Utilization of Bark Condensed Tannin as Natural Preservatives Against Subterranean Termite

Abstract

Extractive-based preservative has been isolated from many parts of plant to protect wood from fungi or pest. This is due to the presence of bioactive chemical as a natural preservative. Present study, the condensed tannin was isolated from bark-waste of Acacia crassicarpa and Acacia mearnsii. The yield of the extracts obtained from A. crassicarpa using a 70% acetone aqueous solution (7% based on bark weight) is less than that obtained from A. mearnsii (34%). To evaluate the termiticidal activity of condensed tannin from both extracts, no-choice tests were conducted using Reticulitermes speratus. After 14 days, mass loss of the dimmer condensed tannin treated was less than 50%, significantly different with control. In addition, a monomer condensed tannin, catechin was presented the similar result. Meanwhile, the termite mortality of catechin is slightly higher than the dimmer. According to both parameter, the medium level of mass loss and termite mortality, the dimmer suggested as antifeedant in mechanism of termiticidal. The feeding activity is decreased after contact with the treated paper disc. In polymer condensed tannin, the result seems similar to dimmer condensed tannin. Condensed tannin and hydrolyzable tannin which were contained in the bark effected termite consumption because it caused inactivation of enzyme in termite digestion system. In fact, many factors effect termite activity from natural extractives such as compound type, quantity and also extract retention activity. The finding of this study should contribute to the developing of natural wood preservative from extractive-based. Especially, the study of structure-active relationship (SAR) of condensed tannin from A. crassicarpa, which can improve the utilization of bark-waste from pulp industry.