Identification of rutin deglycosylated metabolites produced by human intestinal bacteria using UPLC–Q-TOF/MS

In this paper, rutin was metabolized by human intestinal bacteria and five isolated strains including Bacillus sp. 52, Bacteroides sp. 45, 42, 22 and Veillonella sp. 32, the metabolites were identified using ultra performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF/MS). As a result, Bacillus sp. 52 and Bacteroides sp. 45 could metabolize rutin to quercetin 3-O-glucoside and leucocyanidin. Bacteroides sp. 42 and Veillonella sp. 32 could convert rutin to leucocyanidin. Bacteroides sp. 22 could hydrolyze rutin to quercetin-3-O-glucoside. In order to further explain the metabolism pathway of rutin, the β-D-glucosidase and α-L-rhamnosidase activities of five strains were determined. Bacteroides sp. 22 could produce α-L-rhamnosidase but did not produce β-D-glucosidase or β-D-glucosidase activity was too low to be detected. The other four strains all demonstrated α-L-rhamnosidase and β-D-glucosidase activities. Furthermore, α-L-rhamnosidase and β-D-glucosidase activities of Veillonella sp. 32 and Bacteroides sp. 42 were higher than those of Bacteroides sp. 45 and Bacillus sp. 52. Based on these results, we can propose the deglycosylated rout of rutin: rutin was metabolized to be quercetin-3-O-glucoside by α-L-rhamnosidase produced from these bacteria, thereafter, quercetin-3-O-glucoside was further metabolized by β-D-glucosidase to form leucocyanidin. Because of the higher enzyme activity in Veillonella sp. 32 and Bacteroides sp. 42, quercetin-3-O-glucoside was completely metabolized to leucocyanidin by these two bacteria. Due to the lack of β-D-glucosidase activity, Bacteroides sp. 22 could not further metabolize quercetin-3-O-glucoside to leucocyanidin. This study will be helpful for understanding the deglycosylated rout of rutin and the role of different intestinal bacteria on the metabolism of natural compounds.