Ten sesterterpenoids, leucosceptroids E-N (1-10), possessing an α,β-unsaturated γ-lactone moiety, were isolated from the leaves and flowers of a woody Labiatae, Leucosceptrum canum. Their structures including relative stereochemistry were determined by comprehensive 1D and 2D NMR, MS, and in the case of 1 and 10, by single crystal X-ray diffraction analyses. This class of unique plant terpenoids was designated as leucosceptrane sesterterpenoids (=leucosceptroids). The potent antifeedant activity of the most abundant compound, leucosceptroid G (3), and a representative compound, leucosceptroid N (10), against the generalist plant-feeding insect Helicoverpa armigera suggested that they might also be defense compounds of L. canum against insects. © 2012 Elsevier Ltd. All rights reserved.
Luo, S. H., Hua, J., Niu, X. M., Liu, Y., Li, C. H., Zhou, Y. Y., … Li, S. H. (2013). Defense sesterterpenoid lactones from Leucosceptrum canum. Phytochemistry, 86, 29–35. https://doi.org/10.1016/j.phytochem.2012.11.008