Beta-Glucuronidase Inhibition by Constituents of Mulberry Bark

Abstract

Intestinal bacterial β-glucuronidases, the key enzymes responsible for the hydrolysis of various glucuronides into free aglycone, have been recognized as key targets for treating various intestinal diseases. This study aimed to investigate the inhibitory effects and mechanisms of the Mulberry bark constituents on E. coli β-glucuronidase (EcGUS), the most abundant β-glucuronidases produced by intestinal bacteria. The results showed that the flavonoids isolated from Mulberry bark could strongly inhibit E. coli β-glucuronidase, with IC50 values ranging from 1.12 µM to 10.63 µM, which were more potent than D-glucaric acid-1,4-lactone. Furthermore, the mode of inhibition of 5 flavonoids with strong E. coli β-glucuronidase inhibitory activity (IC50 ≤ 5 µM) was carefully investigated by a set of kinetic assays and in silico analyses. The results demonstrated that these flavonoids were noncompetitive inhibitors against E. coli β-glucuronidase-catalyzed 4-nitrophenyl β-D-glucuronide hydrolysis, with Ki values of 0.97 µM, 2.71 µM, 3.74 µM, 3.35 µM, and 4.03 µM for morin (1), sanggenon C (2), kuwanon G (3), sanggenol A (4), and kuwanon C (5), respectively. Additionally, molecular docking simulations showed that all identified flavonoid-type E. coli β-glucuronidase inhibitors could be well-docked into E. coli β-glucuronidase at nonsubstrate binding sites, which were highly consistent with these agentsʼ noncompetitive inhibition mode. Collectively, our findings demonstrated that the flavonoids in Mulberry bark displayed strong E. coli β-glucuronidase inhibition activity, suggesting that Mulberry bark might be a promising dietary supplement for ameliorating β-glucuronidase-mediated intestinal toxicity.

Mulberry plant as a source of functional food with therapeutic and nutritional applications: A review

“…Another research assessed the in vitro E. coli β-glucuronidase inhibitory activity of isolated flavonoids (kuwanon G, sanggenol A, sanggenon C, kuwanon C, morin) with IC50 value from 1.12 μM to 10.63 μM from M. alba bark. All flavonoids ameliorated β-glucuronidase mediated gut toxicity via non-competitive inhibition mode (Bai et al, 2021).…”

“…Another research assessed the in vitro E. coli β‐glucuronidase inhibitory activity of isolated flavonoids (kuwanon G, sanggenol A, sanggenon C, kuwanon C, morin) with IC50 value from 1.12 μM to 10.63 μM from M. alba bark. All flavonoids ameliorated β‐glucuronidase mediated gut toxicity via non‐competitive inhibition mode (Bai et al, 2021). Water extract of mulberry (0.3 g/kg) prevented the disruption of hepatic cells and nuclei and the dysbiosis of gut microbiota in vivo ethanol‐induced hepatic steatosis (Park et al, 2018).…”

Synthesis, Biological Evaluation, and In Silico Studies of Novel Coumarin-Based 4H,5H-pyrano[3,2-c]chromenes as Potent β-Glucuronidase and Carbonic Anhydrase Inhibitors

“…298−300 °C; yield: 96%; solubility: DMSO; IR, KBr (cm −1 ): 1699 (>C�O), 2194 (−CN), 3320, 3394 (NH 2 -str. ); 1 2a shows the inhibition after 15 min of incubation as there is no difference of inhibitory power when the enzyme and inhibitor are kept for a long period in incubation. The amount of product obtained during the reaction was recorded for 30 min in a spectrophotometer with an interval of 1 min at 400 nm.…”

“…β-Glucuronidase belongs to the family of lysosomal enzymes, which brings about the cleavage of glucuronosyl- O -bond, thus removing individual sugars from glycosaminoglycans (GAGs). 1 The shortage of β-glucuronidase in body tissues consequently results in proliferation of GAGs inside the lysosomes, leading to the enlargement of their size. 2 As a consequence of over-expression of this enzyme in various cancers like the neoplasm of bladder, 3 liver cancer, 4 and colon carcinoma, 5 , 6 the quantitative measurement of β-glucuronidase has been proved as a detection tool at the initial stage diagnosis of cancer and the assessment of therapeutic treatments.…”

“…β-Glucuronidase belongs to the family of lysosomal enzymes, which brings about the cleavage of glucuronosyl- O -bond, thus removing individual sugars from glycosaminoglycans (GAGs) . The shortage of β-glucuronidase in body tissues consequently results in proliferation of GAGs inside the lysosomes, leading to the enlargement of their size .…”