Antitermitic activity of extractives from three Brazilian hardwoods against Nasutitermes corniger

Antitermitic activity of extractives from three Brazilian hardwoods timber known for their high resistance to biodegradation, Bowdichia virgilioides, Anadenanthera colubrina, and Hymenaea stigonocarpa, were evaluated in laboratory tests against termites Nasutitermes corniger. The data obtained in this study suggest that all extracts tested contained antitermitic compounds against this termite species. Alkaloidal extract from B. virgilioides heartwood exhibited the highest antitermitic activity (LC50 = 7.2 mg ml−1 after 4 days) followed by cyclohexane extracts from the same species (LC50 = 12.2 mg ml−1 after 4 days) and H. stigonocarpa heartwood (LC50 = 11.9 mg ml−1 after 4 days) and ethyl acetate extract from Anadenanthera colubrina wood (LC50 = 17.3 mg ml−1 after 4 days). Exposure of N. corniger to the other extracts from A. colubrina wood and H. stigonocarpa heartwood resulted in a higher termite survival rate than for the above mentioned extracts, but still reduced the survival of termites compared to a corresponding control. Only B. virgilioides cyclohexane extract presented repellent properties. The termite resistance of these hardwoods can be attributed to antitermitic activity of secondary metabolites present in the extracts.