(W1030-12-67) Optimization of the In Vitro Skin Permeation of Resveratrol from Microemulsions

Purpose: Resveratrol is a naturally occurring polyphenol with well-studied antioxidant and anti-inflammatory activity [1]. Microemulsions are spontaneously forming, thermodynamically stable, colloidal formulations, enabling resveratrol’s solubility and stability, as well as transdermal delivery [2]. The aim of the present study was the formulation and optimization of resveratrol microemulsions, and the assessment of their in vitro skin permeation.

Methods: Formulating for Efficacy® software was used to determine the qualitative composition of the microemulsion, i.e., the surfactants and the oil phase excipients [3]. The quantitative composition was carried out with a mixture design using the Design Expert® software [4], with factors Oil Phase: Surfactant System: Water. Formulations were optimized regarding the minimum droplet size of the oil phase and the maximum cumulative permeation of resveratrol at 24h. Droplet size of the oil phase was measured using light scattering (Malvern Zetasizer 3000HAS). Permeation studies were performed using Franz-type diffusion cells with either StratM® (Merck® KGaA, Darmstadt, Germany) artificial membrane or human epidermal membrane [5]. The receptor medium was water: glycerin (50:50) to maintain sink conditions, and was kept under continuous magnetic stirring, thermostated at 32^oC. Samples were taken at 3,6,12 and 24h and analysed applying a UV-HPLC method [6]. At the end of the experiment mass balance study of resveratrol was performed [7].

Results: Microemulsions’ oil phase consisted of Transcutol®: Labrasol® (24:76) and the surfactant system of Tween 80: Span 68 (50:50), according to Formulating for Efficacy®. From the analysis of the Experimental Design results two mathematical models were derived for each response, a quadratic for the droplet size (Figure.1), and a linear model for the cumulative resveratrol permeation (Figure.2), using StratM® membrane. Optimization was performed and resulted in the optimal microemulsion with the highest desirability factor (Figure.3) to the previously stated criteria, which consisted of Oil Phase: Surfactant System: Water (26: 7: 67) and a load of 1.9% resveratrol. In vitro permeation study through human epidermal membrane showed no significant resveratrol permeation. However, in the mass balance studies, a significant skin retention percentage of resveratrol was found (4.4% of applied dose). This formulation was found stable over a six-month period at room temperature.

Conclusion: Resveratrol was successfully formulated in stable microemulsions. Resveratrol permeated StratM® artificial membrane and showed a significant retention in human epidermal membrane. Based on the results of epidermal retention, further in vivo studies are in process in order to confirm the promising results for topical application of resveratrol.

References: 1. Amri, A., Chaumeil, J. C., Sfar, S., & Charrueau, C. (2012). Administration of resveratrol: What formulation solutions to bioavailability limitations? Journal of Controlled Release, 158(2), 182–193. https://doi.org/10.1016/j.jconrel.2011.09.083
2. Juškaite, V., Ramanauskiene, K., & Briedis, V. (2017). Testing of resveratrol microemulsion photostability and protective effect against UV induced oxidative stress. Acta Pharmaceutica, 67(2), 247–256. https://doi.org/10.1515/acph-2017-0018
3. Wiechers, J. W., Kelly, C. L., Blease, T. G., & Dederen, J. C. (2004). Formulating for efficacy. International Journal of Cosmetic Science, 26(4), 173–182. https://doi.org/10.1111/j.1467-2494.2004.00211.x
4. Korakianiti, E., & Rekkas, D. M. (2011). Statistical Thinking and Knowledge Management for Quality-Driven Design and Mnaufacturing in Pharmaceuticals (pp. 1465–1479). Pharm Res.
5. Uchida, T., Kadhum, W. R., Kanai, S., Todo, H., Oshizaka, T., & Sugibayashi, K. (2015). Prediction of skin permeation by chemical compounds using the artificial membrane, Strat-MTM. European Journal of Pharmaceutical Sciences, 67, 113–118. https://doi.org/10.1016/j.ejps.2014.11.002
6. Polonini H.C., de Almeida Bastos C., de Oliveira M.A.L., da Silva C.G.A., Collins C.H., Marcos Antônio Fernandes Brandão A.F. and Raposo N.R.B. (2014). In vitro drug release and ex vivo percutaneous absorption ofresveratrol cream using HPLC with zirconized silica stationary phase, Journal of Chromatography B, 947– 948, pp. 23-31
7. Bortolotti, F., Balducci, A. G., Sonvico, F., Russo, P., & Colombo, G. (2009). In vitro permeation of desmopressin across rabbit nasal mucosa from liquid nasal sprays: The enhancing effect of potassium sorbate. European Journal of Pharmaceutical Sciences, 37(1), 36–42. https://doi.org/10.1016/j.ejps.2008.12.015

Acknowledgements: Professor P. Dallas would like to thank the Special Account for
Research Grants and the National and Kapodistrian University of
Athens for funding his participation in this meeting


Figure 1. Response surface Contour Plot of the Quadratic model describing droplet size of oil phase of the microemulsions (Factor A: Oil phase, Factor B: Surfactant System, Factor C: Water)


Figure 2. Response surface Contour Plot of Resveratrol’s Cumulative Permeation linear model. (Factor A: Oil phase, Factor B: Surfactant System, Factor C: Water)


Figure 3. Desirability function for the optimization of resveratrol microemulsions, based on maximum in vitro permeation and minimum microemulsion droplet size. (ME :Microemulsion containing 1.9% resveratrol Factor A: Oil phase, Factor B: Surfactant System, Factor C: Water)