Regulatory ligand binding in plant chalcone isomerase-like (CHIL) proteins.

Chalcone isomerase-like (CHIL) protein is a noncatalytic protein that enhances flavonoid content in green plants by serving as a metabolite binder and a rectifier of chalcone synthase (CHS). Rectification of CHS catalysis occurs through direct protein-protein interactions between CHIL and CHS, which alter CHS kinetics and product profiles, favoring naringenin chalcone (NC) production. These discoveries raise questions about how CHIL proteins interact structurally with metabolites and how CHIL-ligand interactions affect interactions with CHS. Using differential scanning fluorimetry on a CHIL protein from Vitis vinifera (VvCHIL), we report that positive thermostability effects are induced by the binding of NC, and negative thermostability effects are induced by the binding of naringenin. NC further causes positive changes to CHIL-CHS binding, whereas naringenin causes negative changes to VvCHIL-CHS binding. These results suggest that CHILs may act as sensors for ligand-mediated pathway feedback by influencing CHS function. The protein X-ray crystal structure of VvCHIL compared with the protein X-ray crystal structure of a CHIL from Physcomitrella patens reveals key amino acid differences at a ligand-binding site of VvCHIL that can be substituted to nullify the destabilizing effect caused by naringenin. Together, these results support a role for CHIL proteins as metabolite sensors that modulate the committed step of the flavonoid pathway.

Aim18p and Aim46p are chalcone isomerase domain-containing mitochondrial hemoproteins in Saccharomyces cerevisiae.

Chalcone isomerases (CHIs) have well-established roles in the biosynthesis of plant flavonoid metabolites. Saccharomyces cerevisiae possesses two predicted CHI-like proteins, Aim18p (encoded by YHR198C) and Aim46p (YHR199C), but it lacks other enzymes of the flavonoid pathway, suggesting that Aim18p and Aim46p employ the CHI fold for distinct purposes. Here, we demonstrate using proteinase K protection assays, sodium carbonate extractions, and crystallography that Aim18p and Aim46p reside on the mitochondrial inner membrane and adopt CHI folds, but they lack select active site residues and possess an extra fungal-specific loop. Consistent with these differences, Aim18p and Aim46p lack CHI activity and also the fatty acid-binding capabilities of other CHI-like proteins, but instead bind heme. We further show that diverse fungal homologs also bind heme and that Aim18p and Aim46p possess structural homology to a bacterial hemoprotein. Collectively, our work reveals a distinct function and cellular localization for two CHI-like proteins, introduces a new variation of a hemoprotein fold, and suggests that ancestral CHI-like proteins were hemoproteins.

Structural insights into catalytic promiscuity of chalcone synthase from Glycine max (L.) Merr.: Coenzyme A-induced alteration of product specificity.

Catalytic promiscuity of enzymes plays a pivotal role in driving the evolution of plant specialized metabolism. Chalcone synthase (CHS) catalyzes the production of 2',4,4',6'-tetrahydroxychalcone (THC), a common precursor of plant flavonoids, from p-coumaroyl-coenzyme A (-CoA) and three malonyl-CoA molecules. CHS has promiscuous product specificity, producing a significant amount of p-coumaroyltriacetic lactone (CTAL) in vitro. However, mechanistic aspects of this CHS promiscuity remain to be clarified. Here, we show that the product specificity of soybean CHS (GmCHS1) is altered by CoA, a reaction product, which selectively inhibits THC production (IC50, 67 µM) and enhances CTAL production. We determined the structure of a ternary GmCHS1/CoA/naringenin complex, in which CoA is bound to the CoA-binding tunnel via interactions with Lys55, Arg58, and Lys268. Replacement of these residues by alanine resulted in an enhanced THC/CTAL production ratio, suggesting the role of these residues in the CoA-mediated alteration of product specificity. In the ternary complex, a mobile loop ("the K-loop"), which contains Lys268, was in a "closed conformation" placing over the CoA-binding tunnel, whereas in the apo and binary complex structures, the K-loop was in an "open conformation" and remote from the tunnel. We propose that the production of THC involves a transition of the K-loop conformation between the open and closed states, whereas synthesis of CTAL is independent of it. In the presence of CoA, an enzyme conformer with the closed K-loop conformation becomes increasingly dominant, hampering the transition of K-loop conformations to result in decreased THC production and increased CTAL production.

Improving plant adaptation to soil antimony contamination: the synergistic contribution of arbuscular mycorrhizal fungus and olive mill waste.

BACKGROUND: This study aimed to investigate the alterations in biochemical and physiological responses of oat plants exposed to antimony (Sb) contamination in soil. Specifically, we evaluated the effectiveness of an arbuscular mycorrhizal fungus (AMF) and olive mill waste (OMW) in mitigating the effects of Sb contamination. The soil was treated with a commercial strain of AMF (Rhizophagus irregularis) and OMW (4% w/w) under two different levels of Sb (0 and 1500 mg kg-1 soil). RESULTS: The combined treatment (OMW + AMF) enhanced the photosynthetic rate (+ 40%) and chlorophyll a (+ 91%) and chlorophyll b (+ 50%) content under Sb condition, which in turn induced more biomass production (+ 67-78%) compared to the contaminated control plants. More photosynthesis in OMW + AMF-treated plants gives a route for phenylalanine amino acid synthesis (+ 69%), which is used as a precursor for the biosynthesis of secondary metabolites, including flavonoids (+ 110%), polyphenols (+ 26%), and anthocyanins (+ 63%) compared to control plants. More activation of phenylalanine ammonia-lyase (+ 38%) and chalcone synthase (+ 26%) enzymes in OMW + AMF-treated plants under Sb stress indicated the activation of phenylpropanoid pathways in antioxidant metabolites biosynthesis. There was also improved shifting of antioxidant enzyme activities in the ASC/GSH and catalytic pathways in plants in response to OMW + AMF and Sb contamination, remarkably reducing oxidative damage markers. CONCLUSIONS: While individual applications of OMW and AMF also demonstrated some degree of plant tolerance induction, the combined presence of AMF with OMW supplementation significantly enhanced plant biomass production and adaptability to oxidative stress induced by soil Sb contamination.

Methylated chalcones are required for rhizobial nod gene induction in the Medicago truncatula rhizosphere.

Legume nodulation requires the detection of flavonoids in the rhizosphere by rhizobia to activate their production of Nod factor countersignals. Here we investigated the flavonoids involved in nodulation of Medicago truncatula. We biochemically characterized five flavonoid-O-methyltransferases (OMTs) and a lux-based nod gene reporter was used to investigate the response of Sinorhizobium medicae NodD1 to various flavonoids. We found that chalcone-OMT 1 (ChOMT1) and ChOMT3, but not OMT2, 4, and 5, were able to produce 4,4'-dihydroxy-2'-methoxychalcone (DHMC). The bioreporter responded most strongly to DHMC, while isoflavones important for nodulation of soybean (Glycine max) showed no activity. Mutant analysis revealed that loss of ChOMT1 strongly reduced DHMC levels. Furthermore, chomt1 and omt2 showed strongly reduced bioreporter luminescence in their rhizospheres. In addition, loss of both ChOMT1 and ChOMT3 reduced nodulation, and this phenotype was strengthened by the further loss of OMT2. We conclude that: the loss of ChOMT1 greatly reduces root DHMC levels; ChOMT1 or OMT2 are important for nod gene activation in the rhizosphere; and ChOMT1/3 and OMT2 promote nodulation. Our findings suggest a degree of exclusivity in the flavonoids used for nodulation in M. truncatula compared to soybean, supporting a role for flavonoids in rhizobial host range.

Pre-clinical evaluation of 99mTc-labeled chalcone derivative for amyloid-ß imaging post-head trauma.

Aß42 plaque formation is one of the preliminary pathologic events that occur post traumatic brain injury (TBI) which is also among the most noteworthy hallmarks of AD. Their pre symptomatic detection is therefore vital for better disease management. Chalcone-picolinic acid chelator derivative, 6-({[(6-carboxypyridin-2-yl)methyl](2-{4-[(2E)-3-[4-(dimethyl amino)phenyl]prop-2-enoyl]phenoxy}ethyl)amino}methyl)pyridine-2-carboxylic acid, Py-chal was synthesized to selectively identify amyloid plaques formed post head trauma using SPECT imaging by stable complexation to 99mTc with > 97% efficiency without compromising amyloid specificity. The binding potential of the Py-chal ligand to amyloid plaques remained high as confirmed by in vitro binding assay and photophysical spectra. Further, the Py-chal complex stained amyloid aggregates in the brain sections of rmTBI mice model. In vivo scintigraphy in TBI mice model displayed high uptake followed by high retention while the healthy rabbits displayed higher brain uptake followed by a rapid washout attributed to absence of amyloid plaques. Higher uptake in brain of TBI model was also confirmed by ex vivo biodistribution analysis wherein brain uptake of 3.38 ± 0.2% ID/g at 2 min p.i. was observed for TBI mice model. This was followed by prolonged retention and more than twofold higher activity as compared to sham mice brain. This preliminary data suggests the specificity of the radiotracer for amyloid detection post head trauma and applicability of 99mTc labeled Py-chal complex for TBI-induced ß-amyloid SPECT imaging.

Merging Photocatalytic Doubly-Decarboxylative Csp 2 -Csp 2 Cross-Coupling for Stereo-Selective (E)-α,ß-Unsaturated Ketones Synthesis.

A photocatalytic domain of doubly decarboxylative Csp 2 -Csp 2 cross coupling reaction is disclosed. Merging iridium and palladium photocatalysis manifested carbon-carbon bonds in a tandem dual-radical pathway. Present catalytic platform efficiently cross-coupled α, ß-unsaturated acids and α-keto acids to afford a variety of α, ß-unsaturated ketones with excellent (E)-selectivity and functional group tolerance. Mechanistically, photocatalyst implicated through reductive quenching cycle whereas cross coupling proceeded over one electron oxidative pallado-cycle.

A fluorescent probe based on cyclochalcone for detecting peroxynitrite.

A novel cyclic chalcone fluorescent probe C-PN was synthesized to detect ONOO-. After reaction with peroxynitrite, the double bond of C-PN in the cyclic chalcone structure was disconnected, which caused the change of intramolecular charge transfer (ICT) effect, emitting blue fluorescence and quenching orange red fluorescence. Visible to the naked eye, the color of the probe solution changed. The probe showed low sensitivity (detection limit = 20.2 nm), short response time (less than 60 s) at low concentration of ONOO-, good visibility, and good selectivity and stability for ONOO-.

Design, synthesis, and biological evaluation of chalcone acetamide derivatives against triple negative breast cancer.

Chalcones are chemical scaffolds found in natural products, particularly in plants, and are considered for structural diversity in medicinal chemistry for drug development. Herein, we designed and synthesised novel acetamide derivatives of chalcone, characterizing them using 1H NMR, 13C NMR, HRMS, and IR spectroscopic methods. These derivatives were then screened against human cancer cells for cytotoxicity using the SRB assay. Among the tested derivatives, 7g, with a pyrrolidine group, exhibited better cell growth inhibition activity against triple-negative breast cancer (TNBC) cells. Further assays, including SRB, colony formation, and fluorescent dye-based microscopic analysis, confirmed that 7g significantly inhibited MDA-MB-231 cell proliferation. Furthermore, 7g promoted apoptosis by upregulating cellular reactive oxygen species (ROS) levels and disrupting mitochondrial membrane potential (MMP). Elevated expression of pro-apoptotic proteins (Bax and caspase-3) and a higher Bax/Bcl-2 ratio with downregulation of anti-apoptotic (Bcl-2) protein levels were observed in TNBC cells. The above results suggest that 7g can promote cellular death through apoptotic mechanisms in TNBC cells.

A Chalcone-based Fluorescence Probe for H2S Detecting Utilizing ESIPT Coupled ICT Mechanism.

The accurate and effective identification of hydrogen sulfide holds great significance for environmental monitoring. Azide-binding fluorescent probes are powerful tools for hydrogen sulfide detection. We combined the 2'-Hydroxychalcone scaffold with azide moiety to construct probe Chal-N3, the electron-withdrawing azide moiety was utilized to block the ESIPT process of 2'-Hydroxychalcone and quenches the fluorescence. The fluorescent probe was triggered with the addition of hydrogen sulfide, accompanied by great fluorescence intensity enhancement with a large Stokes shift. With excellent fluorescence properties including high sensitivity, specificity selectivity, and wider pH range tolerance, the probe was successfully applied to natural water samples.

Ultrasound-Assisted Synthesis of Chalcone: A Highly Sensitive and Selective Fluorescent Chemosensor for the Detection of Fe3+ in Aqueous Media.

The chalcone compound DHPO was synthesized through a chemical reaction between 1-(2-hydroxyphenyl)-ethanone and 3,4-dimethoxy benzaldehyde under ultrasound irradiation. The interaction between the DHPO compound and several metal ions was studied using fluorescence behavior, revealing that the chalcone function as a "turn on and turn off" switch fluorescent sensor, for selectively and sensitively detecting Fe3+ ions. The process of fluorescence quenching and complexation of DHPO with Fe3+ ion was further studied using methods such as Benesi-Hildebrand, Stern-Volmer plot, and job plot.

Design and synthesis of novel imidazole-chalcone derivatives as microtubule protein polymerization inhibitors to treat cervical cancer and reverse cisplatin resistance.

Using the licochalcone moiety as a lead compound scaffold, 16 novel imidazole-chalcone derivatives were designed and synthesized as microtubule protein polymerization inhibitors. The proliferation inhibitory activities of the derivatives against SiHa (human cervical squamous cell carcinoma), C-33A (human cervical cancer), HeLa (human cervical cancer), HeLa/DDP (cisplatin-resistant human cervical cancer), and H8 (human cervical epithelial immortalized) cells were evaluated. Compound 5a exhibited significant anticancer activity with IC50 values ranging from 2.28 to 7.77 µM and a resistance index (RI) of 1.63, while showing minimal toxicity to normal H8 cells. When compound 5a was coadministered with cisplatin, the RI of cisplatin to HeLa/DDP cells decreased from 6.04 to 2.01, while compound 5a enhanced the fluorescence intensity of rhodamine 123 in HeLa/DDP cells. Further studies demonstrated that compound 5a arrested cells at the G2/M phase, induced apoptosis, reduced colony formation, inhibited cell migration, and inhibited cell invasion. Preliminary mechanistic studies revealed that compound 5a decreased the immunofluorescence intensity of α-/ß-tubulin in cancer cells, reduced the expression of polymerized α-/ß-tubulin, and increased the expression of depolymerized α-/ß-tubulin. Additionally, the molecular docking results demonstrate that compound 5a can interact with the tubulin colchicine binding site and generate multiple types of interactions. These results suggested that compound 5a has anticancer effects and significantly reverses cervical cancer resistance to cisplatin, which may be related to its inhibition of microtubule and P-glycoprotein (P-gp) activity.

Design, synthesis, and ex vivo anti-drug resistant cervical cancer activity of novel molecularly targeted chalcone derivatives.

Chemotherapy toxicity and tumor multidrug resistance remain the main reasons for clinical treatment failure in cervical cancer. In this study, 79 novel chalcone derivatives were designed and synthesized using the principle of active substructure splicing with the parent nucleus of licorice chalcone as the lead compound and VEGFR-2 and P-gp as the target of action and their potentials for anticervical cancer activity were preliminarily evaluated. The results showed that the IC50 values of candidate compound B20 against HeLa and HeLa/DDP cells were 3.66 ± 0.10 and 4.35 ± 0.21 µΜ, respectively, with a resistance index (RI) of 1.18, which was significantly higher than that of the positive drug cisplatin (IC50:13.60 ± 1.63, 100.03 ± 7.94 µΜ, RI:7.36). In addition, B20 showed significant inhibitory activity against VEGFR-2 kinase and P-gp-mediated rhodamine 123 efflux, as well as the ability to inhibit the phosphorylation of VEGFR-2 and downstream PI3K/AKT signaling pathway proteins, inducing apoptosis, blocking cells in the S-phase, and inhibiting invasive migration and tubule generation by HUVEC cells. Acceptable safety was demonstrated in acute toxicity tests when B20 was at 200 mg/kg. In the nude mouse HeLa/DDP cell xenograft tumor model, the inhibition rate of transplanted tumors was 39.2 % and 79.2 % when B20 was at 10 and 20 mg/kg, respectively. These results suggest that B20 is a potent VEGFR-2 and P-gp inhibitor with active potential for treating cisplatin-resistant cervical cancer.

Development of multi-targetable chalcone derivatives bearing N-aryl piperazine moiety for the treatment of Alzheimer's disease.

The multi-target directed ligand (MTDL) discovery has been gaining immense attention in the development of therapeutics for Alzheimer's disease (AD). The strategy has been evolved as an auspicious approach suitable to combat the heterogeneity and the multifactorial nature of AD. Therefore, multi-targetable chalcone derivatives bearing N-aryl piperazine moiety were designed, synthesized, and evaluated for the treatment of AD. All the synthesized compounds were screened for thein vitro activityagainst acetylcholinesterase (AChE), butylcholinesterase (BuChE), ß-secretase-1 (BACE-1), and inhibition of amyloid ß (Aß) aggregation. Amongst all the tested derivatives, compound 41bearing unsubstituted benzylpiperazine fragment and para-bromo substitution at the chalcone scaffold exhibited balanced inhibitory profile against the selected targets. Compound 41 elicited favourable permeation across the blood-brain barrier in the PAMPA assay. The molecular docking and dynamics simulation studies revealed the binding mode analysis and protein-ligand stability ofthe compound with AChE and BACE-1. Furthermore,itameliorated cognitive dysfunctions and signified memory improvement in thein-vivobehavioural studies (scopolamine-induced amnesia model). Theex vivobiochemical analysis of mice brain homogenates established the reduced AChE and increased ACh levels. The antioxidant activity of compound 41 was accessed with the determination of catalase (CAT) and malondialdehyde (MDA) levels. The findings suggested thatcompound 41, containing a privileged chalcone scaffold, can act as a lead molecule for developing AD therapeutics.

Probing the Deoxyflavonoid Biosynthesis: Naringenin Chalcone Is a Substrate for the Reductase Synthesizing Isoliquiritigenin.

Isoliquiritigenin formation is a key reaction during deoxyflavonoid biosynthesis, which is catalyzed by two enzymes, chalcone synthase (CHS) and reductase (CHR). The substrates for CHS are established. However, the substrate for CHR is unknown. In this study, an in vitro reaction was performed to confirm whether naringenin chalcone can be a substrate. Naringenin chalcone was used as a substrate during the CHR reaction. Analyzing the product revealed that isoliquiritigenin was produced from naringenin chalcone, indicating that naringenin chalcone is a substrate. This study is the first to identify a substrate for CHR, reveals that deoxyflavonoid biosynthesis diverges from naringenin chalcone, endorses the term "chalcone reductase," and answers the long-standing questions about doubly-labeled acetic acid uptake pattern in deoxyflavonoid biosynthesis.

Organohalogen chalcones: design, synthesis, ADMET prediction, molecular dynamics study and inhibition effect on acetylcholinesterase and carbonic anhydrase.

In an effort to discover potential acetylcholinesterase (AChE) and carbonic anhydrase (CA) inhibitors, a novel series of organohalogen chalcone derivatives (12-20, 23-30) was synthesized, and their chemical structures were characterized by spectral analysis. They showed a highly potent inhibition effect on AChE and hCAs (Ki values range from 5.07 ± 0.062 to 65.53 ± 4.36 nM for AChE, 13.54 ± 2.55 to 94.11 ± 10.39 nM for hCA I, and 5.21 ± 0.54 to 57.44 ± 3.12 nM for hCA II). In addition, the chalcone derivatives with the highest inhibitor score docked into the active site of the indicated metabolic enzyme receptors, and their absorption, metabolism, and toxic properties were evaluated according to ADMET's estimation.Compounds 16 and 19 exhibited the highest inhibition score, emerged as lead compounds, and inspired the development of more potent compounds.

Antiviral activity evaluation and action mechanism of chalcone derivatives containing phenoxypyridine.

In this paper, a series of phenoxypyridine-containing chalcone derivatives (L1-L28) were designed and synthesized, characterized on NMR and HRMS. Ningnanmycin (NNM) was used as a control agent. The results of the antiviral activity testing showed that the curative activity EC50 values of L1 and L4 against TMV were 140.5 and 90.7 µg/mL, respectively, which were superior to that of NNM (148.3 µg/mL). The EC50 values of 154.1, 102.6 and 140.0 µg/mL for the anti-TMV protective activities of L1, L4 and L15 were superior to that of NNM (188.2 µg/mL). The mechanism of action between L4 and NNM and tobacco mosaic virus capsid protein (TMV-CP) was preliminarily investigated. The results of microscale thermophoresis (MST) experiments showed that L4 had a strong binding affinity for TMV-CP with a dissociation constant Kd value of 0.00149 µM, which was better than that of NNM (2.73016 µM). The results of molecular docking experiments showed that L4 formed shorter hydrogen bonds with amino acid residues of TMV-CP than NNM and formed more amino acid residues than NNM, which indicated that L4 was more tightly bound to TMV-CP. This study suggested that phenoxypyridine-containing chalcone derivatives can be used as new anti-TMV drugs through further research and development.

Design, synthesis, and biological evaluation of new biaryl derivatives of cycloalkyl diacetamide bearing chalcone moiety as type II c-MET kinase inhibitors.

Many human cancers have been associated with the deregulation of the mesenchymal-epithelial transition factor tyrosine kinase (MET) receptor, a promising drug target for anticancer drug discovery. Herein, we report the discovery of a novel structure of potent chalcone-based derivatives type II c-Met inhibitors which are comparable to Foretinib (IC50 = 14 nM) as a potent reference drug. Based on our design strategy, we also expected an anti-tubulin activity for the compounds. However, the weak inhibitory effects on microtubules were confirmed by cell cycle analyses implicated that the observed cytotoxicity against HeLa cells probably was not derived from tubulin inhibition. Compounds 14q and 14k with IC50 values of 24 nM and 45 nM, respectively, demonstrated favorable inhibition of MET kinase activity, and desirable bonding interactions in the ligand-MET enzyme complex stability in molecular docking studies.

Exploring chalcone-sulfonyl piperazine hybrids as anti-diabetes candidates: design, synthesis, biological evaluation, and molecular docking study.

To address the escalating rates of diabetes mellitus worldwide, there is a growing need for novel compounds. The demand for more affordable and efficient methods of managing diabetes is increasing due to the inevitable side effects associated with existing antidiabetic medications. In this present research, various chalcone-sulfonyl piperazine hybrid compounds (5a-k) were designed and synthesized to develop inhibitors against alpha-glucosidase and alpha-amylase. In addition, several spectroscopic methods, including FT-IR, 1H-NMR, 13C-NMR, and HRMS, were employed to confirm the exact structures of the synthesized derivatives. All synthesized compounds were evaluated for their ability to inhibit alpha-glucosidase and alpha-amylase in vitro using acarbose as the reference standard and they showed excellent to good inhibitory potentials. Compound 5k exhibited excellent inhibitory activity against alpha-glucosidase (IC50 = 0.31 ± 0.01 µM) and alpha-amylase (IC50 = 4.51 ± 1.15 µM), which is 27-fold more active against alpha-glucosidase and 7-fold more active against alpha-amylase compared to acarbose, which had IC50 values of 8.62 ± 1.66 µM for alpha-glucosidase and 30.97 ± 2.91 µM for alpha-amylase. It was discovered from the Lineweaver-Burk plot that 5k exhibited competitive inhibition against alpha-glucosidase. Furthermore, cytotoxicity screening assay results against human fibroblast HT1080 cells showed that all compounds had a good level of safety profile. To explore the binding interactions of the most potent compound (5k) with the active site of enzymes, molecular docking research was conducted, and the results obtained supported the experimental data.

A selective bis-thiophene chalcone-based spectrofluorimetric sensor for Fe3.

A highly selective bis thiophene-based chalcone as a chemosensor for detecting Fe3+ metal ions in DMF: H2O (9:1). This sensor was selective toward ferric ions over other metal ions with a detection limit in micromolar range.