3 research outputs found
Biodegradation of Punicalagin into Ellagic Acid by Selected Probiotic Bacteria: A Study of the Underlying Mechanisms by MS-Based Proteomics
Pomegranate (Punica granatum L.)
is a well-known source of bioactive phenolic compounds such as ellagitannins,
anthocyanins, and flavanols. Punicalagin, one of the main constituents
of pomegranate, needs to be biodegraded by bacteria to yield metabolites
of medicinal interest. In this work, we tested 30 lactic acid bacteria
(LAB) and their capacity to transform punicalagin from a punicalagin-rich
pomegranate extract into smaller bioactive molecules, namely, ellagic
acid and urolithins. These were identified and quantified by high-performance
liquid chromatography-electrospray ionization tandem mass spectrometry
(HPLC-ESI-MS2). Further, we evaluated the molecular mechanism
governing this transformation through label-free comparative MS-based
proteomics. All tested LAB strains were capable of transforming punicalagin
into ellagic acid, while the biosynthesis of urolithins was not observed.
Proteomic analysis revealed an increase of generic transglycosylases
that might have a hydrolytic role in the target phenolic molecule,
coupled with an increase in the quantity of ATP-binding cassette (ABC)
transporters, which might play a relevant role in transporting the
resulting byproducts in and out of the cell
Separation of Isomeric Forms of Urolithin Glucuronides Using Supercritical Fluid Chromatography
Urolithins are gut microbiota metabolites produced in
humans after
consuming foods containing ellagitannins and ellagic acid. Three urolithin
metabotypes have been reported for different individuals depending
on the final urolithins produced. After absorption, they are conjugated
with glucuronic acid (phase II metabolism), and these are the main
circulating metabolites in plasma and reach different tissues. Different
regioisomeric isomers of urolithin glucuronides have been described.
Still, their identification and quantification in humans have not
been properly reported due to resolution limitations in their analysis
by reversed-phase high-performance liquid chromatography. In the present
study, we report a novel method for separating these isomers using
supercritical fluid chromatography. With this method, urolithin A
3- and 8-glucuronide, isourolithin A 3- and 9- glucuronide, and urolithin
B 3-glucuronide (8-hydroxy urolithin 3-glucuronide; 3-hydroxy urolithin
8-glucuronide; 3-hydroxyurolithin 9-glucuronide; 9-hydroxyurolithin
3-glucuronide; and urolithin 3-glucuronide) were separated in less
than 15 min. The proposed method was applied to successfully analyze
these metabolites in urine samples from different volunteers belonging
to different metabotypes
Metabolism of Oak Leaf Ellagitannins and Urolithin Production in Beef Cattle
Oak leaves have a high concentration of ellagitannins.
These phytochemicals
can be beneficial or poisonous to animals. Beef cattle are often intoxicated
by oak leaf consumption, particularly after suffering feed restriction.
The severity of the poisoning has recently been associated with the
ruminal microbiota, as different bacterial populations were found
in animals that tolerated oak leaves and in those that showed clinical
and pathological signs of toxicity. Intoxication has previously been
linked to the production of phenolic metabolites, particularly catechol,
phloroglucinol, and resorcinol. This suggested that the microbial
metabolism of ellagitannins could also be associated with its tolerance
or intoxication in different animals. Therefore, it is essential to
understand the metabolism of ellagitannins in cattle. Here we show
that ellagitannins are metabolized in the cattle rumen to urolithins.
Different urolithins were detected in ruminal fluid, feces, urine,
and plasma. Oak leaf ellagitannins declined as they were converted
to urolithins, mainly isourolithin A and urolithin B, by the ruminal
and fecal microbiota. Urolithin aglycons were observed in rumen and
feces, and glucuronide and sulfate derivatives were detected in plasma
and urine. Sulfate derivatives were the main metabolites detected
in plasma, while glucuronide derivatives were the main ones in urine.
The main urolithins produced in cattle were isourolithin A and urolithin
B. This is a relevant difference from the monogastric mammals studied
previously in which urolithin A was the main metabolite produced.
Low molecular weight phenolics of the benzoic, phenylacetic, and phenylpropionic
groups and metabolites such as catechol, resorcinol, and related compounds
were also detected. There was a large variability in the kinetics
of production of these metabolites in individual animals, although
they produced similar metabolites in all cases. This large variability
could be associated with the large variability in the rumen and intestine
microbiota that has previously been observed. Further studies are
needed to demonstrate if the efficiency in the metabolism of ellagitannins
by the microbiota could explain the differences observed in susceptibility
to intoxication by the different animals