title: Insect-antifeedant and antibacterial activity of diterpenoids from species of Plectranthus.
abstract: Bio-assay guided fractionation of an acetone extract of leaf material from Plectranthus saccatus Benth. resulted in the isolation of a beyerane diterpenoid. This compound, characterised by spectroscopic methods as ent-3beta-(3-methyl-2-butenoyl)oxy-15-beyeren-19-oic acid, showed insect antifeedant activity against Spodoptera littoralis. Known quinonoid abietane diterpenoids obtained from new sources included a mixture of the (4R,19R) and (4R,19S) diastereoisomers of coleon A from P. aff. puberulentus J.K. Morton, coleon A lactone from P. puberulentus J.K. Morton, and coleon U and coleon U quinone from P. forsteri 'Marginatus' Benth. These compounds, and the crude acetone extracts from the leaf surfaces of 11 species of Plectranthus, were tested for antifeedant activity against S. littoralis, antibacterial activity against Bacillus subtilis and Pseudomonas syringae and antifungal activity against Cladosporium herbarum. The coleon A mixture showed potent antifeedant activity against S. littoralis, whereas coleon U showed the greatest antimicrobial activity.
authors.affiliation: Royal Botanic Gardens, Biological Interactions, Kew, Richmond, Surrey TW9 3AB, UK.
authors.forename: Julia
authors.initials: J
authors.lastname: Wellsow
authors.forename: Renée J
authors.initials: RJ
authors.lastname: Grayer
authors.forename: Nigel C
authors.initials: NC
authors.lastname: Veitch
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Kokubun
authors.forename: Roberto
authors.initials: R
authors.lastname: Lelli
authors.forename: Geoffrey C
authors.initials: GC
authors.lastname: Kite
authors.forename: Monique S J
authors.initials: MS
authors.lastname: Simmonds
mesh_terms: D045784:Abietanes / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D005247:Feeding Behavior / Q000187:drug effects*; D007313:Insecta / Q000502:physiology*; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D031346:Plectranthus / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013056:Spectrophotometry, Ultraviolet
chemical_list: D045784:Abietanes; D000900:Anti-Bacterial Agents; C560600:coleon A lactone