ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

5-Bromo- and 3,5-dibromo-2-hydroxy-N-phenylbenzamides — inhibitors of photosynthesis

Katarína Kráľová, František Šeršeň, Matúš Peško, Karel Waisser, and Lenka Kubicová

Institute of Chemistry, Comenius University, SK-842 15, Bratislava, Slovakia

E-mail: kralova@fns.uniba.sk

Abstract: 5-Bromo-(Br-PBA) and 3,5-dibromo-2-hydroxy-N-phenylbenzamides (Br₂-PBA) inhibited photosynthetic electron transport (PET) and their inhibitory efficiency depended on the compound lipophilicity as well as on the electronic properties of the R substituent in the N-phenyl moiety. Br-PBA showed higher PET inhibiting activity than Br₂-PBA with the same R substituent. The most effective inhibitors in the tested series were the derivatives with R = 3-F (Br-PBA; IC₅₀ = 4.3 μmol dm⁻³) and R = 3-Cl (Br₂-PBA; IC₅₀ = 8.6 μmol dm⁻³). Bilinear dependence of the PET inhibiting activity on the lipophilicity of the compounds as well as on the Hammett constant, σ, of the R substituent was observed for both investigated series. Using EPR spectroscopy it was found that the site of action of the tested compounds in the photosynthetic apparatus is situated on the donor side of PS 2, in D^· or in the Z^·/D^· intermediates. Interaction of the studied compounds with chlorophyll a and aromatic amino acids present in the pigment-protein complexes mainly in photosystem 2 was documented by fluorescence spectroscopy.

Keywords: salicylanilides – EPR spectroscopy – fluorescence spectroscopy – photosynthetic electron transport – site of action

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-013-0416-7

Chemical Papers 68 (1) 46–52 (2014)