ISSN print edition: 0366-6352
ISSN electronic edition: 1336-9075
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The Physiological Response of Green Algae (Chlorella vulgaris) to pH-Dependent Inhibitory Activity of Some Zinc(II) Compounds: Carboxylato- and Halogenocarboxylatozinc(II) Complexes

K. Kráľová, E. Masarovičová, and K. Gyoryová

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

 

E-mail: kralova@fns.uniba.sk

Received: 13 October 2003

Abstract: The inhibition of chlorophyll content in statically cultivated green algae Chlorella vulgaris caused by ZnSO4 ·H2O and nine carboxylatozinc(II) complexes was observed at pH = 5.8 and 7.2, respectively. At pH = 5.8 comparable inhibitory activity with that of ZnSO4 ·H2O was shown only by Zn(ClCH2COO)2 ·2H2O (IC50 = 0.111 mmol dm−3 and 0.104 mmol dm−3, respectively). The inhibitory activity of all other compounds was lower (the corresponding IC50 values varied in the range of 0.204—0.571 mmol dm−3) and it showed a decrease in the following order: Zn(ICH2COO)2, Zn(BrCH2COO)2 ·2H2O, Zn(CH3COO)2 · 2.5H2O, Zn(ClCH2CH2COO)2, Zn(CH3CH2CH2COO)2 or Zn(CH3CH2COO)2, Zn(CH3CH(Cl)COO)2, Zn((CH3)2CHCOO)2. At pH = 7.2 the inhibitory activity of all tested halogenocarboxylatozinc(II) complexes was higher than that of ZnSO4 ·H2O (0.300 mmol dm−3). The inhibition of chlorophyll a by ZnSO4 ·H2O and by the studied zinc(II) complexes was more strongly affected than that of chlorophyll b. The insertion of halogen atom into ligand led to the increase of biological activity whereas the branching of the alkyl chain was connected with activity decrease. In aqueous solutions in the investigated zinc(II) complexes zinc atom is coordinated with carboxylato ligands as well as with H2O molecules. We assume that its toxic effect can be manifested after exchange of these ligands (mainly H2O) with potential O- and N-donor ligands occurring in the algal cells. The higher the complex stability, i.e. the lower is the complex ability to exchange its ligands, the lower is its biological activity. Organic ligands could also affect the transport of metal ions through the lipophilic regions of cell membranes.

Full paper in Portable Document Format: 585a353.pdf

 

Chemical Papers 58 (5) 353–356 (2004)

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