Determination of diosgenin in Dioscorea deltoidea and Dioscorea sylvatica by using gas-liquid chromatography

A method for the determination of diosgenin in yams has been developed by using gas chromatography. The minced undried sample from large tubers, or sliced dried sample from small tubers, is hydrolysed by refluxing with 2 N hydrochloric acid, dried, extracted with light petroleum and the solvent removed. No further clean-up is necessary (in different species of Dioscorea, there may be interference from other sapogenins), and the residue, dissolved in 2-ethoxyethanol, is used for injection. The method has been checked against normal gravimetric determination by using an aliquot part of a large sample. An undried sample weight of 5 g is adequate, but a sample of 1 g or less gives a low value, presumably because of manipulative losses in the hydrolysis and extraction stages. As the gravimetric technique requires at least 50 g of tuber, the gas-chromatographic method can be used at a much earlier stage of plant growth, effecting considerable saving of time in a breeding programme.