Evidence of deep percutaneous penetration associated with anti-inflammatory activity of topically applied Helicteres gardneriana extract: a photoacoustic spectroscopy study.

PURPOSE: To apply the photoacoustic spectroscopy technique to investigate the penetration rate of topically applied Helicteres gardneriana extract used as anti-inflammatory agent.
METHODS: Experiments were performed ex vivo in a well-controlled group of mice. The crude extract was obtained from leaves of the plant Helicteres gardneriana. Croton oil was applied into the ventral surface of the mouse's right and left auricles in order to induce an inflammatory response. The left auricle was treated with crude extract, while the right one served as the control. After 6 h, the auricles were sectioned for measurements of edema intensity, myeloperoxidase activity and the formulation penetration rate.
RESULTS: Croton oil induced inflammatory response in both auricles. The application of Helicteres gardneriana extract reduced significantly the edema of the auricle and inhibited the activity of the myeloperoxidase enzyme. The photoacoustic data showed that the propagation of the formulation was efficient to reach the deep region of the auricle, crossing the cartilage. The strong anti-inflammatory effect was associated with the observed deep penetration of the formulation.
CONCLUSION: This pre-clinical study showed the anti-inflammatory effect of Helicteres gardneriana extract. The photoacoustic technique was useful to demonstrate that this anti-inflammatory activity was associated with deep percutaneous penetration.