Development of microemulsion of a potent anti-tyrosinase essential oil of an edible plant.

The aim of this study is to develop a microemulsion product from a plant essential oil having the highest anti-tyrosinase activity. The in vitro anti-tyrosinase activity of six essential oils extracted from six edible plants was compared. The oil of Cymbopogon citratus demonstrated the highest activity which was significantly nontoxic to normal human cells. The GC-MS data indicated that geranial and neral are the major compounds in the oil. The phase diagram composed of C. citrates oil, water, and surfactant mixture was conducted by a titration method. Ethyl alcohol was found to be the most suitable cosurfactant for the C. citrates oil microemulsion. The results revealed that the amount of oil and water played an important role in microemulsion conductivity and type. The most desirable o/w type of C. citratus oil microemulsion was found to be composed of 20% oil, 30% water, and 50% surfactant mixture of a 2:1 weight ratio of Tween 20 and ethyl alcohol.

Skin improvement and stability of Echinacea purpurea dermatological formulations.

Echinacea purpurea contains many beneficial constituents for protection of skin from oxidative stress and for improving hydration of skin. This study aimed to investigate the stability and dermatological efficacy of E. purpurea cream and gel. Echinacea purpurea extract was incorporated into suitable cream and gel bases. Stability of the extract in the formulations was investigated by determining its residual total phenolic content and antioxidant activity after storage at 4°C, 30°C and 40°C for 6 months. The effect of those formulations on skin irritation, hydration level and wrinkle reduction was evaluated in 10 healthy volunteers, aged 25-40 years. The shelf lives of E. purpurea cream and gel in terms of total phenolic content and antioxidant activity were only 2 and 4 months respectively at 4°C and could be extended up to 7 months by incorporation of α-tocopherol or disodium editate. The corneometer hydration indices increased up to 10.6 AU and 11.4 AU, and the wrinkles decreased 9.47% and 14.92% because of the application of E. purpurea cream and gel for 1 month. Both formulations showed no irritation to skin. Echinacea purpurea cream and gel developed in this study were effective in improving skin hydration and reducing wrinkle, but showed low storage stability.

Characterisation of microemulsions containing orange oil with water and propylene glycol as hydrophilic components.

The current study aims to investigate the effect of incorporation of orange oil, mainly consisting of the cyclic mono-terpene linolene, a known skin penetration enhancer, as oil component on microemulsion formation both in water and propylene glycol containing systems. Phase diagrams of pseudoternary mixtures containing orange oil, ethyloleate or a 1:1 mixture (w/w) of orange oil and ethyloleate as oil components, a 6:4 (w/w) mixture of polyoxyethylene 20 sorbitan monooleate and sorbitan monolaurate as surfactant components and water or propylene glycol as hydrophilic components were investigated. Smaller microemulsion regions were observed when orange oil was used as a substitute for ethyloleate in both water and propylene glycol containing systems. Polarising light microscopy, viscosity measurements, electrical conductivity measurements and cryo-field emission scanning electron microscopy were used to identify structural features of the microemulsions. Solution-type, w/o droplet-type microemulsions and microemulsion areas containing liquid crystals were found in varying areas in the phase diagrams of water containing systems. Liquid crystals formation occurs when the water concentration reaches 20%-22.5% (w/w). Only solution-type microemulsions were observed in propylene glycol containing systems. The dimension of solution-type microemulsion areas in the phase diagrams is likely to depend on the miscibility of components and larger microemulsion areas were found when ethyloleate was used instead of orange oil and propylene glycol was used instead of water. W/o droplet-type microemulsions of systems containing orange oil and ethyloleate as oil components appear in different areas of the phase diagrams. Incorporation of orange oil as a penetration enhancer into a topical microemulsion affects its physical characteristics. This in turn may lead to instability of the microemulsion and/or can influence the release patterns of drugs from these microemulsions when applied as topical formulations.