Essential oils from sweet basil (Ocimum basilicum) as novel enhancers to accelerate transdermal drug delivery

The purpose of this study was to evaluate the essential oils from sweet basil (Ocimum basilicum, OB) as skin permeation enhancers to promote the percutaneous absorption of drugs. The in vitro and in vivo irritancy of the essential oils was also examined. Terpenes with various carbon numbers (mono-, sesqui-, di-, and tri-) were identified in both the lower-polarity fraction (OB-1) and higher-polarity fraction (OB-2). In vitro skin permeation and deposition of indomethacin were significantly enhanced after treatment with OB essential oils. The enhancing effect of OB-1 was greater than that of OB-2 in the in vitro permeation and in vivo cutaneous microdialysis analyses as well as in the plasma concentration of indomethacin. On the other hand, the in vivo study showed that OB-2 had a greater ability to retain the drug within the skin than did OB-1. Enhancement of the skin permeation of drugs by OB essential oils might be mainly due to improvement in the partitioning of the drugs to the stratum corneum. Both in vitro cell cultures (keratinocytes and skin fibroblasts) and in vivo transepidermal water loss showed no or only negligible irritation to skin by OB essential oils.