TITLE:
Triterpenes from Cabralea canjerana as in Vitro Inhibitors to Light Reactions of Photosynthesis
AUTHORS:
Beatriz King-Díaz, Márcio S. Soares, Maria Fátima das G. F. da Silva, Blas Lotina-Hennsen, Thiago A. M. Veiga
KEYWORDS:
Cabralea canjerana, Cabraleadiol, Ocotilone, Odoratone, Photosynthesis
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.5 No.16,
July
31,
2014
ABSTRACT:
Aims: Cabraleadiol (1), Ocotilone (2) and Odoratone (3) are three triterpenes isolated from Cabralea
canjerana (Vell.) Mart. (Meliaceae).
They were chemically characterized, and their effect was tested on the light reaction of
photosynthesis. Study Design: Natural products were used as models to find new
models for inhibitors of photosynthesis. Place and Duration of Study: Departmento
de Química, Universidade Federal de São Carlos and Departmento de Bioquímica,
Facultad de Química, Universidad Nacional Autonoma de México, between May 2013
and January 2014. Methodology: The natural products had their effect on the
light reaction of photosynthesis studied by pollarography and Chlorophyll a
(Chl a) fluorescence
transients. Results: The compounds inhibited ATP synthesis and electron
transport rate (basal, phosphorylating and uncoupled). Therefore, they act as
Hill reactions inhibitors. Their inhibition site were located in the range of
electron flow from OEC complex and between P680 to QA of
PS II, and inhibited the photosystem II (PS II) by inducing the appearance of a
K-band which is an indicative that the photochemical apparatus is failing at
the donor side of PS II interacting at the OEC complex and by transforming
active reaction centers to “heat sinks” or the formation of silent reaction
centers unable to reduce QA. Conclusion: Furthermore, these
triterpenes inhibit PS II and induce the appearance of small G band which is
related with the decreased plastoquinone (PQ) pool reduction.