Biology Reference
In-Depth Information
volunteers regarding the levels of excretion of this metabolite. The third
study reporting on ET bioavailability was carried out in a group (n = 15)
of patients with stable chronic obstructive pulmonary disease (COPD).
The volunteers were given pomegranate juice supplementation for 5
weeks in a randomized, double blind, placebo-controlled trial (Cerdá
et
al.
, 2005c). Urolithins A and B (3,8-dihydroxydibenzopyran-6-one and
3-hydroxydibenzopyran-6-one) were detected in both the plasma and
urine of patients and a large inter-individual variability was again
observed.
7.6 What Bioavailability and Metabolism Events Take Place in
Different Human Body Sites?
ETs are large molecules usually quite polar and therefore, according to
the pharmacokinetics general knowledge, they should be poorly absorbed
or not absorbed at all. The experimental data available indicates that
dietary ETs are generally not detected in plasma or in other biological
fluids after the intake of ET-rich foods. Exceptionally, when a very large
dose of ETs is provided, low concentrations of these compounds are
found in plasma and urine (Cerdá
et al
., 2003a). In a dietary context in
humans or animal models, no ET from ET-rich foods (
e.g.
, strawberries,
walnuts, raspberries, acorns) is detected in plasma or urine (Cerdá
et al.
,
2005a).
7.6.1 Absorption of free EA
Free ellagic acid (EA) is already present in most ET-rich foods, and is
also produced during food processing and storage. Free EA is quite
insoluble in aqueous solvents and precipitates in juices and liquors. Some
pharmacokinetic studies show that EA can be absorbed as such within 30
to 60 minutes after the intake of several foods (Seeram
et al
., 2004). This
suggests that absorption of EA already begins in the stomach and can be
detected in peripheral blood. EA disappears from plasma after 2 hours of
intake. However, other pharmacokinetic studies carried out with different
foods containing similar amounts of free EA have shown no absorption
