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

Biological Activity of Copper(II) N-Salicylideneaminoacidato Complexes. Reduction of Chlorophyll Content in Freshwater Alga Chlorella vulgaris and Inhibition of Photosynthetic Electron Transport in Spinach Chloroplasts

K. Kráľová, K. Kissová, O. Švajlenová, and J. Vančo

Institute of Chemistry, Faculty of Natural Sciences, Comenius University, SK-842 15 Bratislava

E-mail: kralova@fns.uniba.sk

Received: 5 November 2003

Abstract: The effects of CuCl₂ and 12 Cu(II) complexes on reduction of chlorophyll content in statically cultivated green alga Chlorella vulgaris and inhibition of photosynthetic electron transport in spinach chloroplasts were studied. The studied complexes were six chelate cuprates of the composition M⁺[Cu(TSB)(X)]⁻ containing tridentate Schiff base dianion ligands (TSB²⁻) of N-salicylideneaminoacidato type (derived from α-alanine or β-alanine, valine, phenylalanine), additional pseudohalogeno ligands (NCS⁻ or NCO⁻), and M (K, NH₄ or Na) as well as six molecular (N-salicylidene-β-alaninato)copper(II) complexes of the composition [Cu(sal-β-ala)(L)] with additional organic molecular ligands (L = imidazole, pyrazole, pyridine, quinoline, urea or thiourea). The toxic effects of the investigated Cu(II) complexes were compared with those of CuCl₂ and copper(II) acetate and the influence of the coordination mode of ligands in the tested Cu(II) complexes on the biological activity was discussed. It was found that in the set of Cu(II) cuprates, the inhibitory activity of the compound concerning reduction of chlorophyll content in Ch. vulgaris strongly depended on the applied amino acid and decreased in the following order: β-alanine, α-alanine, phenylalanine, valine. The differences between inhibitory effectiveness of six molecular (N-salicylidene-β-alaninato)copper(II) complexes with additional molecular ligands against Ch. vulgaris were not too high, indicating that the effect of additional organic ligands on the inhibitory activity is not significant. The lower inhibitory effect of both types of Cu(II) chelates in comparison to that of CuCl₂ and copper(II) acetate probably results from their higher stability in aqueous solutions. The Cu(II) compounds also decreased fluorescence intensity of chlorophyll a that is present in pigment-protein complexes of photosynthetic centres (mainly in photosystem 2) of spinach chloroplasts. It could be assumed that the toxic effects of the studied copper(II) complexes are probably due to the substitution of their additional ligands with N-, S- or O-donor ligands present in proteins of algal and higher plant cells.

Full paper in Portable Document Format: 585a357.pdf

Chemical Papers 58 (5) 357–361 (2004)