The chemotaxonomic significance of two bioactive caffeic acid esters, nepetoidins A and B, in the Lamiaceae

• Published in: Phytochemistry (Oxford) 2003-09, Vol.64 (2), p.519-528
• Main Authors: Grayer, Renée J, Eckert, Maria R, Veitch, Nigel C, Kite, Geoffrey C, Marin, Petar D, Kokubun, Tetsuo, Simmonds, Monique S.J, Paton, Alan J
• Format: Article
• Language: English
• Subjects: ( Z,E)-[2-(3,4-dihydroxyphenyl)ethenyl] 3-(3,4-dihydroxyphenyl)-2-propenoate; ( Z,E)-[2-(3,5-dihydroxyphenyl)ethenyl] 3-(3,4-dihydroxyphenyl)-2-propenoate; Acanthaceae; Animals; Antifungal; Antifungal Agents - chemistry; Antifungal Agents - isolation & purification; Antifungal Agents - pharmacology; Aspergillus niger - drug effects; Biological and medical sciences; Buddlejaceae; Caffeic acid esters; Caffeic Acids - isolation & purification; Caffeic Acids - metabolism; Caffeic Acids - pharmacology; Chemosystematics; Dose-Response Relationship, Drug; Ecology; Esters - isolation & purification; Esters - metabolism; Esters - pharmacology; Feeding Behavior - drug effects; Free Radical Scavengers - chemistry; Free Radical Scavengers - isolation & purification; Free Radical Scavengers - pharmacology; Free radical scavenging activity; Fundamental and applied biological sciences. Psychology; Insect phagostimulant; Lamiaceae; Lamiaceae - classification; Lamiaceae - embryology; Lamiaceae - metabolism; Larva - drug effects; Magnetic Resonance Spectroscopy; Nepetoideae; Ocimum basilicum; Plant cytology, morphology, systematics, chorology and evolution; Plectranthus; Pollen - chemistry; Pollen - classification; Rosmarinus; Scrophulariaceae; Spectrophotometry, Ultraviolet; Spermatophyta; Spodoptera - drug effects; Systematics (diagnosis, chromosome numbers); Thymus; Verbenaceae
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/S0031-9422(03)00192-4

A survey of leaf surface constituents in the family Lamiaceae using HPLC with diode array detection revealed the presence of two characteristic phenolic compounds in many species. The distribution of these phenolics in the Lamiaceae was found to be of taxonomic significance, as they were present in the great majority of species investigated for the subfamily Nepetoideae, including representatives of the well-known genera of culinary herbs, mint, rosemary, sage, thyme and basil. In contrast, they were absent from species of the other subfamilies of Lamiaceae studied and from the related families Verbenaceae, Scrophulariaceae, Acanthaceae and Buddlejaceae. The compounds were isolated from Plectranthus crassus and identified by NMR spectroscopy as the known caffeic acid esters ( Z,E)-[2-(3,5-dihydroxyphenyl)ethenyl] 3-(3,4-dihydroxyphenyl)-2-propenoate and ( Z,E)-[2-(3,4-dihydroxyphenyl)ethenyl] 3-(3,4-dihydroxyphenyl)-2-propenoate, for which the trivial names nepetoidins A and B are proposed. The presence of this pair of caffeic acid esters adds another character to the chemical, palynological and embryological features distinguishing the Nepetoideae from the other subfamilies of Lamiaceae and related families, and supports the view that the Nepetoideae are a specialised and monophyletic group within the family. Nepetoidin B was shown to have a greater antioxidant activity than gallic, rosmarinic and caffeic acids, and showed activity as an insect phagostimulant. Both compounds were antifungal. ( Z,E)-[2-(3,5-dihydroxyphenyl)ethenyl]3-(3,4-dihydroxyphenyl)-2-propenoate ( 1) and ( Z,E)-[2-(3,4-dihydroxyphenyl)ethenyl]3-(3,4-dihydroxyphenyl)-2-propenoate ( 2) were detected in leaf surface extracts of the great majority of species investigated for subfamily Nepetoideae of the Lamiaceae, whereas they were absent from species of the other subfamilies examined. Hence they are of chemotaxonomic significance. Compound 2 showed a high antioxidant activity.