Investigation of enhancing activity and skin irritation of Zingiber officinale, Zingiber cassumunar and Curcuma zedoaria

The penetration enhancing effect of essential oils extracted from rhizomes of Zingiber officinale, Zingiber cassumunar and Curcumar zedoaria on the skin permeation of diclofenac sodium was evaluated in vitro using modified Franz diffusion cell and Wistar rat skin. The essential oils were tested at 1, 3 and 5% (w/v) in the vehicle hydroalcoholic mixture (ethanol: water (1:1 v/v)). The skin permeation of diclofenac sodium was remarkably enhanced in the presence of these three essential oils. Overall, the rank order of the enhancing activities of these oils was Zingiber officinale > Zingiber cassumunar > Curcuma zedoaria. Furthermore, the essential oil at 5% appeared to give the greatest enhancement. For the in vivo skin irritation study, these oils were tested at 1 and 5% in the vehicle and at 100%. These test solutions including the vehicle were applied to the abdominal surfaces of the Wistar rats and kept in contact with these areas for 24 h. After a biopsy technique, the skin irritation was evaluated under microscopic observation and histological scores were used as an index of skin damage caused by the test compounds. The skin irritation study revealed that the vehicle had no discernible effects in histological appearance in rat skin. The essential oils at concentrations of 1 and 5% in hydroalcoholic mixture and at 100% were found to cause skin irritation in different degrees. The most severe skin damage was observed with the 1% of these oils whereas the 5% of these oils were classified as mild irritants.