Insights in the Recalcitrance of Theasinensin A to Human Gut Microbial Degradation

Abstract

Due to low bioavailability of dietary phenolic compounds in small intestine, their metabolism by gut microbiota is gaining increasing attention. The microbial metabolism of theasinensin A (TSA), a bioactive catechin dimer found in black tea, has not been studied yet. Here, TSA was extracted and purified for in vitro fermentation by human fecal microbiota, and epigallocatechin gallate (EGCG) and procyanidin B2 (PCB2) were used for comparison. Despite the similarity in their flavan-3-ol skeletons, metabolic fate of TSA was distinctively different. After degalloylation, its core biphenyl-2,2′,3,3′,4,4′-hexaol structure remained intact during fermentation. Conversely, EGCG and PCB2 were promptly degraded into a series of hydroxylated phenylcarboxylic acids. Computational analyses comparing TSA and PCB2 revealed that TSA’s stronger interflavanic bond and more compact stereo-configuration might underlie its lower fermentability. These insights in the recalcitrance of theasinensins to degradation by human gut microbiota are of key importance for a comprehensive understanding of its health benefits.

Role of Polyphenols on Gut Microbiota and the Ubiquitin-Proteasome System in Neurodegenerative Diseases

“…Generally, the dimerization and oxidation of one of the most significant phenolic compounds in green tea, catechins, can result in the production of TFs through peroxidases, polyphenol oxidases, as well as the fermentation flow of black tea. 212,213 TFDG, among other TF groups, can be found in black tea more than other foods and drinks. On the whole, the fusion of catechol-type and pyrogallol-type B rings of epicatechin gallate (ECG) as well as epigallocatechin gallate (EGCG) makes these two compounds, i.e., ECG and EGCG, become condensed and form the TFDG.…”

“…The bioavailability of TFDG depends on the function of the gut microbiota since TFDG can be slightly absorbed in the small intestine. 212 Investigations have revealed that TFDG can undergo the gut microbiota and convert into TF, TF3′G, and TF3G. 214,215 TFs can be influenced by the gut microbiota, and following the degalloylation, they can convert into other smaller phenolic compounds, namely 3-(3′,4′-dihydroxyphenyl)propionic acid and 5-(3′,4′-dihydroxyphenyl)-γ-valerolactone.…”

“…214,215 TFs can be influenced by the gut microbiota, and following the degalloylation, they can convert into other smaller phenolic compounds, namely 3-(3′,4′-dihydroxyphenyl)propionic acid and 5-(3′,4′-dihydroxyphenyl)-γ-valerolactone. 212 As condensed catechins help with producing TFs, it might be expected that the microbial metabolites gained from catechins are analogous with metabolites obtained from TFs. 212 In other words, the modulatory impacts of catechin and TFs on the composition of the gut microbiota and on the formation of microbial metabolites (mainly, hydroxylated phenylcarboxylic acids) are similar to each other due to sharing common flavan-3-ol building blocks with each other.…”

“…212 As condensed catechins help with producing TFs, it might be expected that the microbial metabolites gained from catechins are analogous with metabolites obtained from TFs. 212 In other words, the modulatory impacts of catechin and TFs on the composition of the gut microbiota and on the formation of microbial metabolites (mainly, hydroxylated phenylcarboxylic acids) are similar to each other due to sharing common flavan-3-ol building blocks with each other.…”

“…280 TFs can change the composition of the gut microbiota and its metabolic activity toward a healthier profile. 212 Accordingly, even though the microbial metabolism of TFDG to yield the microbial metabolites, especially TNQ (Theanaphthoquinone), is accompanied by a slower degradation rate as compared to the microbial metabolism of EGCG, TFDG and EGCG have similar impacts on the modulation of the gut microbiota composition. These impacts can be both growthpromoting effects on Faecalibacterium, Parabacteroides, Bacteroides, and Bif idobacterium and growth-inhibiting effects on Fusobacterum and Prevotella, 212 thereby leading to creating a healthier profile.…”