Leakage of Dhurrin and p-Hydroxybenzaldehyde from Young Sorghum Shoots Immersed in Various Solvents.

Spectral scanning was used to provide estimates of the leakage of the cyanogenic glucoside, dhurrin ( p -hydroxy-[ S ]-mandelonitrile-β-d-glucoside), and its metabolite, p -hydroxybenzaldehyde ( p -HB), from young light-grown shoots of Atlas sorghum ( Sorghum bicolor [L.] Moench) when these shoots were immersed in water, toluene, chloroform or mixtures of water and toluene or water and chloroform. Minimal leakage of dhurrin and virtually no leakage of p -HB occurred with water as the solvent. The 0.5% concentration (v/v) of both toluene and chloroform was more effective than either the 1.0 or 2.0% concentrations in effecting leakage of the two solutes. With either 0.5% toluene or 0.5% chloroform as the solvent, 80 to 90% of the total dhurrin was extracted from shoots in a 3-hour period. Breakdown of dhurrin during extraction was much more extensive with 0.5% chloroform than with 0.5% toluene. Some loss of p -HB occurred during 3- or 6-hour extractions in the water-organic solvent mixtures; spectral and chromatographic evidence suggested partial conversion of p -HB to p -hydroxybenzoic acid. With undiluted toluene or chloroform as solvents, extracts contained appreciable amounts of free p -HB but essentially no dhurrin. These solvents were less effective than the water-organic solvent mixtures in extracting the solutes from the shoot issue.