Novel Catabolic Pathway of Quercetin-3--Rutinose-7--α-L-Rhamnoside by GDMCC 1.140: The Direct Fission of C-Ring.

Lychee pulp phenolics (LPP) is mainly catabolized in the host colon, increasing the abundances of and . Herein, five selected gut microbial strains (, and ) were separately incubated with LPP to ascertain the specific strains participating in phenolic metabolism and the corresponding metabolites. The results indicated that , and were involved in LPP utilization, contributing to 52.37, 28.33, and 45.11% of LPP degradation after 48 h fermentation, respectively. Unprecedentedly, the metabolic pathway of the major phenolic compound quercetin-3--rutinose-7--α-L-rhamnoside by , appeared to be the direct fission of C-ring at C2-O1 and C3-C4 bonds, which was proved from the occurrence of two substances with the deprotonated molecule [M-H] ion at 299 and 459, respectively. Meanwhile, it was fully confirmed that participated in the catabolism of isorhamnetin glycoside and procyanidin B2. In the culture, kaempferol was synthesized through dehydroxylation of quercetin which could be catabolized into alphitonin by . Furthermore, LPP metabolites exerted higher antioxidant activity than their precursors and gave clues to understand the interindividual differences for phenolic metabolism by gut microbiota.