A new transdermal delivery system that controls cellulitis is evaluated using reversed-phase high-performance liquid chromatography coupled with photodiode array detection. An extraction procedure and the validation of the analytical method to assay the active excipients from the Centella asiatica plant (asiaticoside, madacessic acid, and asiatic acid) are described. Excellent results are obtained in terms of linearity, accuracy, and specificity of the analytical method. Experimental Materials

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... rtho-phosphoric acid (99% crystal, Merck, Darmstadt, Germany) and bidistilled water (Carlo Erba, Milan, Italy) were used to prepare the phosphoric acid solution at 0.3%; this solution and acetonitrile (gradient-grade for chromatography, Merck) were both freshly filtered on 0.2-µm membrane filters (Merck) and used as the HPLC eluent. The eluent was degassed with helium throughout the chromatographic run. Standards Reference samples of asiatic acid, madecassic acid, and asiaticoside (Indena, Milan, Italy) were used to set up the analytical method. Instrumentation An HPLC system (Star 9012 SDS, Varian, Palo Alto, CA) possessing an integrated proportioning solvent delivery system was used. The system was equipped with a photodiode array detector (9065 polychrom, Varian). The entire analytical