Rhamnosidase from Parabacteroides distasonis exhibit the catabolism of epimedin C in the human gut microbiota

Epimedin C, an anti-cardiovascular disease natural compound derived from Herba Epimedii , exhibits low oral bioavailability, with its metabolism closely related to the gut microbiota. In this study, we investigated the roles of intestinal bacteria in the catabolism of epimedin C. We discovered that a strain of Parabacteroides distasonis QZH 1201 ( P. distasonis ) from human fecal samples can convert epimedin C to 2”-O-rhamnosylicariside II and baohuoside I. More importantly, we identified an α-L-rhamnosidase enzyme from P. distasonis (PdRha), which plays a crucial role in this process by efficiently transforming epimedin C into icariside I. PdRha showed optimal activity at pH 6 and a temperature of 50 °C. Under the condition that the final concentration of epimedin C was 0.5 mM, its conversion efficiency reached 78.72 %. Additionally, we investigated the substrate profile of PdRha and discovered that it can hydrolyze rutin, naringin, and icariin, releasing isoquercitrin, prunin, and icariside I. Molecular docking was performed to gain insights into the enzymatic mechanism. This study provides valuable insights into how a common intestinal symbiotic bacterium processes an important natural flavonoid.