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3
Many
Adhesins
cagPAI-coded
type IV secretion
system apparatus
(T4SS)
Flagella
H.pylori cagA +
strain
Mucus layer
BabA,AlpA,
AlpB,HopZ
Alteration of mucus
glycoproteins
1
2
Mucosa
CagA
VacA
Apoptosis
NF-kB
AP-1
CagA
P
GRO-
α
Urease
LPS
IgG
IgA
ENA-78
TNF-
α
IL-1
β
4
INF-
γ
IL-8
IL-8
porins
5
B Cells
Th2
IL-12
Inflammation
Macrophage
Th1
ROS
Cytokine-induced
changes in
gastric physiology
PMN recruitment
Th0
Neutrophil
Fig. 2.3.
Potential sites of action of polyphenols as cytoprotective agents and anti-
H. pylori
. Numbers in
bold represent the effects detailed in the text.
Ramassamy, 2006; Perron and Brumaghim,
2009; Chong
et al
., 2010; Ostertag
et al
.,
2010; Vauzour
et al
., 2010; Weseler
et al
.,
2011). A crucial aspect of research on the
antioxidant capacity of natural products is,
however, the correct choice of the measure-
ment tools. The state of the art approach
indicates that it is becoming necessary to
have a battery of tests that allow us to obtain
complementary information. In this regard,
the use of coloured stable radicals such
as 1,1-diphenyl-2-picrylhydrazyl (DPPH),
2,2′-azino-bis(3-ethylbenzothiazoline-6-
sulfonic acid) (ABTS), N,N-dimethyl-p-
phenylenediamine (DMPD), or reagents
such as ferric reducing antioxidant power
(FRAP) and cupric ion reducing antioxidant
capacity (CUPRAC) are recommended as a
preliminary ranking criterion for different
vegetal sources, extracts or fractions thereof,
according to their antioxidant power.
Electron transfer and/or hydrogen reactions
occur in these assays. Adequate knowledge
of the chemistry of such systems is therefore
a prerequisite for correctly interpreting the
results, particularly when these tests are
applied to highly complex samples such as
biological fluids. In the following sections
we will review some of the methods used
for the determination of antioxidant cap-
acity with emphasis on those considered
most useful and innovative.
2.5 Antioxidant Assays
using Cell-free Media
As shown in many studies, data of antioxi-
dant capacity for plant and foods are often
crossed with the total polyphenol content,
determined as gallic acid equivalents (GAE).
It is, however, increasingly frequent recourse
to separation techniques coupled to online
detection systems, such as diode array
(DAD) or mass spectrometry (LC-MS). Such
techniques help to better dissect the anti-
oxidant activity and assign it to a specific
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