Observations on the cyanide content and toxicity of tropical pulses

ABSTRACT

The content of cyanogenetic glucosides in West Indian and other pulses was estimated by the release of hydrocyanic acid on hydrolysis. In the varieties of phaseolus lunatus (lima bean) examined, the CN content was under 20mg. per cent, and not of the order previously known to cause acute poisoning. Trace amounts were found in 5 other species, and a high content was found in a variety of vicia sativa seeds (common vetch). A comparison of hydrolytic procedures in ph. lunatus showed that whereas the cyanogenetic glucoside is stable on cooking the intact bean, neither human saliva nor dilute hydrochloric acid at 37oC was effective in releasing free HCN from beans crushed after cooking. Animal feeding tests of crushed uncooked beans showed that the toxicity of these varieties was unrelated to their CN content. Severe 'toxicity' of ph. vulgaris (kidney bean, red pea) in rats and guinea pigs was mainly, if not entirely, due to unpalatability, causing starvation. Palatability was much improved by cooking. Absorption and utilisation of other species were good when fed to rats, even at 50 per cent level. There was some evidence of pancreatic hypertrophy and of impaired absorption or utilization of vigna sp. (black-eye pea) and cajanus cajan (gungo pea) in guinea pigs. No neurological lesions were detected in rats in feeding tests of up to 6 month's duration (AU)