Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 2, pp. 252−255.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © O.V. Smirnova, I.V. Eﬁ mova, S.L. Khil’ko, S.S. Zlotskii, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 2, pp. 263−266.
AND INDUSTRIAL ORGANIC CHEMISTRY
Antioxidant and Pro-oxidant Activity of Ascorbic
and Humic Acids in Radical-Chain Oxidation Processes
O. V. Smirnova, I. V. Eﬁ mova, and S. L. Khil’ko
Litvinenko Institute of Physicoorganic and Coal Chemistry, National Academy of Sciences of Ukraine, Donetsk, Ukraine
Received July 19, 2011
Abstract—Joint action of ascorbic and humic acids in radical-chain oxidation of model hydrocarbons was studied.
This effect is promising for development of complex directed-action preparations with controllable redox properties
and development of antioxidants and pro-oxidants for medicinal purposes and technical applications.
At present, the number of natural substances for
which an antioxidant activity have been revealed is
rapidly growing. A search for new sources of inexpensive
and readily available raw materials for manufacture of
effective natural antioxidants for medicinal purposes,
liquid fuels, technical oils and lubricants, and food
products is a topical task .
It is known that humic acids (HAs) produced from
peats and brown coal exhibit a pronounced biological
activity [2, 3], which is due to the pronounced afﬁ nity
of humic acids for biological membranes, involvement
of the acids in the ion transport, and their effect on the
activity of enzymes [1, 2].
The antioxidant activity is one of pharmaceutical
tests for biologically active substances, and the presence
of active acid groups (–COOH, –OH) in macromolecules
of humic acids assumes that these substances are capable
of an antioxidant effect. However, no detailed studies of
these properties of humic acids have been reported in
The ability of humic acids to exhibit antioxidant and
pro-oxidant activity, as well as the joint action of vita-
min C with humic acids, may be promising for develop-
ment of complex directed-action preparations with con-
trollable redox properties. It is of interest in this context
to examine speciﬁ c features of processes in which or-
ganic substrates undergo radical-chain oxidation in the
presence of ascorbic (AA) and humic acids.
We have shown previously [4, 5] that ascorbic acid
exhibits antioxidant properties in both aqueous and
organic phases; irrespective of the nature of a solvent,
the action duration of vitamin C is determined by its
concentration in the system. We found the range of
ascorbic acid concentrations in the reaction mixture
at which its efﬁ ciency as an inhibitor of radical-chain
oxidation in an organic medium is the highest.
The goal of our study was to examine the antioxidant
activity of mixtures of ascorbic and humic acids in
radical-chain oxidation of aromatic hydrocarbons.
As the model system was chosen liquid-phase
oxidation of cumene, initiated by azodiisobutyronitrile
(AIBN), whose mechanism and all elementary stages
are well understood .
As the reaction medium served dimethyl sulfoxide
(DMSO) in which all the components of the system
under study are well soluble and thereby a study of the
process under homophase conditions is provided.
Humic acids are attributed to the class of macromo-
lecular aromatic polyoxypolycarboxylic acids, which
are natural polyelectrolytes. HA macromolecules
comprise a central part containing an aromatic carbon
skeleton and a peripheral part enriched in functional