Report No xxxx - Instytut Fizyki JÄ drowej PAN

ROLE OF THE CHELATING PROCESS OF FLAVONOIDS REDUCING
THE INTERACTION BETWEEN ORGANOMETALLIC COMPOUNDS
AND THE LIPID BILAYER – AS INFERRED
FROM THE 1H-NMR STUDY
1 Janina Gabrielska, 2 Monika Soczyńska–Kordala, 1 Stanisław Przestalski
1 Department of Physics and Biophysics, 2 Department of Food, Vegetables and Cereals,
Agricultural University, 50-375 Wrocław, Norwida 25, Poland, jaga@ozi.ar.wroc.pl
The toxicity of organic tin compounds (OC) with respect to biological membranes
depends, among others, on the degree of adsorption in the lipid phase of the membrane. The
ionic forms of organometallic compounds, once localized in the membrane bilayer, interact
with the polar membrane region [Kaszuba and Hant, 1990; Gabrielska et al., 1997]. It seems
possible that the interaction may decrease when the OC molecules are engaged in a donoracceptor
interaction leading to the formation of associates. As ligands in the complexes can
occur, e. g., natural compounds of the flavonoid family, such as kempferol, quercetin and
mirycetin (FL) [Morel et al., 1998; Dyba et al., 1999; Cornard and Merlin, 2001].
The present work determines the degree of the interaction between equimolar mixtures
of selected organometallic compounds (dichloro-diphenyltin – DPhT and chlorides of
triphenyltin – TPhT and triphenyllead – TPhL, with kempferol, quercetin, mirycetin) and the
phosphate grouping of the phosphatidylcholine (PC) liposome membrane. That interaction
was compared with both FL and OC compounds interacting alone with that grouping. As a
parameter of the interaction was assumed the competitive release of praseodymium ions (Pr 3+ )
from membranes induced by the compounds studied, measured with the proton nuclear
magnetic resonance (H 1 -NMR) method.
The results obtained allow to conclude that, as a result of chelating by FL the ionic
forms of OC compounds, changes their coulombic interaction with phosphate group of the
bilayer. Consequently, undergoes reduction also the degree of the competitive praseodymium
ions release from the membrane bilayer by equimolar mixtures of FL with OC, compared with
release of the ions effected by the compounds added separately. The decrease is especially
conspicuous for mixtures of flavonoids with DPhT (ca. 90%), and much lower for mixtures of
flavonoids with triphenyltin chlorides (ca. 40 %).
Natural flavonoid compounds, such as kempferol, quercetin and mirycetin, due to their
metal chelating properties [Cornard and Merlin, 2001; Soczyńska-Kordala et al., 2000], lead
and tin including, constitute a good protection against the toxic forms of OC compounds
acting on PC membranes.
Work supported by KBN grant No 4 PO6 019 21
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