Interaction of hydroxyaryl aldehydes with α-hydroxyethyl radicals

Article abstract of DOI:10.1134/S0018143911030040

The effect of some hydroxylated aromatic aldehydes on the radiation-chemical transformations of deaerated ethanol during continuous radiolysis has been studied. The data obtained show that these compounds effectively inhibit radiation-induced processes involving α-hydroxyethyl radicals (α-HER). Benzaldehyde and its hydroxylated derivatives (II, III) predominantly oxidize, and compounds containing the cinnamic moiety, (IV-VI), add α-HER to a carbonyl group or -C=C bond. Pleiades Publishing, Ltd., 2011.

Full text of DOI:10.1134/S0018143911030040

ISSN 0018ꢀ1439, High Energy Chemistry, 2011, Vol. 45, No. 3, pp. 196–201. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © S.N. Gapan’kova, S.D. Brinkevich, I.P. Edimecheva, V.P. Kurchenko, O.I. Shadyro, 2011, published in Khimiya Vysokikh Energii, 2011, Vol. 45, No. 3,
pp. 227–232.
RADIATION CHEMISTRY
Interaction of Hydroxyaryl Aldehydes with αꢀHydroxyethyl Radicals
S. N. Gapan’kovaa , b, S. D. Brinkevicha, I. P. Edimechevaa, V. P. Kurchenkob, and O. I. Shadyroa, b
a Research Institute for Physicochemical Problems, Belarussian State University,
ul. Leningradskaya 14, Minsk, 220030 Belarus
b Belarussian State University, pr. Nezavisimosty 4, Minsk, 220030 Belarus
Eꢀmail: shadyro@open.by
Received June 22, 2010
Abstract—The effect of some hydroxylated aromatic aldehydes on the radiationꢀchemical transformations
of deaerated ethanol during continuous radiolysis has been studied. The data obtained show that these comꢀ
pounds effectively inhibit radiationꢀinduced processes involving
dehyde and its hydroxylated derivatives (II, III) predominantly oxidize, and compounds containing the cinꢀ
namic moiety, (IV–VI), add ꢀHER to a carbonyl group or –C=C bond.
α
ꢀhydroxyethyl radicals ( ꢀHER). Benzalꢀ
α
α
DOI: 10.1134/S0018143911030040
Hydroxylated aromatic aldehydes (hydroxyarene
carbaldehydes) refer to the numerous class of plant
phenols. Exhibiting antioxidant properties, they are
able to regulate free radical processes in biological sysꢀ
tems and, as such, have useful medical properties [1].
Plant phenols also exhibit radioprotective properties
due to the inhibition of radiationꢀinduced free radical
oxidation and degradation of vital components of livꢀ
ing organisms [2]. The antioxidant properties of pheꢀ
nolic compounds are generally related to their ability
to reduce the peroxyl radicals (ROO•) resulting from
the action of radiation or free radical agents on organic
compounds in the presence of oxygen. Satisfactory
correlations between the reducing properties dependꢀ
ing on the –O–H bond strength of phenols and their
antioxidant activity were obtained [3, 4].
Studying the reactions of hydroxylated aromatic
aldehydes with ꢀHER is of interest partly due to the
necessity of evaluation of hepatoprotective properties
of these compounds, since the cytotoxic and
mutagenic properties of ethanol are largely related to
α
the ꢀHER formation during its metabolic conversion
α
in human liver by the action of cytochrome Р450 [11],
with the degree of damage to biomolecules being
directly dependent on the concentration of natural
scavengers of radical intermediates [12]. A number of
alcoholic beverages that are produced through longꢀ
term storage in oak barrels as a manufacturing techꢀ
nology step accumulate significant amounts of
hydroxylated derivatives of cinnamaldehyde and benꢀ
zaldehyde as a result of the lignin ethanolysis and
hydrolysis processes [13].
In our studies we have shown that the fragmentaꢀ
tion reactions, proceeding through the stage of the forꢀ
mation and subsequent decay of ꢀhydroxylated carꢀ
α
bonꢀcentered radicals of parent compounds, make a
considerable contribution to the radiationꢀinduced
transformations of hydroxylꢀcontaining compounds,
such as lipids, carbohydrates, and peptides [5–7]. It
has been established that these processes are inhibited
by quinones and other carbonyl compounds [8–10]. It
is unknown whether hydroxylated aromatic aldehydes
EXPERIMENTAL
4ꢀHydroxyꢀ3ꢀmethoxybenzaldehyde (II), 4ꢀhydroxyꢀ
3,5ꢀdimethoxybenzaldehyde (III), transꢀcinnamaldeꢀ
hyde or cinnamaldehyde (IV), transꢀ4ꢀhydroxyꢀ3ꢀ
methoxycinnamaldehyde (V), transꢀ4ꢀhydroxyꢀ3,5ꢀ
dimethoxycinnamaldehyde (VI), acetaldehyde (AA),
and (+/ꢀ)ꢀmesoꢀ2,3ꢀbutanediol (2,3ꢀBD) (Sigma
Aldrich) and 2ꢀmethoxyphenol (VII) (Fluka) were
used without further purification. Benzaldehyde (I)
was distilled at 10 mmHg before using. Rectified ethaꢀ
nol (96 vol %) was purified by sorption on Wolfen
Zeosorb LA zeolite followed by fractional distillation.
can interact with
α
ꢀhydroxylated carbonꢀcentered
radicals and block the fragmentation or not. Such
information can be obtained by studying the effect of
hydroxyaryl aldehydes on the formation of final prodꢀ
ucts of radiolysis of deaerated ethanol, which yields ꢀ
α
hydroxyethyl radicals (
α
ꢀ
HER) during its ꢀirradiaꢀ
γ
tion.
196

INTERACTION OF HYDROXYARYL ALDEHYDES WITH
α
ꢀHYDROXYETHYL RADICALS
197
H
O
H
O
H
O
OCH3
H3CO
O
OCH3
OH
(II)
OH
(III)
(I)
H
H
O
H
O
OCH3
OCH3
H3CO
OCH3
OH
(VII)
OH
(V)
OH
(IV)
(VI)
Solutions of test compounds were prepared by disꢀ retention times relative to standards; the concentraꢀ
solving their weighed portions in ethanol. Because of tions were calculated using calibration coefficients.
the solvent high volatility, oxygen removal and sealing
Molecular products of ꢀHER reactions with the
α
of ampoules with deaerated solutions were carried out
as described in [14]. Irradiation was performed on a
γ
test compounds were identified by gas chromatograꢀ
phy using a Shimadzu GCMSꢀQP2010 Plus massꢀ
selective detector with a Equityꢀ5 column (length
30 m, inner diameter 0.25 mm, stationaryꢀphase
MPXꢀ
ꢀ25M facility with a 60Co source. The absorbed
dose rate was 0.45 0.005 Gy/s, and the absorbed dose
range was 0.27–1.35 kGy.
thickness 0.25 m). The analysis conditions: carrier
µ
Acetaldehyde and 2,3ꢀbutanediol were determined
by gas–liquid chromatography on a Shimadzu GCꢀ
17A instrument with a flameꢀionization detector and a
RTXꢀWAX capillary column (length 30 m, inner
diameter 0.32 mm, stationaryꢀphase film thickness
gas, helium; superficial gas velocity in the column,
0.365 m/s; column oven program, heating from 60 to
270°С at a rate of 5°C/min; injector temperature,
270°С; ion source and interface temperatures, 280°С
.
0.5 m). The analysis conditions were as follows: carꢀ
µ
The radiationꢀchemical yields of radiolysis prodꢀ
ucts and solute consumption were calculated from the
linear portions of concentration versus absorbed dose
curves by the least squares technique.
rier gas, nitrogen; column oven program, heating from
40 to 200°С with a gradient of 13°C/min; and superfiꢀ
cial gas velocity in the column, 0.25 m/s. The injector
and detector temperatures were 220°С. The concenꢀ
trations of hydroxyaryl aldehydes in the initial and
irradiated solutions were determined by gas–liquid
chromatography on the Shimadzu GCꢀ17A with a
RTXꢀ1 capillary column (length 30 m, inner diameter
RESULTS AND DISCUSSION
The radiationꢀchemical transformations of ethanol
0.32 mm, stationaryꢀphase film thickness 0.5 m). have been studied in detail [15]. The main molecular
µ
The analysis conditions: carrier gas, nitrogen; column products of the radiolysis of deaerated ethanol in the
oven program, heating from 60 to 290°С at a rate of absence of additives are 2,3ꢀBD and AA, which are
8°C/min and volumetric gas flow rate in the column, predominantly generated the in equiprobable combiꢀ
4 ml/min. The injector and detector temperatures nation (1) and disproportionation (2) reactions of
were 270°С. The substances were identified by their
α
ꢀHER:
CH CH(OH)CH(OH)CH ,
3
(1)
(2)
•
3
γ
CH CHOH
•
CH CHOH
3
CH CH OH
3
2
3
CH CHO + CH CH OH.
3
3
2
For this reason, the comparison of the radiationꢀ the radiolysis of deaerated ethanol in the presence and
chemical yields of products of these reactions during absence of various additives makes it possible to deterꢀ
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198
GAPAN’KOVA et al.
mine the reactivity of the test compounds and the tionꢀinduced decomposition of the additive barely
mechanism of their reaction with ꢀHER. occurs. These findings show that guaiacol VII has low
reactivity toward ꢀHER. Consequently, the aldehyde
α
α
The radiationꢀchemical yields of the main prodꢀ
ucts of deaeratedꢀethanol radiolysis in the presence of
the test compounds are given in the table. These data
indicate that the admixture of compounds I–VI
changes the ratio between the main deaeratedꢀethanol
radiolysis products in favor of AA. This fact demonꢀ
strates the ability of test compounds I–VI to oxidize
group, rather than the phenol moiety, in the structure
of the test compounds is responsible for the effects
observed during the radiolysis of deaerated ethanol in
the presence of compounds I–VI.
It has been shown that carbonyl compounds, such
as aldehydes [16], quinones [8], and flavonoids [10],
are able to efficiently oxidize hydroxyalkyl radicals. In
the ꢀHER.
α
Notably, the AA and 2,3ꢀBD radiationꢀchemical the case of aliphatic aldehydes, it was proved that the
yields remain unchanged during the radiolysis of ꢀHER oxidation reaction proceeds through the stage
α
deaerated ethanol in the presence of guaiacol VII, as of radical addition to the carbonyl group yielding radꢀ
compared to the additiveꢀfree system, and the radiaꢀ ical adduct VIII [16]:
H3C
OH
CH
CH
•
•
CH3CHOH + RCH=O
CH3CHO + RCHOH.
(3)
•
R
O
(VIII)
In the case of compounds I–VI, the occurrence of chemical yields, which can be represented by the folꢀ
a reaction of this type should lead to an increase in the lowing scheme for benzaldehyde and its derivatives
AA formation and solute degradation radiationꢀ (II, III):
H
H3C
C
OH
•
O
H
O
•
HC OH
HC
•
CH3CHOH
(4)
+
CH3CHO
+
.
R3
R1
R3
R1
R3
R1
R2
R2
R2
However, the data obtained (table) show that during relatively low decomposition yields are observed for these
the radiolysis of deaerated ethanol in the presence of substances. This suggests the possibility of regeneration
compounds I–III, the decrement in the 2,3ꢀBD is of the radicals, produced via reaction (4), back to the parꢀ
greater than the increment in the AA yield. In addition, ent compounds through the following process:
H
O
•
HC OH
•
CH3CHOH
.
(5)
+
+
CH3CH2OH
R1
R3
R1
R3
R2
R2
The consecutive occurrence of reactions (4) and
In the case of radiolysis of deaerated ethanol in the
(5) results in a significant decrease in the 2,3ꢀBD presence of cinnamic aldehyde and its derivatives V
yield, an increase in AA yield, and the regeneration of and VI, the yield of 2,3ꢀBD considerable decreased
compounds I–III.
and the radiationꢀinduced decomposition of the addiꢀ
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INTERACTION OF HYDROXYARYL ALDEHYDES WITH
α
ꢀHYDROXYETHYL RADICALS
199
Effect of hydroxyaryl aldehydes and 2ꢀmethoxyphenol on the radiationꢀchemical yields of the main radiolysis products of deꢀ
aerated ethanol
Radiationꢀchemical yield (G), molecule/100 eV
Additive, c = 10–3 mol/l
acetaldehyde
2,3ꢀbutanediol
additive decomposition
Additiveꢀfree
1.60 0.07
2.37 0.07
2.06 0.12
2.25 0.10
1.47 0.06
1.54 0.18
1.63 0.07
1.42 0.06
1.56 0.03
0.35 0.01
0.56 0.04
0.47 0.03
0.02 0.01
0.07 0.01
0.05 0.02
1.51 0.07
–
I
–1.79 0.07
–1.21 0.08
–1.93 0.10
–4.28 0.09
–4.45 0.15
–3.40 0.11
–0.07 0.05
II
III
IV
V
VI
VII
tives was significant; however, the AA yield remained radiolysis of the cinnamic compounds. The main
molecular products of radiolysis of compounds IV–VI
are adducts with a molecular mass greater than that
of the parent compounds, M(additive) M(ethanol)
(water) (figure, spectrum a). Based on the analysis of
almost unchanged as compared to that for the addiꢀ
tiveꢀfree system. This difference of cinnamic comꢀ
pounds IV–VI from benzaldehyde and its derivatives
II and III is an indication of the likelihood of addiꢀ
M
M
=
+
–
M
the mass spectra patterns for radiolysis products havꢀ
ing the aboveꢀspecified molecular masses, we have
assumed that the identified substances are formed as
tional mechanisms of interaction between
compounds containing the acrolein moiety.
α
ꢀHER and
We have identified the molecular products of radiꢀ
olysis of compounds I–VI in deaerated ethanol by gas
chromatography–mass spectrometry. The figure
the result of ꢀHER addition to the carbonyl group of
α
compounds IV–VI followed by the dehydration of
intermediate radical adducts IX according to the
shows typical mass spectra of the major products of scheme:
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200
GAPAN’KOVA et al.
l
, %
206
100
75
50
25
0
(а)
91
124
131
147
77
119
65
55
102
191
175 189
163
40
60
80
100
120
140
160
180
200
220
m/z
l, %
100
137
(b)
44
124
119
75
50
25
0
180
91
152
147
55
77
65
119
206
107
224
40
60
80
100
120
140
160
180
200
220
m/z
l
, %
150
(c)
100
75
44
50
25
0
135
220
77
107
55
91
40
60
80
100
120
140
160
180
200
220
m/z
Mass spectra of the products of
namaldehyde (IV).
α
ꢀHER addition to (a) the C=O group and (b, c) the –C=C bond of 3ꢀmethoxyꢀ4ꢀhydroxycinꢀ
OH
•
O
O
H3C
•
CH3CHOH
+
R1
R3
R1
R3
R2
R2
(6)
OH
O
O
OH
•
H3C
H3C
H3C
•
+ H
–H O
2
.
R1
R3
R1
R3
R1
R3
R2
R2
R2
(IX)
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INTERACTION OF HYDROXYARYL ALDEHYDES WITH
α
ꢀHYDROXYETHYL RADICALS
201
The above mechanism of interaction with
α
ꢀHER masses of
M
=
M(additive)
+ M(ethanol) and M = M(additive) +
during the radiolysis of compounds IV–VI in deaerꢀ
ated ethanol can explain both the almost complete
suppression of the radiationꢀchemical yield of 2,3ꢀBD
and high radiationꢀchemical yields for the decomposiꢀ
tion of the test compounds.
M(ethanol)
⎯ 2 were identified as minor products of
radiolysis of cinnamic aldehyde and its derivatives
V and VI (figure; spectra b, c). This finding demꢀ
onstrates that compounds of the cinnamic
series are capable of addition of
α
ꢀHER across
the C=C bond conjugated with the carbonyl
⎯
Along with the ꢀHER adducts to the carbonyl
α
group, a series of compounds with molecular group:
O
O
O
OH
OH
OH
•
(X)
CH3
CH3
R3
CH3
+
O
(7)
(8)
,
R1
R3
R1
R1
R3
R2
(X)
R2
R2
•
CH3CHOH
O
O
O
HO
HO
HO
R1
R3
•
H3C
H3C
H3C
R2
(XI)
+
R1
R3
R1
R3
R1
R3
.
R2
(XI)
R2
R2
7. Shadyro, O.I., Sosnovskaya, A.A., and Vrublevskaya, O.N.,
Comparing the data obtained in the deaeratedꢀethꢀ
anol radiolysis study, we can conclude that the comꢀ
pounds examined effectively interact with ꢀhydroxyꢀ
ethyl radicals via different mechanisms. The ability of
hydroxyaryl aldehydes to oxidize or attach alcohol
radicals should be taken into account when they are
used as modulators of free radical processes in human
body, since they affect in different manners the yields
of toxic products of freeꢀradical transformations of
alcohols.
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