Effects of Usnic, Barbatic and Fumarprotocetraric acids on Survival of Nasutitermes corniger (Isoptera: Termitidae: Nasutitermitinae)

Abstract

Lichens (Algal-Fungal association) synthesize unique chemical substances with different biological activities. Three pure lichen compounds were assayed to evaluate their potential insecticidal activity against the termite Nasutitermes corniger on Petri dishes. Usnic, fumarprotocetraric and barbatic acids were isolated and purified from the lichens Cladonia substellata, C. verticillaris and Cladia aggregata, respectively, using thin-layer and high-performance liquid chromatography for attesting their purity. Nuclear proton magnetic resonance and infrared spectrophotometry was used for their chemical characterization. After exposure, mortality of termites (workers and soldiers) was determined during 11 days period. The termiticidal effect was influenced by the exposure time and the type of member colony. The results showed that lichen substances, tested at 5, 7 and 10 mg mL-1, have a termiticidal activity (~100%) on worker termites after eight days of treatment, in comparison with controls. However, no significant effect on soldiers was found. These findings indicate that usnic, fumarprotocetraric and barbatic acids are potential compounds for use in the control of this urban pest.