A simplified method of extraction of diosgenin from Dioscorea tubers and its determination by gas-liquid chromatography

Abstract

A simple method for determining diosgenin in Dioscorea tubers involving extraction and gas-liquid chromatography has been developed and used in our laboratory for the last 6 years. A small amount (600 mg) of the ground, dried tuber is hydrolysed by refluxing it for 4 hours with a 1 + 1 mixture of 3 N aqueous hydrochloric acid solution and xylene, after adding a suitable internal standard. After centrifuging the mixture, a portion of the xylene layer is injected on to the gas-chromatographic column, without any further manipulations. Hydrolysis conditions were examined to ensure that the release of diosgenin was complete and its degradation at a minimum. The proposed method enables pennogenin to be separated from diosgenin, but yamogenin is poorly resolved. The relative standard deviation for the determination of diosgenin was about 1·5 per cent. Good agreement with a gravimetric method was found.