Influence of extraction solvent and temperature on the quantitative determination of oligosaccharides from plant materials by high-performance liquid chromatography

The effect of extraction solvents and temperatures on extraction yields of monosaccharides, sucrose, and raffinose oligosaccharides from plant materials was investigated. Toasted soybean meal, cotton seed meal, field peas, and a feed mixture were extracted in either water, 50% (v/v), or 80% (v/v) aqueous methanol or ethanol at 20 or 50 degrees C or at the boiling point of the solvent. Extraction in 80% (v/v) alcohol was strongly influenced by the extraction temperature and maximum extraction was only achieved at the boiling point. Extraction in water and 50% (v/v) methanol or ethanol was less heat sensitive and gave comparable results. Aqueous ethanol (50%, v/v) was as effective as 50% (v/v) methanol, whereas lower yields were seen at higher alcohol strength. There was no consistent difference in the extraction yield when comparing reflux with constant stirring and water bath with occasional mixing for any of the extraction solvents used.