title: Peltate glandular trichomes of Colquhounia seguinii harbor new defensive clerodane diterpenoids.
abstract: Glandular trichomes produce a wide variety of secondary metabolites that are considered as major defensive chemicals against herbivore attack. The morphology and secondary metabolites of the peltate glandular trichomes of a lianoid Labiatae, Colquhounia seguinii Vaniot, were investigated. Three new clerodane diterpenoids, seguiniilactones A-C (1-3), were identified through precise trichome collection with laser microdissection, metabolic analysis with ultra performance liquid chromatography-tandem mass spectrometer, target compound isolation with classical phytochemical techniques, structure elucidation with spectroscopic methods. All compounds showed significant antifeedant activity against a generalist plant-feeding insect Spodoptera exigua. Seguiniilactone A (1) was approximately 17-fold more potent than the commercial neem oil. α-Substituted α,β-unsaturated γ-lactone functionality was found to be crucial for strong antifeedant activity of this class of compounds. Quantitative results indicated that the levels of these compounds in the peltate glandular trichomes and leaves were sufficiently high to deter the feeding by generalist insects. Moderate antifungal activity was observed for seguiniilactone C (3) against six predominant fungal species isolated from the diseased leaves of C. seguinii, while seguiniilactones A and B were generally inactive. These findings suggested that seguiniilactones A-C might be specialized secondary metabolites in peltate glandular trichomes for the plant defense against insect herbivores and pathogens.
authors.affiliation: State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming, 650201, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Chun-Huan
authors.initials: CH
authors.lastname: Li
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Juan
authors.initials: J
authors.lastname: Hua
authors.forename: Shi-Hong
authors.initials: SH
authors.lastname: Luo
authors.forename: Sheng-Hong
authors.initials: SH
authors.lastname: Li
mesh_terms: D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology; D002853:Chromatography, Liquid; D045785:Diterpenes, Clerodane / Q000378:metabolism* / Q000494:pharmacology; D005247:Feeding Behavior / Q000187:drug effects; D019686:Lamiaceae / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D019906:Nuclear Magnetic Resonance, Biomolecular; D018411:Spodoptera / Q000502:physiology; D053719:Tandem Mass Spectrometry; D064201:Trichomes / Q000378:metabolism*
chemical_list: D000935:Antifungal Agents; D045785:Diterpenes, Clerodane
keywords: Colquhounia seguinii Vaniot; antifeedant and antifungal activities; clerodane diterpenoids; laser microdissection; peltate glandular trichomes