Metabolic pathways of the colonic metabolism of flavonoids (flavonols, flavones and flavanones) and phenolic acids

Catabolism of raw and cooked green pepper ( Capsicum annuum ) (poly)phenolic compounds after simulated gastrointestinal digestion and faecal fermentation

“…However, the recovered amount of quercetin after 5 h did not correspond to the total of the native quercetin derivatives, indicating that also the aglycone, once released, could be rapidly degraded, in agreement with previously reported results (Serra et al, 2012). Similarly, luteolin aglycone was rapidly released at the beginning of the fecal incubation.…”

“…Actually, some authors (Aura et al, 2002) detected a higher concentration of dihydroxyphenylacetic acid within 2 h of incubation, a time point not considered in the present study. Like dihydroxyphenylacetic acid, other minor catabolites previously reported as being generated after (poly)phenol compound fecal biotransformation, such as phenylacetic acid, hydroxyphenylacetic acid, hydroxybenzoic acid or benzoic acid (Aura et al, 2002;Ludwig et al, 2013;Serra et al, 2012) were not detected in the present study. This could be due to the different fermentation times applied, as 3-hydroxyphenylacetic acid was formed by dehydroxylation of 3,4-dihydroxyphenylacetic acid after 8 h incubation (Aura et al, 2002), while other catabolites presented the maximum amount after 48 h of fecal incubation and only low quantities were detected after 24 h (Serra et al, 2012).…”

“…In accordance with Serra et al (2012), quercetin is subjected to ring fission, resulting in the formation of dihydrocaffeic acid, which could be then further degraded to new catabolites. Ring fission could also result in the formation of protocatechuic acid (Rechner et al, 2004).…”

“…Ring fission could also result in the formation of protocatechuic acid (Rechner et al, 2004). In the case of luteolin, according to Serra et al (2012), only dihydrocaffeic acid could be generated.…”

Plasma kinetics and microbial biotransformation of grape seed flavanols in rats

“…These early metabolites undergo microbial cleavage of the lactone ring by acidic hydrolysis (Dall'Asta et al, 2012;Del Rio et al, 2013) to form valeric acid metabolites, which were also not detected in rat plasma as they are intermediate compounds (data not shown). Although no valeric acid or propan-2-ol metabolites were detected in rat plasma, previous in vitro studies with rat (Serra et al, 2011(Serra et al, , 2012 or human (Cueva et al, 2013;Sánchez-Patán et al, 2012a,b) faecal microflora detected these compounds. This study found that these intermediates do not reach the systemic circulation at sufficient concentration levels to be detected and quantified by MS, which suggests that they may remain in the colon to be subject to the microbial metabolism.…”