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

Abstract

Lychee pulp phenolics (LPP) is mainly catabolized in the host colon, increasing the abundances of Bacteroides and Lactobacillus. Herein, five selected gut microbial strains (Bacteroides uniformis, B. thetaiotaomicron, Lactobacillus rhamnosus, L. plantarum, and L. acidophilus) were separately incubated with LPP to ascertain the specific strains participating in phenolic metabolism and the corresponding metabolites. The results indicated that B. uniformis, L. rhamnosus, and L. plantarum 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-O-rutinose-7-O-α-L-rhamnoside by L. plantarum, 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 m/z 299 and 459, respectively. Meanwhile, it was fully confirmed that B. uniformis participated in the catabolism of isorhamnetin glycoside and procyanidin B2. In the B. uniformis culture, kaempferol was synthesized through dehydroxylation of quercetin which could be catabolized into alphitonin by L. rhamnosus. Furthermore, LPP metabolites exerted higher antioxidant activity than their precursors and gave clues to understand the interindividual differences for phenolic metabolism by gut microbiota.

Lychee pulp phenolics fermented by mixed lactic acid bacteria strains promote the metabolism of human gut microbiota fermentation in vitro

“…19 With the deprotonated molecular ion, [M − H] − , at m / z 755 and the mass fragments in the MS 2 spectrum at m / z 489 (the fission of rhamnoside) and 300 (loss of rhamnose), compound 12 was identified as quercetin-3- O -rutinose-7- O -α- l -rhamnoside. 11…”

“…The extraction of free phenolics was carried out in accordance with the method of Huang et al 11 The samples were mixed with 4 mL of methanol and sonicated for 10 min. The resulting mixture was centrifuged at 6200 g for 15 min at 4 °C.…”

“…19 With the deprotonated molecular ion, [M − H] − , at m/z 755 and the mass fragments in the MS 2 spectrum at m/z 489 (the fission of rhamnoside) and 300 (loss of rhamnose), compound 12 was identified as quercetin-3-O-rutinose-7-O-α-L-rhamnoside. 11 After the metabolism of gut microbiota, six new phenolic compounds (catechol, 2-hydroxyphenylacetic acid, phenylacetic acid, 3,4-dihydroxyphenylpropionic acid, vanillic acid, and 3-(3-hydroxyphenyl) propionic acid) were produced in the samples. In addition, nine phenolics (isorhamicin-3-O-rutinoside, catechin, ferulic acid, quercetin-3-rhamnoside, proanthocyanidin B2, rutin, caffeic acid, isoquercitrin, and isoferulic acid) were completely degraded by the gut microbiota and were not detected in all samples, while the QRR was only detected in the LR group and not in the LR and LP + LR groups, as shown in Table 2.…”

“…In addition, it has been reported that QRR is catabolized into rutin by L. rhamnosus, while the metabolic pathways to break down QRR in L. plantarum could be the direct fission of its C-ring. 11,35 The product of the above two phenolics is quercetin, which explains the increase in quercetin content. The gut microbiota in the human body plays a critical role in improving the release of phenolic compounds.…”

“…According to previous research, Lactobacillus fermentation could alter the physicochemical properties of lychee polysaccharides, which was beneficial to the phenolic metabolism in lychee pulp. 10,11 However, changes in the phenolic content of lychee pulp fermented by lactic acid bacteria in the human intestinal tract and their metabolic pathways via microorganisms are still under research. Thus, to clarify the mechanism of in vivo metabolic regulation of lychee pulp phenolics, it is important to study changes in phenolics during the colonic fermentation process.…”