Purification and partial characterisation of camel milk xanthine oxidoreductase

Unveiling potent Schiff base derivatives with selective xanthine oxidase inhibition: In silico and in vitro approach

This research describes the synthesis by an environmentally-friendly method, microwave irradiation, development and analysis of three novel and one previously identified Schiff base derivative as a potential inhibitor of bovine xanthine oxidase (BXO), a key enzyme implicated in the progression of gout. Meticulous experimentation revealed that these compounds (10, 9, 4, and 7) have noteworthy inhibitory effects on BXO, with IC50 values ranging from 149.56 µM to 263.60 µM, indicating their good efficacy compared to that of the standard control. The validation of these results was further enhanced through comprehensive in silico studies, which revealed the pivotal interactions between the inhibitors and the catalytic sites of BXO, with a particular emphasis on the imine group (-C = N-) functionalities. Intriguingly, the compounds exhibiting the highest inhibition rates also showcase advantageous ADMET profiles, alongside encouraging initial assessments via PASS, hinting at their broad-spectrum potential. The implications of these findings are profound, suggesting that these Schiff base derivatives not only offer a new vantage point for the inhibition of BXO but also hold considerable promise as innovative therapeutic agents in the management and treatment of gout, marking a significant leap forward in the quest for more effective gout interventions.

Cupressus sempervirens L. flavonoids as potent inhibitors to xanthine oxidase: in vitro, molecular docking, ADMET and PASS studies

Excessive intake of purine-rich foods such as seafood and red meat leads to excess xanthine oxidase activity and provokes gout attacks. The aim of this paper is to evaluate in vitro and in silico, the inhibition effect of Cupressus sempervirens plant extracts (flavonoids (Cae) and alkaloids (CaK)) and its six derivative compounds on bovine xanthine oxidase (BXO). The in silico study consists of molecular docking with GOLD v4.0 based on the best PLPchem score (PLP) and prediction of biological activity with the PASS server tool. The inhibitors used were lignan (cp1), Amentoflavone (cp2), Cupressuflavone (cp3), Isocryptomerin (cp4), Hinokiflavone (cp5), and Neolignan (cp6). The in vitro results showed that CaK gives an IC50 of 3.52 ± 0.04 μg/ml. Similarly, Cae saved an IC50 of 8.46 ± 1.98 μg/ml compared with the control (2.82 ± 0.10 μg/ml). The in silico results show that cp1 was the best inhibitor model (PLP of 88.09) with approved pharmacokinetics. These findings suggest that cp1 and cp2 may offer good alternatives for the treatment of hyperuricemia; cp3 was moderate, while the others (cp4 to cp6) were considered weak inhibitors according to their PLP.Communicated by Ramaswamy H. Sarma.

The inhibitory kinetics of vitamins B9, C, E, and D3 on bovine xanthine oxidase: Gout treatment

BACKGROUND

Over-consumption of foods high in purines like seafood, red meat, and alcoholic beverages leads to hyperuricemia causing gout attacks. Xanthine oxidase was reported responsible for the overproduction of uric acid.

MATERIAL AND METHODS

We intend to test in silico and in vitro, the inhibition effect of four vitamins against bovine milk xanthine oxidase (BXO). We performed Molecular docking with GOLD v4.0, and the biological activity prediction with the PASS server. The best-selected vitamins were chosen based on their best PLPchem score. The BXO constant K_m and V_max were determined in vitro, and then the vitamins were tested for their inhibition effect to BXO. Furthermore, the inhibition constant Ki of each inhibitor were determined using Dixon method, the vitamins chosen were vitamin E, vitamin B9, vitamin D3, and vitamin C.

RESULTS

The in silico results show that the tested vitamins were the best inhibitors model with PLPchem scores up to 70 comparing to the control. The in vitro results show that BXO have a K_m value of 163.55 μM with V_max of 37 U, vitamins B9, E, C, and D3 were potent inhibitors to BXO with an IC50 of 34.10 ± 0.21, 36.68 ± 1.50, 39.01 ± 0.02, and 100.28 ± 0.33 μM, respectively comparing to the control (32.03 ± 0.73 μM). The kinetic study shows that all tested vitamins were Non-competitive inhibitors, the Ki values were 15 ± 1.76 μM, 29 ± 1.06 μM, 12 ± 1.41 μM, and 20 ± 0.71 μM, for respectively vitamins B9, E, C, and D3.

CONCLUSION

The obtained results promise an excellent strategy using vitamins to enhance immunity, treat hyperuricemia, and minimize the usual drug side effects.

Anti-inflammatory drugs as new inhibitors to xanthine oxidase: In vitro and in silico approach

The two important targets to treat gout disease are (1) control the hyperuricemia by the inhibition of Xanthine Oxidase (XO) and (2) treatment of acute attacks of gout by the use of anti-inflammatory drugs. It is important to distinguish between therapy to manage hyperuricemia and to reduce acute inflammation. While reducing hyperuricemia is resolved very slowly with available drugs, gout symptoms like pain and inflammation may become persistent. The objective of this study is to find a relevant treatment with a beneficial double effect. (1) As an anti-inflammatory, analgesic, and antipyretic effect and (2) as XO inhibitory effect, which is the main objective of this study. We investigated the effect of five non-steroidal anti-inflammatory drugs (NSAIDs) against human and bovine milk xanthine oxidases (HXO and BXO) using the double enzyme detection method (DED) and molecular docking with the Autodock vina program. in vitro results show that the NSAIDs give an important inhibition to HXO and BXO with an IC₅₀ of 2.04 ± 0.13 μg/ml, 2.75 ± 0.23 μg/ml, 1.45 ± 0.19 μg/ml, 0.31 ± 0.13 μg/ml and 1.27 ± 0.11 μg/ml, for HXO, and 2.96 ± 0.27 μg/ml, 9.46 ± 0.13 μg/ml, 6.21 ± 1.17 μg/ml, 0.83 ± 0.11 μg/ml, and 3.48 ± 0.13 μg/ml, for BXO, for respectively, Naproxen, Ibuprofen, Diclofenac, Indomethacin, and Celecoxib. Testing the inhibitory activity of these drugs on both XOs shows an important inhibition, especially from Indomethacin, which could be a promising lead compound for reducing acute inflammation and at the same time controlling hyperuricemia.

Hispidin, Harmaline, and Harmine as potent inhibitors of bovine xanthine oxidase: Gout treatment, in vitro, ADMET prediction, and SAR studies

Alkaloids and phenols are potent inhibitors family for many enzymes used in many therapies. We aim to evaluate in vitro and in silico, the inhibition effect of Hispidin, Harmaline, and Harmine as pure molecules to bovine milk xanthine oxidase (BXO), Molecular docking and SAR study with GOLD was done to explain the mechanism of action related to its inhibition, ADMET parameters were checked to confirm their pharmacokinetics (PK) using preADMET 2.0 server, we classified our inhibitors by applying five drug-likeness rules, the best-ranked inhibitors were chosen based on the approved ADMET properties, drug-likeness qualifications, and the best PLPchem score generated by GOLD. The in vitro results show important inhibition activity to BXO comparing to the control with an IC50 of 39.72 ± 3.60 µM, 51.00 ± 1.0 µM, and 48.52 ± 1.76 µM for Hispidin, Harmaline, and Harmine respectively. The in silico results show that Hispidin was the best inhibitor model with approved ADMET properties and qualification in all drug-likeness rules; Harmaline was saved second-best model to BXO with suitable ADMET properties and qualified in most drug-likeness rules. Eventually, Harmine was ranked third potent inhibitor model with acceptable ADMET properties, drug-likeness rules, and PLPchem score. The tested inhibitors could be significant in drug discovery, especially in treating gout disease; therefore, drug development, including clinical trials, should be done with promising results.

Lanthanide (III) complexes of bis-coumarins as strong inhibitors of bovine xanthine oxidase - molecular docking and SAR studies

The gout disease is spreading worldwide and its drug target is the human xanthine oxidase. Through this work, we investigated the inhibitory effect of the ten lanthanide(III) complexes of biologically active bis-coumarins on xanthine oxidase. We achieved molecular docking studies using GOLD software to study the formed interactions in the enzyme-inhibitor complex. The results confirm the inhibitory effect of the lanthanide complexes showing the best Nd(III) complex with IC50 of 12.91 nM. The docking results confirm this inhibition. We saved nearly the same interactions between the two inhibitors allopurinol and the Nd(III) complex according to the docking results. No further studies have been found in this context. The ADMET analysis show that the three complexes are nontoxic.Communicated by Ramaswamy H. Sarma.

A sensitive and high-throughput fluorescent method for determination of oxidase activities in human, bovine, goat and camel milk

Milk oxidases are an integral part of milk immune system, and good indicators for milk thermal history. Current assay methods for milk oxidases are either insensitive, tedious or not cost-effective. In this study, a high-throughput fluorescence assay method for determination of xanthine oxidase (XO) and polyamine oxidase (PAO) activities in milk samples was developed. The hydrogen peroxide generated by XO catalysed oxidation of hypoxanthine, and PAO catalysed oxidation of spermine, was coupled to horseradish peroxidase conversion of Amplex® Red (1-(3,7-dihydroxyphenoxazin-10-yl)ethanone) to the fluorescent product resorufin. The assay was highly sensitive, with limits of detection of activity in milk being 3 × 10^-7 and 7 × 10^-7 U/mL for XO and PAO, respectively. Intra-run and inter-run results showed good assay repeatability and reproducibility. The assay was successfully applied to survey the XO and PAO activities in human, bovine, goat and camel milk samples, and it can be readily adapted for measurements of other oxidase activities.

INVESTIGATION OF ANTIHEMOLYTIC, XANTHINE OXIDASE INHIBITION, ANTIOXIDANT AND ANTIMICROBIAL PROPERTIES OF SALVIA VERBENACA L. AERIAL PART EXTRACTS

BACKGROUND

In this study, Salvia verbenaca L. aerial part extracts (SVEs): were screened for their antihemolytic, xanthine oxidase (XO) inhibition, antioxidant and antimicrobial activities.

MATERIAL AND METHODS

To investigate SVEs antihemolytic activity, the 2,2,-azobis (2-amidinopropane) dihydrochloride (AAPH) was used to induce erythrocyte oxidative hemolysis. In XO inhibition test, xanthine was used as substrate and cytochrome c for generating superoxide anions. The antioxidant activity of SVEs was examined by means of reducing power, DPPH free radical scavenging and iron chelating assays. In addition, SVEs were tested for their antimicrobial effects by evaluating antibacterial and antifungal activities.

RESULTS

Ethyl acetate extract (EAE) contains the highest amount of total polyphenols and flavonoids (661.78 ± 4.00 mg GAE / g E) and (28.81 ± 0.38 mg QE / g E) respectively. In antihemolytic test EAE was the most active extract with an HT₅₀ value of 165 min. SVEs gave significant inhibitory effects on XO, especially the chloroform extract (ChE) with IC₅₀ value of 0.0088 ± 0.000 mg/ml. EAE was the most active extract in reducing power essay (EC₅₀: 0.0047 ± 0.000 mg/ml) and in DPPH radical scavenging essay (IC₅₀: 0.0086 ± 0.000 mg/ml). Finally, the EAE has inhibited the growth of nine bacterial strains with inhibition zone diameters of (12 to 16 mm), but no activities have found against fungal strains.

CONCLUSION

S. verbenaca could be considered as a potential source of natural antihemolytic, enzyme modulator, antioxidant and antibacterial agents.

In Vitro Anti-inflammatory and Xanthine Oxidase Inhibitory Activity of Tephrosia purpurea Shoot Extract

The methanolic extract of Tephrosia purpurea (Leguminosae) shoots was evaluated in-vitro for its anti-inflammatory and xanthine oxidase inhibitory activity. Anti-inflammatory activity was measured by the Diene-conjugate, HET-CAM and β-glucuronidase methods. The enzyme inhibitory activity was tested against isolated cow milk xanthine oxidase. The average anti-inflammatory activity of T. purpurea shoot extract in the concentration range of 1-2 μg/mL in the reacting system revealed significant anti-inflammatory activities, which, as recorded by the Diene-conjugate, HET-CAM and β-glucuronidase assay methods, were 45.4, 10.5, and 70.5%, respectively. Screening of the xanthine oxidase inhibitory activity of the extract in terms of kinetic parameters revealed a mixed type of inhibition, wherein the Km and Vmax values in the presence of 25 to 100 μg/mL shoot extract was 0.20 mM/mL and 0.035, 0.026, 0.023 and 0.020 μg/min, while, for the positive control, the Km and Vmax values were 0.21 mM/mL and 0.043 μg/min, respectively. These findings suggest that T. purpurea shoot extract may possess constituents with good medicinal properties that could be exploited to treat the diseases associated with oxidative stress, xanthine oxidase enzyme activity and inflammation.

The role of human xanthine oxidoreductase (HXOR), anti-HXOR antibodies, and microorganisms in synovial fluid of patients with joint inflammation

This work is to investigate the levels of human xanthine oxidoreductase (HXOR), its antibodies, and microorganisms in synovial fluid of patients with untreated rheumatoid joint diseases. Synovial fluids were collected from sixty-four patients with rheumatoid joint diseases. Sixty-four age-matched individuals were included as control. Xanthine oxidoreductase (XOR) proteins level and anti-XOR antibodies were determined in the blood and synovial fluid, using human XOR as antigen, by enzyme-linked immunosorbent (ELISA) assay. Synovial fluids were cultured for bacteria and fungi. The titers of XOR protein in the synovial fluid of patients with rheumatoid arthritis were 90.43 ± 23.37 μg/ml (mean ± SD, n = 29) and up to 62.42 ± 8.74 μg/ml (mean ± SD, n = 35) in other joint inflammation. Anti-HXOR antibodies titers in patients were 167.72 ± 23.64 μg/ml, n = 64, which was significantly higher in rheumatoid arthritis patients. The results indicated that anti-HXOR antibodies in synovial fluids have a protective role as high concentrations against XOR were detected in inflammatory arthritis. These antibodies play a role in eliminating XOR from synovial fluids. However, immune complex formation could activate complement and participate in propagating the inflammatory cycle. Synovial aspirate ordinary microbial cultures were negative for any bacteria or fungi, but that does not exclude organisms of special culture requirements.

Sequencing, analysis, and annotation of expressed sequence tags for Camelus dromedarius

Despite its economical, cultural, and biological importance, there has not been a large scale sequencing project to date for Camelus dromedarius. With the goal of sequencing complete DNA of the organism, we first established and sequenced camel EST libraries, generating 70,272 reads. Following trimming, chimera check, repeat masking, cluster and assembly, we obtained 23,602 putative gene sequences, out of which over 4,500 potentially novel or fast evolving gene sequences do not carry any homology to other available genomes. Functional annotation of sequences with similarities in nucleotide and protein databases has been obtained using Gene Ontology classification. Comparison to available full length cDNA sequences and Open Reading Frame (ORF) analysis of camel sequences that exhibit homology to known genes show more than 80% of the contigs with an ORF>300 bp and ∼40% hits extending to the start codons of full length cDNAs suggesting successful characterization of camel genes. Similarity analyses are done separately for different organisms including human, mouse, bovine, and rat. Accompanying web portal, CAGBASE (http://camel.kacst.edu.sa/), hosts a relational database containing annotated EST sequences and analysis tools with possibility to add sequences from public domain. We anticipate our results to provide a home base for genomic studies of camel and other comparative studies enabling a starting point for whole genome sequencing of the organism.

Interaction between mercaptopurine and milk

Mercaptopurine is a purine analog used for acute lymphoblatic leukemia and chronic myelogenous leukemias. Since it is inactivated by xanthine oxidase (XO), concurrent intake of substances containing XO may potentially reduce bioavailability of mercaptopurine. Cow's milk is known to contain a high level of XO. In vitro and in vivo data suggest that concurrent intake of cow's milk may reduce the bioavailability of mercaptopurine. This interaction may be clinically significant. Therefore most patients should try to separate the timing of taking mercaptopurine and drinking milk.

Physicochemical and kinetic properties of purified sheep's milk xanthine oxidoreductase

Xanthine oxidoreductase (XOR) was purified for the first time from sheep's milk. The ultraviolet-visible absorption spectrum was essentially identical to those of the corresponding bovine, human, and goats' milk enzymes and showed an A280/A450 ratio of 5.35 +/- 0.24, indicating a high degree of purity. Like milk XOR from other species, sheep's milk enzyme showed a single band on SDS-PAGE corresponding to a subunit with approximate Mr 150,000. Xanthine oxidase activity of purified sheep's milk XOR (0.69 +/- 0.04 micromole urate min(-1) mg(-1)) was low relative to that of the bovine milk enzyme (1.83 +/- 0.02 micromole urate min(-1) mg(-1)), but higher than those of human or goats' milk XOR. As in the latter 2 cases, the low activity of sheep's milk XOR can be attributed to its relatively low molybdenum content (0.18 atoms per subunit), compared with that of the bovine milk enzyme (0.56 atoms Mo per subunit). Consistent with this, NADH oxidase activity of sheep's milk XOR was similar to that of enzymes purified from bovine, human, or goats' milk. The presence of desulpho-enzyme in sheep's milk XOR was demonstrated by resulfuration experiments, whereby xanthine oxidase activity was increased by approximately 75%.