1990 Volume 36 Issue 3 Pages 277-285
In earlier experiments in our laboratory, a lectin from the Kintoki bean (Phaseolus vulgaris) was found to have not only erythrocyte agglutinating activity but also toxicities for mice and rats, including growth inhibitory activity and even lethal activity. A number of studies on legume lectins have been carried out in other laboratories as well. But relatively little attention has been paid to lectins from non-leguminous foods. In the present study, we chose Taro tuber as a source of non-leguminous lectins and prepared two types of Taro tuber lectin. One was crude lectin precipitated with ammonium sulfate from the aqueous extract and the other was pure lectin isolated as we described previously. The two were compared with regards to the antinutritional functions in mice. The daily doses were 100mg for either intact or autoclaved crude lectin, which was a maximum amount available to give to mice in 1ml, and 30mg for the pure lectin which was equivalent to 100mg of the crude lectin in hemagglutinating activity. Control mice were given 1ml of water and the experiment was conducted for 6 days. Growth retardation was found in the mice given either lectin, but no significant difference was found in the weight increase between the control group and the auto-claved lectin group. For 3 days during the experimental period, physical activity was measured as an index of vigor of mice. The activities of the crude lectin and the pure lectin groups leveled down to 62.9 and 64.2% of that of thecontrol group, respectively. No apparent difference was observed in the tissue weights among the groups at the end of the experiment. Protein efficient ratio (PER) values indicated worse effi-ciency of protein utilization in the lectin groups. Enzyme activities of sucrase, leucine aminopeptidase, and particularly of alkaline phosphatase were lower in the small intestine of the experimental groups. These results indicate that Taro tuber lectin has toxicity inhibiting regular biological functions in the intestine of mice, leading to growth retardation. Since Taro tuber lectin is more resistant to heat treatment than legume lectins, the present results suggest a need for care in cooking Taro tuber.
