Isolation and identification of galactinol from castor oilseed meal

Galactinol, 1‐ O ‐α‐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.