Inhibitory effects of flavonoids on molybdenum hydroxylases activity

A comprehensive review of in silico approaches for the prediction and modulation of aldehyde oxidase-mediated drug metabolism: The current features, challenges and future perspectives

The importance of aldehyde oxidase (AOX) in drug metabolism necessitates the development and application of the in silico rational drug design methods as an integral part of drug discovery projects for the early prediction and modulation of AOX-mediated metabolism. The current study represents an up-to-date and thorough review of in silico studies of AOX-mediated metabolism and modulation methods. In addition, the challenges and the knowledge gap that should be covered have been discussed. The importance of aldehyde oxidase (AOX) in drug metabolism is a hot topic in drug discovery. Different strategies are available for the modulation of the AOX-mediated metabolism of drugs. Application of the rational drug design methods as an integral part of drug discovery projects is necessary for the early prediction of AOX-mediated metabolism. The current study represents a comprehensive review of AOX molecular structure, AOX-mediated reactions, AOX substrates, AOX inhibition, approaches to modify AOX-mediated metabolism, prediction of AOX metabolism/substrates/inhibitors, and the AOX related structure-activity relationship (SAR) studies. Furthermore, an up-to-date and thorough review of in silico studies of AOX metabolism has been carried out. In addition, the challenges and the knowledge gap that should be covered in the scientific literature have been discussed in the current review.

Poziotinib and bovine serum albumin binding characterization and influence of quercetin, rutin, naringenin and sinapic acid on their binding interaction

Serum albumin is the major transporter protein present in systemic circulation and the ability to transport ligands can be influenced in presence of other ligands. This interaction can influence the pharmacodynamic and pharmacokinetic property of certain ligands. Spectroscopic and molecular docking studies were conducted to understand the poziotinib binding interaction to bovine serum albumin (BSA). Further, influence of different flavonoids (quercetin, rutin, naringenin and sinapic acid) on displacing poziotinib from BSA binding sites was also studied. The BSA and poziotinib followed a static quenching mechanism as the Stern-Volmer constant showed decrease (7.6 × 10⁴-6.0 × 10⁴) when the temperature increased from 298 K to 310 K. The BSA and poziotinib interaction was spontaneous and enthalpy driven. Involvement of Van der Waals forces and hydrogen bonding in the binding interaction was suggested on the basis of thermodynamic study results. Conformational changes were suggested in the BSA on its interaction with poziotinib based on fluorescence experimental data. The binding constant for BSA-poziotinib showed a maximum decrease in presence of quercetin followed by naringenin, rutin and sinapic acid respectively. Site displacement studies suggested binding of poziotinib site I of BSA.

Inhibition of vertebrate aldehyde oxidase as a therapeutic treatment for cancer, obesity, aging and amyotrophic lateral sclerosis

The aldehyde oxidases (AOXs) are a small sub-family of cytosolic molybdo-flavoenzymes, which are structurally conserved proteins and broadly distributed from plants to animals. AOXs play multiple roles in both physiological and pathological processes and AOX inhibition is of increasing significance in the development of novel drugs and therapeutic strategies. This review provides an overview of the evolution and the action mechanism of AOX and the role of each domain. The review provides an update of the polymorphisms in the human AOX. This review also summarises the physiology of AOX in different organs and its role in drug metabolism. The inhibition of AOX is a promising therapeutic treatment for cancer, obesity, aging and amyotrophic lateral sclerosis.

Baicalein decreases uric acid and prevents hyperuricemic nephropathy in mice

Baicalein, a natural flavonoid, is structurally advantageous for binding to xanthine oxidoreductase. In our study, molecular docking analysis and Surface Plasmon Resonance revealed a direct interaction between baicalein and xanthine oxidoreductase. Moreover, 50 mg/kg/d baicalein treatment significantly suppressed the viability of xanthine oxidoreductase in hyperuricemia mouse model. The data showed that baicalein remarkably prevented renal dysfunction, ameliorated kidney fibrosis, alleviated epithelial-mesenchymal transition and oxidative stress in hyperuricemia mice. Thus, we concluded that baicalein executed a kidney-protection action in hyperuricemia and therefore may be used as a therapeutic alternative for hyperuricemic nephropathy.

Resonance light scattering determination of 6-mercaptopurine coupled with HPLC technique

A simple, fast, costless, sensitive and selective method of resonance light scattering coupled with HPLC was established for the determination of 6-mercaptopurine in human urine sample. In a Britton-Robinson buffer solution of pH5.5, the formation of coordination complex between 6-mercaptopurine and metal palladium (II) led to enhance the RLS intensity of the system. The RLS signal was detected by fluorescence detector at λ(ex)=λ(em)=315 nm. The analytical parameters were provided by the coupled system, the linear of 6-mercaptopurine response from 0.0615 to 2.40 μg L(-1) and the limit of detection (S/N=3) was 0.05 μg L(-1). The presented method has been applied to determine 6-mercaptopurine in human urine samples which obtained satisfactory results. Moreover, the reaction mechanism and possible reasons for enhancement of RLS were fully discussed.

In vitro inhibitory potential of Cynara scolymus, Silybum marianum, Taraxacum officinale, and Peumus boldus on key enzymes relevant to metabolic syndrome

Boldocynara®, a proprietary dietary supplement product consisting of the plants Cynara scolymus, Silybum marianum, Taraxacum officinale, and Peumus boldus, used to promote functions of the liver and the gallbladder. It was the aim of the present study to look from a different perspective at the product by investigating the in vitro potential of Boldocynara® as a combination product and its individual extracts on key enzymes relevant to metabolic syndrome. Peumus boldus extract exhibited pronounced inhibitory activities on α-glucosidase (80% inhibition at 100 µg/ml, IC50: 17.56 µg/ml). Silybum marianum had moderate pancreatic lipase (PL) inhibitory activities (30% at 100 µg/ml) whereas Cynara scolymus showed moderate ACE inhibitory activity (31% at 100 µg/ml). The combination had moderate to weak effects on the tested enzymes. In conclusion, our results indicate some moderate potential of the dietary supplement Boldocynara® and its single ingredients for the prevention of metabolic disorders.

Evaluation of general toxicity, anti-oxidant activity and effects of ficus carica leaves extract on ischemia/reperfusion injuries in isolated heart of rat

PURPOSE

This study was aimed to evaluate general toxicity, anti-oxidant activity and effects of Ficus carica leaves extract on ischemia/reperfusion injuries.

METHODS

Antioxidant activity, total phenolic and flavonoid compounds of 70% methanolic extract of Ficus carica leaves were measured. The general toxicity test was carried out by brine shrimp lethality assay. Isolated hearts of male rats were mounted on a Langendorff apparatus and perfused with modified Krebs-Henseleit solution. In control group, the hearts were perfused with normal Krebs solution, however, treatment groups received enriched solution with the extract (0.04, 0.2 and 1 mg/ml) during stabilization and reperfusion (after 30 min global ischemia), respectively. Cardiac arrhythmias were analyzed and TTC method was used for infarct size determination.

RESULTS

The extract displayed antioxidant activity in the DPPH assay (RC50=0.06666 mg/ml). Total phenolic content was 12.29 mg GAE/100 g dry sample and the amount of flavonoids was calculated 40.729 mg/g. LD50 value by brine shrimp test was 0.158 mg/ml. The extract decreased number of VEBs, incidence and duration of Rev VF with clear reduction in infarct size and infarct volume (P<0.001).

CONCLUSION

Ficus carica decreased ischemia/reperfusion-induced injuries. These protections are probably due to antioxidant capacity and the existence of flavonoid and phenolic compounds in the extract.

Influence of vitamin E and quercetin on Nigerian Bonny Light crude oil-induced neuronal and testicular toxicity in Wistar rats

BACKGROUND

Mounting experimental evidence highlights the testicular and neuronal toxicity of environmental/industrial chemicals in experimental animals via the mechanism involving oxidative damage. Nigerian Bonny Light crude oil (BLCO) has been reported to exhibit reproductive and neuronal toxicity in male rats. Studies have shown that vitamin E and quercetin protect rat neuronal and testicular cells from environmental chemical-induced oxidative damage. We investigated the possible protective role of quercetin and vitamin E in BLCO induced-neuronal and testicular toxicity.

METHODS

Male rats were administered BLCO at doses of 400 and 800 mg/kg body wt/day p.o. three times/week for 6 weeks. Other groups were co-administered BLCO (400 and 800 mg/kg body wt/day p.o.) with/without vitamin E (50 mg/kg body wt/day p.o.) or quercetin (10 mg/kg body wt/day p.o.) three times/week for 6 weeks, respectively.

RESULTS

Semen quality deteriorated, testosterone and luteinizing hormone (LH) levels were significantly decreased, and follicle stimulating hormone (FSH) increased following BLCO reatment. There was a significant decline in the activities of superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), and glutathione-S-transferase (GST) with concomitant increased levels of lipid peroxidation and activities of xanthine oxidase (XO) in a dose-dependent manner, in testes and brain of rats. Co-administration with vitamin E or quercetin reversed BLCO-induced neuronal and testicular toxicity by preventing oxidative stress, improving sperm quality, and restoring hormonal levels relative to controls.

CONCLUSIONS

BLCO altered reproductive indices and induced neuronal toxicity via the mechanism of oxidative stress. Quercetin and vitamin E showed possible chemoprotection against the toxicity.

Aldehyde and xanthine oxidase activities in tissues of streptozotocin-induced diabetic rats: effects of vitamin E and selenium supplementation

Effects of vitamin E and selenium supplementation on aldehyde oxidase (AO) and xanthine oxidase (XO) activities and antioxidant status in liver, kidney, and heart of streptozotocin (STZ)-induced diabetic rats were examined. AO and XO activities increased significantly after induction of diabetes in rats. Following oral vitamin E (300 mg/kg) and sodium selenite (0.5 mg/kg) intake once a day for 4 weeks, XO activity decreased significantly. AO activity decreased significantly in liver, but remained unchanged in kidney and heart of vitamin E- and selenium-treated rats compared to the diabetic rats. Total antioxidants status, paraoxonase-1 (PON1) and erythrocyte superoxide dismutase activities significantly decreased in the diabetic rats compared to the controls, while a higher fasting plasma glucose level was observed in the diabetic animals. The glutathione peroxidase activity remained statistically unchanged. Malondialdehyde and oxidized low-density lipoprotein levels were higher in the diabetic animals; however, these values were significantly reduced following vitamin E and selenium supplementation. In summary, both AO and XO activities increase in STZ-induced diabetic rats, and vitamin E and selenium supplementation can reduce these activities. The results also indicate that administration of vitamin E and selenium has hypolipidemic, hypoglycemic, and antioxidative effects. It decreases tissue damages in diabetic rats, too.

Antioxidant, total phenol and flavonoid contents of two pedicularis L. Species from eastern azerbaijan, iran

INTRODUCTION

Pedicularis sibthorpii and P. wilhelmsiana are endemic species mainly found in North-West of Iran. Plants of genus Pedicularis produce some important poly-phenols and flavonoids. In the present work, total phenol and flavonoid contents of the mentioned species as well as their antioxidant capacity have been evaluated.

METHODS

Methanol extract of samples was fractionated by SPE method using an ODS cartridge and their (1)H-NMR spectra were recorded. Total phenols and flavonoids of methanol extracts were determined using Folin- Ciocalteu and aluminum chloride methods. For determining antioxidant activity of the extracts and fractions, bleaching of purple color methanol solu-tion of 1, 1-diphenylpycryl hydrazyl (DPPH) was measured by spectrophotometric assay.

RESULTS

Total phenols of Pedicularis sibthorpii and P. wilhelmsiana were in the range of 8-30 mg g(-1) and 9-20 mg g(-1), respectively. The 40% and 60% fractions of P. sibthorpii and the 20%, 40% and 60% fractions of P. wilhelmsiana showed higher amounts of phenolic compounds. The total flavonoid contents of P. sibthorpii and P. wilhelmsiana were in the range of 0-215 mg g(-1) and 0-177 mg g(-1), respectively, whereas the 40% and 60% fractions showed higher flavonoid amounts. Antioxidant activity of P. sibthorpii and P. wil-helmsiana were in the range of 0.01-0.7 mg mL(-1) and 0.01-1.02 mg mL(-1). In the same manner, the 20% and 40% fractions of P. sibthorpii and the 40% and 60% fractions of P. wilhelmsiana had lower RC50 than that of other fractions.

CONCLUSION

Fractions with lower RC50 had higher contents of phenolic and flavonoid compounds. The results of NMR spectra were parallel with these findings and show that it is worth to do phytochemi-cal studies on P. sibthorpii and P. wilhelmsiana.

A new multi-wavelength model-based method for determination of enzyme kinetic parameters

Lineweaver-Burk plot analysis is the most widely used method to determine enzyme kinetic parameters. In the spectrophotometric determination of enzyme activity using the Lineweaver-Burk plot, it is necessary to find a wavelength at which only the substrate or the product has absorbance without any spectroscopic interference of the other reaction components. Moreover, in this method, different initial concentrations of the substrate should be used to obtain the initial velocities required for Lineweaver-Burk plot analysis. In the present work, a multi-wavelength model-based method has been developed and validated to determine Michaelis-Menten constants for some enzyme reactions. In this method, a selective wavelength region and several experiments with different initial concentrations of the substrate are not required. The absorbance data of the kinetic assays are fitted by non-linear regression coupled to the numeric integration of the related differential equation. To indicate the applicability of the proposed method, the Michaelis-Menten constants for the oxidation of phenanthridine, 6-deoxypenciclovir and xanthine by molybdenum hydroxylases were determined using only a single initial concentration of the substrate, regardless of any spectral overlap.

Activity and stability of rat liver xanthine oxidase in the presence of pyridine

In the present study, rat liver xanthine oxidase activity and its thermostability in the presence of pyridine were investigated. The activity of the enzyme was determined by following the formation of uric acid spectrophotometrically. The thermal stability of the enzyme was studied in the presence of 0.0%–2.0% of pyridine in Sorenson’s buffer. Thermal stability parameters (half-life, inactivation constant, and activation energies for enzyme inactivation), thermodynamic constants (ΔH*, ΔS*, and ΔG*) and the kinetic parameters (Km and Vmax), were determined in pyridine-free and pyridine-containing buffer solution. A dramatic reduction was observed in xanthine oxidase activity in the presence of pyridine. However, the pyridine-treated enzyme showed a marked enhancement in thermal stability compared with the native enzyme. The ΔG values for the enzyme activity in the presence of pyridine were found to be about 1.5-fold larger than that calculated for the native enzyme, indicating that the enzyme becomes kinetically more stable in the presence of pyridine. The Km value for xanthine oxidase in the presence of 0.5% pyridine increased by 4.8-fold compared with the enzyme in the pyridine-free buffer solution; however, there was 1.8-fold reduction in the Vmax value in the hydro-organic solution compared with the enzyme activity in the buffer solution. As the stability of enzymes is one of the most difficult problems in protein chemistry, this thermostability property of xanthine oxidase could be of great value in developing novel strategies to improve and expand its application in various areas.

FAD-dependent enzymes involved in the metabolic oxidation of xenobiotics

Although the majority of oxidative metabolic reactions are mediated by the CYP superfamily of enzymes, non-CYP-mediated oxidative reactions can play an important role in the metabolism of xenobiotics. Among the major oxidative enzymes, other than CYPs, involved in the oxidative metabolism of drugs and other xenobiotics, the flavin-containing monooxygenases (FMOs), the molybdenum hydroxylases [aldehyde oxidase (AO) and xanthine oxidase (XO)] and the FAD-dependent amine oxidases [monoamine oxidases (MAOs) and polyamine oxidases (PAOs)] are discussed in this minireview. In a similar manner to CYPs, these oxidative enzymes can also produce therapeutically active metabolites and reactive/toxic metabolites, modulate the efficacy of therapeutically active drugs or contribute to detoxification. Many of them have been shown to be important in endobiotic metabolism (e.g. XO, MAOs), and, consequently, interactions between drugs and endogenous compounds might occur when they are involved in drug metabolism. In general, most non-CYP oxidative enzymes (e.g. FMOs, MAOs) appear to be noninducible or much less inducible than the CYP system. Some of these oxidative enzymes exhibit polymorphic expression, as do some CYPs (e.g. FMO3). It is possible that the contribution of non-CYP oxidative enzymes to the overall metabolism of xenobiotics is underestimated, as most investigations of drug metabolism have been performed using experimental conditions optimised for CYP activity, although in some cases the involvement of non-CYP oxidative enzymes in xenobiotic metabolism has been inferred from not sufficient experimental evidence.