Moisturizing and Antiinflammatory Properties of Cosmetic Formulations Containing Centella asiatica Extract.

Centella asiatica extract is a rich source of natural bioactive substances, triterpenoid saponins, flavonoids, phenolic acids, triterpenic steroids, amino acids and sugars. Thus, many scavenging free radicals, exhibit antiinflammatory activity and affect on the stratum corneum hydration and epidermal barrier function. The aim of the present study was to evaluate the in vivo moisturizing and antiinflammatory properties of cosmetic formulations (oil-in-water emulsion cream and hydrogel) containing different concentrations of Centella asiatica extract. The study was conducted over four weeks on a group of 25 volunteers after twice a day application of cosmetic formulations with Centella asiatica extract (2.5 and 5%, w/w) on their forearms. The measurement of basic skin parameters (stratum corneum hydration and epidermal barrier function) was performed once a week. The in vivo antiinflammatory activity based on the methyl nicotinate model of microinflammation in human skin was evaluated after four weeks application of tested formulations. In vivo tests formulations containing 5% of Centella asiatica extract showed the best efficacy in improving skin moisture by increase of skin surface hydration state and decrease in transepidermal water loss as well as exhibited antiinflammatory properties based on the methyl nicotinate model of microinflammation in human skin. Comparative tests conducted by corneometer, tewameter and chromameter showed that cosmetic formulations containing Centella asiatica extract have the moisturizing and antiinflammatory properties.

Evaluation of skin colouring properties of curcuma longa extract.

The aim of this study was to evaluate the skin colouring properties of curcuma extract in cosmetic formulations. Objective measurements of the skin colour changes were done by Chromameter using the CIE L*a*b* colour space parameters. These measurements were correlated with the results of the sensory analysis. The observations showed permanent, visible and statistically significant changing of b* component after one application of emulsions containing 12% and 25% of turmeric extract. The change of skin color remained also after removing the emulsion. Sensory analysis indicated that the tested emulsions with curcuma extract have a significant impact on skin smoothness, spreadability, cosmetic absorption and pillow effect.

Artificial membranes as models in penetration investigations.

BACKGROUND/AIMS: In vitro methods used in the research of transepidermal transport of active substances generally rely on the penetration rate of test compounds through standard membranes. Models typically used in penetration experiments are specially prepared human or animal skin samples or synthetic membranes. The objective of this study was to establish if the test results for an artificial liposome membrane can be extrapolated to determine the actual bioavailability of active substances. METHODS: Tests were conducted in a side-by-side diffusion cell. As model membranes, a liquid-crystal lipid membrane (LM), phospholipid membrane (PM) and pig skin sample were used. The test compounds were eight synthetic dyes used in hair colouring products. RESULTS/CONCLUSION: Research findings reveal that membranes composed of lipids, identical to those present in the epidermis and forming analogical liquid-crystal structures provide a close approximation of the actual bioavailability of active substances (correlation between the results obtained for pig skin and LM was significant: R = 0.95 and R = 0.93 in the presence of a 1% Sodium dodecyl sulphate in donor system). Unlike biological membranes, intercellular cement does not contain phospholipids. The observed correlation between penetration coefficients through the PM and pig skin was not significant (R = 0.82). The experiments confirm that the PM constitutes a less credible model for the studies of transepidermal transport in real life conditions.

The fatty acids as penetration enhancers of amino acids by ion pairing.

The influence of palmitic acid on n-octanol/water partition coefficient (log P) of selected amino acids, alanine, glycine, proline, hydroxyproline, seine, valine, threonine and lysine, was measured at a wide range of pH. A parabolic shape curve was obtained in every case (pH vs. Deltalog P), with maximum depending on the amino acid. In each case in the presence of palmitic acid, the apparent partition coefficient increased. To check the possible mechanism of extraction of amino acids into n-octanol phase in the presence of palmitate additionally, the influence of an amount of counter ion on partition coefficient of lysine was investigated. The results suggest that the enhanced partitioning of lysine results from the ion pair formation with palmitate. The ion pair stratum corneum-lipid membrane transport of the amino acids was investigated as well, using palmitate as a counter ion. The apparent permeability coefficients were enhanced significantly by palmitic acid at pH 7.4. As many substances (e.g. organic solvents, unsaturated fatty acids, etc.) are penetration enhancers which change the structure of intercellular lipid, the influence of palmitic acid on membrane was investigated. After pretreatment of membrane with palmitic acid, no changes in permeation of alanine were observed. Investigations suggest the enhanced permeation of amino acids via ion pairing. The method for prediction of pH in which the possibility of ion pairing is the highest was developed as well.

Common cosmetic hydrophilic ingredients as penetration modifiers of flavonoids.

Nowadays, flavonoids are present in many cosmetic formulations, mainly in the form of plant extracts. The main reason of still increasing popularity of these substances is their beneficial biochemical activity. The main factor affecting activity of flavonoids in the skin is their skin penetration ability. The studies have evidenced that flavonoids from grape leaf extract as well as flavonoids like quercetin, rutin and catechin can migrate through the model lipophilic membrane from aqueous solution. The influence of common hydrophilic cosmetic additives on the permeation profile of flavonoids has been checked. The partition coefficients of examined flavonoids in the octanol-water extraction system were determined. Correlations between permeation coefficients and log P of particular flavonoids were plotted. To determine the mechanism of influence of hydrophilic substances on the permeation profile of flavonoids, the solubility of these compounds was investigated. Studies suggest that the presence of hydrophilic additives causes the increase in the flavonoid solubility that decreases the activity of flavonoids in the vehicle. In such a situation, the driving force for the penetration is reduced and the decrease of permeation coefficient can be observed.