Impact of cooking methods of red-skinned onion on metabolic transformation of phenolic compounds and gut microbiota changes

Abstract

The recipient work investigated on the stability and bioaccessibility of phenolics of red-skinned onion (RSO) differently cooked and in turn on its impact on the gut microbiota and phenolics metabolism....

Quercetins, Chlorogenic Acids and Their Colon Metabolites Inhibit Colon Cancer Cell Proliferation at Physiologically Relevant Concentrations

“…Colon metabolism of glycosylated quercetin derivatives begins with the hydrolysis of the glucoside moiety, releasing the corresponding aglycone that undergoes C-ring fission generating the transient intermediate 3-(3 ,4 -dihydroxyphenyl)propanoic acid that is further dehydroxylated to 3-(3 -hydroxyphenyl)propanoic acid or oxidated to 3-(3 ,4dihydroxyphenyl)acetic acid. These last compounds may finally be converted into 3-(3hydroxyphenyl)acetic acid by oxidation and dehydroxylation, respectively (Figure 4) [27,28,39]. Similarly, the colon metabolism of chlorogenic acids starts with the hydrolysis of the ester bond between quinic acid and hydroxycinnamic acid, producing 3 ,4 -dihydroxycinnamic acid which is further reduced and dehydroxylated to 3-(3 -hydroxyphenyl)propanoic acid (Figure 4) [27,30].…”

“…Similarly, the colon metabolism of chlorogenic acids starts with the hydrolysis of the ester bond between quinic acid and hydroxycinnamic acid, producing 3 ,4 -dihydroxycinnamic acid which is further reduced and dehydroxylated to 3-(3 -hydroxyphenyl)propanoic acid (Figure 4) [27,30]. Thus, the most important metabolites identified after colon fermentation of glycosylated quercetin derivatives are quercetin aglycone, 3-(3 ,4 -dihydroxyphenyl)acetic acid, 3-(3 -hydroxyphenyl)acetic acid and 3-(3hydroxyphenyl)propanoic acid, whereas colon metabolism of chlorogenic acids mainly results in the accumulation of 3-(3 -hydroxyphenyl)propanoic acid [27,28,30,39,40]. In this study, we found that both parent compounds (i.e., glycosylated quercetin derivatives, quercetin aglycone and chlorogenic acids) as well as their most important colon metabolites were able to inhibit colon cancer cell proliferation at a concentration of 100 μmol/L.…”

“…For example, Juániz et al [40] and Cattivelli et al [28] identified 3-(3 -hydroxyphenyl) propanoic acid as the main metabolite produced after fecal fermentation of glycosylated quercetins in green pepper and red-skinned onion. On the other hand, Di Pede et al [39] pointed out 3-(3 ,4 -dihydroxyphenyl)acetic acid as the metabolite generated in higher amounts after quercetin fermentation by gut microbiota.…”

“…There were also differences in the rate of quercetin metabolic conversion. In some studies, quercetin aglycone was still present in high concentrations after 5-6 h of fermentation whereas, in others, quercetin completely disappeared after a few hours of fecal fermentation [28,[39][40][41][42]. Therefore, inter-individual variability determined not only the type and concentration of produced metabolites but also the rate of bioconversion of quercetin.…”

“…Quercetin and quercetin derivatives reaching the colon are subjected to microbiota metabolism that involves a deglycosylation reaction, followed by C-ring fission and βoxidation generating some low-molecular-weight phenolic acids, mainly 3-(3 -hydroxyphenyl) propanoic acid, 3-(3 -hydroxyphenyl)acetic acid and 3-(3 ,4 -dihydroxyphenyl)acetic acid [27,28]. Similarly, the colon metabolism of chlorogenic acids starts with the removal of the quinic acid moiety followed by reduction and de-hydroxylation, which results in the accumulation of 3-(3 -hydroxyphenyl)propanoic acid [29,30].…”