Determination of reserpine and rescinnamine in Rauwolfia serpentina preparations by liquid chromatography with fluorescence detection

A method is presented for the determination of reserpine and rescinnamine in Rauwolfia serpentina powder or tablets by liquid chromatography (LC) with fluorescence detection. The sample is dispersed in CH3OH, 0.5N H2SO4 is added, and the mixture is extracted with five 30 mL portions of CHCl3. The extracts are separated from interfering materials on a Celite-0.1N NaOH column, and the eluates are collected in 50 mL CH3OH. After complete removal of the CHCl3, reserpine and rescinnamine are determined by liquid chromatography on a normal phase column with CH3OH as the mobile phase. Because reserpine and rescinnamine produce a single peak, chromatograms are obtained at different wavelengths. Reserpine is determined at an excitation wavelength of 280 nm and an emission wavelength of 360 nm. Rescinnamine is determined at an excitation wavelength of 330 nm and an emission wavelength of 435 nm. Recovery studies were conducted at 2 different levels to simulate 100 and 50 mg Rauwolfia serpentina tablets. Samples of Rauwolfia serpentina powders and tablets were also examined, and the results were compared with those obtained by the current AOAC official method. The proposed method is applicable to the analysis of ground composites and individual tablets.