Malathion detoxification by human hepatic carboxylesterases and its inhibition by isomalathion and other pesticides

The organophosphorothioate (OPT) pesticide malathion (MAL) in mammals is readily hydrolyzed by mammalian carboxylesterases (CE). The reaction competes with the CYP‐catalyzed formation of malaoxon (MOX), the toxic metabolite. Alterations or individual variations in CE activity may result in increased MOX formation, enhancing MAL toxicity. We have characterized the human hepatic CE activity in a panel of 18 human liver microsomes as well as the inhibitory effect of IsoMAL, a major impurity of MAL commercial formulations, parathion (PAR), chlorpyrifos (CPF), and chlorpyrifos‐oxon (CPFO). CE activity showed a low level of variation among individuals (4‐fold). The reaction consists of two different phases, differing in their affinity for MAL (K_m1 = 0.25–0.69 μM; K_m2 = 10.3–26.8 μM). The relatively low K_m1 values confirmed that human CE efficiently detoxify MAL. IsoMAL was shown to be a potent noncompetitive inhibitor of MAL detoxification (K_i = 0.6 μM), with a higher inhibitory potency than CPF and PAR (K_i = 7.5 μM and 50 μM, respectively). These two latter compounds very likely act as mixed inhibitors. CPFO showed the highest inhibitory potency toward CE‐mediated detoxification, being characterized by a K_i = 22 nM. The present results provide useful information for a better understanding of possible interactions between different OPTs and for assessing the potential cumulative risk for exposure to OPT mixtures. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:406–414, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20106     

Modulation of Anopheles gambiae Epsilon glutathione transferase activity by plant natural products in vitro

Elevated glutathione transferase (GST) E2 activity is associated with DDT resistance in the mosquito Anopheles gambiae. The search for chemomodulators that inhibit the function of AgGSTE2 would enhance the insecticidal activity of DDT. Therefore, we examined the interaction of novel natural plant products with heterologously expressed An. gambiae GSTE 2 in vitro. Five of the ten compounds, epiphyllocoumarin (Tral-1), knipholone anthrone, isofuranonaphthoquinones (Mr 13/2, Mr13/4) and the polyprenylated benzophenone (GG1) were shown to be potent inhibitors of AgGSTE2 with IC₅₀ values of 1.5 μM, 3.5 μM, 4 μM, 4.3 μM and 4.8 μM respectively. Non-competitive inhibition was obtained for Tral 1 and GG1 with regards to GSH (K_i of 0.24 μM and 0.14 μM respectively). Competitive inhibition for Tral1 was obtained with CDNB (K_i = 0.4 μM) whilst GG1 produced mixed type of inhibition. The K_i and K_i' for GSH for Tral-1 and GG1 were 0.2 μM and 0.1 μM respectively. These results suggest that the novel natural plant products, particularly Tral-1, represent potent AgGSTE2 in vitro inhibitors.     

Inhibitory Kinetics of Azachalcones and their Oximes on Mushroom Tyrosinase: A Facile Solid‐state Synthesis

A solid‐state‐based mechanochemical process was used to synthesize novel azachalcones and their oximes as tyrosinase inhibitors. Their inhibitory activities on mushroom tyrosinase using l ‐3,4‐dihydroxyphenylalanine as a substrate were investigated. Two of the novel oxime derivatives synthesized were seen to be more potent than the positive control, kojic acid. Both the compounds 1b and 2b inhibited the diphenolase activity of tyrosinase in a dose‐dependent manner with their IC₅₀ values of 15.3 and 12.7 μm , respectively. The kinetic analysis showed that their inhibition mechanism was reversible. Both the novel oxime compounds displayed competitive inhibition with their K_i values of 5.1 and 2.5 μm , respectively. This method minimizes waste disposal problems and provides a simple, efficient, and benign method for the synthesis of novel tyrosinase inhibitors for use as skin‐whitening agents or as anti‐browning food additives.     

Kinetics of phosphate absorption by mycorrhizal and non-mycorrhizal Scots pine seedlings

Kinetics of net phosphate (P_i) uptake was measured on intact ectomycorrhizal and non‐mycorrhizal Pinus sylvestris seedlings using a semihydroponic cultivation method. The depletion of P_i in a nutrient solution was assessed over a 160–0.2 μM P_i gradient. Growth of the pine seedlings was P limited and measurements were performed 7 and 9 weeks after inoculation. Three ectomycorrhizal fungi were studied: Paxillus involutus, Suillus bovinus and Thelephoraterrestris. P_i uptake was extremely fast in plants colonised by P. involutus. The P_i concentration dropped below 0.2 μM within 4–5 h. In plants colonised with S. bovinus this occurred in 5–6 h and in plants associated with T. terrestris 8 h were needed to run through the whole concentration range. Non‐mycorrhizal plants of similar size and nutrient status decreased P_i to a concentration between 1 and 2 μM in 18 h. Data were curve fitted to a two‐phase Michaelis‐Menten equation. The apparent kinetic constants, K_m and V_max, for the high affinity P_i uptake system of the pine roots could be estimated accurately. V_max of this system was up to 7 times higher in pines associated with P. involutus than in non‐mycorrhizal seedlings. The intact extraradical mycelium greatly increased the absorption surface area of the roots (V_max). Non‐mycorrhizal plants had a K_m between 7.8 and 16.4 μM P_i. Plants mycorrhizal with P. involutus had K_m values between 2.4 and 7.2, plants colonised with S. bovinus had a K_m between 5.1 and 12.3, and seedlings associated with T. terrestris had a K_m from 4.6 to 10.1 μM P_i. All 3 ectomycorrhizal fungi had a strong impact on the P_i absorption capacity of the pine seedlings. The results also demonstrated that there is substantial heterogeneity in kinetic parameters among the different mycorrhizal root systems.     

Properties of brain L-glutamate decarboxylase: inhibition studies

—l -Glutamate decarboxylase purified from mouse brain was found to be highly sensitive to the sulfhydryl reagents, 5,5-dithiobis (2-nitrobenzoic acid) (DTNB) and p-chloromerburibenzoate (PCMB), which were competitive inhibitors (K_i for DTNB is 1·1 · 10^?8m ). Iodoacetamide and iodoacetic acid were less effective inhibitors than DTNB and PCMB. The mercapto acids, 3-mercaptopropionic, 2-mercaptopropionic, and 2-mercaptoacetic acids were potent competitive inhibitors with K_i values of 1·8, 53 and 300 μm , respectively. 2-Mercaptoethanol was less effective. Aminooxyacetic acid was the most potent carbonyl-trapping reagent tested inhibiting the enzyme activity completely at 1·6 μm , followed by hydroxylamine, hydrazine, semicarbazide, and d -penicillamine. Carboxylic acids with a net negative charge were strong competitive inhibitors e.g. d -glutamate (K_i 0·9 mm ), α-ketoglutarate (K_i, l·2mm ), fumarate (K_i,1·8 mm ), dl -β-hydroxyglutamate (K_i, 2·8 mm ), l -aspartate (k_i, 3·1 mm ) and glutarate (K_i, 3·5 mm ). 2-Aminophosphonobutyric and 2-aminophosphonopropionic acids, phosphonic analogs of glutamate and aspartate, respectively, had no effect at l0mm . γ-Aminobutyric acid, l -glutamine, l -γ-methylene-glutamine, and α,γ-diaminoglutaric acid, amino acids with no net negative charge at neutral pH, had no effect at 5 mm . Glutaric and α-ketoglutaric acids were the most potent inhibitors among the various dicarboxylic and α-keto-dicarboxylic acids tested (K_i, 3·5 and 1·2 mm , respectively). Compounds with one carbon less, succinic and oxalacetic acids, or with one carbon more, adipic and α-ketoadipic acids, were less inhibitory. The monovalent cations, Li⁺, Na⁺, NH₄⁺, and Cs⁺ had no effect on l -glutamate decarboxylase activity in concentrations up to 10mm . Divalent cations, on the other hand, were very potent inhibitors. Among eleven divalent cations tested, Zn²⁺ was the most potent inhibitor, inhibiting to the extent of 50 per cent at 10μm . The decreasing order of inhibitory potency was: Zn²⁺ > Cd²⁺, Hg²⁺, Cu²⁺ > Ni²⁺ > Mn²⁺ Co²⁺ > Ba²⁺ > Ca²⁺ > Mg²⁺ > Sr⁺², The anions, I^?, Br^?, Cl^? and F^? were only weak inhibitors. The K_i value for Cl^? was 17mm . The above findings suggest minimally the presence of aldehyde, sulfhydryl and positively charged groups at or near the active site of the holoenzyme. Intermediates of glycolysis had little effect on l -glutamate decarboxylase activity, but intermediates of the tricarboxylic acid cycle, e.g. α-ketoglutarate (K_i= 1·2 mm ) and fumarate (K_i= 1·8 mm ) were relatively potent inhibitors. The nucleotides, ATP, ADP, AMP, cyclic AMP, GTP, GDP, GMP, and cyclic GMP were weak inhibitors. l -Norepinephrine (K_i= 1·3 mm ) and serotonin were potent inhibitors, while acetylcholine, dopamine and histamine were less effective. Ethanol and dioxane inhibited the enzyme activity to the extent of 20-50 per cent at 10 per cent (v/v), while slight activation was observed at low concentrations (0·1-1 per cent) of both solvents. The possible role of Zn²⁺ and some metabolites in the regulation of steady-state levels of γ-aminobutyric acid also was discussed.     

Kinetics of inhibition of Aeromonas aminopeptidase by leucine methyl ketone derivatives

A number of methyl ketones have been prepared from l-leucine and found to be competitive inhibitors of Aeromonas aminopeptidase. These inhibitors were leucine methyl ketone (K_i 18 μm), leucine chloromethyl ketone (K_i 0.67 μm), and leucine bromomethyl ketone (K_i 0.20 μm), and the corresponding succinimido derivative (K_i 170 μm), succinamic acid derivative (K_i 6.9 μm) and phthalimido derivative (K_i 140 μm). Reversible inhibition was observed for all of the inhibitors tested, indicating that the active site of this enzyme is not alkylated or acylated by the nucleophile-sensitive components of some of the inhibitors.The chloromethyl ketones derived from l-leucine and l-phenylalanine were found to have the same relative binding constants as the substrates, l-leucinamide and l-phenylalaninamide.     

Association of human serum paraoxonase‐1 with some respiratory drugs

In this study, we investigated the effects of certain respiratory drugs, which are mainly used on human serum paraoxonase‐1 (hPON1; EC 3.1.8.1). hPON1 was purified from human serum, with 354.91 fold and 45% yield by using two simple step procedures including, first, ammonium sulfate precipitation, then, Sepharose‐4B‐l ‐tyrosine‐1‐naphthylamine hydrophobic interaction chromatography. SDS‐polyacrylamide gel electrophoresis showed a single protein band belonging to hPON1 with 43 kDa. All the pharmaceutical compounds inhibited the PON1 enzyme highly at the micromolar level. The obtained IC₅₀ values for nine different pharmaceutics ranged from 0.219 μM (salbutamol sulfate) to 67.205 μM (montelukast sodium). So, all drugs could be considered as potent hPON1 inhibitors. K_i values and inhibition types were determined by Lineweaver‐Burk graphs. While varenicline tartrate and moxifloxacin hydrochloride inhibited the enzyme in a noncompetitive manner, others inhibited it in a mixed manner.     

Potent and Selective Monoamine Oxidase‐B Inhibitory Activity: Fluoro‐ vs. Trifluoromethyl‐4‐hydroxylated Chalcone Derivatives

For various neurodegenerative disorders like Alzheimer's and Parkinson’s diseases, selective and reversible MAO‐B inhibitors have a great therapeutic value. In our previous study, we have shown that a series of methoxylated chalcones with F functional group exhibited high binding affinity toward human monoamine oxidase‐B (hMAO‐B). In continuation of our earlier study and to extend the understanding of the structure–activity relationships, a series of five new chalcones were studied for their inhibition of hMAO. The results demonstrated that these compounds are reversible and selective hMAO‐B inhibitors with a competitive mode of inhibition. The most active compound, (2E)‐1‐(4‐hydroxyphenyl)‐3‐[4‐(trifluoromethyl)phenyl]prop‐2‐en‐1‐one, exhibited a K_i value of 0.33 ± 0.01 μm toward hMAO‐B with a selectivity index of 26.36. A molecular docking study revealed that the presence of a H‐bond network in hydroxylated chalcone with the N(5) atom of FAD is crucial for MAO‐B selectivity and potency.     

In Vitro Effects of Some Flavones on Human Pyruvate Kinase Isoenzyme M2

PKM2 is an important target for designing anticancer drug. Inhibitors and activators of this enzyme are suitable molecules for use in treating cancer. The aim of the present study was to investigate the effect of certain flavones on PKM2. Apigenin, wogonin, flavone, 3‐hydroxyflavone, 5‐hydroxyflavone, 6‐hydroxyflavone, and 7‐hydroxyflavone effectively inhibited PKM2, with IC₅₀ in the range of 0.99–2.120 μM. The kinetic study indicated that these compounds acted as noncompetitive with K_i values of 3.53–5.67 μM toward phosphoenolpyruvate. Scutellarin and tangeritin demonstrated strong activation effect with AC₅₀ values < 2 μM. Diosmetin, baicalin, baicalein, and luteolin showed an intermediate‐level activator effect. These results demonstrate that flavone and their analogs could serve as leading compounds to develop new potent and selective inhibitor and activator for PKM2.     

Two Novel Potent α‐Amylase Inhibitors from the Family of Acarviostatins Isolated from the Culture of Streptomyces coelicoflavus ZG0656

Two novel aminooligosaccharides were separated from the culture filtrate of Streptomyces coelicoflavus ZG0656. Their chemical structures were determined by acidic hydrolysis, electrospray‐ionization tandem mass spectrometry (ESI‐MS/MS), and NMR spectroscopy. The compounds were named acarviostatins III0(?1) and III23 according to the nomenclature of this group of metabolites. The two novel acarviostatins were both mixed noncompetitive inhibitors of porcine pancreatic α‐amylase (PPA). The inhibition constants (K_i) for acarviostatins III0(?1) and III23 were 0.009 and 0.026 μM , respectively, 151 and 52 times more potent than acarbose.     

Calmodulin Inhibitors from Aspergillus stromatoides

An organic extract was prepared from the culture medium and mycelia of the marine fungus Aspergillus stromatoides Raper & Fennell . The extract was fractionated via column chromatography, and the resulting fractions were tested for their abilities to quench the fluorescence of the calmodulin (CaM) biosensor hCaM M124C‐mBBr. From the active fraction, emodin ( 1 ) and ω‐hydroxyemodin ( 2 ) were isolated as CaM inhibitors. Anthraquinones 1 and 2 quenched the fluorescence of the hCaM M124C‐mBBr biosensor in a concentration‐dependent manner with K_d values of 0.33 and 0.76 μM , respectively. The results were compared with those of chlorpromazine (CPZ), a classical inhibitor of CaM, with a K_d value of 1.25 μM . Docking analysis revealed that 1 and 2 bind to the same pocket of CPZ. The CaM inhibitor properties of 1 and 2 were correlated with some of their reported biological properties. Citrinin ( 3 ), methyl 8‐hydroxy‐6‐methyl‐9‐oxo‐9H‐xanthene‐1‐carboxylate ( 4 ), and coniochaetone A ( 5 ) were also isolated in the present study. The X‐ray structure of 5 is reported for the first time.     

An Interactive SAR Approach to Discover Novel Hybrid Thieno Probes as Ligands for D2‐Like Receptors with Affinities in the Subnanomolar Range

A series of [(phenylpiperazinyl)alkyl]‐isoindole‐1,3‐dione derivatives was synthesized to serve as probes for dopaminergic receptors. Among this series, compound 6a showed the highest affinity towards D4 and D3 receptors with K_i values in the low nanomolar range, and D2/D4‐ and D2/D3‐selectivity indices of 72 and 20, respectively. Optimization rounds were adopted and led to the D4‐selective ligand thiophene‐2‐carboxamide 9a with a K_i(D4) value of 0.62 nM , and to its butyl analog, 10a , with K_i(D4) and K_i(D3) values of 0.03 and 0.26 nM , respectively. Docking experiments revealed the importance of the unique D4 residue Arg186 in manipulating the ligands' D4‐subtype‐receptor selectivity.     

Synthesis of sulfonamide-containing N-hydroxyindole-2-carboxylates as inhibitors of human lactate dehydrogenase-isoform 5

N-Hydroxyindole-2-carboxylates possessing sulfonamide-substituents at either position 5 or 6 were designed and synthesized. The inhibitory activities of these compounds against isoforms 1 and 5 of human lactate dehydrogenase were analysed, and K_i values of the most efficient inhibitors were determined by standard enzyme kinetic studies. Some of these compounds displayed state-of-the-art inhibitory potencies against isoform 5 (K_i values as low as 5.6 μM) and behaved as competitive inhibitors versus both the substrate and the cofactor.     

Phosphonate inhibitors of West Nile virus NS2B/NS3 protease

West Nile virus (WNV) is a member of the flavivirus genus belonging to the Flaviviridae family. The viral serine protease NS2B/NS3 has been considered an attractive target for the development of anti-WNV agents. Although several NS2B/NS3 protease inhibitors have been described so far, most of them are reversible inhibitors. Herein, we present a series of α-aminoalkylphosphonate diphenyl esters and their peptidyl derivatives as potent inhibitors of the NS2B/NS3 protease. The most potent inhibitor identified was Cbz-Lys-Arg-(4-GuPhe)^P(OPh)₂ displaying K_i and k₂/K_i values of 0.4 µM and 28 265 M^?1s^?1, respectively, with no significant inhibition of trypsin, cathepsin G, and HAT protease.     

Novel aromatase and 5α-reductase inhibitors

Inhibitors of aromatase and 5α-reductase may be of use for the therapy of postmenopausal breast cancer and benign prostatic hyperplasia, respectively. FCE 27993 is a novel steroidal irreversible aromatase inhibitor structurally related to exemestane (FCE 24304). The compound was found to be a very potent competitive inhibitor of human placental aromatase, with a K_i of 7.2 nM (4.3 nM for exemestane). In preincubation studies with placental aromatase FCE 27993, like exemestane, was found to cause time-dependent inhibition with a higher rate of inactivation ( ) and a similar K_i(inact) (56 vs 66 nM). The compound was found to have a very low binding affinity to the androgen receptor (RBA 0.09% of dihydrotestosterone) and, in contrast to exemestane, no androgenic activity up to 100 mg/kg/day s.c. in immature castrated rats. Among a series of novel 4-azasteroids with fluoro-substituted-17β-amidic side chains, three compounds, namely FCE 28260, FCE 28175 and FCE 27837, were identified as potent in vitro and in vivo inhibitors of prostatic 5α-reductase. Their IC₅₀ values were found to be 16, 38 and 51 nM for the inhibition of the human enzyme, and 15, 20 and 60 nM for the inhibition of the rat enzyme, respectively. When given orally for 7 days in castrated and testosterone (Silastic implants) supplemented rats, the new compounds were very effective in reducing prostate growth. At a dose of 0.3 mg/kg/day inhibitions of 42, 36 and 41% were caused by FCE 28260, FCE 28175 and FCE 27837, respectively.     

Kinetic Data on the Inhibition of High-affinity Choline Transport into Rat Forebrain Synaptosomes by Choline-like Compounds and Nitrogen Mustard Analogues

Abstract: A series of choline analogues and nitrogen mustard derivatives were evaluated as inhibitors of high-affinity transport of choline in rat forebrain synaptosomes. When synaptosomes were preincubated for 10 min with choline mustard aziridinium ion, monoethylcholine and monoethylcholine mustard aziridinium ion, the agents appeared to be equipotent as inhibitors of high-affinity uptake (K_i=2.63, 3.15 and 2.72 μm , respectively). Acetylcholine mustard aziridinium ion was less potent than these compounds (K_i= 27.8 μm ), but it was more potent than ethoxycholine and ethoxycholine mustard aziridinium ion (K_i= 500 and 403 μm ) as a blocker of choline transport. From study with these compounds it was concluded that the high-affinity choline transport mechanism shows specificity for hydroxylated compounds over those in which the same hydroxyl has been acetylated (10-fold) and that the carbonyl oxygen of the acetylated analogues is important, as its removal (to form the ethylether derivative) decreased affinity another 20-fold. The presence of an aziridinium ring on the quaternary nitrogen in place of two methyl groups did not affect the blocking of transport at 10 min of inhibitor preincubation and replacement of a methyl group on the nitrogen by an ethyl group did not alter affinity for the high-affinity carrier. The aziridinium ring on the nitrogen of the mustard analogues was important, however, in determining the extent of reversibility of the binding of these agents to the carrier protein. Choline transport was not restored by washing synaptosomes that were incubated with choline mustard aziridinium ion or monoethylcholine mustard aziridinium ion, but was readily obtained in washed synaptosomes preincubated with monoethylcholine, hemicholinium-3, or pyrrolcholine. The results indicate that the mustard analogues may be potent alkylators of the high-affinity choline carrier and thus, useful agents in monitoring acetylcholine turnover in systems where the carrier is blocked.     

A New Aromatic Amide from the Roots of Zanthoxylum tessmannii (Rutaceae)

Phytochemical investigation of the methanolic extract of the roots of Zanthoxylum tessmannii Zepernick and Timler (Rutaceae) led to the isolation and characterization of one new aromatic amide named tessmamide ( 1 ) along with twelve known compounds, N‐benzoyltyramine methyl ether ( 2 ), 7,8,9‐trimethoxycoumarin ( 3 ), 7,8‐dimethoxycoumarin ( 4 ), integrifoliodiol ( 5 ), robustin ( 6 ), skimmianine ( 7 ), lupeol ( 8 ), lupenone ( 9 ), a mixture of stigmasterol and β‐sitosterol, and a mixture of their glucosides. The structures of all compounds were determined by comprehensive spectroscopic analyses (1D‐ and 2D‐NMR, EI‐MS, and ESI‐MS) and comparison with known analogs. The determination of the radical scavenging activity using the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay gave moderate antioxidant values for the crude extracts of the roots of Zanthoxylum tessmannii (IC₅₀ 0.8 mg/mL), tessmamide ( 1 ; IC₅₀ 31.8 μm ), and 7,8,9‐trimethoxycoumarin ( 3 ; IC₅₀ 29.3 μm ), compared to the standard ascorbic acid (IC₅₀ 11.6 μm ).     

Purification, characterization and inhibition of sterol C24-methyltransferase from Candida albicans

Solubilized sterol C24-methyltransferase (24-SMT) was purified to homogeneity from a cell extract of the yeast Candida albicans (Ca) by anion exchange chromatography, gel permeation chromatography and fast performance liquid chromatography using a Mono Q column. The purified enzyme has an apparent molecular mass of 178 kDa on gel permeation chromatography and 43 kDa on SDS/PAGE, indicating that it is composed of four identical subunits. The substrate requirement of the native enzyme has an optimal specificity for zymosterol with associated kinetic constants of K_m 50 μM and k_cat of 0.01 s⁻¹. The product of the enzyme incubated with zymosterol was fecosterol. Inhibition of the catalyst was observed with substrate analogs designed as transition state analogs (25-azalanosterol, K_i = 54 nM and 24 (R,S),25-epiminolanosterol, K_i = 11 nM) or as mechanism-based inactivators (26,27-dehydrozymosterol, K_i 9 μM) and k_inact = 0.03 min⁻¹) of the C24-methylation reaction. Product analogs ergosterol and fecosterol, but neither cholesterol nor sitosterol, inhibited activity affording K_i values of 20 and 72 μM, respectively. Ammonium and thia analogs of the intermediates of the sterol C24-methyl reaction sequence were effective growth inhibitors exhibiting IC₅₀ values that ranged from 3 to 20 μM.     

Acetylcholinesterase Inhibitory Activity of Modified Lupane,Oleanane, and Ursane A-seco-Triterpenoids

A series of new lupane, ursane, and oleanane type triterpenic A-seco-derivatives containing bromo-, azido-, alkyne-, 1H-tetrazol-5-yl-, 5-methyloxazol-2-yl-, N-(4-(4-methylpiperazin-1-yl)but-2-yn-1-yl), and a carbonyl group at C2, C24, C28, C30 positions has been synthesized. The bioactivity was evaluated by Ellman's method, and the results showed that most of the compounds displayed moderate acetylcholinesterase inhibitory activities in vitro. Among them, A-seco-derivatives of 28-oxo-allobetuline and betulinic acid with bromo- and azido-groups exhibited the most potent inhibitory activity against AChE. Extra experiments showed methyl 2-cyano-3,4-seco-dibromo- and 2-cyano-3,4-seco-diazido-derivatives of betulinic acid as mixed-type inhibitors, with Ki values as low as K_i=0.18 μM and K_i=0.21 μM, respectively.     

Novel amides of 1,1‐bis‐(carboxymethylthio)‐1‐arylethanes: Synthesis,characterization, acetylcholinesterase,butyrylcholinesterase, and carbonic anhydrase inhibitory properties

The thiolation reaction was carried out in a benzene solution at 80°C and p‐substituted ketones and mercaptoacetic acid in a molar ratio (1:4) of in the presence of a catalytic amount of toluene sulfonic acids. The enzyme inhibition activities of the novel amides of 1,1‐bis‐(carboxymethylthio)‐1‐arylethanes derivatives were investigated. These novel amides of 1,1‐bis‐(carboxymethylthio)‐1‐arylethanes derivatives showed good inhibitory action against acetylcholinesterase (AChE) butyrylcholinesterase (BChE), and human carbonic anhydrase I and II isoforms (hCA I and II). AChE inhibitors, interacting with the enzyme as their primary target, are applied as relevant drugs and toxins. Many clinically established drugs are carbonic anhydrase inhibitors, and it is highly anticipated that many more will eventually find their way into the market. The novel synthesized compounds inhibited AChE and BChE with K_i values in the range of 0.64–1.47 nM and 9.11–48.12 nM, respectively. On the other hand, hCA I and II were effectively inhibited by these compounds, with K_i values between 63.27–132.34 and of 29.63–127.31 nM, respectively.