Evaluation of the topical anti-inflammatory activity of ginger dry extracts from solutions and plasters

In this study the skin permeation and the topical anti-inflammatory properties of ginger extracts were investigated. A commercial ginger dry extract (DE) and a gingerols-enriched dry extract (EDE) were evaluated for their in vivo topical anti-inflammatory activity by inhibition of Croton oil-induced ear oedema in mice. Furthermore, the feasibility of an anti-inflammatory plaster containing DE or EDE was evaluated. Since the in vivo activity was evaluated in mice, the ex vivo skin permeation study was performed by using mouse skin or human epidermis. The DE from the acetonic solution exerted a dose-dependent topical anti-inflammatory activity (ID50 = 142 mu g/cm(2)), not far from that of the potent reference substance indomethacin (ID50 = 93 mu g/cm(2)). Similarly, the EDE induced a dose-dependent oedema reduction though its potency (ID50 = 181 mu g/cm(2)) was slightly lower than that of DE. Increase of the 6-gingerol concentration in the extract did not improve the anti-inflammatory activity. The medicated plasters, containing 1 mg/cm(2) of the commercial DE or EDE, had good technological characteristics and exerted a significant antiphlogistic effect, too. By using the plaster containing EDE, the gingerol amount that permeated through human epidermis was 6.9 mu g/cm(2) while the amount that passed through mouse skin was 22.1 mu g/cm(2). Nevertheless, the amounts of 6-gingerol permeated through human epidermis and mouse skin in the early period (8h) were comparable (p > 0.3). This preliminary result suggests that the anti-inflammatory effect observed in mice could also be exerted in humans.