Natural diterpenes from Croton ciliatoglanduliferus as photosystem II and photosystem I inhibitors in spinach chloroplasts.
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.
Morales-Flores
Félix
F
Department of Biochemistry, National Autonomous University of Mexico, Ciudad Universitaria, Delegación Coyoacán, C.P. 04510, Mexico, D.F., Mexico.
Aguilar
María Isabel
MI
King-Díaz
Beatriz
B
de Santiago-Gómez
Jesús-Ricardo
JR
Lotina-Hennsen
Blas
B
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
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