Summary

Antitermitic activities of catechin-metal complexes were investigated for further utilization of catechin as a termite control agent. Catechin (CA), heavy metal salts (NiCl₂, CuCl₂, ZnCl₂) and CA/metal mixtures with Ni(II), Cu(II) and Zn(II) were subjected to bioassays using a subterranean termite, Coptotermes formosanus Shiraki. The astringent properties of each system were assessed by measuring the weight of precipitate with bovine serum albumin (BSA). Changes in UV spectra of the CA/metal mixtures were also measured. CA caused less than 30% mortality after the 21-day test period, and had no BSA-precipitating capacity. The effects of heavy metals on CA activities varied with metal. CA/Ni(II) showed the highest termiticidal activity among tested materials, but exhibited no BSA-precipitating capacity and little change in UV spectrum. On the other hand, both CA/Cu(II) and CA/Zn(II) increased the BSA-precipitating capacity and UV absorption with time after preparing the CA/metal solutions, but their termiticidal activity was almost equal to CA. Termiticidal activity of CA was improved by the addition of Ni(II) but hardly changed by Cu(II) or Zn(II), while astringent properties of CA were hardly changed by addition of Ni(II) but improved by Cu(II) or Zn(II). Termiticidal activity was negatively correlated with astringent property.