Formulation of Microemulsion Systems for Dermal Delivery of Silymarin

Abstract

Abstract. Silymarin is a standardized extract from Silybum marianum seeds, known for its many skin benefits such as antioxidant, anti-inflammatory, and immunomodulatory properties. In this study, the potential of several microemulsion formulations for dermal delivery of silymarin was evaluated. The pseudo-ternary phase diagrams were constructed for the various microemulsion formulations which were prepared using glyceryl monooleate, oleic acid, ethyl oleate, or isopropyl myristate as the oily phase; a mixture of Tween 20®, Labrasol®, or Span 20® with HCO-40® (1:1 ratio) as surfactants; and Transcutol® as a cosurfactant. Oil-inwater microemulsions were selected to incorporate 2% w/w silymarin. After six heating-cooling cycles, physical appearances of all microemulsions were unchanged and no drug precipitation occurred. Chemical stability studies showed that microemulsion containing Labrasol® and isopropyl myristate stored at 40°C for 6 months showed the highest silybin remaining among others. The silybin remainings depended on the type of surfactant and were sequenced in the order of: Labrasol®>Tween 20®>Span 20®. In vitro release studies showed prolonged release for microemulsions when compared to silymarin solution. All release profiles showed the best fits with Higuchi kinetics. Non-occlusive in vitro skin permeation studies showed absence of transdermal delivery of silybin. The percentages of silybin in skin extracts were not significantly different among the different formulations (p>0.05). Nevertheless, some silybin was detected in the receiver fluid when performing occlusive experiments. Microemulsions containing Labrasol® also were found to enhance silymarin solubility. Other drug delivery systems with occlusive effect could be further developed for dermal delivery of silymarin.

Stability, Cutaneous Delivery, and Antioxidant Potential of a Lipoic Acid and α-Tocopherol Codrug Incorporated in Microemulsions

“…Replacing monocaprylin with oleic acid decreased the isotropic and fluid dark‐shaded area from 52% to 34% (Fig. c), which might be attributed to a decrease in the polarity of the oil phase: although oleic acid was attributed an approximate HLB value of 1, the HLB value of monocaprylin is 8 . This is not surprising as other studies reported similar findings when systems containing monoglycerides, triglycerides, or other less polar oils were compared .…”

“…c), which might be attributed to a decrease in the polarity of the oil phase: although oleic acid was attributed an approximate HLB value of 1, the HLB value of monocaprylin is 8 . This is not surprising as other studies reported similar findings when systems containing monoglycerides, triglycerides, or other less polar oils were compared . The water solubilization capacity of surfactants seems greater when lower molecular weight and more polar components are used …”

Preparation, Characterization and Antioxidant Activity of Xanthone-Loaded Making (Hodgsonia Heteroclita) Microemulsions

“…6 shows that rapid release of xanthone from microemulsion (around 54%; without the initial burst release) occurred in 22 h and that it reached a plateau (almost 100%) in the following 48 h. On the other hand, 19% of xanthone was released from the microemulsion-based gel at 22 h. The xanthone of the microemulsion-based gel was subsequently released for up to 3 d (∼80%) with a plateau formation. The slow release of xanthone from the microemulsionbased gel confirms that there exists the capacity for partitioning between the oil and the aqueous phases and that the controlling of the drug release is affected by the viscosity of the gel [25,26]. Fig.…”

Preparation and evaluation of microemulsion-based transdermal delivery of Cistanche tubulosa phenylethanoid glycosides

“…The permeation profiles of all the tested vehicles followed zero-order release kinetics (26,27) and ME5 provided the highest transdermal flux of PG (86.795±0.23 µg/cm −2 /h −1 ; Fig. 5; Table III).…”