ISOLATION AND IDENTIFICATION OF GALACTINOL FROM CASTOR OILSEED MEAL

Galactinol, 1-O-alpha-D-galactopyranosyl-D-myo-inositol, is an essential intermediate in the biosynthesis of raffinose saccharides in plant tissues. The unavailability of a commercial source for this metabolite has hindered research on raffinose saccharide metabolism to date. The objective of this study was to develop a facile method for obtaining highly purified galactinol from a readily available source. Defatted castor oilseed meal was found to exhibit a simple soluble carbohydrate profile that included galactinol. Purification of galactinol from castor meal was achieved by enzymatic treatment and a series of liquid chromatography steps, including ion-exchange and carbon adsorption. The isolation procedure was reliable with a yield of 278 mg of galactinol from 150 g of defatted meal. The purity of galactinol was estimated at 96.4% by high-performance liquid chromatography. The identity of the purified galactinol was confirmed by enzymatic analysis, identical relative retention times on high-performance liquid chromatography and gas chromatography, and comparison of its mass spectrum to that of authentic galactinol.