Studies on Crude Drugs Effective on Visceral Larva Migrans. III. The Bursting Activity of Tannins on Dog Roundworm Larva

Tannin, both condensed and hydrolyzable, were found to cause bursting of the second-stage larvae of dog roundworm (Toxocara canis), when combined with an appropriate larvicidal compound such as decanoic acid or tetradecanol. This bursting activity of tannins increased with increase of the degree of condensed tannins and with increase of the proportion of phenolic moieties for hydrolyzable tannins. Since tannins are not larvicidal by themselves, the apperance of this bursting activity requires the coexistence of larvicides. The activity was strongly induced by larvicides with a polar functional group such as an acid or an alcohol, but weakly induced by those with a less polar group such as an amide. Tannins were also found to enhance the killing activity of acid larvicides. These facts suggested the practical effectiveness of the combination of tannins and an appropriate anthelmintic for the treatement of parasitic diseases.