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Inhibition of soluble epoxide hydrolase (sEH) is considered to be an effective treatment for inflammation-related diseases, and small molecules origin from natural products show promising activity against sEH. Two undescribed protostanes, 3β-hydroxy-25-anhydro-alisol F (1) and 3β-hydroxy-alisol G (2) were isolated from Alisma orientale and identified as new sEH inhibitors with IC 50 values of 10.06 and 30.45 μM, respectively. Potential lead compound 1 was determined as an uncompetitive inhibitor against sEH, which had a K i value of 5.13 μM. In-depth molecular docking and molecular dynamics simulations revealed that amino acid residue Ser374 plays an important role in the inhibition of 1, which also provides an idea for the development of sEH inhibitors based on protostane-type triterpenoids., (Copyright © 2021 Elsevier B.V. All rights reserved.)

β-Glucuronidase plays a vital role in the metabolism of drugs and endogenous substance. Herein, we assayed the inhibitory effects of thirty-six flavonoids (1-36) toward β-glucuronidase (Escherichia coli) using the probe reaction of DDAO-glu hydrolysis. The results showed that kushenol X (6), (2S)-farrerol (10), 5,7,2'-trihydroxy-8,6'-dimethoxy flavone (20), demethylbellidifolin (31), and gentisin (32) exhibited potent inhibitory activities toward β-glucuronidase with the IC 50 values of 2.07 ± 0.26, 8.95 ± 0.74, 4.97 ± 0.61, 0.91 ± 0.11, and 0.68 ± 0.10 μM, respectively. Furthermore, the inhibition kinetics studies indicated that demethylbellidifolin (31) and gentisin (32) exhibited mixed-type inhibiton toward β-glucuronidase, the K i values were caculated to be 4.05 and 2.02 μM, respectively. Additionally, the circular change of dichroism (CD) spectrum verified the interaction between demethylbellidifolin (31) and gentisin (32) with β-glucuronidase; following by the molecular docking and molecular dynamics further revealed the potential interaction amino acid site in β-glucuronidase. All our findings not only developed some potent novel β-glucuronidase inhibitors but also indicated the potential herb drug interaction (HDI) effects of flavonoids with some clinical drugs which had enterohepatic circulation and further revealed the vital pharamcophoric requirement of natural flavonoids for β-glucuronidase inhibition activity., (Copyright © 2019 Elsevier B.V. All rights reserved.)

As a part of our searching for natural human carboxylesterase 2 (human CES 2) inhibitors from traditional Chinese medicine, we found that the extract of Alisma orientale significantly inhibited human CES 2 in vitro. The investigation on A. orientale led to the isolation of a new protostane-type triterpenoid alismanin I (1). Its structure was determined according to HRESIMS, 1D and 2D NMR spectra. Alismanin I (1) displayed significantly inhibitory activity against human CES 2 with IC 50 value of 1.31 ± 0.09 μM assayed by human CES 2-mediated DDAB hydrolysis. According to its inhibition kinetic result, compound 1 was a noncompetitive type inhibitor, and its Ki was 3.65 μM. Its inhibitory effect was confirmed in living cell level through a visual manner. The potential interaction mechanism of compound 1 with human CES 2 was also analyzed by circular dichroism (CD) spectrum and molecular docking., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Carboxylesterases (CEs) belong to the serine hydrolase family, and are in charge of hydrolyzing chemicals with carboxylic acid ester and amide functional groups via Ser-His-Glu. Uncaria rhynchophylla (Miq.) Miq. ex Havil. is a famous traditional Chinese medicine used in managing hyperpyrexia, epilepsy, preeclampsia, and hypertension in China., Hypothesis/purpose: To discover the potential natural human carboxylesterase 2 (hCE 2) inhibitors from U. rhynchophylla., Methods: Compounds were obtained from the hooks of U. rhynchophylla by silica gel and preparative HPLC. Their structures were elucidated by using HRESIMS, 1D and 2D NMR spectra. Their inhibitory activeties and inhibition kinetics against hCE 2 were assayed by the fluorescent probe, and potential mechanisms were also investigated by molecular docking., Results: Twenty-three compounds, including a new phenolic acid uncariarhyine A (1), eight known triterpenoids (2-9), and ten known aromatic derivatives (10, 13-16, and 19-23), were isolated from U. rhynchophylla. Compounds 1-5, 7, 9, and 15 showed significant inhibitory activities against hCE 2 with IC 50 values from 4.01  ± 0.61 µM to 18.60 ± 0.21 µM, and their inhibition kinetic analysis results revealed that compounds 1, 5, 9, and 15 were non-competitive; compounds 3 and 4 were mixed-type, and compounds 2 and 7 were uncompetitive. Molecular docking studies indicated inhibition mechanisms of compounds 1-5, 7, 9, and 15 against hCE 2., Conclusion: Our present findings highlight potential natural hCE 2 inhibitors from U. rhynchophylla., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

A chemical investigation of the roots of Euphorbia ebracteolata identified eighteen diterpenoids and glycosides. On the basis of spectroscopic data, they were determined to be ent-kauranes, ent-atisanes, tigliane derivatives, ingenane, and ent-abietanes, among which were eleven previously undescribed diterpenoids. The inhibitory effects of the isolated compounds against human carboxylesterase 2 (hCE-2) were evaluated in vitro, which revealed moderate inhibitory effects with IC 50 values < 50 μM. Next, the inhibitory kinetics were evaluated for the putative hCE-2 inhibitor 4β,9α,16,20-tetrahydroxy-14(13 → 12)-abeo-12αH-1,6-tigliadiene-3,13-dione (IC 50 3.88 μM), and results indicated competitive inhibition with K i 4.94 μM. Additionally, none of the diterpenoids showed cytotoxic effects against five human tumor cell lines as determined by MTT assays., (Copyright © 2017 Elsevier Ltd. All rights reserved.)