Inhibition mechanism of cordycepin and ergosterol from Cordyceps militaris Link. against xanthine oxidase and cyclooxygenase-2

Cordyceps militaris Link. (C. militaris) is an entomopathogenic fungus that parasitizes the pupa or cocoon of lepidopteran insect larvae, with various bioactive compounds. Cordycepin and ergosterol are the two active components in C. militaris. This study aimed to evaluate the inhibitory activity of cordycepin and ergosterol against xanthine oxidase (XO) and cyclooxygenase-2 (COX-2), as well as investigate the inhibition mechanism. Cordycepin could better inhibit XO (IC50 = 0.014 mg/mL) and COX-2 (IC50 = 0.055 mg/mL) than ergosterol. Additionally, surface hydrophobicity and circular dichroism (CD) spectra results confirmed the conformational changes in enzymes induced by cordycepin and ergosterol. Finally, cordycepin and ergosterol significantly decreased uric acid (UA) and inflammatory factors to normal level in mice with gouty nephropathy (GN). This study could provide theoretical evidence for utilization of C. militaris in hyperuricemia-management functional foods.

In vitro and In silico Xanthine Oxidase Inhibitory Activities of 3-Aryl-2- thioxo-2,3-dihydroquinazolin-4(1H)-one Derivatives

BACKGROUND

Hyperuricemia is associated with several disease conditions, such as atherosclerosis, arthritis, kidney stones, and many others. Xanthine oxidase (XO) is an enzyme that catalyzes the conversion of xanthine to uric acid. Hence, XO is a major therapeutic drug target in the treatment of hyperuricemia and associated disorders.

OBJECTIVES

The current study aimed to identify XO inhibitors based on quinazoline derivatives, with the potential to be used against gout and other hyperuricemia-associated diseases.

METHODS

In the current study, eighteen quinazoline derivatives 2-19 were synthesized and assessed for their in vitro xanthine Oxidase (XO) inhibitory activity. Furthermore, the most active compounds, 5 and 17, were subjected to kinetics studies, followed by computational docking. Human BJ fibroblast cells were used to measure the cytotoxicity of active compounds.

RESULTS

Compounds 4-6, 8, 10, 13, 15-17, and 19 were found active against XO, with an IC₅₀ values between 33.688 to 362.173μM. The obtained results showed that compounds 5 and 17 possess a significant xanthine oxidase inhibitory activity. The kinetics and molecular docking studies suggested that compounds 5 (IC₅₀ = 39.904 ± 0.21 μM) and 17 (IC₅₀ = 33.688 ± 0.30 μM) bind in the allosteric site of XO and exhibit a non-competitive type of inhibition. The molecular docking studies also predicted that the NH group of the pyrimidine ring binds with Ser344 residues of XO. Furthermore, all active compounds were non-cytotoxic on the human BJ fibroblasts cell line.

CONCLUSION

This study identifies a series of quinazoline compounds as xanthine oxidase inhibitors, with the potential to be further investigated.

Nanohybrid electrochemical enzyme sensor for xanthine determination in fish samples

An amperometric biosensor for xanthine was designed, based on covalent immobilization of xanthine oxidase (XO) of Bacillus pumilus RL-2d onto a screen-printed multi-walled carbon nanotubes gold nanoparticle-based electrodes (Nano-Au/c-MWCNT). The carboxyl groups at the electrode surface were activated by the use of 1-Ethyl-3-(3-dimethylaminopropyl carbodiimide) (EDC) and N-hydroxysuccinimide (NHS). The working electrode was then coated with 6 μL of xanthine oxidase (0.273 U/mg protein). The cyclic voltammetry (CV) study was done for the characterization of the sensor using [K₃Fe(CN)₆] as an artificial electron donor. The sensitivity (S) and the limit of detection (LOD) of the biosensor were 2388.88 µA/cm²/nM (2.388 µA/cm²/µM) and 1.14 nM, respectively. The developed biosensor was used for determination of fish meat freshness.

Gender effect of hyperuricemia on the development of nonalcoholic fatty liver disease (NAFLD): A clinical analysis and mechanistic study

BACKGROUND AND AIMS

Hyperuricemia is a risk factor for nonalcoholic fatty liver disease (NAFLD), however, the effect of gender on the hyperuricemia-related NAFLD development remains unclear. Here, we evaluated the clinical characteristics of NAFLD patients with hyperuricemia, and experimentally recapitulated this condition in male rats in order to gain insights on the possible impact of gender on the development of NAFLD in patients with hyperuricemia.

METHODS

The clinical characteristics of 238 NAFLD patients, together with the impacts of hyperuricemia on the major parameters related to the development of NALFD were analysed. In animal studies, NAFLD with hyperuricemia was induced in male SD rats using high-yeast high-fat diet containing potassium oxonate. The impact of uric acids on liver pathology, and the expression patterns of key molecules involved in the development of NAFLD, including silent information regulator 1 (SIRT1), nuclear factor kappa B subunit p65 (NF-κB p65), fork-head box class O-3a (FOXO3a), androgen receptor (AR), and xanthine oxidase (XO) were analysed.

RESULTS

Male NAFLD patients with hyperuricemia displayed more frequent and extensive liver injury than those in female patients. In male rats, hyperuricemia was associated with increased levels of insulin, alanine aminotransferase (ALT) and triglyceride (TG). At the molecular level, hyperuricemia was associated with decreased expression of SIRT1 and its phosphorylation, phosphorylation of FOXO3a, increased expression of AR and XO, and deacetylation of NF-κB P65.

CONCLUSIONS

Hyperuricemia is a compounding factor for NAFLD, particularly in males. The severer hepatic injury observed in male NAFLD patients may be attributed to the suppression of SIRT1 signalling induced by hyperuricemia.

Xanthine oxidase of Acinetobacter calcoaceticus RL2-M4: Production, purification and characterization

Xanthine oxidase (EC 1.17.3.2) is a key enzyme of purine metabolism and has potential applications in food and pharmaceutical industries. In the present study, a new bacterial source of xanthine oxidase i.e. Acinetobacter calcoaceticus RL2-M4 with high oxidase activity was isolated from soil. The culture conditions were optimized with one variable at a time (OVAT) and response surface methodology (RSM) approaches included: a minimal salt medium (MSM) of pH 7.0 supplemented with 0.8% yeast extract, 8.5 mM xanthine and incubation at 30 °C for 24 h. Under these culture conditions 11.57 fold increase in the production of this enzyme was achieved. The enzyme was purified from A. calcoaceticus RL2-M4 using anion exchange chromatography to 8.18 fold with 31% yield and specific activity of 4.58 U/mg protein. SDS-PAGE analysis of the purified enzyme revealed that it was homodimer of 95 kDa and its native molecular mass was estimated to be 190 kDa. This enzyme was found to be stable at 35 °C for 5 h. The purified xanthine oxidase of A. calcoaceticus RL2-M4 had K_m 0.3 mM and V_max 5.8 U/mg protein using xanthine as substrate. The activity and stability characteristic of xanthine oxidase of A. calcoaceticus RL2-M4 makes it a potentially good enzyme for industrial applications.