1. ECa 233, the standardised extract of Centella asiatica, contains not less than 80% triterpenoid glycosides, in a madecassoside:asiaticoside ratio of 1.5 (±0.5):1. 2. The pharmacokinetic comparison of madecassoside and asiaticoside was performed in rats following intravenous and oral administration of ECa 233, or an equivalent dose of the individual compounds. Blood, tissues, urine and faeces were collected after dosing to determine drug and metabolite levels using liquid chromatography-tandem mass spectrometry. 3. Our study demonstrated that plasma levels of madecassoside, and to a lesser extent asiaticoside, were higher after administration of ECa 233 than the corresponding values for the pure compounds. There was a bidirectional interconversion between asiaticoside and madecassoside consistent with the increased exposure of madecassoside and asiaticoside in ECa 233. 4. Both madecassoside and asiaticoside appeared to be widely distributed in several organs and metabolized extensively; following intravenous administration of either compound, approximately 80-90% of the dose was recovered as madecassic acid and asiatic acid in the faeces.

Centella asiatica is a tropical plant commonly used as an herbal remedy in traditional medicines in many countries. In an attempt to establish an herbal extract with well-defined characteristics, a standardized extract of C. Asiatica, ECa 233, was developed. This extract contains at least 80% triterpenoid glycosides with the major constituents madecassoside and asiaticoside at a ratio of 1.5±0.5:1. In the present study, comparative pharmacokinetics of ECa 233 with its mixture of madecassoside and asiaticoside were conducted in rats. Following intravenous or oral administration of the test compounds, blood, tissues, urine, and feces were collected for the determination of madecassoside, asiaticoside, and their metabolite levels using liquid chromatography tandem mass spectrometry. Plasma levels of madecassoside and asiaticoside in the ECa 233-treated group were found to be higher than their respective counterparts in the mixture. Madecassoside and asiaticoside in both test formulae appeared to be widely distributed in several organs, and more than 50% of the administered doses were recovered as madecassic acid and asiatic acid in the feces within 24 to 48 h. The results clearly demonstrated the pharmacokinetic advantage of a standardized extract of C. Asiatica, ECa 233, compared with a mixture of madecassoside and asiaticoside at an equivalent amount. Other minor constituents that naturally exist in ECa 233 appeared to positively modulate the pharmacokinetics of its major constituents, resulting in relatively better pharmacokinetic profiles than those from a mixture of pure compounds.