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Mechanism of Action of Sulforaphane as a Superoxide Radical Anion and Hydrogen Peroxide Scavenger by Double Hydrogen Transfer: A Model for Iron Superoxide Dismutase

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The mechanism of action of sulforaphane as a scavenger of superoxide radical anion (O2•‾) and hydrogen peroxide (H2O2) has been investigated using density functional theory in both gas phase and aqueous media. Iron-superoxide dismutase (Fe-SOD) involved in scavenging superoxide radical anion from biological media was modeled by a complex consisting of the ferric ion (Fe3+) attached to three histidine rings. Reactions related to scavenging of superoxide radical anion by sulforaphane were studied using density functional theory (DFT) in the presence and absence of Fe-SOD represented by this model in both gas phase and aqueous media. The scavenging action of sulforaphane towards both superoxide radical anion and hydrogen peroxide was found to involve the unusual mechanism of double hydrogen transfer. It was found that sulforaphane alone, without Fe-SOD, cannot scavenge superoxide radical anion in gas phase or aqueous media efficiently as the corresponding reaction barriers are very high. However, in the presence of Fe-SOD represented by the above mentioned model, the scavenging reactions become barrierless and so sulforaphane scavenges superoxide radical anion by converting it to hydrogen peroxide efficiently. Further, sulforaphane has been found to scavenge hydrogen peroxide also very efficiently by converting it into water. Thus the mechanism of action of sulforaphane as an excellent antioxidant has been unravelled.
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Mechanism of Action of Sulforaphane as a Superoxide Radical Anion
and Hydrogen Peroxide Scavenger by Double Hydrogen Transfer: A
Model for Iron Superoxide Dismutase
Ajit Kumar Prasad and P.C. Mishra*
Department of Physics, Banaras Hindu University, Varanasi 221 005, India
*
SSupporting Information
ABSTRACT: The mechanism of action of sulforaphane as a
scavenger of superoxide radical anion (O2
) and hydrogen
peroxide (H2O2) was investigated using density functional
theory (DFT) in both gas phase and aqueous media. Iron
superoxide dismutase (Fe-SOD) involved in scavenging
superoxide radical anion from biological media was modeled by a complex consisting of the ferric ion (Fe3+) attached to
three histidine rings. Reactions related to scavenging of superoxide radical anion by sulforaphane were studied using DFT in the
presence and absence of Fe-SOD represented by this model in both gas phase and aqueous media. The scavenging action of
sulforaphane toward both superoxide radical anion and hydrogen peroxide was found to involve the unusual mechanism of
double hydrogen transfer. It was found that sulforaphane alone, without Fe-SOD, cannot scavenge superoxide radical anion in gas
phase or aqueous media eciently as the corresponding reaction barriers are very high. However, in the presence of Fe-SOD
represented by the above-mentioned model, the scavenging reactions become barrierless, and so sulforaphane scavenges
superoxide radical anion by converting it to hydrogen peroxide eciently. Further, sulforaphane was found to scavenge hydrogen
peroxide also very eciently by converting it into water. Thus, the mechanism of action of sulforaphane as an excellent
antioxidant has been unravelled.
INTRODUCTION
Reactive oxygen species (ROS) and reactive nitrogen oxide
species (RNOS) are mostly free radicals that are produced in
biological systems during metabolic activities, and these can
also be formed due to exposure of biological systems to
radiation or pollution. Because of their high chemical
reactivities, ROS and RNOS can cause oxidation and nitration
of DNA, proteins, and enzymes and thus give rise to several
diseases including cancer.
14
Superoxide radical anion (O2
),
hydroxyl radical (OH), hydrogen peroxide (H2O2), nitrogen
dioxide (NO2
), peroxynitrite (ONOO), etc. belong to the
ROS or RNOS family.
5
The superoxide radical anion is
intrinsically poorly reactive, but in the presence of other
chemical species, it can produce other highly reactive agents.
For example, its reaction with nitric oxide (NO) produces
peroxynitrite (ONOO), both these species being poorly
reactive, but when this reaction occurs in the presence of CO2,
the complex nitrosoperoxycarbonate is formed, which disso-
ciates rapidly into two highly reactive species, that is, nitrogen
dioxide (NO2
) and carbonate radical anion (CO3
).
6
Thus,
superoxide radical anion can play crucial roles in causing DNA
damage, depolymerize polysaccharides, peroxidize lipids, kill
mammalian cells, and inactivate enzymes.
714
Generation of
superoxide radical anion signals the rst sign of oxidative
burst.
15
Superoxide radical anion is produced in the human
body by one-electron reduction of molecular oxygen through
the involvement of various oxidative enzymes.
16,17
The enzyme
xanthine oxidase catalyzes production of superoxide radical
anion,
18
while the enzyme superoxide dismutase (SOD)
catalyzes its conversion to H2O2.
19,20
SOD can have dierent
forms depending on the presence of cation of iron, zinc,
manganese, or copper in it. The enzymes glutathione
peroxidase and catalase serve as strong endogenous antiox-
idants as the former catalyzes conversion of H2O2into water,
while the latter catalyzes its conversion into water and
oxygen.
2124
Certain nonenzymatic exogenous antioxidants, which can be
taken as components of diet, include ascorbic acid, α-
tocopherol, vitamin A, lycopene, etc.
25
Epidemiological studies
have shown that an increased dietary intake of fruits and
vegetables strongly decreases the risk of several chronic diseases
such as cardiovascular diseases, neurological disorders, diabetes,
cancer, etc.
26,27
Several plant metabolites including polyphe-
nolics, glucosinolates, and allyl suldes play crucial roles in the
prevention of several diseases.
28,29
Sulforaphane is also a
naturally occurring sulfur-containing compound that is present
in certain vegetables such as broccoli sprouts, cabbage, Brussels
sprouts, cauliower, bok choy, collards, mustard, turnip, etc.
30
Several studies have revealed that sulforaphane possesses strong
antioxidant and anticancer properties. It has been shown that
sulforaphane inhibits histone deacetylase (HDAC) activity in
human colon, prostate, breast, cervical, and ovarian cancers as
also in human leukemia cells.
3133
In other studies,
combinations of sulforaphane with cytotoxic drugs, for example,
Received: February 13, 2015
Revised: May 28, 2015
Published: May 28, 2015
Article
pubs.acs.org/JPCB
© 2015 American Chemical Society 7825 DOI: 10.1021/acs.jpcb.5b01496
J. Phys. Chem. B 2015, 119, 78257836
cisplatin, gemcitabine, doxorubicin, etc., have been found to
enhance eectiveness of treatment of cancer.
34
Sulforaphane is
highly eective in reducing the androgen receptor (AR) protein
level by decreasing secretion of prostate-specic antigen (PSA),
which is an AR-regulated gene product in human prostate
cancer cells.
35
Sulforaphane has numerous other highly useful
medical applications.
3641
Electronic and vibrational properties of sulforaphane have
been studied using a semiempirical method.
42
Yuan et al.
43
have
shown experimentally that sulforaphane can scavenge both
superoxide radical and hydroxyl radical. Niu et al.
44
have shown
that benzynes are capable of removing two vicinal hydrogen
atoms from a hydrocarbon in a concerted manner, which causes
alkane to alkene conversion. To the best of our knowledge,
double hydrogen abstraction by superoxide radical anion or
hydrogen peroxide from sulforaphane or any other antioxidant
has not yet been studied theoretically. The purpose of the
present study is to show that both superoxide radical anion and
hydrogen peroxide can be scavenged through double hydrogen
abstraction from sulforaphane, the reactions in the former case
being catalyzed by an SOD. Other antioxidants scavenge other
ROS through single hydrogen abstraction or addition reaction
mechanisms.
45
The novelty of the present work is that it is the
rst theoretical study having the following three important
features: (i) it explains the mechanism of scavenging action of
sulforaphane toward superoxide radical anion and hydrogen
peroxide, (ii) it shows double hydrogen transfer from an
antioxidant, that is, sulforaphane, to both superoxide radical
anion and hydrogen peroxide, and (iii) it presents a simple
model for iron superoxide dismutase (Fe-SOD) that explains
well the catalytic activity of the enzyme.
2. COMPUTATIONAL DETAILS
All the calculations reported here were performed at the
B3LYP/6-311+G(d) and M06-2X/6-311+G(d) levels of
theory. Geometries of all the reactant molecules, reactant
complexes (RCs), transition states (TSs), and product
complexes (PCs) were optimized in gas phase at the B3LYP/
6-311+G(d) and M06-2X/6-311+G(d) levels of density
functional theory.
4650
Solvent eect of aqueous media was
treated by single point energy calculations using the gas phase
optimized geometries and employing the integral equation
formalism of the polarizable continuum model (IEF-PCM)
51,52
at the same level of theory at which the gas phase result was
obtained. However, there were certain exceptions as follows: (i)
In certain cases, geometry optimization calculations at the M06-
2X/6-311+G(d) level could not be completed due to internal
errors or lack of convergence. In these cases, as indicated in the
corresponding sections, single point energy calculations were
performed at the M06-2X/6-311+G(d) level using the
geometries optimized at the B3LYP/6-311+G(d) level. And,
(ii) In the study of reactions involving sulforaphane and
hydrogen peroxide, geometries of the RCs, TSs, and PCs were
optimized in both gas phase and aqueous media at both the
B3LYP/6-311+G(d) and M06-2X/6-311+G(d) levels of
density functional theory.
Reactions were considered to initiate from optimized
geometries of RCs. Intrinsic reaction coordinate (IRC)
calculations
53
were performed using optimized TSs to conrm
that hydrogen transfer actually took place from the considered
sites of sulforaphane. Forward Gibbs barrier energies were
calculated as dierences of Gibbs free energies of the
corresponding TSs and RCs, while reverse Gibbs barrier
energies were obtained as dierences of Gibbs free energies of
the corresponding TSs and PCs at 298.15 K. Vibrational
frequency analysis was performed for each optimized geometry.
TSs were found to be associated with one imaginary vibrational
frequency each, whereas all RCs and PCs were characterized by
all real vibrational frequencies. Genuineness of the calculated
transition states was conrmed by visually examining the
vibrational modes related to the imaginary frequencies and
applying the condition that these connected the corresponding
reactant and product complexes properly. Rate constants were
calculated using the transition states theory.
5456
The Windows
version of the Gaussian 09 suite of programs (G09W, ver. B.01)
was used for all the calculations.
57
The optimized geometries
and vibrational modes were visualized using the GaussView
program (ver. 5.0).
58
3. RESULTS AND DISCUSSION
3.1. Scavenging Superoxide Radical Anions (O2
).
(i). Without Iron Superoxide Dismutase (Fe-SOD). Superoxide
radical anion reacts with other molecules to form hydrogen
peroxide.
59,60
Our calculations indicated that double hydrogen
abstraction from sulforaphane by superoxide radical anion can
occur much more easily than single hydrogen abstraction, and
therefore we investigated only the former mechanism. For
example, when a transition state search was made by placing
superoxide radical anion near the (C7,C9) pair of carbon atoms
(Figure 1) such that one of its oxygen atoms was nearer to one
of the hydrogen atoms of the methyl (C9H3) group and the
initial C9H and OH distances were 1.3 Å each. When the
transition state search was continued for 10 steps, the H atom
that was to be abstracted from the C9 site came back near it so
that the C9H and OH distances changed to 1.11 and 1.66 Å.
Thus, the transition state search involving a single hydrogen
abstraction from the C9 site (Figure 1) did not succeed. Similar
observations were made in other cases involving single
hydrogen abstraction by superoxide radical anion also.
By double hydrogen abstraction from an alkyl chain, an
organic molecule would get converted from the alkane to the
alkene form. This transformation is an interesting aspect of
chemical synthesis.
44
Double hydrogen transfer occurring from
sulforaphane can be represented as follows
−+ ⎯⎯⎯⎯ − +
•− Δ
S
HO SH HO
nn2
G
222
n
b
(1)
where ΔGnbis the forward Gibbs barrier energy of the reaction,
SHnis the sulforaphane molecule with nhydrogen atoms, and
SHn2is a form of the molecule with (n2) hydrogen atoms,
the two hydrogen atoms having been abstracted from two
Figure 1. Optimized geometry of sulforaphane at the M06-2X/6-
311+G (d) level of theory and adopted atomic numbering scheme.
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neighboring carbon sites of sulforaphane, and superoxide
radical anion (O2
) is converted to hydrogen peroxide
(H2O2) due to the reaction. Pairs of hydrogen atoms can be
abstracted from the pairs of neighboring sites of sulforaphane,
that is, (C4,C5), (C5,C6), (C6,C7), and (C7,C9) (Figure 1).
Gibbs free energies of RCs, TSs, and PCs corresponding to
double hydrogen abstraction by superoxide radical anion from
dierent pairs of neighboring carbon sites of sulforaphane
obtained using B3LYP and M06-2X functionals along with the
6-311+G(d) basis set in gas phase and aqueous media are
presented in Supporting Information, Table S1. The calculated
Gibbs interaction energies of RCs as well as forward and
reverse Gibbs barrier energies corresponding to double
hydrogen abstraction by superoxide radical anion from
Table 1
serial no. pair of carbon sites interaction energy of RC
a
forward/reverse barrier
b
B3LYP/6-311+G(d) M06-2X/6-311+G(d)
c
1 (C4,C5) 23.33(7.04) forward 40.99(40.51) 45.59(43.01)
29.29(0.95) reverse 16.41(16.79) 21.03(19.44)
2 (C5,C6) 20.99(9.08) forward 38.31(41.69) 40.53(43.67)
28.63(3.04) reverse 20.97(19.84) 13.07(12.18)
3 (C6,C7) 23.34(7.67) forward 36.50(39.24) 34.82(38.49)
26.72(3.33) reverse 4.83(2.86) 6.51(4.51)
4 (C7,C9) 20.46(10.19) forward 45.49(43.27) 49.87(46.31)
26.28(4.32) reverse 0.69(1.44) 2.10(0.70)
d
a
Gibbs interaction energies of reactant complexes: upper values: B3LYP/6-311+G(d) level, lower values: M06-2X/6-311+G(d) level, outside
parentheses: gas phase, inside parentheses: aqueous media.
b
Forward and reverse Gibbs barrier heights (kcal/mol) corresponding to double
hydrogen abstraction by superoxide radical anion from sulforaphane at two dierent levels of theory in gas and aqueous media. Atomic numbering is
given in Figure 1. Barrier energies in aqueous media are given in parentheses.
c
Barrier energies for double hydrogen abstraction from the (C6,C7)
sites were obtained by geometry optimization at the M06-2X/6-311+G(d) level while those from the other pairs of sites were obtained by single
point energy calculations at the M06-2X/6-311+G(d) level using the geometries optimized at the B3LYP/6-311+G(d) level.
d
Negative reverse
barrier energy implies that the corresponding energy lies above the barrier.
Figure 2. Optimized geometries of reactant complexes (RC1RC4) shown in (ad), respectively, involved in double hydrogen abstraction from
dierent sites of sulforaphane by superoxide radical anion (O2
) in aqueous media at the M06-2X/6-311+G(d) level of theory. Certain optimized
interatomic distances (Å) are given.
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sulforaphane in gas and aqueous media are presented in Table
1. The gas phase barrier energies for double hydrogen
abstraction from the (C6,C7) sites given in this table were
obtained by geometry optimization at both the B3LYP/6-
311+G(d) and M06-2X/6-311+G(d) levels, while those from
the other sites were obtained by single point energy calculations
attheM06-2X/6-311+G(d)levelusingthegeometries
optimized at the B3LYP/6-311+G(d) level. The Gibbs barrier
energies in aqueous media were obtained by single point energy
calculations at the same levels at which the gas phase barrier
energies were obtained.
The Gibbs interaction energies of RCs (dened in each case
as Gibbs free energy of the complex sum of Gibbs free
energies of the individual reactants) in gas phase and aqueous
media obtained at both the levels of theory mentioned above
and included in Table 1 reveal the following information. The
calculated gas phase Gibbs interaction energies are all negative,
while those in aqueous media are all positive. When superoxide
radical anion is solvated in aqueous media, it gets highly
stabilized or trapped due to the negative charge and associated
polarization of the aqueous medium. For this reason, the
second term in the above denition of Gibbs interaction energy
in aqueous media becomes highly negative making the
corresponding Gibbs interaction energies positive. Positive
Gibbs interaction energies imply that the reactants under
ambient conditions would not likely make stable complexes,
making the probability of reactions highly reduced.
The optimized structures of reactant complexes (RC1, RC2,
RC3, and RC4) and transition states (TS1, TS2, TS3, and TS4)
involved in double hydrogen transfer from sulforaphane to
superoxide radical anion are shown in Figures 2ad and 3ad,
respectively. In these gures, the corresponding imaginary
vibrational frequencies (ν) are also presented. The optimized
structures of product complexes (PC1, PC2, PC3, and PC4)
formed by double hydrogen abstraction from sulforaphane by
superoxide radical anion are presented in Figure 4ad. Certain
optimized geometrical parameters at the M06-2X/6-311+G(d)
level of theory are also given in Figures 2ad, 3ad, and 4ad.
It is noted that in one case, that is, in the product complex PC2
corresponding to double hydrogen abstraction from the
(C5,C6) pair of carbon sites (Figure 4b), the OSCH3portion
of sulforaphane gets dissociated from the rest of the molecule.
The forward Gibbs barrier energies for double hydrogen
abstraction by superoxide radical anion from the dierent pairs
of carbon sites of sulforaphane in gas phase and aqueous media
presented in Table 1 and obtained at the B3LYP/6-311+G(d)
or M06-2X/6-311+G(d) level of theory lie in the range
between 35 and 50 kcal/mol. All these calculated Gibbs
forward barrier energies in both gas phase and aqueous media
are very high (Table 1). The calculated reverse barrier energies
Figure 3. Optimized geometries of transition states (TS1TS4) shown in (ad), respectively, involved in double hydrogen abstraction from
dierent sites of sulforaphane by superoxide radical anion (O2
) in aqueous media at the M06-2X/6-311+G(d) level of theory. Certain optimized
interatomic distances (Å) are given. Imaginary vibrational frequency (ν,cm
1) in each case is given.
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for double hydrogen abstraction presented in Table 1 are quite
dierent for the dierent pairs of carbon sites. These barrier
energies corresponding to double hydrogen abstraction from
the (C4,C5) and (C5,C6) pairs of sites in gas phase and
aqueous media obtained at both the levels of theory mentioned
above lie in the range from 12 to 21 kcal/mol (Table 1).
The corresponding reverse Gibbs barrier energies for the
reaction from the (C6,C7) pair of sites lie in the range from
2.9 to 6.5 kcal/mol, while those for the reaction involving
the (C6,C7) pair of sites lie in the range from 1.44 to 2.1
kcal/mol (Table 1). The two negative reverse Gibbs barrier
energies (Table 1) imply that the energies under consideration
lie above the Gibbs barrier due to which the reaction cannot
occur. All other reverse Gibbs barrier energies are positive but
appreciably or much smaller than the corresponding forward
Gibbs barrier energies due to which the product complexes
would be appreciably or highly endothermic. The calculated
rate constants for double hydrogen abstraction from the
dierent pairs of sites of sulforaphane at the B3LYP/6-
311+G(d) and M06-2X/6-311+G(d) levels of theory using
the forward Gibbs barrier energies given in Table 1 (not given)
have very small values (<1 ×1013 M1s1). This along with
the fact that the reverse Gibbs barrier energies are appreciably
or much smaller than the forward ones (even small negative)
shows that the double hydrogen transfer reactions between
sulforaphane and superoxide radical anion would not take place.
(ii). With Iron Superoxide Dismutase. Epidemiological
studies have demonstrated that SOD neutralizes superoxide
radical anion by charge transfer and that superoxide radical is
converted to hydrogen peroxide by taking two hydrogens from
an antioxidant molecule.
21,22,59,60
The active site of Fe-SOD
consists of an iron cation (Fe3+) bonded to three histidines, one
aspartic acid, and a water molecule.
61
However, we excluded
aspartic acid and water molecules from our model of Fe-SOD
and considered only Fe3+ bonded to three histidines for
convenience in computations expecting that the main role of
the enzyme would be revealed by it.
20,62
We studied the
catalytic role of Fe-SOD here, but we hope that, broadly
speaking, similar results would be found if other metal SODs
are considered in place of Fe-SOD. We studied formation of
hydrogen peroxide due to the reaction between superoxide
radical anion and sulforaphane in the presence of this model of
Fe-SOD. We will discuss this reaction in this section, while
reduction of hydrogen peroxide into water will be discussed in
the next section. Double hydrogen abstraction from sulfor-
aphane in biological media can be represented as follows.
−+ ⎯⎯⎯⎯⎯⎯⎯ − +
•−
S
HO SH HO
nn2
Fe SOD
222 (2)
The right-hand side of the above scheme represents the
product complex in the presence of Fe-SOD. We optimized the
structure of the Fe-SOD model at the B3LYP/6-311+G(d) and
M06-2X/6-311+G(d) levels of theory and, subsequently, the
Figure 4. Optimized geometries of dierent product complexes (PC1PC4) shown in (ad), respectively, obtained by double hydrogen abstraction
from the dierent sites of sulforaphane by superoxide radical anion (O2
) in aqueous media at the M06-2X/6-311+G(d) level of theory. Certain
optimized geometrical parameters (Å, deg) are given.
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structure of the complex of superoxide radical anion, and the
Fe-SOD model was also optimized at the same two levels in gas
phase. The optimized structure of the Fe-SOD model at the
M06-2X/6-311+G(d) level of theory is presented in Figure S1
(Supporting Information). We attempted to optimize RCs,
TSs, and PCs corresponding to single or double hydrogen
abstraction from the dierent sites or pairs of neighboring sites
of sulforaphane by superoxide radical anion in the presence of
Fe-SOD. With regard to the search for TSs, it was noted that
transfer of two corresponding hydrogens from all the four pairs
of neighboring sites of sulforaphane under the inuence of Fe-
SOD occurred with some delay. Thus, in all the cases, one of
the hydrogens was abstracted generally only after a few cycles
of calculations, while the other got abstracted much later. The
total energies of RCs and TSs changed slowly, and their
gradients with respect to the geometrical parameters continued
to be appreciable. Thus, none of the RCs and TSs could be
located despite repeated attempts. This indicated that all the
reactions might be barrierless and that the Gibbs barrier
energies did not exist.
The optimized geometries of two product complexes at the
B3LYP/6-311+G(d) level (single point energy calculation at
the M06-2X/6-311+G(d) level) in gas phase in the presence of
Fe-SOD model from the (C4,C5) and (C5,C6) sites, that is,
PC1and PC2, are shown in Figure 5a,b, while those of the
other two product complexes in the presence of Fe-SOD, that
is, PC3and PC4, at the same level of theory in gas phase are
shown in Figure 6a,b. The results shown in these gures are
discussed herein later. Certain optimized geometrical parame-
ters are also given in all these gures (Figures 5a,b and 6a,b). As
discussed earlier, the OSCH3group was dissociated from
sulforaphane in PC2when the reactions occurred without Fe-
SOD, but it does not take place in the presence of Fe-SOD.
During the process of double hydrogen abstraction from the C7
and C9 sites of sulforaphane, the geometry of the sulforaphane
moiety is strongly changed since the C7 and C9 sites get
bonded. It is also noted that the Fe-SOD model does not
participate in bonding with any other moiety, and thus its role
as a catalyst is validated.
The lowest total energy points in aqueous media obtained by
searches for RCs (labeled A) and TSs (labeled B) as well as
those corresponding to optimized geometries of PCs (labeled
C) on the potential energy surfaces relevant to double
hydrogen transfer from the (C4,C5), (C5,C6), (C6,C7), and
(C7,C9) pairs of sites of sulforaphane plotted versus the OO
distance in the superoxide radical anion are shown in Figures
S2, S3, S4, and S5 (Supporting Information), respectively. The
Figure 5. Optimized geometries of product complexes of (a) PC1and
(b) PC2obtained by double hydrogen abstraction from dierent sites
of sulforaphane by superoxide radical anion (O2
) in the presence of
SOD in aqueous media obtained at the M06-2X/6-311+G(d) level of
theory. Certain optimized geometrical parameters (Å, deg) are given.
Figure 6. Optimized geometries of dierent product complexes (a)
PC3and (b) PC4, respectively, obtained by double hydrogen
abstraction from the dierent sites of sulforaphane by superoxide
radical anion (O2
) in aqueous media at the M06-2X/6-311+G(d)
level of theory. Certain optimized geometrical parameters (Å, deg) are
given.
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corresponding values of two OC and OH distances for each of
the points A, B, and C are given near these points (O = the two
oxygen atoms of O2
, C = the corresponding two carbon
atoms from where hydrogens are being abstracted, and H =
corresponding two hydrogens being abstracted). The relative
total energies given in these gures were obtained by M06-2X/
6-311+G(d) level calculations in aqueous media employing the
geometries obtained at the B3LYP/6-311+G(d) level. These
gures show that in each case, the point C lies lowest, the point
B lies higher than C, while the point A lies higher than B in
total energy. These gures, particularly as the points B lie much
below the corresponding points A, conrm that RCs and TSs
would not exist as appropriate total energy extrema, and so the
reactions under consideration would be barrierless, leading
directly to the formation of PCs from the reactants under the
inuence of Fe-SOD.
It is quite clear that the reactions involving double hydrogen
transfer from sulforaphane to superoxide radical anion leading
to the formation of hydrogen peroxide and alkene forms of
sulforaphane are strongly catalyzed by Fe-SOD such that large
positive barrier energies in aqueous media are changed to no
barrier energies. This drastic change in the nature of reactions
can be ascribed to delocalization of charges over the entire
system consisting of the iron cation and the histidine rings of
the Fe-SOD model, superoxide radical anion, or H2O2to which
it is converted by double hydrogen transfer and sulforaphane in
alkane or alkene forms. Mulliken charges in its dierent
complexes are presented in Tables S2S7 (Supporting
Information). Isolated sulforaphane is electrically neutral
though certain of its sites; for example, C4, C7, S8, O8, and
C9 carry large net charges (Table S2, Supporting Information).
In the complex of superoxide radical anion with the Fe-SOD
model (Table S3, Supporting Information), the former carries a
small positive charge (0.222) instead of 1, Fe3+ looks like
neutral Fe (net charge 0.29), and the three rings carry a net
charge of 0.5 each.
In the product complex (PC1) formed by double hydrogen
abstraction by superoxide radical anion from the (C4,C5) sites
of sulforaphane in the presence of the Fe-SOD model in
aqueous media, the Mulliken net charges are as follows (Table
S4, Supporting Information): Sulforaphane is almost electrically
neutral here also though some of its sites carry large positive or
negative charges, H2O2carries a net positive charge of 0.4,
overall the three rings carry a net charge of 1.5, while the iron
cation is almost electrically neutral. Thus, a large part of the
positive charge of the iron cation is transferred to the three
rings in PC1. In the product complex (PC2) formed by
double hydrogen abstraction by superoxide radical anion from
the (C5,C6) sites of sulforaphane in the presence of Fe-SOD in
aqueous media, the Mulliken charges are as follows (Table S5,
Supporting Information): Sulforaphane carries a positive charge
of 0.3, H2O2carries a positive charge of 0.2, the iron center
carries a charge of ca. 0.4, thus becoming negatively charged
instead of remaining positively charged, while overall the three
rings carry a net charge of 1.9.
In the product complex (PC3) where two hydrogens were
abstracted from the (C6,C7) pair of sites of sulforaphane
(Table S6, Supporting Information), sulforaphane carries a
positive charge of 0.6, H2O2carries a positive charge of 0.28,
the iron center carries a charge of ca. 0.7, thus becoming
appreciably negatively charged instead of being positively
charged, and overall the three rings carry a charge of 1.8. In
the product complex (PC4) formed by double hydrogen
abstraction by superoxide radical anion from the (C7,C9) pair
of sites of sulforaphane in the presence of Fe-SOD in aqueous
media, the Mulliken charge distribution is as follows (Table S7,
Supporting Information): Sulforaphane carries a positive charge
of 0.35, H2O2carries a net positive charge of 0.2, the iron
center carries a charge of ca. 0.28, while overall the three rings
carry an appreciable positive charge of 1.7. There are two
notable points that emerge from the above analysis of the net
Mulliken charge distributions. First, the iron center that
originally carried a net charge of +3 becomes almost electrically
neutral or even carries signicant negative charges. Second,
overall the three rings carry a net positive charge lying in the
range from 1.5 to 1.9. The net charges in each component of
the product complex are strongly delocalized due to which
there is no single isolated entity like superoxide radical anion
that carries a large positive or negative charge, which can
drastically polarize the aqueous medium locally. In this
situation, the eect of polarization of aqueous media by
individual components would be absent. This seems to be the
main reason for Fe-SOD being a strong catalyst. To the best of
our knowledge, no such model has been employed earlier for
this enzyme. Models of other metal SODs can be obtained by
replacing the iron cation of Fe-SOD by other metal cations.
3.2. Scavenging of Hydrogen Peroxide. As shown in
Section 3.1, sulforaphane scavenges superoxide radical anion by
double hydrogen transfer in aqueous media in the presence of
superoxide dismutase barrierlessly, and hydrogen peroxide is
formed as the product consequent to this reaction. Though, as
such, hydrogen peroxide is poorly reactive, it can be readily
converted into hydroxyl radicals (OH)bytheFenton
mechanism, and these radicals are highly reactive and can
damage most biomolecules.
21,22,63,64
Therefore, scavenging of
superoxide radical anion by sulforaphane by converting it to
hydrogen peroxide would be fully benecial only if it can also
convert hydrogen peroxide to a harmless form, for example,
water. This aspect was studied in this section.
Double hydrogen abstraction by hydrogen peroxide from
sulforaphane can be represented as follows
−+ ⎯⎯⎯⎯⎯ − +
Δ
S
HHO SH 2H
O
nn22
G
22
n
b
(3)
where ΔGnbis the forward Gibbs barrier energy required for
the reaction, SHnrepresents sulforaphane having nhydrogen
atoms, while Hn2represents the form of sulforaphane from
which two hydrogen atoms have been abstracted by hydrogen
peroxide.
Gibbs free energies of RCs, TSs, and PCs corresponding to
double hydrogen abstraction by hydrogen peroxide from the
dierent pairs of neighboring carbon sites of sulforaphane
obtained at the B3LYP/6-311+G(d) and M06-2X/6-311+G(d)
levels of theory in gas phase and aqueous media are presented
in Table S8. The calculated forward and reverse Gibbs barrier
energies for double hydrogen abstraction by hydrogen peroxide
from the dierent pairs of sites of sulforaphane obtained at two
dierent levels of theory in gas phase and aqueous media are
presented in Table 2. Optimized geometries of reactant
complexes between H2O2and sulforaphane at the M06-2X/6-
311+G(d) level of theory are shown in Figure 7, while those of
transition states involved in the corresponding double hydro-
gen transfer reactions are shown in Figure 8. The products
formed due to these reactions are shown in Figure 9. It is found
that the forward Gibbs barrier energies for double hydrogen
abstraction by hydrogen peroxide from the pairs of sites
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(C4,C5), (C5,C6), and (C6,C7) obtained at the B3LYP/6-
311+G(d) and M06-2X/6-311+G(d) levels of theory in both
gas phase and aqueous media (Table 2) are negative or small
positive, the largest forward Gibbs barrier energy being 1.62
kcal/mol (Table 2). However, the forward Gibbs barrier
energies corresponding to double hydrogen abstraction from
the pair of sites (C7,C9) in both gas phase and aqueous media
obtained at both B3LYP/6-311+G(d) and M06-2X/6-
311+G(d) levels of theory are very large lying between 21.7
and 31.4 kcal/mol. The reason for high Gibbs barrier energies
in this case appears to be the fact that double hydrogen
abstraction from the (C7,C9) pair of sites requires S8 to make
three double bonds (Figure 1). The reverse Gibbs barrier
energies for double hydrogen abstraction by hydrogen peroxide
from the pairs of sites (C4,C5), (C5,C6), and (C6,C7) lie in
the range 42.6 to 56.3 kcal/mol in gas phase and in the
range 46 to 54 kcal/mol in aqueous media (Table 2). For
double hydrogen transfer from the (C7,C9) pair of sites of
sulforaphane, the calculated reverse Gibbs barrier energies are
smaller than the forward ones, and therefore, this reaction
would be endothermic.
The structures of transition states involved in the four double
hydrogen transfer reactions between hydrogen peroxide and
sulforaphane in aqueous media optimized at the M06-2X/6-
311+G(d) level of theory and denoted by TS1TS4along
with the corresponding imaginary vibrational frequencies (ν)
are presented in Figure 8. Certain optimized interatomic
distances (Å) are also given in each case in this gure. We
observed that in each of these reactions, a hydrogen peroxide
molecule positions itself near sulforaphane such that its oxygen
atoms can interact eectively with selected sites of the latter.
Table 2
serial
no. pair of
carbon sites forward/reverse
barrier
a
B3LYP/
6-311+G(d) M06-2X/
6-311+G(d)
1 (C4,C5) forward 5.69(8.83) 1.57(0.52)
reverse 50.48(48.59) 50.59(46.77)
2 (C5,C6) forward 1.62(0.46) 0.14(1.76)
reverse 47.56(49.02) 42.56(45.85)
3 (C6,C7) forward 3.83(0.08) 8.61(5.14)
reverse 56.25(53.97) 50.67(50.51)
4 (C7,C9) forward 21.74(14.61) 31.42(26.22)
reverse 18.39(10.16) 26.09(19.55)
a
Forward and reverse Gibbs barrier energies (kcal/mol) correspond-
ing to double hydrogen abstraction by hydrogen peroxide (H2O2)
from sulforaphane at two dierent levels of theory in gas and aqueous
media. Atomic numbering is given in Figure 1. Barrier energies in
aqueous media are given in parentheses.
Figure 7. Optimized geometries of reactant complexes (RC1RC4) shown in (ad), respectively, involved in double hydrogen abstraction from
the dierent pairs of sites of sulforaphane by hydrogen peroxide (H2O2) in aqueous media obtained at the M06-2X/6-311+G (d) level of theory.
Certain optimized interatomic distances (Å) are given.
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These interactions dissociate H2O2into two OH groups each of
which, in turn, abstracts a hydrogen atom from a nearby site of
sulforaphane resulting in the formation of two water molecules.
A graphical comparison of the Gibbs barrier energies involved
in double hydrogen abstraction by hydrogen peroxide from the
dierent pairs of sites of sulforaphane in aqueous media
optimized at the B3LYP/6-311+G(d) and M06-2X/6-
311+G(d) levels of theory is made in Figure S6 (Supporting
Information). It clearly shows that the Gibbs barrier energies
for double hydrogen abstraction from sulforaphane by
hydrogen peroxide in aqueous media from the (C4,C5),
(C5,C6), and (C6,C7) pairs of sites are small, or the reactions
are barrierless, while the double hydrogen transfer reactions
from the (C7,C9) pair sites involves a much higher barrier
energy. The calculated rate constants for double hydrogen
abstraction from the dierent pairs of carbon sites obtained at
the B3LYP/6-311+G(d) and M06-2X/6-311+G(d) levels of
theory using the forward Gibbs barriers energies given in Table
2 are presented in Table 3. Negative barrier energies were taken
to be zero implying barrierless reactions for calculating rate
constants. We note that double hydrogen transfer from the
three pairs of sites (C4,C5), (C5,C6), and (C6,C7), in
conformity with the calculated barrier energies, would occur
with very high rate constants (1×1012 M1s1), while those
from the sites (C7,C9) would occur very slowly.
The optimized structures of the product complexes resulting
from double hydrogen abstraction by hydrogen peroxide from
sulforaphane denoted by PC1PC4are presented in Figure
9. Each of these complexes includes two water molecules and a
form of sulforaphane that has lost two hydrogen atoms from
vicinal sites. Note that the bonds between carbon atoms that
have lost one hydrogen atom each due to the reactions under
consideration acquire typical double (CC) bond lengths
(1.3261.332 Å), and thus sulforaphane transforms from the
alkane to the alkene form. The results discussed above clearly
show that sulforaphane can scavenge both superoxide radical
anion (in the presence of Fe-SOD) and hydrogen peroxide
(without involving any catalyst) very eciently. Since super-
oxide radical anion is a deadly oxidizing agent that plays crucial
roles in DNA damage, sulforaphane is a very ecient and
valuable antioxidant.
4. CONCLUSION
We arrive at the following conclusions from this study:
1. Sulforaphane scavenges both superoxide radical anion
(which is converted to hydrogen peroxide) and hydrogen
peroxide (which is converted to water) by double
hydrogen transfer barrierlessly or with low barrier
energies. Presence of Fe-SOD is required for scavenging
Figure 8. Optimized geometries of transition states (TS1TS4) shown in (ad), respectively, involved in double hydrogen abstraction from the
dierent pairs of sites of sulforaphane by hydrogen peroxide (H2O2) in aqueous media obtained at the M06-2X/6-311+G(d) level of theory. Certain
optimized interatomic distances (Å) are given. Imaginary vibrational frequency (ν,cm
1) in each case is given.
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superoxide radical anion, but hydrogen peroxide is
scavenged without any additional agent.
2. The calculated Gibbs interaction energies of reactant
complexes between sulforaphane and superoxide radical
anion as well as forward and reverse Gibbs barrier
energies for double hydrogen transfer from the former to
the latter show that the reactions under consideration
would be very unlikely to occur in the absence of a
catalyst. The fact that superoxide radical anion gets
trapped in water due to its negative charge and associated
polarization of the medium plays an important role in
making the reactions unlikely to occur. The presence of
superoxide dismutase changes this situation drastically as
the charges get widely spread on the dierent
components preventing superoxide radical anion from
getting trapped due to local polarization of the aqueous
medium. It results in barrierless scavenging of superoxide
radical anion by sulforaphane in aqueous media in the
presence of Fe-SOD.
3. We employed a model for Fe-SOD that consists of Fe3+
cation bonded to three histidine rings. The model works
well in conformity with the known catalytic role of SOD.
ASSOCIATED CONTENT
*
SSupporting Information
Tabulated Gibbs free energies and Mulliken charge distribu-
tions, Gibbs barrier heights of hydrogen abstraction sites,
variation of total energy as a function of OO bond distance,
optimized geometry of SOD model. The Supporting
Information is available free of charge on the ACS Publications
website at DOI: 10.1021/acs.jpcb.5b01496.
Figure 9. Optimized geometries of product complexes (PC1PC4) shown in (ad), respectively, formed by double hydrogen abstraction from
the dierent pairs of sites of sulforaphane by hydrogen peroxide in aqueous media obtained at the M06-2X/6-311+G(d) level of theory. Certain
optimized interatomic distances (Å) are given.
Table 3
serial no. hydrogen abstraction sites B3LYP/6-311+G(d)
a
M06-2X/6-311+G(d)
a
1 (C4,C5) 6.2 ×1012 (6.2 ×1012) 4.4 ×1011 (6.2 ×1012)
2 (C5,C6) 4.0 ×1011 (6.2 ×1012) 6.2 ×1012 (6.2 ×1012)
3 (C6,C7) 6.2 ×1012 (6.2 ×1011) 6.2 ×1012 (6.2 ×1012)
4 (C7,C9) 7.0 ×104(0.1 ×103) 5.6 ×1011 (3.6 ×107)
a
Rate constants (M1s1) for double hydrogen abstraction by hydrogen peroxide from the dierent pairs of sites of sulforaphane obtained at two
dierent levels of theory in gas phase and aqueous media. Results obtained in aqueous media are given in parentheses. Transition states involved in
these reactions are shown in Figure 8, while the products due to these reactions are shown in Figure 9.
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AUTHOR INFORMATION
Corresponding Author
*E-mail: pcmishra_in@yahoo.com.
Notes
The authors declare no competing nancial interest.
ACKNOWLEDGMENTS
One of the authors (P.C.M.) thanks the National Academy of
Sciences, India (NASI), for the award of a NASI Senior
Scientist Fellowship. The authors are thankful to the University
Grants Commission (New Delhi) for nancial support.
REFERENCES
(1) Matés, J. M.; Perez-Gomez, C.; Nunez de Castro, I. Antioxidant
Enzymes and Human Diseases. Clin. Biochem. 1999,32, 595603.
(2) Auroma, O. I. Nutrition and Health Aspects of Free Radicals and
Antioxidants. Food Chem. Toxicol. 1994,32, 671683.
(3) Jena, N. R. DNA Damage by Reactive Species: Mechanisms,
Mutation and Repair. J. Biosci. 2012,37, 503517.
(4) Jena, N. R.; Mishra, P. C. Mechanisms of Formation of 8-
Oxoguanine Due to Reactions of One and Two OH Radicals and
H2O2Molecule with Guanine: A Quantum Computational Study. J.
Phys. Chem. B 2005,109, 1420514218.
(5) Mishra, P. C.; Singh, A. K.; Suhai, S. Interaction of Singlet
Oxygen and Superoxide Radical Anion with Guanine and Formation
of its Mutagenic Modification 8-Oxoguanine. Int. J. Quantum Chem.
2005,102, 282301.
(6) Crean, C.; Geacintov, N. E.; Shafirovich, V. Oxiadtion of Guanine
and 8-Oxo-7,8-Dihydroguanine by Carbonate Radical Anions: Insight
from Oxygen-18 Labeling Experiments. Angew. Chem., Int. Ed. 2005,
44, 50575060.
(7) Goldstein, I. M.; Weissman, G. Effects of Generation of
Superoxide Anion on Permeability of Liposomes. Biochem. Biophys.
Res. Commun. 1977,75, 604609.
(8) Gutteridge, J. M.C. The Protective Action of Superoxide
Dismutase on Metal-ion Catalysed Peroxidation of Phospholipids.
Biochem. Biophys. Res. Commun. 1977,77, 379386.
(9) McCord, J. M. Free Radicals and Inflammation: Protection of
Synovial Fluid by Superoxide Dismutase. Science 1974,185, 529531.
(10) Wong, K.; Morgan, A. R.; Paranchych, W. Controlled Cleavage
of Phage R17 RNA within the Virion by Treatment with Ascorbate
and Copper (II). Can. J. Biochem. 1974,52, 950958.
(11) Van Hemmen, J. J.; Meuling, W. J. A. Inactivation of Biologically
Active DNA by X-ray-induced Superoxide Radicals and their
Dismutation Products Singlet Molecular Oxygen and Hydrogen
Peroxide. Biochim. Biophys. Acta 1975,402, 133141.
(12) Morgan, A. R.; Cone, R. L.; Elgert, T. M. The Mechanism of
DNA Strands Breakage by Vitamin C and Superoxide and the
Protective Roles of Catalase and Superoxide Dismutase. Nucleic Acids
Res. 1976,3, 11391149.
(13) Cone, R.; Hasan, S. K.; Lown, J. W.; Morgan, A. R. The
Mechanism of the Degradation of DNA by Streptonigrin. Can. J.
Biochem. 1976,54, 219223.
(14) Lin, W. S.; Armstrong, D. A.; Lal, M. Effects of Superoxide
Dismutase, Di thiothreitol and Formate Ion on the Inactivation of
Papain by Hydroxyl and Superoxide Radicals in Aerated Solutions. Int.
J. Radiat. BioI. 1978,33, 231243.
(15) Asada, K.; Takahashi, M. Production and Scavenging of Active
Oxygen in Chloroplasts. In Photoinhibition; Kyle, D.J., Osmond, C.B.,
Arntzen, C.J., Eds.; Elsevier: Amsterdam, 1987; Vol. 9, pp 227287.
(16) Haraguchi, H.; Ishikawa, H.; Mizutani, K.; Tamura, Y.;
Kinoshita, T. Antioxidative and Superoxide Scavenging Activities of
Retrochalcones in Glycyrrhiza Inflata. Bioorg. Med. Chem. 1998,6,
33947.
(17) McCord, J. M.; Fridovich, I. The Reduction of Cytochrome cby
Milk Xanthine Oxidase. J. Biol. Chem. 1968,243, 57535760.
(18) Fridovich, I. Quantitative Aspects of the Production of
Superoxide Anion Radical by Milk Xanthine Oxidase. J. Biol. Chem.
1970,245, 40534057.
(19) Granger, D. N. Role of Xanthine Oxidase and Granulocytes in
Ischemia-Reperfusion Injury. Am. J. Physiol. 1988,255, H126975.
(20) Halliwell, B.; Gutteridge, J. M. C. Role of Free Radicals and
Catalytic Metal Ions in Human Disease. Methods Enzymol. 1990,186,
185.
(21) Sroka, Z.; Cisowski, W. Hydrogen Peroxide Scavenging,
Antioxidant and Anti-radical Activity of some Phenolic Acids. Food
Chem. Toxicol. 2003,41, 753758.
(22) Halliwell, B.; Gutteridge, J. M. C. Hydrogen Peroxide. In Free
Radicals in Biology and Medicine; Halliwell, B., Gutteridge, J. M. C.,
Eds.; Oxford University Press: Oxford, U.K., 1999; pp 8283.
(23) Halliwell, B.; Gutteridge, J. M. C. Free Radicals in Biology and
Medicine, 2nd ed.; Oxford Clarendon: Oxford, U.K., 1989.
(24) Halliwell, B.; Gutteridge, J. M. C.; Cross, C. E. Free Radicals,
Antioxidants, and Human Disease: Where Are We Now? J. Lab. Clin.
Med. 1992,119, 598620.
(25) Hall, L.; Williams, K.; Perry, A. C. F.; Frayne, J.; Jury, J. A. The
Majority of Human Glutathione Peroxidase type 5 (GPX5) Tran-
scripts are Incorrectly Spliced: Implications for the Role of GPX5 in
the Male Reproductive Tract. J. Biochem. 1998,333,59.
(26) Haraguchi, H.; Ishikawa, H.; Mizutani, K.; Tamura, Y.;
Kinoshita, T. Antioxidative and Superoxide Scavenging Aactivities of
Retrochalcones in Glycyrrhiza Inflata. Bioorg. Med. Chem. 1998,6,
33947.
(27) Patil, B. S.; Jayaprakasha, G. K.; Chidambara, K. N.; Vikram, A.
Bioactive Compound: Historical Perspectives, Opportunities, and
Challenges. J. Agric. Food Chem. 2009,57, 81428160.
(28) Kris-Etherton, P. M.; Hecker, K. D.; Bonanome, A.; Coval, S.
M.; Binkoski, A. E.; Hilpert, K. F.; Griel, A. E.; Etherton, T. D.
Bioactive Compounds in Foods: Their Role in the Prevention of
Cardiovascular Disease and Cancer. Am. J. Med. 2002,113, 71S88S.
(29) Prasad, A. K.; Mishra, P. C. Study of Scavenging Action of
Zingerone towards the OH Radical: Formation of Vanillin and Ferulic
Acid. J. Phys. Org. Chem. 2014,27,1826.
(30) Zhang, Y.; Talalay, P.; Cho, C. G.; Posner, G. H. A Major
Inducer of Ant-Carcinogenic Protective Enzymes from Broccoli:
Isolation and Elucidation of Structure. Proc. Natl. Acad. Sci. U.S.A.
1992,89, 23992403.
(31) Pledgie-Tracy, A.; Sobolewski, M. D.; Davidson, N. E.
Sulforaphane Induces Cell type-Specific Apoptosis in Human Breast
Cancer Cell Lines. Mol. Cancer Ther. 2007,6, 10131021.
(32) Myzak, M. C.; Hardin, K.; Wang, R.; Dashwood, R. H.; Ho, E.
Sulforaphane Inhibits Histone Deacetylase Activity in BPH-1, LnCaP
and PC-3 Prostate Epithelial Cells. Carcinogenesis 2006,27, 811819.
(33) Sharma, C.; Sadrieh, L.; Priyani, A.; Ahmed, M.; Hassan, A. H.;
Hussaina, A. Anti-carcinogenic Effects of Sulforaphane in Association
with its Apoptosis Inducing and Anti-inflammatory Properties in
Human Cervical Cancer Cells. Cancer Epidemiol. 2011,35, 272278.
(34) Kallifatidis, G.; Labsch, S.; Rausch, V.; Mattern, J.; Gladkich, J.;
Moldenhauer, G.; Büchler, M. W.; Salnikov, A. V.; Herr, I.
Sulforaphane Increases Drug-mediated Cytotoxicity Toward Cancer
Stem-like Cells of Pancreas and Prostate. Mol. Ther. 2011,19, 188
195.
(35) Chang, C.-C.; Hung, C.-M.; Yang, Y.-R.; Lee, M.-J.; Hsu, Y. C.
Sulforaphane Induced Cell Cycle Arrest in the G2/M Phase via the
Blockade of Cyclin B1/CDC2 in Human Ovarian Cancer Cells. J.
Ovarian Res. 2013,6, 41.
(36) Carlos, E. G.-B.; Mukhopadhyay, P.; Horvath, B.; Rajesh, M.;
Tapia, E.; Garcia-Torres, I.; Pedraza-Chaverri, J.; Pacher, P.
Sulforaphane a Natural Constituent of Broccoli, Prevents Cell Death
and Inflammation in Nephropathy. J. Nutr. Biochem. 2012,23, 494
500.
(37) Singh, K.; Connorsa, S. L.; Macklinc, E. A.; Smithd, K. D.;
Faheye,J.W.;Talalaye,P.;Zimmerman,A.W.Sulforaphane
Treatment for Autism Spectrm Disorder (ASD). Proc. Natl. Acad.
Sci. U. S. A. 2014,111, 1555015555.
The Journal of Physical Chemistry B Article
DOI: 10.1021/acs.jpcb.5b01496
J. Phys. Chem. B 2015, 119, 78257836
7835
(38) Fahey, J. W.; Talalay, P. Antioxidant Functions of Sulforaphane:
A Potent Inducer of Phase II Detoxication Enzymes. Food Chem.
Toxicol. 1999,37, 973979.
(39) Chu, W.; Wu, D.; Liu, W.; Wu, L.; Li, D.; Xu, D. Y.; Wang, X. F.
Sulforaphane Induces G2-M Arrest and Apoptosis in High Metastasis
Cell Line of Salivary Gland Adenoid Cystic Carcinoma. Oral Oncol.
2009,45, 9981004.
(40) Huang, T.-Y.; Chang, W.-C.; Wang, M.-Y.; Yang, Y.-R.; Hsu, Y.-
C. Effect of Sulforaphane on Growth Inhibition in Human Brain
Malignant Glioma GBM 8401 Cells by Means of Mitochondrial and
MEK/ERK-Mediated Apoptosis Pathway; Cell. Biochem. Biophys.
2012,63, 247259.
(41) Talalay, P.; Fahey, J. W.; Healy, Z. R.; Wehage, S. L.; Benedict,
A. L.; Min, C.; Dinkova-Kostova, A. T. Sulforaphane Mobilizes
Cellular Defenses that Protect Skin against Damage by UV Radiation.
Proc. Nat. Acad. Sci. U. S. A. 2007,144, 1750017505.
(42) Erkoc, S.; Erkoc, F. Theoretical Investigation of Sulforaphane
Molecule. J. Mol. Struct.: THEOCHEM 2005,714,8185.
(43) Yuan, H.; Yao, S.; You, Y.; Xiao, G.; You, Q. Antioxidant
Activity of Isothiocyanate Extracts from Broccoli. Chin. J. Chem. Eng.
2010,18, 312321.
(44) Niu, D.; Willoughby, P. H.; Woods, B. P.; Baire, B.; Hoye, T. R.
Alkane Desaturation by Concerted Double Hydrogen Atom Transfer
to Benzyne. Nature 2013,501, 531534.
(45) Jena, N. R.; Agnihotri, N.; Mishra, P. C. In Application of
Computational Techniques in Pharmacy and Medicine; Gorb, L.,
Kuzmin, V., Muratov, E., Leszczynski, J., Eds.; Series on Challenges
and Advances in Computational Chemistry and Physics; Springer:
Dordrecht, The Netherlands, 2014.
(46) Becke, A. D. Density-Functional Thermochemistry. III. The
Role of Exact Exchange. J. Chem. Phys. 1993,98, 56485652.
(47) Becke, A. D. Density-Functional Exchange-Energy Approx-
imation with Correct Asymptotic Behavior. Phys. Rev. A 1988,38,
30983100.
(48) Vosko, S. H.; Wilk, L.; Nusair, M. Accurate Spin-Dependent
Electron Liquid Correlation Energies for Local Spin Density
Calculations: A Critical Analysis M. Can. J. Phys. 1980,58, 12001211.
(49) Lee, C.; Yang, W.; Parr, R. G. Development of the Colle-Salvetti
Correlation-Energy Formula into a Functional of the Electron Density.
Phys. Rev. B 1988,37, 785789.
(50) Zhao, Y.; Truhlar, D. G. The M06 Suite of Density Functionals
for Main Group Thermochemistry, Thermochemical Kinetics, Non-
covalent Interactions, Excited States, and Transition Elements: Two
New Functionals and Systematic Testing of Four M06-class
Functionals and 12 Other Functional. Theor. Chem. Acc. 2008,120,
215241.
(51) Miertus, S.; Scrocco, E.; Tomasi, J. Electrostatic Interaction of a
Solute with a Continuum. A Direct Utilization of Ab Initio Molecular
Potentials for the Prevision of Solvent Effects. Chem. Phys. 1981,55,
117129.
(52)Cossi,M.;Scalmani,G.;Rega,N.;Barone,V.New
Developments in the Polarizable Continuum Model for Quantum
Mechanical and Classical Calculations on Molecules in Solution. J.
Chem. Phys. 2002,117,4354.
(53) Ayala, P. Y.; Schlegel, H. B. A Combined Method for
Determining Reaction Paths, Minima and Transition State Geo-
metries. J. Chem. Phys. 1997,107, 37584.
(54) Levine, I. N. Quantum Chemistry, 4th ed.; Prentice-Hall:
Englewood Clis, NJ, 1994.
(55) Ramalho, S. S.; Vilela, A. F. A.; Barreto, P. R. P.; Gargano, R.
Theoretical Rate Constants for the Reaction BF2+NF=BF
3+Nof
Importance in Boron Nitride Chemistry. Chem. Phys. Lett. 2005,413,
151156.
(56) Carstensen, H. H.; Dean, A. M. Rate Constant Rules for the
Automated Generation of Gas-Phase Reaction Mechanisms. J. Phys.
Chem. A 2009,113, 367380.
(57) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria,G. E.;
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci,
B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Hratchian, X.; Li, H.
P.; Izmaylov,A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.;
Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,
T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.;
Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin,
K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.;
Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega,
N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.;
Adamo, C.; Jaramillo, J.; Gomperts, R. E.; Stratmann, O.; Yazyev, A. J.;
Austin, R.; Cammi, C.; Pomelli, J. W.; Ochterski, R.; Martin, R. L.;
Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.;
Dannenberg,J.J.;Dapprich,S.;Daniels,A.D.;Farkas,O.;
Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09,
Revision A.1; Gaussian Inc: Wallingford, CT, 2009.
(58) Frisch, A. E.; Dennington, R. D.; Keith, T. A.; Nielsen, A. B.;
Holder, A. J. Gauss View, rev. 3.9; Gaussian Inc: Pittsburg, PA, 2003.
(59) Miller, A.-F. Superoxide Dismutases: Active Sites that Save, but
a Protein that Kills. Curr. Opin. Chem. Biol. 2004,8, 162168.
(60) Zanzinger, J.; Czachurski, J. Chronic Oxidative Stress in the
RVLM Modulates Sympathetic Control of Circulation in Pigs. Pflugers
Arch. 2009,439, 489494.
(61) Lieberman, M.; Kunishi, A. T.; Mapson, L. W.; Wardale, B. A.
Ethylene Production from Methionine. Biochem. J. 1965,97, 449459.
(62) Bull, C.; Fee, J. A. Steady-State Kinetic Studies of Superoxide
Dismutase: Properties of the Iron Containing Protein from Escherichia
coli.J. Am. Chem. Soc. 1985,107, 32953304.
(63) Fenton, H. J. Oxidation of Tartaric Acid in Presence of Iron. J.
Chem. Soc. 1894,65, 899910.
(64) Walling, C. Fentons Reagent Revisited. Acc. Chem. Res. 1975,8,
125131.
The Journal of Physical Chemistry B Article
DOI: 10.1021/acs.jpcb.5b01496
J. Phys. Chem. B 2015, 119, 78257836
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... The experimental results have been recently supplemented with two theoretical works. The calculations performed by Prasad et al. (Prasad and Mishra 2015) indicate that SFN alone cannot efficiently scavenge superoxide radical anion in gas phase or aqueous media because the corresponding reaction barriers are very high. However, the reaction with O 2 ...
Chapter
Naturally occurring isothiocyanates (ITCs), products of hydrolysis of glucosinolates (GSLs), attract great attention due to their well-defined indirect antioxidant and antitumor properties, which come as a result of their ability to regulate transcription factors, signaling pathways, cell cycle and apoptosis. Majority of studies on antioxidant activity of ITCs, in particular of those present in Brassica vegetables (sulforaphane, sulforaphene, erucin), indicate that some health-promoting effects might be connected rather with their indirect antioxidant mechanism of action. In this chapter several aspects of chemical and biological activity of ITCs and some parent GSLs are presented, with emphasis on chemical structure, reactivity of isothiocyanate moiety (-NCS) and the role of side chain during reactions with the reactive oxygen species and with model radicals used in common antioxidant assays. The literature survey indicates that at ambient temperatures ITCs are preventive antioxidants removing hydroperoxides and they are not radical trapping agents. However, chain-breaking character can be observed at elevated temperatures during oxidation of bulk phase lipids. https://doi.org/10.1007/978-3-030-87222-9_13
... Our results showed that the expression levels of most genes related to ROS in H. pluvialis treated with blue light were significantly higher than those in white light, indicating that the damage of blue light to H. pluvialis was higher than that of white light (Figure 9). Previous studies showed that APX, CAT, GRX, GPX, and PRDX removed hydrogen peroxide [64], while SOD scavenged superoxide to form hydrogen peroxide [65]. Studies have shown that the antioxidant systems in different species of plants respond differently to the treatment with SA. ...
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Haematococcus pluvialis accumulates a large amount of astaxanthin under various stresses, e.g., blue light and salicylic acid (SA). However, the metabolic response of H. pluvialis to blue light and SA is still unclear. We investigate the effects of blue light and SA on the metabolic response in H. pluvialis using both transcriptomic and proteomic sequencing analyses. The largest numbers of differentially expressed proteins (DEPs; 324) and differentially expressed genes (DEGs; 13,555) were identified on day 2 and day 7 of the treatment with blue light irradiation (150 μmol photons m−2s−1), respectively. With the addition of SA (2.5 mg/L), a total of 63 DEPs and 11,638 DEGs were revealed on day 2 and day 7, respectively. We further analyzed the molecular response in five metabolic pathways related to astaxanthin synthesis, including the astaxanthin synthesis pathway, the fatty acid synthesis pathway, the heme synthesis pathway, the reactive oxygen species (ROS) clearance pathway, and the cell wall biosynthesis pathway. Results show that blue light causes a significant down-regulation of the expression of key genes involved in astaxanthin synthesis and significantly increases the expression of heme oxygenase, which shows decreased expression by the treatment with SA. Our study provides novel insights into the production of astaxanthin by H. pluvialis treated with blue light and SA.
... SFN is an organosulfur dietary phytochemical which shows cancer prevention agent, hostile to -provocative and antitumor exercises. SFN can rummage various ROS, for example, superoxide radical anion (O2-•) and hydrogen peroxide (H2O2) [69] , regardless of whether different examinations have contended that the searching capacity of SFN for peroxynitrite anion, superoxide anion, singlet oxygen, peroxyl radicals, hydrogen peroxide and hydroxyl radicals was low [70] . It can possibly treat or forestall malignancy and different neurological clutters [71 -73] . ...
... SFN is an organosulfur dietary phytochemical which displays antioxidant, anti-inflammatory and antitumor activities. SFN can scavenge different ROS, such as superoxide radical anion (O 2 -• ) and hydrogen peroxide (H 2 O 2 ) [69], even if other studies have argued that the scavenging ability of SFN for peroxynitrite anion, superoxide anion, singlet oxygen, peroxyl radicals, hydrogen peroxide and hydroxyl radicals was very low [70]. It has the potential to treat or prevent cancer and various neurological disorders [71][72][73]. ...
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Monoclonal antibodies targeting the programmed-death 1 (PD-1) immune checkpoint or its ligand PD-L1 have significantly improved the treatment of cancers but more efficient drugs and combinations are still needed to increase the therapeutic efficacy. As the oxidative state of the immune microenvironment plays a critical role in the antitumor immune response, it is important to evaluate the impact of molecules and drugs used for oxidative stress control on PD-L1 expression and functions. Here we have reviewed the functional relationship between reactive oxygen species (ROS) and PD-L1 expressed on cancer cells, and analyzed the effects of 15 pharmacological ROS modulators - both ROS inducers and attenuators - on PD-L1 expression. The interplay between tumor hypoxia, the HIF-1α/YAP1/NFκB signaling routes and PD-L1 expression has been analyzed and specific non-cytotoxic ROS-associated drugs known to modulate this system are discussed. A complex interplay between ROS effectors and PD-L1 expression is revealed, showing that depending on their targets and mechanisms, ROS effectors can engender an up or down-regulation of PD-L1 expression in cancer cells. An enhanced generation of ROS often promotes PD-L1 expression and, conversely, ROS scavenging generally represses PD-L1. But there are noticeable exceptions with drugs that augment ROS production while reducing PD-L1 expression and vice versa. The variable PD-L1 response to ROS modulation reflects the complexity of ROS biology in the tumor microenvironment. A deeper knowledge of the contribution of ROS to PD-(L)1 immune checkpoint control is warranted.
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Gut microbiota plays a fundamental role in host's physiology. However, the effect of organic UV filters, an emerging contaminant on gut microbiota is poorly understood. Here, fish (Carassius auratus) were exposed to 2, 20 and 200 μg/L of benzophenone-3 (BP3) for 28 days to explore the toxicological effects and its association with the changes in the gut microbiota. The BP3 accumulation is time and dose dependent in the liver and intestine. Under BP3 subchronic exposure, fish's body and intestinal weights, reactive oxygen species (ROS), immunoglobulin M (IgM) and vitellogenin (VTG) levels, as well as 7-benzyloxy-4-trifluoromethylcoumarin-O-debenzyloxylase (BFCOD) activities, were decreased. BP3 exposure has increased the abundance of Bacteroidetes phylum and Mycobacterium genus. Bioinformatic analysis revealed that the levels of ROS, IgM, estrogen receptor and VTG, activities of lysozyme, BFCOD and 7-ethoxyresorufin-O-deethylase were significantly correlated with the relative abundance of intestinal microbial genus (p < 0.05). These results highlight for the first time the association between the effects of organic UV filters on the antioxidant, immune, endocrine, and metabolic systems of the fish and changes in the gut microbiota, which extend knowledge of the role of gut microbiota in ecotoxicology.
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Reactions of sulforaphane, the most important component of broccoli, with radicals have been studied using theoretical chemistry. Reliable methods of density functional theory have been used to study mechanisms of reaction of sulforaphane with reactive oxygen species: •OH, •OCH3, •OOH and O2·-. Three mechanisms of radical reactions have been considered: radical adduct formation (RAF), hydrogen atom transfer (HAT) and single electron transfer (SET). All studied reactions have been studied in gas phase, water and n-octanol solutions. Water is used as a model for blood serum and n-octanol mimics the role of lipid environment. In order to design more effective molecules, some derivatives of sulforaphane have been studied in terms of solubility and antioxidant activities. Radical stabilization energies are studied to determine radical scavenging ability of sulforaphane and its derivatives.
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The aggregation of hydrophobic photosensitizers limits the therapeutic effect of photodynamic therapy (PDT). Improving the hydrophilicity of photosensitizers can reduce their aggregation for enhancing PDT. Herein, a nanosystem (TPFcNP) is developed by a hydrophobic photosensitizer 5,10,15,20-tetrakis (4-methacryloyloxyphenyl) porphyrin (TMPP) containing multiple carbon-carbon double bonds and a ferrocene-containing amphiphilic block copolymer (PEG-b-PMAEFc), which catalyzes hydrogen peroxide (H2O2) to produce hydroxyl radicals (·OH) in tumor microenvironment by Fenton reaction. ·OH could catalyze the addition reaction between carbon-carbon double bonds of TMPP and over-expressed water-soluble glutathione (GSH) in tumor cells, which greatly improves the hydrophilicity of photosensitizers and reduces their aggregation. Experiments in vitro and in vivo have proved that this strategy significantly enhances therapeutic efficacy of PDT. Catalyzing intracellular reactions in situ by making use of tumor microenvironment will open up a new opportunity to solve the aggregation of materials in tumor for cancer treatment.
Article
Numerous plant extracts used as feed additives in aquaculture have been shown to stimulate appetite, promote growth and enhance immunostimulatory and disease resistance in cultured fish. However, there are few studies on the famous Chinese herbal medicine Gelsemium elegans, which attracts our attention. In this study, we used the Megalobrama amblycephala to investigate the effects of G. elegans alkaloids on fish intestinal health after diet supplementation with 0, 5, 10, 20 and 40 mg/kg G. elegans alkaloids for 12 weeks. We found that dietary G. elegans alkaloids at 40 mg/kg improved intestinal morphology by increasing villus length, muscle thickness and villus number in the foregut and midgut and muscle thickness in the hindgut (P < 0.05). These alkaloids also significantly improved intestinal antioxidant capabilities by increasing superoxide dismutase, catalase, total antioxidant capacity and malondialdehyde levels and up-regulated intestinal Cu/Zn-SOD and Mn-SOD (P < 0.05) at 20 and 40 mg/kg. Dietary G. elegans alkaloids improved intestinal immunity via up-regulating the pro-inflammatory cytokines IL-1β, IL-8, TNF-α and IFN-α and down-regulating expression of the anti-inflammatory cytokines IL-10 and TGF-β (P < 0.05) at 20 and 40 mg/kg. The expression of Toll-like receptors TRL1, 3, 4 and 7 were also up-regulated in intestine of M. amblycephala (P < 0.05). In intestinal microbiota, the abundance of Proteobacteria was increased while the Firmicutes abundance was decreased at phylum level after feeding the alkaloids (P < 0.05). The alkaloids also increased the abundance of the probiotic Rhodobacter and decreased the abundance of the pathogenic Staphylococcus at genus level (P < 0.05). In conclusion, dietary G. elegans alkaloid supplementation promoted intestine health by improving intestine morphology, immunity, antioxidant abilities and intestinal microbiota in M. amblycephala.
Thesis
Patienten mit erhöhten Aldosteronspiegeln zeigen eine gesteigerte Inzidenz für Malignome, insbesondere von Nierenzellkarzinomen. Das Ziel dieser Arbeit war es, die Aldosteron-vermittelte oxidative Nierenschädigung näher zu analysieren sowie die auf Zellebene gezeigte Beeinflussung der antioxidativen Schutzmechanismen im lebenden Organismus nachzuweisen und mögliche therapeutische Ansatzpunkte zu identifizieren. Dazu wurde ein Interventions-versuch über 28 Tage durchgeführt. Neben einer Aldosterongabe wurden folgende Interventionen verwendet: Spironolacton zur Blockade des Mineralkortikoid-Rezeptors (MR), Apocynin als Hemmstoff der NADPH-Oxidasen (Nox), L-NAME zur Blockade der NO-Synthasen (NOS), PDTC, einen Hemmstoff des Transkriptionsfaktors NF-kB sowie Sulforaphan, ein natürlicher Nrf2-Induktor. Eine weitere Gruppe erhielt Sulforaphan ohne additive Aldosterongabe. Die Nierenschäden wurden mittels histopathologischer Schädigungsscores und der Anzahl an DNA-Doppelstrangbrüche analysiert. Die Beeinflussung der antioxidativen Abwehr wurde durch die Aktivierung des Transkriptionsfaktors Nrf2 und durch die Quantifizierung antioxidativer Enzyme bestimmt. Im Nierengewebe führte Aldosteron zu einer Zunahme von oxidativem Stress. Histologisch zeigte sich ein Anstieg von glomerulären Schäden. Auch kam es zu einer deutlichen Zunahme von Doppelstrangbrüchen der DNA. Des Weiteren konnten wir zeigen, dass Aldosteron auch in vivo zu einer Zunahme der Nrf2-Aktivität führte, wobei sich dies auf Proteinebene nicht in einer (dauerhaften) Synthesesteigerung von antioxidativen Enzymen wiederspiegelte und keinen ausreichenden Schutz des Nierengewebes bot. Für die Interventionsgruppen konnte keine signifikante Auswirkung auf das Vorliegen von oxidativem Stress gezeigt werden. Dies könnte an der Versuchsdauer bzw. an der gewählten Nachweismethode gelegen haben. Nichtsdestotrotz zeigte die Blockade der Nox durch Apocynin bzw. der NOS durch L-NAME eine effektive Reduktion der histologischen und genomischen Schäden. Die L-NAME-Gruppe wies dabei die höchsten Blutdruckwerte auf, diese waren auch zur Aldosterongruppe signifikant gesteigert. Die beobachteten Effekte waren folglich nicht durch den in der Aldosterongruppe erfolgten Blutdruckanstieg, sondern vielmehr durch den Anstieg von oxidativem Stress zu erklären. Ebenfalls blieb die Nrf2-Aktivität bei der Gabe von Apocynin und L-NAME weitgehend auf Kontrollniveau, was dafürspricht, dass der in der Aldosterongruppe messbare Nrf2-Anstieg am ehesten als Reaktion auf chronisch erhöhten oxidativen Stress erfolgte, welcher durch die Interventionen ausblieb. Die Blockade von NF-κB mittels PDTC führte zu vergleichbaren Effekten wie Apocynin und L-NAME. Das deutet darauf hin, dass Aldosteron über die Aktivierung von NF-κB die vermehrte Synthese von pro-oxidativen Enzymen wie Nox und NOS anregt. Die Gabe von Spironolacton hatte den stärksten protektiven Effekt, sowohl auf histologische Veränderungen als auch auf das Entstehen von DNA-Doppelstrangbrüchen, wobei die Nrf2-Aktivität in dieser Gruppe ebenfalls auf Kontrollniveau blieb. Die Aldosteroneffekte wurden folglich über den MR vermittelt. Eine additive Nrf2-Induktion mittels Sulforaphan konnte auch keinen (dauerhaften) Effekt auf die Synthese antioxidativer Enzyme zeigen. Dennoch zeigte diese Gruppe einen ähnlich effektiven Schutz vor den oxidativen Nierenschäden wie die Gabe von Spironolacton. Vieles spricht dafür, dass die Wirkung von Sulforaphan dabei über seine Wirkung als direktes Antioxidans bzw. Radikalfänger und nicht über den Nrf2-Weg zu erklären ist. Aldosteron führt in der Niere über oxidativen Stress zu glomerulärer Fibrose und DNA-Schäden. Das könnte eine Erklärung für die gesteigerte Inzidenz von Nierenzellkarzinomen in Patienten mit erhöhten Aldosteronspiegeln darstellen. Unsere Ergebnisse sprechen dafür, dass Aldosteron über eine Signalkaskade über den MR zu einer Aktivierung von Nox und NOS führt. Der Aktivierung des Transkriptionsfaktors NF-κB scheint dabei durch die Synthese pro-oxidativer Enzyme eine Art Verstärker-Effekt zuzukommen. Als Reaktion auf den durch Aldosteron gesteigerten oxidativen Stress kommt es zu einer Aktivierung des antioxidativen Transkriptionsfaktors Nrf2, jedoch ohne dass dies zu einem ausreichenden Schutz des Nierengewebes führt. Mögliche therapeutische Ansatzpunkte für einen Schutz vor den durch Aldosteron vermittelten oxidativen Nierenschäden scheinen eher innerhalb der Aldosteronsignalkaskade, insbesondere in der Blockade des MR, als in der antioxidativen Abwehr zu liegen.
Article
The present study aim to investigate the effects of dietary Gelsemium elegans alkaloids supplementation in Megalobrama amblycephala. A basal diet supplemented with 0, 5, 10, 20 and 40 mg/kg G. elegans alkaloids were fed to M. amblycephala for 12 weeks. The study indicated that dietary 20 mg/kg and 40 mg/kg G. elegans alkaloids supplementation could significantly improve final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER) (P < 0.05). The 20 mg/kg and 40 mg/kg G. elegans alkaloids groups showed significantly higher whole body and muscle crude protein and crude lipid contents compared to the control group (P < 0.05). The amino acid contents in muscle were also significantly increased in 20 mg/kg and 40 mg/kg groups (P < 0.05). Dietary 40 mg/kg G. elegans alkaloids had a significant effect on the contents of LDH, AST, ALT, ALP, TG, TC, LDL-C, HDL-C, ALB and TP in M. amblycephala (P < 0.05). Fish fed 20 mg/kg and 40 mg/kg dietary G. elegans alkaloids showed significant increase in complement 3, complement 4 and immunoglobulin M contents. The liver antioxidant enzymes (SOD, CAT and T-AOC) and MDA content significantly increased at 20 mg/kg and 40 mg/kg G. elegans alkaloids supplement (P < 0.05). The mRNA levels of immune-related genes IL-1β, IL8, TNF-α and IFN-α were significantly up-regulated, whereas TGF-β and IL10 genes were significantly down-regulated in the liver, spleen and head kidney of fish fed dietary supplementation with 20 mg/kg and 40 mg/kg G. elegans alkaloids. After challenge with Aeromonas hydrophila, significant higher survival rate was observed at 20 mg/kg and 40 mg/kg G. elegans alkaloids supplement (P < 0.05). Therefore, these results indicated that M. amblycephala fed a diet supplemented with 20 mg/kg and 40 mg/kg G. elegans alkaloids could significantly promote its growth performance, lipids and amino acids deposition, immune ability and resistance to Aeromonas hydrophila.
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The scavenging action of zingerone, a phenolic anti-oxidant, toward the hydroxyl radical has been studied employing density functional theory. All the relevant potential energy surface extrema were located by optimizing geometries of the reactant complexes, transition states, and product complexes in gas phase. Solvent effect of aqueous media was treated by performing single point energy calculations using the polarizable continuum model. It has been shown how following certain steps of hydrogen abstraction and addition reactions and using a few OH radicals along with zingerone or its degradation products, two other anti-oxidants, namely vanillin and ferulic acid can be formed. The mechanism of anti-oxidant action of zingerone through single electron transfer has also been studied. Copyright © 2013 John Wiley & Sons, Ltd.
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Malignant tumors are the single most common cause of death and the mortality rate of ovarian cancer is the highest among gynecological disorders. The excision of benign tumors is generally followed by complete recovery; however, the activity of cancer cells often results in rapid proliferation even after the tumor has been excised completely. Thus, clinical treatment must be supplemented by auxiliary chemotherapy or radiotherapy. Sulforaphane (SFN) is an extract from the mustard family recognized for its anti-oxidation abilities, phase 2 enzyme induction, and anti-tumor activity. This study investigated the cell cycle arrest in G2/M by SFN and the expression of cyclin B1, Cdc2, and the cyclin B1/CDC2 complex in PA-1 cells using western blotting and co-IP western blotting. This study investigated the anticancer effects of dietary isothiocyanate SFN on ovarian cancer, using cancer cells line PA-1. SFN-treated cells accumulated in metaphase by CDC2 down-regulation and dissociation of the cyclin B1/CDC2 complex. Our findings suggest that, in addition to the known effects on cancer prevention, SFN may also provide antitumor activity in established ovarian cancer.
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In this lecture, evidence is presented to support the following hypothesis regarding the roles of xanthine oxidase-derived oxidants and granulocytes in ischemia-reperfusion-induced microvascular injury. During the ischemic period, ATP is catabolized to yield hypoxanthine. The hypoxic stress also triggers the conversion of NAD-reducing xanthine dehydrogenase to the oxygen radical-producing xanthine oxidase. During reperfusion, molecular oxygen is reintroduced into the tissue where it reacts with hypoxanthine and xanthine oxidase to produce a burst of superoxide anion and hydrogen peroxide. In the presence of iron, superoxide anion and hydrogen peroxide react via the Haber-Weiss reaction to form hydroxyl radicals. This highly reactive and cytotoxic radical then initiates lipid peroxidation of cell membrane components and the subsequent release of substances that attract, activate, and promote the adherence of granulocytes to microvascular endothelium. The adherent granulocytes then cause further endothelial cell injury via the release of superoxide and various proteases.
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Significance Autism spectrum disorder (ASD), encompassing impaired communication and social interaction, and repetitive stereotypic behavior and language, affects 1–2% of predominantly male individuals and is an enormous medical and economic problem for which there is no documented, mechanism-based treatment. In a placebo-controlled, randomized, double-blind clinical trial, daily oral administration for 18 wk of the phytochemical sulforaphane (derived from broccoli sprouts) to 29 young men with ASD substantially (and reversibly) improved behavior compared with 15 placebo recipients. Behavior was quantified by both parents/caregivers and physicians by three widely accepted measures. Sulforaphane, which showed negligible toxicity, was selected because it upregulates genes that protect aerobic cells against oxidative stress, inflammation, and DNA-damage, all of which are prominent and possibly mechanistic characteristics of ASD.
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The removal of two vicinal hydrogen atoms from an alkane to produce an alkene is a challenge for synthetic chemists. In nature, desaturases and acetylenases are adept at achieving this essential oxidative functionalization reaction, for example during the biosynthesis of unsaturated fatty acids, eicosanoids, gibberellins and carotenoids. Alkane-to-alkene conversion almost always involves one or more chemical intermediates in a multistep reaction pathway; these may be either isolable species (such as alcohols or alkyl halides) or reactive intermediates (such as carbocations, alkyl radicals, or σ-alkyl-metal species). Here we report a desaturation reaction of simple, unactivated alkanes that is mechanistically unique. We show that benzynes are capable of the concerted removal of two vicinal hydrogen atoms from a hydrocarbon. The discovery of this exothermic, net redox process was enabled by the simple thermal generation of reactive benzyne intermediates through the hexadehydro-Diels-Alder cycloisomerization reaction of triyne substrates. We are not aware of any single-step, bimolecular reaction in which two hydrogen atoms are simultaneously transferred from a saturated alkane. Computational studies indicate a preferred geometry with eclipsed vicinal C-H bonds in the alkane donor.
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Mapping out a reaction mechanism involves optimizing the reactants and products, finding the transition state and following the reaction path connecting them. Transition states can be difficult to locate and reaction paths can be expensive to follow. We describe an efficient algorithm for determining the transition state, minima and reaction path in a single procedure. Starting with an approximate path represented by N points, the path is iteratively relaxed until one of the N points reached the transition state, the end points optimize to minima and the remaining points converged to a second order approximation of the steepest descent path. The method appears to be more reliable than conventional transition state optimization algorithms, and requires only energies and gradients, but not second derivative calculations. The procedure is illustrated by application to a number of model reactions. In most cases, the reaction mechanism can be described well using 5 to 7 points to represent the transition state, the minima and the path. The computational cost of relaxing the path is less than or comparable to the cost of standard techniques for finding the transition state and the minima, determining the transition vector and following the reaction path on both sides of the transition state.
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The polarizable continuum model (PCM), used for the calculation of molecular energies, structures, and properties in liquid solution has been deeply revised, in order to extend its range of applications and to improve its accuracy. The main changes effect the definition of solute cavities, of solvation charges and of the PCM operator added to the molecular Hamiltonian, as well as the calculation of energy gradients, to be used in geometry optimizations. The procedure can be equally applied to quantum mechanical and to classical calculations; as shown also with a number of numerical tests, this PCM formulation is very efficient and reliable. It can also be applied to very large solutes, since all the bottlenecks have been eliminated to obtain a procedure whose time and memory requirements scale linearly with solute size. The present procedure can be used to compute solvent effects at a number of different levels of theory on almost all the chemical systems which can be studied in vacuo. © 2002 American Institute of Physics.