Competitive Inhibitor Of Type Research Articles

Design, synthesis, biological evaluation, kinetic studies and molecular modeling of imidazo-isoxazole derivatives targeting both α-amylase and α-glucosidase inhibitors

Herein, a novel set of imidazo-isoxazole derivatives containing thiourea and urea scaffolds were synthesized, characterized (1H NMR, 13C NMR, and elemental analysis). These compounds were biologically evaluated for their α-amylase and α-glucosidase inhibitory activity, identifying 5f as the most active (IC50 26.67 ± 1.25 μM and 39.12 ± 1.83 μM against α-amylase α-glucosidase, respectively), better than the standard, acarbose. Enzymatic kinetic results showed that 5f and acarbose complete competitive type inhibitors. The structure-activity relationship (SAR) demonstrated that undergoing substitutions on R1 and R2 groups attached to the thiourea/urea moiety chains controlled the activity. Besides, in-silico ADMET study showed that almost title compounds exhibited satisfactory pharmacokinetic properties. In molecular docking study, the top performing compound (5f) exhibited higher binding energies (−5.501 and −6.414 kcal/mol, respectively) showing crucial interactions and that snuggly fit in their active site. To shed light on their mechanism of action, molecular dynamic (MD) simulations approach executed at 100 ns duration authenticated the high stability of 5f-1B2Y and 5f-3A4A complexes. The results of this investigation disclosed that compound 5f may serve as a potential lead, accomplished with in vivo studies, for the management of diabetes.

Stereo- and Regio-selective benzo- and Benzohalo-conduritols: Anti-diabetes &anti-tumor activity investigation, kinetic and molecular docking studies

In this study, benzoconduritols, benzohalogenoconduritol, and benzodihalogenoconduritols with conduritol-A and –C structures from oxo-norbornene derivative endo-10 b, exo-11 b cleavaged by Lewis acids (BBr3, BCl3, BF3· OEt2) and Ac2O/H2SO4 were defined. These compounds (10a, 24, 25, 26, 27, 28, 29, 34, and 35) have been evaluated for their potential to inhibit the α-glucosidase enzyme against acarbose-positive control. Among the compounds, halogen-substituted compounds 24, 25, 27, and 34 showed potent inhibition of the α-glucosidase enzyme compared with acarbose, while other compounds showed moderate inhibition. The kinetic studies of the most active compounds 24, 25, 27, and 34 were evaluated, then determined that they were mixed, non-competitive, and competitive type inhibitors. In addition, the in vitro cytotoxicity activities of these compounds were tested against human breast (BT-20), melanoma (SK-MEL128), prostate (DU-145), liver (SNU-398), lung (A549) cancer, and normal human fibroblast (HFC) cell lines. Among these compounds, the dichloro-substituted compound 25 showed the highest cytotoxic effect in the range of CC50 = 11.5–31.6 μg/mL against SNU-398, DU-145, SK-MEL128, A549, and HFC cell lines. The experimentally determined α-glucosidase and anticancer activity were studied by docking studies to demonstrate the binding orientation and interaction of the synthesized compound with amino acid residues present in the active site of human Maltase–Glucoamylase, topoisomerase II alpha, and Anaplastic Lymphoma Kinase enzymes.

Inhibition of plant essential oils and their interaction in binary combinations against tyrosinase.

Essential oils (EOs), derived from aromatic plants, exhibit properties beneficial to health, such as anti-inflammatory, anti-oxidative, antidiabetic, and antiaging effects. However, the effect of EOs and their interaction in binary combinations against tyrosinase is not yet known. To evaluate the underlying mechanisms of EOs and their interaction in binary combinations against tyrosinas. We explored to investigate the inhibitory effect of 65 EOs and the interaction among cinnamon, bay, and magnolia officinalis in their binary combinations against tyrosinase. In addition, the main constituents of cinnamon, bay, and magnolia officinalis were analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that the most potent EOs against tyrosinase were cinnamon, bay, and magnolia officinalis with IC50 values of 25.7, 30.8, and 61.9 μg/mL, respectively. Moreover, the inhibitory mechanism and kinetics studies revealed that cinnamon and bay were reversible and competitive-type inhibitors, and magnolia officinalis was a reversible and mixed-type inhibitor. In addition, these results, assessed in mixtures of three binary combinations, indicated that the combination of cinnamon with bay at different dose and at dose ratio had a strong antagonistic effect against tyrosinase. Magnolia officinalis combined with cinnamon or bay experienced both antagonistic and synergistic effect in anti-tyrosinase activity. It is revealed that natural EOs would be promising to be effective anti-tyrosinase agents, and binary combinations of cinnamon, bay, and magnolia officinalis might not have synergistic effects on tyrosinase under certain condition.

A new series of chrysin derivatives as potent non-saccharide ⍺-glucosidase inhibitors

Twenty-three chrysin derivatives were designed and synthesized by alkylation and bromination reactions. Their structures were confirmed by NMR and mass spectrometry, and their in vitro ⍺-glucosidase (AG) inhibitory activity was investigated. Chrysin derivatives except for 3a, 3b, 2q, and 2r, revealed better activity than the reference acarbose with moderate to very strong inhibition against AG. Notably, 2f, 2j, and 4 showed very strong and strong effects on AG ⍺-glucosidase inhibitory activity with IC50 values of 0.08, 3.47, and 2.97 μM, respectively. Simultaneously, enzyme kinetics study indicated that 2f was a competitive-type inhibitor, while 2j and 4 were mixed-type inhibitors.

Design, synthesis, and in silico studies of quinoline-based-benzo[d]imidazole bearing different acetamide derivatives as potent α-glucosidase inhibitors

In this study, 18 novel quinoline-based-benzo[d]imidazole derivatives were synthesized and screened for their α-glucosidase inhibitory potential. All compounds in the series except 9q showed a significant α-glucosidase inhibition with IC50 values in the range of 3.2 ± 0.3–185.0 ± 0.3 µM, as compared to the standard drug acarbose (IC50 = 750.0 ± 5.0 µM). A kinetic study indicated that compound 9d as the most potent derivative against α-glucosidase was a competitive type inhibitor. Furthermore, the molecular docking study revealed the effective binding interactions of 9d with the active site of the α-glucosidase enzyme. The results indicate that the designed compounds have the potential to be further studied as new anti-diabetic agents.

The novel homologue of the human α-glucosidase inhibited by the non-germinated and germinated quinoa protein hydrolysates after in vitro gastrointestinal digestion.

Quinoa (Chenopodium quinoa Willd) is a potential source of protein with ideal amino acid profiles which its bioactive compounds can be improved during germination and gastrointestinal digestion. The present investigation studies the impact of germination for 24hr and simulated gastrointestinal digestion on α-glucosidase inhibitory activity of the quinoa protein and bioactive peptides against the novel homologue of human α-glucosidase, PersiAlpha-GL1. The sprouted quinoa after gastroduodenal digestion was the most effective α-glucosidase inhibitor showing 81.10% α-glucosidase inhibition at concentration 4mg/ml with the half inhibition rate (IC50 ) of 0.07mg/ml. Based on the kinetic analysis, both the germinated and non-germinated samples before and after digestion were competitive-type inhibitors of α-glucosidase. Results of this study showed the improved α-glucosidase inhibitory activity of the quinoa bioactive peptides after germination and gastrointestinal digestion and highlighted the potential of metagenome-derived PersiAlpha-GL1 as a novel homologue of the human α-glucosidase for developing the future anti-diabetic drugs. PRACTICAL APPLICATIONS: This study aimed to evaluate the effect of germination and gastrointestinal digestion of the quinoa protein and bioactive peptides on α-glucosidase inhibitory activity against the novel PersiAlpha-GL1. Metagenomic data were used to identify the novel α-glucosidase structurally and functionally homologue of human intestinal. The results showed the highest inhibition on PersiAlpha-GL1 by a germinated quinoa after gastroduodenal digestion and confirmed the potential of PersiAlpha-GL1 to enhance theeffectivenessof the anti-diabetic drugs for industrial application.

In Vitro Pancreatic Lipase Inhibition by Marine Fungi Purpureocillium lilacinum Associated with Stylissa sp. Sponge as Anti-obesity Agent

This study aimed to evaluate the potential of marine fungus Purpureocillium lilacinum isolated from an Indonesian marine sponge Stylissa sp. as an anti-obesity agent through pancreatic lipase inhibition assay. The fungus was identified as P. lilacinum through morphological and molecular characteristics. The fungal extract’s inhibition activity and kinetics were evaluated using spectrophotometry and Lineweaver-Burk plots. Ethyl acetate and butanol were used for extraction. Both extracts showed pancreatic lipase inhibition in a concentration-dependent manner. Both crude extracts were then fractionated once. All fractionated extracts showed inhibitory activity above 50%, with the highest activity found in fraction 5 of ethyl acetate at 93.41% inhibition. The best fractionated extract had an IC50value of 220.60 µg.mL-1. The most active fraction of P. lilacinum had a competitive-type inhibitor behavior as shown by the value of Vmax not significantly changing from 388.80 to 382.62 mM pNP.min-1, and the Michaelis-Menten constant (KM) increased from 2.02 to 5.47 mM in the presence of 500 µg.mL-1 fractionated extract. Metabolite identification with LC-MS/MS QTOF suggested that galangin, kaempferol, and quercetin were responsible for the observed lipase inhibition.

Alpha-glucosidase inhibitors from Nervilia concolor, Tecoma stans, and Bouea macrophylla

Tecoma stans (L.) Juss. Ex Kunth is widely used in folk medicine. In ethnomedicine, it is applied as a cardioprotective, hepatoprotective, antiarthritic, antinociceptive, anti-inflammatory, and antimicrobial. The aqueous extract is considered antidiabetic, and is used as a traditional remedy in Mexico. More than 120 chemical constituents have been identified in its leaves, barks, and roots. However, less is known about the phytochemical properties of T. stans flower extracts. The herbal plant Nervilia concolor (Blume) Schltr. is native to Vietnam, and is used in traditional Chinese medicine to treat diseases such as bronchitis, stomatitis, acute pneumonia, and laryngitis. Only two previous reports have addressed the chemical content of this plant. Bouea macrophylla Griff., commonly known as marian plum or plum mango, is a tropical plant that is used to treat a range of illnesses. Phytochemical analysis of B. macrophylla suggests the presence of volatile components and flavonoids. However, existing data have been obtained from screening without isolation. As part of our ongoing search for alpha-glucosidase inhibitors from Vietnamese medicinal plants, we conducted bioactive-guided isolation of the whole plant N. concolor, the flowers of T. stans, and the leaves of B. macrophylla. We isolated and structurally elucidated five known compounds from T. stans: ursolic acid (TS1), 3-oxours-12-en-28-oic acid (TS2), chrysoeriol (TS3), ferulic acid (TS4), and tecomine (TS5). Three known compounds were isolated from Nervilia concolor: astragalin (NC1), isoquercitrin (NC2), and caffeic acid (NC3). From B. macrophylla, betullinic acid (BM1), methyl gallate (BM2), and 3-O-galloyl gallic acid methyl ester (BM3) were isolated. All compounds showed promising alpha-glucosidase inhibition, with IC50 values ranging from 1.4 to 143.3 µM. The kinetics of enzyme inhibition showed BM3 to be a competitive-type inhibitor. An in silico molecular docking model confirmed that compounds NC1, NC2, and BM3 were potential inhibitors of the α-glucosidase enzyme. Molecular dynamics simulations were carried out with compound BM3 demonstrating the best docking model during simulation up to 100 ns to explore the stability of the complex ligand–protein.

Antimelanogenesis Effects of Leaf Extract and Phytochemicals from Ceylon Olive (Elaeocarpus serratus) in Zebrafish Model.

The melanogenesis inhibition effect in zebrafish (Danio rerio) and antityrosinase activity of the ethanolic extract and its phytochemicals from Ceylon olive (Elaeocarpus serratus Linn.) leaves were investigated in this study. Among the leaf extract and four soluble fractions, the ethyl acetate soluble fraction exhibits the best antityrosinase and antimelanogenesis activities. One phenolic acid, gallic acid, and two flavonoids, myricetin and mearnsetin, are isolated from the active subfractions through the bioassay-guided isolation; their structures are elucidated based on the 1D and 2D NMR, FTIR, UV, and MS spectroscopic analyses. These compounds have significant antityrosinase activity whether using l-tyrosine or l-DOPA as the substrate; mearnsetin shows the optimal activity. In the enzyme kinetic investigation, both gallic acid and mearnsetin are the competitive-type inhibitors against mushroom tyrosinase, and myricetin acts as a mixed-type tyrosinase inhibitor. Leaf extract and an ethyl acetate soluble fraction show effective performance in the inhibition of melanin formation in zebrafish embryos. Mearnsetin also possesses a promising antimelanogenesis effect, which is superior to the positive control, arbutin. Results reveal that the Ceylon olive leaf extract and its phytochemicals, especially mearnsetin, have the potential to be used as antimelanogenesis and skin-whitening ingredients.

Design, synthesis and biological evaluation of novel FXIa inhibitors with 2-phenyl-1H-imidazole-5-carboxamide moiety as P1 fragment.

Factor XIa, as a blood coagulation enzyme, amplifies the generation of the last enzyme thrombin in the blood coagulation cascade. It was proved that direct inhibition of factor XIa could reduce pathologic thrombus formation without an enhanced risk of bleeding. WSJ-557, a nonpurine imidazole-based xanthine oxidase inhibitor in our previous reports, could delay blood coagulation during its animal experiments, which prompted us to investigate its action mechanism. Subsequently, during the exploration of the action mechanism, it was found that WSJ-557 exhibited weak invitro factor XIa binding affinity. Under the guide of molecular modeling, we adopted molecular hybridization strategy to develop novel factor XIa inhibitors with WSJ-557 as an initial compound. This led to the identification of the most potent compound 44g with a Ki value of 0.009μM, which was close to that of BMS-724296 (Ki=0.0015μM). Additionally, serine protease selectivity study indicated that compound 44g display a desired selectivity, more 400-fold than those of thrombin, factor VIIa and factor Xa in coagulation cascade. Moreover, enzyme kinetics studies suggested that the representative compound 44g acted as a competitive-type inhibitor for FXIa, and molecular modeling revealed that it could tightly bind to the S1, S1' and S2' pockets of factor XIa. Furthermore, invivo efficacy in the rabbit arteriovenous shunt model suggested that compound 44g demonstrated dose-dependent antithrombotic efficacy. Therefore, these results supported that compound 44g could be a potential and efficacious agent for the treatment of thrombotic diseases.

Removal pattern of vinasse phenolics by Phlebia rufa, characterization of an induced laccase and inhibition kinetics modeling.

Vinasse from the distillation of winemaking residues is a wastewater characterized by high levels of aromatic compounds. Batch cultures of Phlebia rufa showed a significant (p < 0.05) correlation between laccase activity and initial vinasse concentration. The pattern of biodegradation of hydroxybenzoic acids, hydroxycinnamic acids and flavonoids, assessed by HPLC-DAD, revealed that p-hydroxybenzoic acid is the most recalcitrant compound. Vinasse-induced laccase showed electrophoretic homogeneity and molecular weight of 62 kDa after being purified 21-fold. Optimum pH for oxidation of 2,6-dimethoxyphenol (2,6-DMP) was 3.5 and optimum temperature was 50 °C, with an activation energy of 42.8 kJ mol-1. Catalytic efficiency of 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) oxidation is about two orders of magnitude higher than 2,6-DMP oxidation, being their Km values 36.2 ± 2.6 μM and 303.0 ± 44.7 μM, respectively and kcat values 486.1 s-1 and 179.6 s-1, respectively. Akaike information criterion and Akaike weights were used to discriminate inhibition models that best fitted 2,6-DMP oxidation in the presence of inhibitors. Inhibition constants of mixed-type inhibitors azide and fluoride, and competitive-type inhibitor chloride, showed the following inhibitors potency: azide > fluoride > chloride. Taken together, this study is consistent with the assumption that P. rufa could be a useful tool for aerobic degradation of phenolic-rich wastewaters.

Natural soluble epoxide hydrolase inhibitors from Inula helenium and their interactions with soluble epoxide hydrolase

The inhibition of soluble epoxide hydrolase (sEH) is regarded as a promising therapeutic approach to treat inflammation and its related disorders. In present work, we investigated inhibitory effects of forty-nine kinds of traditional Chinese medicines against sEH. Inula helenium showed significant inhibitory effect against sEH, and the extract of I. helenium was isolated to obtain eight compounds, including 4H-tomentosin (1), xanthalongin (2), linoleic acid (3), 8-hydroxy-9-isobutyryloxy-10(2)-methylbutyrylthymol (4), dehydrocostus lactone (5), alantolactone (6), costunolide (7), and isoalantolactone (8). Among them, 4H-tomentosin (1), xanthalongin (2), and linoleic acid (3) showed significantly inhibitory activities on sEH with half maximal inhibitory concentration (IC50) from 5.88 ± 0.97 μM to 11.63 ± 0.58 μM. The inhibition kinetics suggested that 4H-tomentosin (1) and xanthalongin (2) were mixed-competitive type inhibitors with inhibition constants (Ki) of 7.02 and 6.57 μM, respectively, and linoleic acid (3) was a competitive type inhibitor with a Ki values of 3.52 μM. The potential interactions of 4H-tomentosin (1), xanthalongin (2), and linoleic acid (3) with sEH were analyzed by molecular docking, which indicated that these bioactive compounds had interactions with key amino acid residues Tyr343, Ile363, Tyr383, and His524.

Thiazolidin-2-cyanamides derivatives as novel potent Escherichia coli β-glucuronidase inhibitors and their structure–inhibitory activity relationships

Gut microbial β-glucuronidases have the ability to deconjugate glucuronides of some drugs, thus have been considered as an important drug target to alleviate the drug metabolites-induced gastrointestinal toxicity. In this study, thiazolidin-2-cyanamide derivatives containing 5-phenyl-2-furan moiety (1–13) were evaluated for inhibitory activity against Escherichia coli β-glucuronidase (EcGUS). All of them showed more potent inhibition than a commonly used positive control, d-saccharic acid 1,4-lactone, with the IC50 values ranging from 1.2 µM to 23.1 µM. Inhibition kinetics studies indicated that compound 1–3 were competitive type inhibitors for EcGUS. Molecular docking studies were performed and predicted the potential molecular determinants for their potent inhibitory effects towards EcGUS. Structure–inhibitory activity relationship study revealed that chloro substitution on the phenyl moiety was essential for EcGUS inhibition, which would help researchers to design and develop more effective thiazolidin-2-cyanamide type inhibitors against EcGUS.

Computational insights into β-site amyloid precursor protein enzyme 1 (BACE1) inhibition by tanshinones and salvianolic acids from Salvia miltiorrhiza via molecular docking simulations

The rhizome of Salvia miltiorrhiza has emerged as a rich source of natural therapeutic agents, and its several compounds are supposed to exhibit favorable effects on Alzheimer’s disease (AD). The present work investigate the anti-AD potentials of 12 tanshinones, three salvianolic acids and three caffeic acid derivatives from S. miltiorrhiza via the inhibition of β-site amyloid precursor protein cleaving enzyme 1 (BACE1). Among the tested compounds, deoxyneocryptotanshinone (1), salvianolic acid A (13) and salvianolic acid C (15) displayed good inhibitory effect on BACE1 with IC50 values of 11.53 ± 1.13, 13.01 ± 0.32 and 9.18 ± 0.03 μM, respectively. Besides this, enzyme kinetic analysis on BACE1 revealed 13, a competitive type inhibitor while 1 and 15 showed mixed-type inhibition. Furthermore, molecular docking simulation displayed negative binding energies (AutoDock 4.2.6 = −10.0 to −7.1 kcal/mol) of 1, 13, and 15 for BACE1, indicating these compounds bound tightly to the active site of the enzyme with low energy and high affinity. The results of the present study clearly demonstrate that S. miltiorrhiza and its constituents have potential anti-AD activity and can be used as a therapeutic agent for the treatment of AD.

Dihydroxanthyletin-type coumarins from Angelica decursiva that inhibits the formation of advanced glycation end products and human recombinant aldose reductase.

The formation of advanced glycation end-products (AGE) and aldose reductase activity have been implicated in the development of diabetic complications. The present study was aimed to evaluate human recombinant aldose reductase (HRAR) and AGE inhibitory activity of seven natural dihydroxanthyletin-type coumarins, 4-hydroxy Pd-C-III (1), 4'-methoxy Pd-C-I (2), Pd-C-I (3), Pd-C-II (4), Pd-C-III (5), decursidin (6), and (+)-trans-decursidinol (7) from Angelica decursiva. Coumarins 1-7 showed potent HRAR and AGE inhibitory activities with ranges of IC50 values of 1.03-21.31 and 0.41-5.56µM, respectively. In the kinetic study for HRAR enzyme inhibition, coumarins 1, 3, 4, and 7 were competitive-type inhibitors, 6 was a mixed-type inhibitor, whereas 2 and 5 were noncompetitive-type inhibitors. Furthermore, we also predicted the docking interactions of HRAR with coumarins 1-7 using AutoDock Vina, and as a result, the simulated enzyme-inhibitor complexes exhibited negative binding energies (Autodock Vina=-9.6 to -8.1kcal/mol for HRAR), indicating a high affinity and tight binding capacity for the HRAR active site. Our results clearly indicate the potential HRAR and AGE formation inhibitory activities of dihydroxanthyletin-type coumarins, which could be further explored to develop therapeutic modalities for the treatment of diabetes and related complications.

Further insight into the pH effect on the catalysis of mushroom tyrosinase

The pH has a great physiological effect on the catalysis of tyrosinase because protons can act as competitive-type inhibitors. In this work, a reaction mechanism is proposed whereby only the protonation of the free forms Em (met-tyrosinase) and Eox (oxy-tyrosinase) has a significant kinetic effect. The pKa value calculated for tyrosinase is 4.63±0.04. This pKa value could correspond to a residue that acts as a gatekeeper of the active site, controlling the access of the substrate depending on its protonation state. Regarding the location and the nature of the responsible residue, we propose that glutamic acid E322 could be a key residue in the pH effect on the enzyme activity. Moreover, the substrate nature has a large effect on the kinetic behavior as a function of pH, depending on the pKa values of the phenolic hydroxyl groups and, to a lesser extent, on the charge of the R group. The sigmoid behavior of the initial rate vs. pH due to the pKa of the enzyme in the pH range studied could change to a bell-shaped behavior when the pKa values of the hydroxyl groups are low enough, and the R group is negatively charged. These aspects are interesting for controlling food browning and understanding the relationship melanosome pH plays in human skin pigmentation.

FYX-051: A Novel and Potent Hybrid-Type Inhibitor of Xanthine Oxidoreductase

4-[5-(Pyridin-4-yl)-1H-1,2,4-triazol-3-yl]pyridine-2-carbonitrile (FYX-051) is a potent inhibitor of bovine milk xanthine oxidoreductase (XOR). Steady-state kinetics study showed that it initially behaved as a competitive-type inhibitor with a K(i) value of 5.7 × 10(-9) M, then after a few minutes it formed a tight complex with XOR via a Mo-oxygen-carbon atom covalent linkage, as reported previously (Proc Natl Acad Sci USA 101:7931-7936, 2004). Thus, FYX-051 is a hybrid-type inhibitor exhibiting both structure- and mechanism-based inhibition. The FYX-051-XOR complex decomposed with a half-life of 20.4 h, but the enzyme activity did not fully recover. This was found to be caused by XOR-mediated conversion of FYX-051 to 4-[5-(2-hydroxypyridin-4-yl)-1H-1,2,4-triazol-3-yl]pyridine-2-carbonitrile (2-hydroxy-FYX-051), as well as formation of 6-hydroxy-4-[5-(2-hydroxypyridin-4-yl)-1H-1,2,4-triazol-3-yl]pyridine-2-carbonitrile (dihydroxy-FYX-051) and 4-[5-(2,6-dihydroxypyridin-4-yl)-1H-1,2,4-triazol-3-yl]-6-hydroxypyridine-2-carbonitrile (trihydroxy-FYX-051) during prolonged incubation for up to 72 h. A distinct charge-transfer band was observed concomitantly with the formation of the trihydroxy-FYX-051-XOR complex. Crystallographic analysis of the charge-transfer complex indicated that a Mo-nitrogen-carbon bond was formed between molybdenum of XOR and the nitrile group of trihydroxy-FYX-051. FYX-051 showed a potent and long-lasting hypouricemic effect in a rat model of potassium oxonate-induced hyperuricemia, and it seems to be a promising candidate for the clinical treatment of hyperuricemia.

Understanding the Key Factors that Control the Inhibition of Type II Dehydroquinase by (2R)‐2‐Benzyl‐3‐dehydroquinic Acids

The binding mode of several substrate analogues, (2R)-2-benzyl-3-dehydroquinic acids 4, which are potent reversible competitive inhibitors of type II dehydroquinase (DHQ2), the third enzyme of the shikimic acid pathway, has been investigated by structural and computational studies. The crystal structures of Mycobacterium tuberculosis and Helicobacter pylori DHQ2 in complex with one of the most potent inhibitor, p-methoxybenzyl derivative 4 a, have been solved at 2.40 Å and 2.75 Å, respectively. This has allowed the resolution of the M. tuberculosis DHQ2 loop containing residues 20-25 for the first time. These structures show the key interactions of the aromatic ring in the active site of both enzymes and additionally reveal an important change in the conformation and flexibility of the loop that closes over substrate binding. The loop conformation and the binding mode of compounds 4 b-d has been also studied by molecular dynamics simulations, which suggest that the benzyl group of inhibitors 4 prevent appropriate orientation of the catalytic tyrosine of the loop for proton abstraction and disrupts its basicity.

2‐Substituted‐3‐Dehydroquinic Acids as Potent Competitive Inhibitors of Type II Dehydroquinase

Potential antibiotics: The substitution of either the pro-R or pro-S hydrogen of the 3-dehydroquinic acid, the natural substrate of type II dehydroquinase, by a group (R) that is able to interact with the base responsible for enzymatic catalysis, tyrosine, is used as a strategy for the development of reversible competitive inhibitors of this enzyme. Synthesised compounds were also subjected to molecular modelling studies to investigate their binding mode.

Discovery of 4-functionalized phenyl -O-β- d-glycosides as a new class of mushroom tyrosinase inhibitors

A series of 4-functionalized phenyl -O-β- d-glycosides were designed, synthesized and evaluated as a new class of mushroom tyrosinase inhibitors. The results demonstrated that compounds 6a– 13a bearing a thiosemicarbazide moiety exhibited potent activities with IC 50 values range from 0.31 to 52.8 μM. Particularly, compound 9a containing acetylated glucose moiety was found to be the most active molecule with an IC 50 value of 0.31 μM. SARs analysis suggested that (1) the thiosemicarbazide moiety remarkably contributed to the increase of inhibitory effects on tyrosinase; (2) the configuration and bond type of sugar moiety also played a very important role in determining their inhibitory activities. The inhibition kinetics and inhibition mechanism study revealed that compound 9a was reversible and competitive type inhibitor, whereas compound 13a was reversible and competitive–uncompetitive mixed-II type inhibitor.