food Plant Residues.

Ceramides (Cers) are major components of the outermost layer of the skin, the stratum corneum, and play a crucial role in permeability barrier functions. Alterations in Cer composition causing skin diseases are compensated with semisynthetic skin-identical Cers. Plants constitute new resources for Cer production as they contain glucosylceramides (GluCers) as major components. GluCers were purified from industrial waste plant materials, apple pomace (Malus domestica), wheat germs (Triticum sp.), and coffee grounds (Coffea sp.), with GluCer contents of 28.9 mg, 33.7 mg, and 4.4 mg per 100 g of plant material. Forty-five species of GluCers (1-45) were identified with different sphingoid bases, saturated or monounsaturated α-hydroxy fatty acids (C15-28), and ß-glucose as polar headgroup. Three main GluCers were hydrolyzed by a recombinant human glucocerebrosidase to produce phyto-Cers (46-48). These studies showed that rare and expensive phyto-Cers can be obtained from industrial food plant residues.

Controlled penetration of ceramides into and across the stratum corneum using various types of microemulsions and formulation associated toxicity studies.

Several skin diseases such as psoriasis and atopic dermatitis are associated with the depletion or disturbance of stratum corneum (SC) lipids such as ceramides (CERs), free fatty acids and cholesterol. Studies suggested that replenishment of these lipids might help to treat diseased, affected or aged skin. With this premises in mind, there are some formulations in the market that contain SC lipids and currently, to facilitate permeation of the lipids deep into the SC, various CERs, and other SC lipid microemulsions (MEs) were developed and characterised using lecithin or TEGO® CARE PL 4 (TCPL4) as base surfactants. However, to date, there are no reports that involve the permeability of SC lipids into and across the SC, and therefore, the penetration of CER [NP] as a model ceramide from various formulations was investigated ex vivo using Franz diffusion cell. Besides, the toxicity of the MEs was assessed using hen's egg test chorioallantoic membrane (HET-CAM). The results of the study showed that CER [NP] could not permeate into deeper layers of the SC from a conventional hydrophilic cream. Unlike the cream, CER [NP] permeated into the deeper layers of the SC from both type of MEs, where permeation of the CER was more and into deeper layers from droplet type and lecithin-based MEs than bicontinuous (BC) type and TCPL4 based MEs, respectively. The CER also permeated into deeper layers from ME gels which was, however, shallow and to a lesser extent when compared with the MEs. The results of HET-CAM showed that both MEs are safe to be used topically, with lecithin-based MEs exhibiting better safety profiles than TCPL4 based MEs. Concluding, the study showed that the MEs are safe to be used on the skin for the controlled penetration of CER [NP] deep into the SC.

Lecithin-based microemulsions for targeted delivery of ceramide AP into the stratum corneum: formulation, characterizations, and in vitro release and penetration studies.

PURPOSE: To improve the solubility and penetration of Ceramide AP (CER [AP]) into the stratum corneum that potentially restores the barrier function of aged and affected skin. METHODS: CER [AP] microemulsions (MEs) were formulated using lecithin, Miglyol® 812 (miglyol) and water-1,2 pentandiol (PeG) mixture as amphiphilic, oily and hydrophilic components, respectively. The nanostructure of the MEs was revealed using electrical conductivity, differential scanning calorimeter (DSC) and electron paramagnetic resonance (EPR) techniques. Photon correlation spectroscopy (PCS) was used to measure the sizes and shape of ME droplets. The release and penetration of the CER into the stratum corneum was investigated in vitro using a multi-layer membrane model. RESULTS: The MEs exhibited excellent thermodynamic stability (>2 years) and loading capacity (0.5% CER [AP]). The pseudo-ternary phase diagrams of the MEs were obtained and PCS results showed that the droplets are spherical in shape and bigger in size. In vitro investigations showed that the MEs exhibited excellent rate and extent of release and penetration. CONCLUSIONS: Stable lecithin-based CER [AP] MEs that significantly enhance the solubility and penetration of CER [AP] into the stratum corneum were developed. The MEs also have better properties than the previously reported polyglycerol fatty acid surfactant-based CER [AP] MEs.

Dermal targeting of tacrolimus using colloidal carrier systems.

In the therapy of chronic inflammatory skin diseases, the epicutaneous application of anti-inflammatory drugs in combination with maintenance therapy leads to ideal therapeutic long term effects. In this work, the development of well-tolerated colloidal carrier systems (ME) containing tacrolimus is described. A comprehensive physico-chemical characterization of the novel systems was performed using different techniques. The potential of three ME compared to an ointment as suitable carrier for dermal delivery of tacrolimus was determined. The penetration studies demonstrated that in comparison to the standard vehicle ointment, all three ME resulted in higher concentrations of tacrolimus in the deeper skin layers independent of the time of incubation. Particularly, the percentage of the bioavailable amount of tacrolimus (sum of the amount found in the dermis and acceptor compartment) from the ME with concentrations up to 20.95 ± 12.03% after 1000 min incubation time differed significantly (p<0.01), when compared to the ointment which yielded a concentration of 6.41 ± 0.57%. As a result of these experiments, using colloidal carrier systems, the penetration profile of tacrolimus was enhanced significantly (p<0.01). High drug amounts penetrated the target site in a short period of time after applying the ME.

Studies of the retrogradation process for various starch gels using Raman spectroscopy.

The retrogradation of untreated wild-type starches (potato, maize, and wheat), waxy maize starches, and one pregelatinized, modified amylose-rich starch was investigated continuously using Raman spectroscopy. The method detects conformational changes due to the multi-stage retrogradation, the rate of which differs between the starches. The pregelatinized, modified amylose-rich starch shows all stages of retrogradation in the course of its Raman spectra. In comparison to amylose, the retrogradation of amylopectin is faster at the beginning of the measurements and slower in the later stages. The untreated starches can be ranked in the order of their rate of retrogradation as follows: potato>maize>wheat.

The examination of polysaccharides as potential antioxidative compounds for topical administration using a lipid model system.

Aim of this study was the detection of polysaccharides with antioxidative properties as potential lipid protectors for topical administration. The effects of eight different polysaccharides on UV irradiation induced lipid peroxidation were investigated in a concentration dependent manner. An aqueous linolenic acid dispersion was used as an in vitro test system to examine the influences of acacia gum, agar agar, alginic acid, guar gum, novelose 330 and xanthan gum on the lipid peroxidation level after UV exposure. Four different samples of pectin and locust bean gum resulting from a swing mill grinding series were tested as well. Iron ions were added as transition metal catalysts. A UV irradiation device was used to create high level radiation. The amount of lipid peroxidation secondary products was quantified by the thiobarbituric acid assay detecting malondialdehyde. All of the tested polysaccharides showed antioxidative effects at least at one concentration. For acacia and xanthan gum, a concentration dependency of the protective effects was measured. The samples of agar agar, guar gum and novelose 330 acted antioxidatively without showing any concentration dependency. For alginic acid, prooxidative effects were determined. A correlation between grinding time and the effects of pectin and locust bean gum on the model lipid was not observed. The administration of lipid protective polysaccharides in cosmetic formulations or sunscreens could be helpful for the protection of the human skin against UV induced damage. In vivo experiments with the lipid protective polysaccharides found in this study should follow.

Influence of extraction parameters on the phytochemical characteristics of extracts from buckwheat (Fagopyrum esculentum) herb.

In recent years, the interest in herbal medicinal products, especially in the field of dermatology and cosmetics, has risen enormously. Many plant-derived substances show photoprotective properties in terms of absorption of UV radiation and preventing photodamage to molecular structures of human skin. Modern phytopharmaceutics as well as phytocosmetics require standardized, defined extracts from the herbal matrix. Buckwheat herb is rich in flavonoids, which have been identified as potent antioxidants. Up to now, there have been no systematic investigations available concerning the extraction conditions for phenolic substances from buckwheat herb. In this paper, we report the influence of three extraction parameters, ethanol concentration, temperature, and extraction time, on the response variables extractable matter, antioxidant activity, and content of fagopyrin, rutin, and chlorogenic acid. Our results suggest that an extract with good antioxidant activity, a high content of phenolics, and a low content of the phototoxic fagopyrin can be yielded by agitated maceration with 30% ethanol at 60 degrees C for 2 h. Furthermore, there is good correlation between the antioxidant activity and the rutin content, whereas the extractable matter is not an appropriate parameter for extract quality. Huge differences in the content of rutin and chlorogenic acid when using herbal drugs from different suppliers confirm the demand of standardized procedures for the production of herbal drugs.

Screening for new antioxidative compounds for topical administration using skin lipid model systems.

PURPOSE: The effects of forty seven different substances (drugs, plant extracts, plant ingredients and polysaccharides) on UV irradiation induced lipid peroxidation were investigated. METHODS: Two lipid systems of different complexity were used as in vitro screening models. Iron ions were added as transition metal catalysts. A UV irradiation device was used to create high level radiation. The amount of lipid peroxidation secondary products was quantified by the thiobarbituric acid assay detecting malondialdehyde. RESULTS: The screening for antioxidative compounds for topical administration resulted in new, interesting findings. In the drug testings amantadine, bufexamac, tryptophan, melatonin, propranolol and hyaluronic acid were found to act antioxidatively whereas for ascorbic acid pro-oxidative effects were determined. Buckwheat extract significantly reduced the level of irradiation induced lipid peroxidation as well as the extracts of St. John's Wort, melissa and sage. The resistant starch novelose 330 and the samples of locust bean gum from a swing mill grinding series showed lipid protection after UV irradiation in the polysaccharide test rows. CONCLUSIONS: Human skin is constantly exposed to UV light and oxygen. Therefore, the administration of protectors in cosmetic formulations or sunscreens, as found in this study, may be helpful for the protection of the human skin against UV induced damage. In vivo experiments with substances found as protectors should follow to allow in vitro-in vivo correlation and clinical interpretation of the data.