Agronomy and Horticulture Department


Date of this Version



Published in Crop Science (November-December 1984) 24(6): 1,158-1,163.


When dhurrin [p-hydroxy-(S)-mandelonitrile-β-D-glucoside], the cyanogenic glucoside of sorghum [Sorghum bicolor (L.) Moench], is hydrolyzed by autoclaving, p-hydroxybenzaldehyde (p-HB) is released. The spectrophotometric determination of p-HB concentration in autoclaved sorghum leaf extracts provides a measure of the hydrocyanic acid potential (HCN-p) of leaf tissue. Extracts of field-grown sorghum leaves contained substances that interfered with this procedure, but ether extraction effectively separated p-HB from these interfering materials. We observed that when flag leaf tissue from field-grown sorghum was dried at 75°C and then autoclaved, HCN-p values were about three times as high as those based on tissue that was autoclaved without drying. Investigations of this apparent enhancement supported the conclusion that when fresh field-grown sorghum leaf tissue was autoclaved, dhurrin was extensively altered or lost, but neither p-HB nor HCN was produced. Drying the tissue at 75°C prior to autoclaving effectively reduced this loss. Inclusion of tissue drying and ether extraction steps in the spectrophotometric assay made this procedure, which was designed for use with sorghum seedlings, satisfactory for use with field-grown sorghum leaves.