Investigation of the interaction between benzaldehyde thiosemicarbazone compounds and xanthine oxidase

Oxidative metabolism mechanism of terpenoid compound ZQ-8 by cytochrome P450 enzyme in Helicoverpa armigera

In our previous research, we identified that treatment of Helicoverpa armigera with ZQ-8 led to upregulation of CYP450 genes. To clarify the metabolic pathway of ZQ-8, this study analyzed the expression of CYP450 genes and proteins in H. armigera after ZQ-8 treatment through transcriptomics and proteomics. Molecular docking, recombinant protein expression, and surface plasmon resonance techniques were employed to investigate the interactions between ZQ-8 and P450 proteins. The oxidative reduction related pathways were significantly enriched in H. armigera larvae treated with ZQ-8, with an increase in the expression of CYP6B2 and CYP6B6 genes. The CYP6B2 and CYP6B6 proteins exhibited significant expression following ZQ-8 treatment. ZQ-8 demonstrated rapid binding and stable dissociation characteristics with CYP6B6, characterized by a dissociation constant (KD) of 88.15 μM. In contrast, ZQ-8 also showed rapid binding and dissociation with CYP6B2, but with a lower KD of 74.77 μM indicating that CYP6B2 has a stronger binding affinity for ZQ-8 compared to CYP6B6, and is capable of oxidizing ZQ-8 to the corresponding carboxylic acid. This study provides a reference for the metabolism and mechanism of action of ZQ-8 as a potential drug molecule, laying the foundation for future drug design and optimization, paving the way for environmentally sustainable pest control strategies and reducing reliance on traditional chemical pesticides.

Synthesis of 5-hydroxyisatin thiosemicarbazones, spectroscopic investigation, protein-ligand docking, and in vitro anticancer activity

A series of novel modifications were performed at the N(4) position of 5-hydroxyisatin thiosemicarbazone (TSC). The structure-activity approach is applied to design and synthesize derivatives by condensing thiosemicarbazides with 5-hydroxy isatin. The TSCs were characterized by various spectroscopic techniques viz. FTIR, 1H NMR, 13C NMR, UV-Vis, HRMS data, CHN elemental analysis, and single crystal X-ray diffraction. Biological evaluation of the synthesized compounds revealed the anticancer potency of the TSC analogues against breast cancer (MD-AMD-231, MCF-7), lung cancer (A549, NCI-H460), prostate cancer (PC3), and skin cancer (A431). The molecules, L2, L3, and L6 showed activity in the micromolar range (IC50; 0.19-2.19 μM). L6 exhibited the highest potency against skin cancer A431 cell line, with an IC50 of 0.19 μM compared to 1.8 μM with triapine and showed low toxicity against PNT-2 cells with an SI index of >100 μM. The mechanistic study revealed that L6 inhibited cancer cell proliferation, colony formation, and 3-dimensional spheroid formation by targeting the Ras/MAPK axis. It induced DNA damage and impaired DNA damage repair machinery, which led to the accumulation of DSB. Also, it lowered the ERK1/2 expression, which affected the caspase 3 activity and showed higher binding affinity compared to the FDA-approved drug Lenalidomide in molecular docking studies. Our findings demonstrated the possible future anticancer drug potency of L6 in the skin cancer A431 cells.

A potential therapeutic agent for the treatment of hyperuricemia and gout: 3,4-Dihydroxy-5-nitrobenzaldehyde phenylthiosemicarbazide

Uric acid, the metabolic product of purines, relies on xanthine oxidase (XOD) for production. XOD is a target for the development of drugs for hyperuricemia (HUA) and gout. Currently, treatment options remain limited for gout patients. 3, 4-Dihydroxy-5-nitrobenzaldehyde (DHNB) is a derivative of the natural product protocatechualdehyde with good biological activity. In this work, we identify a DHNB thiosemicarbazide class of compounds that targets XOD. 3,4-Dihydroxy-5-nitrobenzaldehyde phenylthiosemicarbazone can effectively inhibit XOD activity (IC50 value: 0.0437 μM) and exhibits a mixed inhibitory effect. In a mouse model of acute hyperuricemia, a moderate dose (10 mg/kg.w) of 3,4-dihydroxy-5-nitrobenzaldehyde phenylthiosemicarbazide effectively controlled the serum uric acid content and significantly inhibited serum XOD activity. In addition, 3,4-Dihydroxy-5-nitrobenzaldehyde phenylthiosemicarbazide showed favorable safety profiles, and mice treated with the target compound did not show any symptoms of general toxicity following a single dose of 500 mg/kg. In the allopurinol group, 50 % of the mice died. These results provide a structural framework and mechanism of XOD inhibition that may facilitate the design of hyperuricemia and gout treatments.

Exploring the effect of a series of flavonoids on tyrosinase using integrated enzyme kinetics, multispectroscopic, and molecular modelling analyses

The control of food browning can be achieved by inhibiting tyrosinase (TY) activity, but current studies on the interaction of flavonoids as potent inhibitors with TY are inadequate. Herein, the effect of a library of flavonoids on TY was investigated using enzyme kinetics, multispectroscopic methods, and molecular modelling. Some flavonoids including 4, 8, 10, 17, 18, 28, 30, 33, and 34 exhibited potent TY inhibitory activity, with compound 10 demonstrating reversible inhibition in a mixed-competitive manner. Ultraviolet-visible spectral changes confirmed the formation of flavonoid-TY complexes. Fluorescence quenching analysis suggested effective intrinsic fluorescence quenching by flavonoids through static quenching with the ground-state complex formation. Synchronous fluorescence spectra showed the microenvironment change around the fluorophores induced by flavonoids. ANS-binding fluorescence assay indicated TY's surface hydrophobicity change by flavonoids and highlighted the change in secondary structure conformation, which was further confirmed by Fourier-transform infrared spectra. Molecular modelling results helped visualize the preferred binding conformation at the active site of TY, and demonstrated the important role of hydrophobic interaction and hydrogen bonding in stabilizing the flavonoid-TY complexes. These findings prove that diverse flavonoid structures distinctly impact their binding behavior on TY and contribute to understanding flavonoids' potential as TY inhibitors in controlling food browning.

Past, present and future of xanthine oxidase inhibitors: design strategies, structural and pharmacological insights, patents and clinical trials

Xanthine oxidase, a molybdo-flavoenzyme, and an isoform of xanthine dehydrogenase both exist as xanthine oxidoreductase and are responsible for purine catabolism. Xanthine oxidase is more involved in pathological conditions when extensively modulated. Elevation of xanthine oxidase is not only the prime cause of gout but is also responsible for various hyperuricemia associated pathological conditions like diabetes, chronic wounds, cardiovascular disorders, Alzheimer's disease, etc. Currently available xanthine oxidase inhibitors in clinical practice (allopurinol, febuxostat and topiroxostat) suffer from fatal side effects that pose a serious problem to the healthcare system, raising global emergency to develop novel, potent and safer xanthine oxidase inhibitors. This review will provide key and systematic information about: a. design strategies (inspired from both marketed drugs in clinical practice and natural products), structural insights and pharmacological output (xanthine oxidase inhibition and associated activities) of various pre-clinical candidates reported by various research groups across the globe in the past two decades; b. patented xanthine oxidase inhibitors published in the last three decades and c. clinical trials and their outcomes on approved drug candidates. Information generated in this review has suggested fragment-based drug design (FBDD) and molecular hybridization techniques to be most suitable for development of desired xanthine oxidase inhibitors as one provides high selectivity toward the enzyme and the other imparts multifunctional properties to the structure and both may possess capabilities to surpass the limitations of currently available clinical drugs. All in combination will exclusively update researchers working on xanthine oxidase inhibitors and allied areas and potentially help in designing rational, novel, potent and safer xanthine oxidase inhibitors that can effectively tackle xanthine oxidase related disease conditions and disorders.

5-Methoxyisatin N(4)-Pyrrolidinyl Thiosemicarbazone (MeOIstPyrd) Restores Mutant p53 and Inhibits the Growth of Skin Cancer Cells, In Vitro

A series of novel thiosemicarbazone derivatives containing 5-methoxy isatin were designed and synthesized with modification on N(4) position. Derivatives considering structure-activity relationship have been designed and synthesized by condensing thiosemicarbazide with 5-methoxy isatin. The synthesized compounds were characterized by elemental analysis, FT-IR spectroscopy, UV-visible spectroscopy, NMR (1H, 13C) spectroscopy, mass spectrometry, and a single-crystal study. Biological evaluation of the synthesized compounds revealed that MeOIstPyrd is the most promising compound against skin cancer cell line, A431, with an IC50 value of 0.9 μM. In addition, MeOIstPyrd also exhibited low toxicity against the normal human fibroblast and the human embryonic kidney 293 cell line, HLF-1, and HEK293, respectively. Furthermore, the mechanistic study revealed that MeOIstPyrd efficiently inhibited cell proliferation, migration, and spheroid formation by activating the mitochondrial intrinsic apoptotic pathway. MeOIstPyrd also induces DNA damage and activates p53 irrespective of the p53 status. It increases the half-life of p53 and stabilizes p53 by phosphorylating it at ser15. Moreover, MeOIstPyrd was found to bind to MDM2 in the p53 sub-pocket and, therefore, block p53-MDM2 interaction. Our result exhibited potential anticancer activity of MeOIstPyrd in the A431 cell line and its ability in restoring mutant p53, which is an interesting and promising strategy for cancer therapeutics.

Chalcone derivatives as xanthine oxidase inhibitors: synthesis, binding mode investigation, biological evaluation, and ADMET prediction

Xanthine oxidase (XO) is a crucial target for the treatment of hyperuricemia and gout. A series of derivatives based on natural 3,4-dihydroxychalcone, obtained from Carthamus tinctorious and Licorice, were designed and synthesized. Nine derivatives (9a-e, 10b,c, and 15a,b) exhibited apparent XO inhibitory activity in vitro (IC₅₀ values varied from 0.121 to 7.086 μM), 15b presented the most potent inhibitory activity (IC₅₀ = 0.121 µM), which was 27.47-fold higher than that of allopurinol (IC₅₀ = 3.324 µM). The SAR analysis indicated that introducing hydroxyl groups at 3'/4'/5'-position on ring A was more beneficial to the inhibition of XO than at 2'/6'-position; the removal of 3‑hydroxyl group on ring B could weaken the inhibitory potency of hydroxychalcones on XO, but it was beneficial to the XO inhibitory potency of methoxychalcones. Molecule modeling studies afforded insights into the binding mode of 15b with XO and supported the findings of SAR analysis. Additionally, kinetics studies demonstrated that 15b presented a reversible and competitive XO inhibitor, which spontaneously combined with XO through hydrophobic force, and finally changed the secondary conformation of XO. Furthermore, the acute hyperuricemia model was employed to investigate the hypouricemic effect of 15b, which could effectively reduce the serum uric acid levels of rats at an oral dose of 10 mg/kg. ADMET prediction suggested that compound 15b possessed good pharmacokinetic properties. Briefly, compound 15b emerges as an interesting XO inhibitor for the treatment of hyperuricemia and gout with beneficial effects on serum uric acid levels regulating. Meanwhile, the XO inhibitors with chalcone skeleton will deserve further attention and discussion.

Insights into the Inhibitory Mechanism of Viniferifuran on Xanthine Oxidase by Multiple Spectroscopic Techniques and Molecular Docking

Viniferifuran was investigated for its potential to inhibit the activity of xanthine oxidase (XO), a key enzyme catalyzing xanthine to uric acid. An enzyme kinetics analysis showed that viniferifuran possessed a strong inhibition on XO in a typical anti-competitive manner with an IC₅₀ value of 12.32 μM (IC₅₀ for the first-line clinical drug allopurinol: 29.72 μM). FT-IR and CD data analyses showed that viniferifuran could induce a conformational change of XO with a decrease in the α-helix and increases in the β-sheet, β-turn, and random coil structures. A molecular docking analysis revealed that viniferifuran bound to the amino acid residues located within the activity cavity of XO by a strong hydrophobic interaction (for Ser1214, Val1011, Phe914, Phe1009, Leu1014, and Phe649) and hydrogen bonding (for Asn768, Ser876, and Tyr735). These findings suggested that viniferifuran might be a promising XO inhibitor with a favorable mechanism of action.

The inhibitory kinetics and mechanism of quercetin-3-O-rhamnoside and chlorogenic acid derived from Smilax china L. EtOAc fraction on xanthine oxidase

Smilax china L. showed various biological activities mainly due to its phenolic components; however, the mechanism of isolated phenolic fraction against xanthine oxidase (XO) has not been investigated. Quercetin-3-O-rhamnoside (QORh) and chlorogenic acid (CGA) extracted from Smilax china L. ethyl acetate fraction was analyzed for its XO inhibitory kinetics and mechanism using multispectroscopic methods and molecular docking techniques. QORh and CGA reversibly inhibited XO activity in competitive and non-competitive modes, respectively. The bioactive compounds bound with XO were dominated mainly by hydrogen bonds and van der Waals forces to form QORh-XO, and CGA-XO complexes with one affinity binding site. The synchronous fluorescence, circular dichroism, three-dimensional (3D) fluorescence, and Fourier transform infrared spectra exhibited that XO binding with QORh or CGA leads to the secondary and tertiary structural variation of the protein. Additionally, molecular docking further revealed that QORh binds to the active site of XO and forms hydrogen coupling with amino acid residues. The results showed that QORh and CGA had inhibitory activity on XO, which might be further used to modify the bioactive compounds and improve their efficacy to treat gout.

Synthetic heterocyclic derivatives as promising xanthine oxidase inhibitors: An overview

Inhibition of xanthine oxidase is an effective and most prominent therapeutic approach for the management of gout. Discovery of its association in the pathophysiology of diabetes, cardiovascular disorders, etc., widened its therapeutic horizons. Limited drug candidates in clinical practice along with side effects forced researchers to develop more efficacious and safer xanthine oxidase inhibitors for the management of gout and other disorders associated with xanthine oxidase hyperactivity. In this regard, this review focus on: (a) Various drug candidates in clinical practice and under clinical trials, (b) Development of various heterocyclic motifs as xanthine oxidase inhibitors in last two decades and (c) Various patented synthetic xanthine oxidase inhibitors.

Network Pharmacology-Based Investigation of the Mechanism of Action of Plantaginis Herba in Hyperuricemia Treatment

This study used a network pharmacology approach to investigate the potential active ingredients of Plantaginis Herba and its underlying mechanisms in hyperuricemia treatment. The potential active ingredients of Plantaginis Herba were obtained from TCMSP and ETCM databases, and the potential targets of the active ingredients were predicted using the Swiss TargetPrediction database. The potential therapeutic targets of hyperuricemia were retrieved from the GeneCards, DisGeNET, and Online Mendelian Inheritance in Man (OMIM) databases. Then, the integrative bioinformatics analyses of candidates were performed by GO analysis, KEGG analysis, and PPI network construction. There were 15 predicted active ingredients in Plantaginis Herba and 41 common targets that may be involved in the treatment of hyperuricemia. A total of 61 GO annotations and 35 signaling pathways were identified by enrichment analysis (P < 0.01). The underlying mechanisms of Plantaginis Herba may be related to insulin resistance, PI3K/AKT, TNF, VEGF, AMPK, and glucagon signaling pathways. Thus, the present study provided potential and promising strategies of Plantaginis Herba for hyperuricemia treatment.

Interaction mechanism of flavonoids on bovine serum albumin: Insights from molecular property-binding affinity relationship

The molecular structure properties-binding affinity relationship of a series of flavonoids and bovine serum albumin (BSA) was investigated in vitro from comparing the binding constants determined through the fluorescence method. As a result, the binding process was greatly influenced by different structural elements or substituents of flavonoids under analysis. The hydroxylation at the positions C3, C6, C4', C5' (for type I) and C5, C3' (for type II) were in favor of forming hydrogen bonds with the amino acids of BSA, which was of great importance in the binding and interaction between flavonoids and the protein. The decreased affinity could be realized by the methoxylation (C8, C3' and C4') and glycosylation (C3 and C7) of flavonoid type I. However, the adverse trend on binding affinity was observed when the methoxylation and glycosylation appeared at the sites C4' and C7, C4' of structure type II, respectively. Meanwhile, glycosylation at C7 mainly induced the decline in the affinity of flavonoids (type III), and the hydrogenation of the C2C3 double bond for type I was beneficial to increase the affinity on BSA. Moreover, part of flavonoids could mediate the conformational alteration of secondary structures of the protein during the interaction process, which was inferred by means of the synchronous fluorescence spectra. The determinations of ANS fluorescence probe suggested that hydrophobic interaction played an important role in the binding of a majority of flavonoids to BSA. Further evidences from the site-specific experiments revealed that the location of flavonoids 19, 29 and 34 binding on BSA mainly belonged to site I, while compound 3 bound to both sites I and II. Additionally, molecular modelling studies further confirmed the indispensable character of hydrophobic interaction and hydrogen bonds, and illustrated the preferred complex binding behaviors.

Mechanistic insights on the mode of action of an antiproliferative thiosemicarbazone-nickel complex revealed by an integrated chemogenomic profiling study

Thiosemicarbazones (TSC) and their metal complexes display diverse biological activities and are active against multiple pathological conditions ranging from microbial infections to abnormal cell proliferation. Ribonucleotide reductase (RNR) is considered one of the main targets of TSCs, yet, the existence of additional targets, differently responsible for the multifaceted activities of TSCs and their metal complexes has been proposed. To set the basis for a more comprehensive delineation of their mode of action, we chemogenomically profiled the cellular effects of bis(citronellalthiosemicarbazonato)nickel(II) [Ni(S-tcitr)₂] using the unicellular eukaryote Saccharomyces cerevisiae as a model organism. Two complementary genomic phenotyping screens led to the identification of 269 sensitive and 56 tolerant deletion mutant strains and of 14 genes that when overexpressed make yeast cells resistant to an otherwise lethal concentration of Ni(S-tcitr)₂. Chromatin remodeling, cytoskeleton organization, mitochondrial function and iron metabolism were identified as lead cellular processes responsible for Ni(S-tcitr)₂ toxicity. The latter process, and particularly glutaredoxin-mediated iron loading of RNR, was found to be affected by Ni(S-tcitr)₂. Given the multiple pathways regulated by glutaredoxins, targeting of these proteins by Ni(S-tcitr)₂ can negatively affect various core cellular processes that may critically contribute to Ni(S-tcitr)₂ cytotoxicity.

Exploring the structure–activity relationship and interaction mechanism of flavonoids and α-glucosidase based on experimental analysis and molecular docking studies

An integrated method was explored to investigate the structure–activity relationship and interaction mechanism between a library of natural flavonoids and α-glucosidase.

NanoPOP: Solution-Processable Fluorescent Porous Organic Polymer for Highly Sensitive, Selective, and Fast Naked Eye Detection of Mercury

Fluorescence-based detection is one of the most efficient and cost-effective methods for detecting hazardous, aqueous Hg²⁺. We designed a fluorescent porous organic polymer (TPA-POP-TSC), with a "fluorophore" backbone and a thiosemicarbazide "receptor" for Hg²⁺-targeted sensing. Nanometer-sized TPA-POP-TSC spheres (nanoPOP) were synthesized under mini-emulsion conditions and showed excellent solution processability and dispersity in aqueous solution. The nanoPOP sensor exhibits exceptional sensitivity (K_sv = 1.01 × 10⁶ M^-1) and outstanding selectivity for Hg²⁺ over other ions with rapid response and full recyclability. Furthermore, the nanoPOP material can be easily coated onto a paper substrate to afford naked eye-based Hg²⁺-detecting test strips that are convenient, inexpensive, fast, highly sensitive, and reusable. Our design takes advantage of the efficient and selective capture of Hg²⁺ by thiosemicarbazides (binding energy = -29.84 kJ mol^-1), which facilitates electron transfer from fluorophore to bound receptor, quenching the sensor's fluorescence.

Integrated multi-spectroscopic and molecular modelling techniques to probe the interaction mechanism between salvianolic acid A and α‑glucosidase

α-Glucosidase (AG) is an important drug target for the treatment of type 2 diabetes mellitus in humans due to the potential effect of down regulating glucose absorption in patients. In our previous study, salvianolic acid A (SAA) was found to exhibit potent AG inhibitory activity, whereas the interaction mechanism was still ambiguous. Herein, the interaction mechanism of SAA and AG was investigated by multi-spectroscopic methods along with molecular docking. As a result, it was found that SAA reversibly inhibited AG in a competitive manner with IC₅₀ of 16.44 ± 0.18 μM, and the inhibition belonged to a multi-phase kinetics process with a first-order reaction. The intrinsic fluorescence of AG could be strongly quenched by SAA through a static quenching mechanism. The negative Gibbs free energy change and positive values of enthalpy and entropy change revealed that the binding of SAA to AG was spontaneous and dominated mainly by hydrophobic interactions, and only a single binding site was determined for them. Analysis of synchronous fluorescence, ANS-binding fluorescence, circular dichroism and Fourier transform infrared spectra suggested that the binding of SAA to AG induced rearrangement and conformational changes of the enzyme. Besides, further molecular modelling validated that SAA could bind to the active domain and prevent the entrance of substrate, resulting in the inhibition of AG activity. These findings provide new insights into understanding the interaction mechanism of SAA on AG.

Effect of Salvia miltiorrhiza on acetylcholinesterase: Enzyme kinetics and interaction mechanism merging with molecular docking analysis

Acetylcholinesterase (AchE) serves as an important target for Alzheimer's disease. Salvia miltiorrhiza has been used to treat cardiovascular disease for hundreds of years. However, the interaction between S. miltiorrhiza and AchE is still inadequate. Herein, an integrated method including molecular docking and experimental studies was employed to investigate the interaction. Consequently, some components were screened as potent AchE inhibitors by in silico and in vitro. Among them, miltirone (MT) and salvianolic acid A (SAA) reversibly inhibited AchE in a mixed-competitive manner. Fluorescence data revealed that SAA and salvianolic acid C (SAC) strongly quenched the intrinsic fluorescence of AchE through a static quenching mechanism, and the binding was spontaneous and dominated by hydrophobic interaction inferred by the thermodynamic parameters. The synchronous and ANS-binding fluorescence spectra suggested that SAA and SAC could bind to the enzyme and induce its conformation changes of secondary structures, which was further confirmed by Fourier transform infrared spectra. Meanwhile, molecular docking presented the probable binding modes of inhibitors to AchE and highlighted the key role of hydrophobic interaction and hydrogen bonds for the stability of docking complex. These findings put more insights into understanding the interaction of S. miltiorrhiza chemicals and AchE, as well as Alzheimer's disease.

Investigation of the interaction between salvianolic acid C and xanthine oxidase: Insights from experimental studies merging with molecular docking methods

Xanthine oxidase (XO) has emerged as an important target for gout. In our previous study, salvianolic acid C (SAC) was found to show potent XO inhibitory activity, whereas the interaction mechanism was still not clear. Herein, an integrated approach consisting of enzyme kinetics, multi-spectroscopic methods and molecular docking was employed to investigate the interaction between SAC and XO. Consequently, SAC exhibited a rapid and mixed-type inhibition of XO with IC₅₀ of 5.84 ± 0.18 μM. The fluorescence data confirmed that SAC presented a strong fluorescence quenching effect through a static quenching procedure. The values of enthalpy change, entropy change and Gibbs free energy change indicated that their binding was spontaneous and driven mainly by hydrophobic interactions. Analysis of synchronous fluorescence, circular dichroism and fourier transform infrared spectra demonstrated that SAC induced conformational changes of the enzyme. Besides, further molecular docking revealed that SAC occupied the catalytic center resulting in the inhibition of XO activity. This study provides a comprehensive understanding on the interaction mechanism of SAC on XO.