Bioaccessibility and Bioavailability of Bioactive Compounds in Food and Plant Determination - Natural Antioxidants and Biocides from Wild Medicinal Plants - page 46

reflect the amount that is available in the
organism; only a fraction of the contami-
nant could be bioavailable after oral expo-
sure and exert their toxic action (Brandon
et al. , 2006).

digestion polyphenols might interact with
other food constituents (ion chelation), could
be degraded or metabolized by hydrolysis as
in de-glycosylation (Bouayed et al. , 2012).
After in vitro digestion, rather than
evaluating the polyphenols content, we
want to know what changes have occurred
with regard to antioxidant capacity. A study
of different fruit juices determined that the
antioxidant capacity of the bioaccessible
fractions increased, whereas ascorbic acid
content and polyphenols decreased by 36%
and 16%, respectively. Although the con-
tent of polyphenol decreased, there was an
increase in the antioxidant capacity that
could be formed owing to unknown or
undetected compounds with different
chemical properties. It could also be pos-
sible that in vitro digestion releases interfer-
ing compounds that lead to overestimating
the antioxidant capacity; moreover, pancre-
atic enzymes and bile salts are capable of
binding to metals and/or trapping free radi-
cals, which could increase the antioxidant
capacity (Cilla et al. , 2011).
Generally, as a food is consumed, it is
consumed not only as one single type but as
part of a complex meal. For example, a meal
could consist of a source of carbohydrates,
meat and a glass of wine or juice. In the case
of the polyphenols present in wine, they
have chemical affinity with proteins and Fe,
which can form chelates with the phenolic
compounds in the lumen. A mixture of Fe
and red wine after digestion has less capac-
ity than the consumed wine antioxidant
alone; this is due to the chelates Fe-phenols.
Also mixing red wine with proteins (meat
or casein) after digestion also decreases
their antioxidant capacity (Argyri et al. ,
2006).
The hydroxycinnamic acid more abun-
dant in apples is chlorogenic acid, which is
reduced in concentration from gastric diges-
tion to the intestine. However, during intes-
tinal digestion the isomers neochlorogenic
acid and criptochlorogenic acid appear.
Moreover, during the gastric digestion there
is an increase of phloridzin and quercetin
3-o-glucoside, indicating that gastric condi-
tions are efficient in extraction and poten-
tial availability (Bouayed et al. , 2012).

4.2 Bioaccessibility

It is widely accepted that not all constitu-
ents present in the food matrix might be
completely bioaccessible; it depends on
several parameters, including their initial
concentration in the food matrix, matrix
composition and factors related to the host,
such as enzyme concentration (Bouayed
et al. , 2012). The in vitro digestion methods
are extremely useful to study the effects of a
food matrix, conditions or interactions with
other compounds, stability and properties
of compounds that could affect the bioac-
cessibility (Bermudez-Soto et al. , 2007).
One of the main groups of compounds
under study are phenolic compounds; these
compounds, because they are being recog-
nized as beneficial to human health, have
generated researchers' interest to know
whether their beneficial properties are able
to survive the gastrointestinal conditions
that occur once ingested. Minerals have also
been extensively studied, trying different
food matrixes, because minerals are gener-
ally used in the fortification of food.

4.3 Phenolic Compounds

Polyphenols can exert their bioactive prop-
erties via their antioxidant properties or
additional mechanisms such as those affect-
ing intracellular signalling and gene expres-
sion. The antioxidant properties of phenolic
compounds may contribute to protect health
against cardiovascular disease and cancer
(among others). The bioavailability of
polyphenols depends on a variety of factors,
including their release from the matrix dur-
ing digestion (i.e. bioavailability), cell intake,
metabolism and subsequent transport to the
circulatory system. An important factor to
consider

is that during gastrointestinal