Synthesis and Biological Activity of Metal Chitosan Complexes
P. S. Vlasov
, A. A. Kiselev
, N. S. Domnina
, E. V. Popova
, and S. L. Tyuterev
St. Petersburg State University, St. Petersburg, Russia
All-Russia Research Institute of Plant Protection, Russian Academy of Agricultural Sciences, St. Petersburg, Russia
Received April 8, 2008
Abstract—A series of complexes of chitosans of various molecular weights (3000–150000) with copper, iron(II),
and zinc sulfates were examined. Participation of amino groups of the polymer in coordination bonding with
the metal was proved by IR spectroscopy. The affinity of chitosan for iron ions was enhanced by introducing
phenolic fragments into the polymer.
AND POLYMERIC MATERIALS
ISSN 1070-4272, Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 9, pp. 1675–1681. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © P.S. Vlasov, A.A. Kiselev, N.S. Domnina, E.V. Popova, S.L. Tyuterev, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82,
No. 9, pp. 1571–1576.
Chitosan attracts attention of a wide range of
researchers owing to a set of valuable chemical and
biological properties [1, 2]. Availability of raw
materials for its preparation and polysaccharide nature
determining its affinity for living bodies make chitosan
an accessible and promising polymer for agriculture, in
particular, in plant growing for treatment of seeds and
vegetating plants .
Chitosan derivatives are major components of cell
walls of many parasitic microorganisms and phyto-
pathogens. Plant treatment with chitosan-based prepara-
tions simulates contact of plants with a phytopathogen
and activates their natural protective resources .
Advantages of this approach consist in doubtless
environmental safety, prolonged action of preparations
taken in low concentrations, and stimulation of the
resistance to any stress situations such as night frosts,
drought, and water logging.
One of possible ways to enhance valuable
biological properties of chitosan is its chemical
modification via reactive functional groups present in
the chitosan macrochain. Particularly attractive is
preparation of soluble metal chitosan complexes whose
application will provide plants with microelements and
thus enhance the capability of plants for adaptation to
unfavorable factors of the environment .
Commercial chemicals [chitosan (MW 150000,
degree of deacetylation 85%, Aldrich), sodium nitrite,
p-hydroxybenzaldehyde, sodium borohydride, copper
sulfate pentahydrate, zinc sulfate, iron(II) sulfate
heptahydrate, sodium hydroxide, potassium hydroxide,
glacial acetic acid] were used without additional
purification. The solvents (acetone, ethanol) were
purified by standard procedures .
The UV spectra were recorded on an SF-56 device
(Leningrad Optical and Mechanical Association,
Russia) in 1-cm quartz cells. The content of incur-
porated p-hydroxybenzaldehyde (BA) fragments in
chitosan was calculated using the extinction of a model
compound, 4-(dimethylaminomethyl)phenol, at a
wavelength of 274 nm in a mixed solvent CH
O : C
OH = 0.2 : 1 : 1. The IR spectra of chitosan
and its complexes (KBr pellets) were recorded in the
range 5000–400 cm
with a Specord IR-75
H NMR spectra were taken
on a Bruker DPX-300 spectrometer (300.13 MHz),
solvent 1 M DCl/D
O. The signal positions were
determined using as reference the signals of methyl
protons of the nondeacetylated units of the polymer
(2.06 ppm) . The viscosity of polymer solutions was
determined with an Ubbelohde viscometer at 25°C in a
mixed solvent 4% CH
COOH : 0.6 M NaCl = 1 : 1.
The molecular weight was calculated by the procedure
suggested in .
Oxidative degradation of chitosan. Chitosan (5 g)
was dissolved in 50 ml of 4% acetic acid. To the
resulting solution we added 5 ml of a solution
containing appropriate amount of NaNO
, after which