Repellent and Insecticidal Activity of Naphthoquinones from the Heartwood of Tectona grandis on Incisitermes marginipennis (Latreille)

Abstract

Wood is a lignocellulosic material that, because of its organic nature, is a source of nutrients for bacteria, fungi, and insects. Incisitermes marginipennis (Latreille) is an interesting dry wood-boring termite. Because it is an extremely destructive pest, difficult to control due to its cryptic lifestyle, and for its role in the biogeochemical cycle of carbon and other elements; it is a fundamental organism. The use of less toxic and eco-friendly substances is important for protecting domestic, cultural, and historical heritage made of wood or lignocellulosic materials. The aim of this study was to evaluate the biological activity of various naphthoquinones extracted from the heartwood of T. grandis on I. marginipennis. First, heartwood flour was used for Soxhlet-type extractions to isolate and characterize the heartwood compounds by thin-layer chromatography. To identify the heartwood compounds, nuclear magnetic resonance and gas chromatography coupled to a mass spectrometer were used. The information obtained was supported using the Interactive Spectroscopy software. The identified heartwood compounds were lapachol, tectoquinone, deoxylapachol, dehydro-α-lapachone, tectol and tecomaquinone-I. Using nymphal termites of I. marginipennis as a biological model, the isolated and identified molecules were under three different tests (repellent, insecticide and protective) and their biological activity was individually evaluated. The results showed that the molecules obtained have a repellent-protective effect against I. marginipennis, although not in all cases, these molecules have high percentages of mortality and decreased the weight loss of the treated material exposed to I. marginipennis.