title: Natural diterpenes from Croton ciliatoglanduliferus as photosystem II and photosystem I inhibitors in spinach chloroplasts.
abstract: In our search for new natural photosynthetic inhibitors that could lead to the development of "green herbicides" less toxic to environment, the diterpene labdane-8alpha,15-diol (1) and its acetyl derivative (2) were isolated for the first time from Croton ciliatoglanduliferus Ort. They inhibited photophosphorylation, electron transport (basal, phosphorylating and uncoupled) and the partial reactions of both photosystems in spinach thylakoids. Compound 1 inhibits the photosystem II (PS II) partial reaction from water to Na(+) Silicomolibdate (SiMo) and has no effect on partial reaction from diphenylcarbazide (DPC) to 2,6-dichlorophenol indophenol (DCPIP), therefore 1 inhibits at the water splitting enzyme and also inhibits PS I partial reaction from reduced phenylmetasulfate (PMS) to methylviologen (MV). Thus, it also inhibits in the span of P(700) to Iron sulfur center X (F(X)). Compound 2 inhibits both, the PS II partial reactions from water to SiMo and from DPC to DCPIP; besides this, it inhibits the photosystem I (PS I) partial reaction from reduced PMS to MV. With these results, we concluded that the targets of the natural product 2 are located at the water splitting enzyme, and at P(680) in PS II and at the span of P(700) to F(X) in PS I. The results of compounds 1 and 2 on PS II were corroborated by chlorophyll a fluorescence.
authors.affiliation: Department of Biochemistry, National Autonomous University of Mexico, Ciudad Universitaria, Delegación Coyoacán, C.P. 04510, Mexico, D.F., Mexico.
authors.forename: Félix
authors.initials: F
authors.lastname: Morales-Flores
authors.forename: María Isabel
authors.initials: MI
authors.lastname: Aguilar
authors.forename: Beatriz
authors.initials: B
authors.lastname: King-Díaz
authors.forename: Jesús-Ricardo
authors.initials: JR
authors.lastname: de Santiago-Gómez
authors.forename: Blas
authors.initials: B
authors.lastname: Lotina-Hennsen
mesh_terms: D002734:Chlorophyll / Q000737:chemistry; D000077194:Chlorophyll A; D029802:Croton / Q000737:chemistry*; D004224:Diterpenes / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D004579:Electron Transport / Q000187:drug effects; D010785:Photophosphorylation / Q000187:drug effects; D010788:Photosynthesis / Q000187:drug effects; D045331:Photosystem I Protein Complex / Q000037:antagonists & inhibitors*; D045332:Photosystem II Protein Complex / Q000037:antagonists & inhibitors*; D010936:Plant Extracts / Q000737:chemistry; D018724:Spinacia oleracea / Q000187:drug effects / Q000378:metabolism; D020524:Thylakoids / Q000187:drug effects / Q000378:metabolism
chemical_list: D004224:Diterpenes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010936:Plant Extracts; C521330:labdane-8alpha,15-diol; D002734:Chlorophyll; D000077194:Chlorophyll A