Penetration of a biologically active triterpene extract (TE) through the stratum corneum of human epidermis
Aims: Pentacyclic triterpenes such as betulin (BE) and betulinic acid (BA) display amongst others anti-tumor and anti-inflammatory effects in vitro and in vivo [1, 2]. A highly purified triterpene extract (TE) of the outer bark of birch that contains BE as the major compound (80% w/w), but also BA, lupeol, erythrodiol and oleanolic acid is able to form a TE-oleogel which can be applied topically .
Objective: Penetration of the lead compound BE from the TE-oleogel through the stratum corneum of human epidermis was investigated.
Methods: TE-oleogel (150±5mg) was applied to the skin of 6 healthy volunteers for 0.5–6h. The stratum corneum was removed by a standardized tape-stripping method. Subsequently, the triterpenes were extracted from the strips and the penetration of BE was determined by GC-analysis .
Results: BE penetrates through the stratum corneum within 2h. At the junction of the stratum corneum and the stratum granulosum 0.13±0.007µg BE per cm2 skin were detected (n=6). By variation of the application period (0.5–6.0h; n=3) a time-dependent penetration of BE was observed, which was significantly higher after 6h.
Conclusion: BE from a standardized TE-oleogel penetrates through the stratum corneum in a time-dependent manner. Thus, TE-oleogel could offer a new possibility to provide the highly bioactive triterpenes for the treatment of skin diseases, e.g. actinic keratoses, which was shown recently .
Acknowledgement: Birken GmbH, Niefern-Öschelbronn, Germany; Software AG Stiftung, Darmstadt, Germany
References: 1. Laszczyk, M.N. et al. (2006) Planta Med 72: 1389–95. 2. Alakurtti, S. et al. (2006) Eur J Pharm Sci 29: 1–13. 3. Huyke, C. et al. (2006)J Dtsch Dermatol Ges 4: 132–6.