In vitro inhibition of salicylic acid derivatives on human cytosolic carbonic anhydrase isozymes I and II

Synthesis of 4-sulfamoyl phenyl diazocarboxylic acid derivatives as novel non-classical inhibitors of human carbonic anhydrase II activity: an in vitro study

The first class of carbonic anhydrase inhibitors (CAIs) discovered was sulfonamides, but their clinical use is limited due to side effects caused by their inhibition of multiple CA isoforms. To overcome this, researchers have focused on developing isoform-selective CAIs. This study involved the synthesis and characterization of novel carboxylic acid/sulfonamide derivatives. We investigated the interaction between these compounds and the human carbonic anhydrase II (hCA II) isoform using spectroscopic and computational methods. The synthesized compounds were evaluated based on their IC50, Kd and Ki values, and it was found that the inhibitory potency and binding affinity of the compounds increased with the number of carboxylic acids zinc binding groups. Specifically, the compound C4, with three carboxylic acid groups, showed the strongest inhibitory potency. Fluorescence measurements revealed that all compounds quenched the intrinsic fluorescence of hCA II through a dynamic quenching process, and each compound had one binding site in the hCA II structure. Thermodynamic analysis indicated hydrogen bonds and van der Waals interactions played key roles in the binding of these compounds to hCA II. Docking studies showed that the carboxylic acid groups directly attached to the zinc ion in the active site, displacing water/hydroxide ions and causing steric hindrance. Overall, the strengthening of inhibitory activity and the binding power of these carboxylic acid derivatives for the hCA II makes these compounds interesting for designing novel hCA II inhibitors.Communicated by Ramaswamy H. Sarma.

Enzyme inhibitory potential of some indole Schiff bases on acetylcholinesterase and human carbonic anhydrase isoforms I and II enzymes: an in vitro and molecular docking study

In this study, the in vitro effects of some indole Schiff bases on acetylcholinesterase and human carbonic anhydrase isoforms I and II were investigated. A series of N-methylindole hydrazide/hydrazone derivatives (1a-1t) were tested on these enzymes. The interactions of the synthesized indole derivatives with target enzymes were studied by molecular docking methodology. The results revealed that indole derivative Schiff base compounds inhibited the enzymes significantly. Ki values for hCAI isoenzyme were determined to be in the range of 36.18 ± 3.07-224.29 ± 5.78 nM; for the hCAII isoenzyme in the range of 31.30 ± 2.63-201.64 ± 7.25 nM; for acetylcholinesterase in the range of 6.82 ± 0.72-110.30 ± 9.26 nM. Compared to the control compound Acetazolamide (AZA), 1k and 1p were found to have the best inhibitory effect for hCAI; 1p was found to be the best inhibitory effect for hCAII. Compared to the control compound Tacrine (TAC), 1s showed the best inhibitory effect for AChE. In vitro results were verified with the results obtained by docking studies and interactions with enzymes were demonstrated.Communicated by Ramaswamy H. Sarma.

Upconverting Nanoparticle-Based Photoactive Probes for Highly Efficient Labeling and Isolation of Target Proteins

Photoaffinity labeling (PAL) has blossomed into a powerful and versatile tool for capture and identification of biomolecular targets. However, low labeling efficiency for specific targets such as lectins, the tedious process for protein purification, inevitable cellular photodamage, and less tissue penetration of UV light are significant challenges. Herein, we reported a near-infrared (NIR) light-driven photoaffinity labeling approach using upconverting nanoparticle (UCNP)-based photoactive probes, which were constructed by assembling photoactive groups and ligands onto NaYF4:Yb,Tm nanoparticles. The novel probes were easily prepared and functionalized, and the labeled proteins can be isolated and purified through simple centrifugation and washing. The advantages of this approach were demonstrated by labeling and isolation of peanut agglutinin (PNA), asialoglycoprotein receptor (ASGPR), and human carbonic anhydrase II (hCAII) from mixed proteins or cell lysates with good selectivity and efficiency, especially for PNA and ASGPR, two lectins that showed low binding affinity to their ligands. More importantly, successful labeling of PNA through pork tissues and ASGPR in mice strongly proved the good tissue penetrating capacity of NIR light and the application potential of UCNP-based photoactive probes for protein labeling in vivo. Biosafety of this approach was experimentally validated by enzyme, cell, and animal work, and we demonstrated that NIR light caused minimal photodamage to enzyme activity compared to UV light, and the UCNP-based photoactive probe presents good biosafety both in vitro and in vivo. We believe that this novel PAL approach will provide a promising tool for study of ligand-protein interactions and identification of biomolecular targets.

Repurposing of World-Approved Drugs for Potential Inhibition against Human Carbonic Anhydrase I: A Computational Study

Human carbonic anhydrases (hCAs) have enzymatic activities for reversible hydration of CO2 and are acknowledged as promising targets for the treatment of various diseases. Using molecular docking and molecular dynamics simulation approaches, we hit three compounds of methyl 4-chloranyl-2-(phenylsulfonyl)-5-sulfamoyl-benzoate (84Z for short), cyclothiazide, and 2,3,5,6-tetrafluoro-4-piperidin-1-ylbenzenesulfonamide (3UG for short) from the existing hCA I inhibitors and word-approved drugs. As a Zn2+-dependent metallo-enzyme, the influence of Zn2+ ion models on the stability of metal-binding sites during MD simulations was addressed as well. MM-PBSA analysis predicted a strong binding affinity of -18, -16, and -14 kcal/mol, respectively, for these compounds, and identified key protein residues for binding. The sulfonamide moiety bound to the Zn2+ ion appeared as an essential component of hCA I inhibitors. Vina software predicted a relatively large (unreasonable) Zn2+-sulfonamide distance, although the relative binding strength was reproduced with good accuracy. The selected compounds displayed potent inhibition against other hCA isoforms of II, XIII, and XIV. This work is valuable for molecular modeling of hCAs and further design of potent inhibitors.

Shared and Related Molecular Targets and Actions of Salicylic Acid in Plants and Humans

Salicylic acid (SA) is a phenolic compound produced by all plants that has an important role in diverse processes of plant growth and stress responses. SA is also the principal metabolite of aspirin and is responsible for many of the anti-inflammatory, cardioprotective and antitumor activities of aspirin. As a result, the number of identified SA targets in both plants and humans is large and continues to increase. These SA targets include catalases/peroxidases, metabolic enzymes, protein kinases and phosphatases, nucleosomal and ribosomal proteins and regulatory and signaling proteins, which mediate the diverse actions of SA in plants and humans. While some of these SA targets and actions are unique to plants or humans, many others are conserved or share striking similarities in the two types of organisms, which underlie a host of common biological processes that are regulated or impacted by SA. In this review, we compare shared and related SA targets and activities to highlight the common nature of actions by SA as a hormone in plants versus a therapeutic agent in humans. The cross examination of SA targets and activities can help identify new actions of SA and better explain their underlying mechanisms in plants and humans.

Carbonic Anhydrase Inhibitors from Marine Natural Products

Carbonic anhydrases (CAs, EC 4.2.1.1) are widespread metalloenzymes in organisms in all life kingdoms, being involved in pH regulation, metabolic processes and many other physiological and pathological conditions. CA inhibitors and activators thus possess applications as pharmacological agents in the management of a range of diseases. Marine natural products have allowed the identification of some highly interesting CA inhibitors, among which are sulfonamides, phenols, polyamines, coumarins and several other miscellaneous inhibitors, which are reviewed here. Psammaplin C and some bromophenols were the most investigated classes of such marine-based inhibitors and have been used as lead molecules for developing interesting types of potent and, in some cases, isoform-selective inhibitors, with applications as antitumor agents by inhibiting human CA XII and P-glycoprotein activities. Some phenols have shown interesting bacterial and fungal β-CA inhibitory effects. Marine natural products thus constitute a gold mine for identifying novel CA inhibitors, some of which may lead to the development of novel types of pharmacological agents.

Tip60 might be a candidate for the acetylation of hepatic carbonic anhydrase I and III in mice

BACKGROUND

Carbonic anhydrases (CAs) play a significant role in maintaining pH balance by catalyzing the conversion of carbon dioxide to bicarbonate. The regulation of pH is critical for all living organisms. Although there are many studies in the literature on the biochemical, functional, and structural features of CAs, there is not sufficient information about the epigenetic regulation of CAs.

METHODS AND RESULTS

The lysine acetyltransferase TIP60 (60 kDa Tat-interactive protein) was knocked out specifically in mouse liver using the Cre/loxP system, and knockout rate was shown as 83-88% by Southern blot analysis. The impact of Tip60 on the expression of Ca1, Ca3, and Ca7 was investigated at six Zeitgeber time (ZT) points in the control and liver-specific Tip60 knockout mice (mutant) groups by real-time PCR. In the control group, while Ca1 showed the highest expression at ZT8 and ZT12, the lowest expression profile was observed at ZT0 and ZT20. Hepatic Ca1 displayed robust circadian expression. However, hepatic Ca3 exhibited almost the same level of expression at all ZT points. The highest expression of Ca7 was observed at ZT12, and the lowest expression was determined at ZT4. Furthermore, hepatic Ca7 also showed robust circadian expression. The expression of Ca1 and Ca3 significantly decreased in mutant mice at all time periods, but the expression of Ca7 used as a negative control was not affected.

CONCLUSIONS

It was suggested for the first time that Tip60 might be considered a candidate protein in the regulation of the Ca1 and Ca3 genes, possibly by acetylation.

Reconsidering anion inhibitors in the general context of drug design studies of modulators of activity of the classical enzyme carbonic anhydrase

Inorganic anions inhibit the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) generally by coordinating to the active site metal ion. Cyanate was reported as a non-coordinating CA inhibitor but those erroneous results were subsequently corrected by another group. We review the anion CA inhibitors (CAIs) in the more general context of drug design studies and the discovery of a large number of inhibitor classes and inhibition mechanisms, including zinc binders (sulphonamides and isosteres, dithiocabamates and isosteres, thiols, selenols, benzoxaboroles, ninhydrins, etc.); inhibitors anchoring to the zinc-coordinated water molecule (phenols, polyamines, sulfocoumarins, thioxocoumarins, catechols); CAIs occluding the entrance to the active site (coumarins and derivatives, lacosamide), as well as compounds that bind outside the active site. All these new chemotypes integrated with a general procedure for obtaining isoform-selective compounds (the tail approach) has resulted, through the guidance of rigorous X-ray crystallography experiments, in the development of highly selective CAIs for all human CA isoforms with many pharmacological applications.

A novel class for carbonic anhydrases inhibitors and evaluation of their non-zinc binding

In this study, 23 different imidazole derivatives were synthesized, and the inhibitory properties of these derivatives against carbonic anhydrase I and II isoenzymes were investigated for the first time. The inhibition concentrations of the imidazole derivatives were found to be in the range of 2.89-115.5 nM. Docking studies examined the binding properties of the imidazole derivatives, and the structure-activity relationship is discussed. Theoretical calculations showed that the binding mode of the imidazole ring was non-zinc binding.

Evaluation of single and combined effects of two pharmaceuticals on the marine gastropod Phorcus lineatus enzymatic activity under two different exposure periods

Pharmaceutical drugs are among the most used chemicals for human and veterinary medicines, aquaculture and agriculture. Pharmaceuticals are environmentally persistent, biologically active molecules, thereby having the potential to exert biological effects on non-target species. Among the most used pharmaceuticals, one may find salicylic acid (SA), a non-steroid anti-inflammatory drug (NSAID) that acts by inhibiting the enzymes cyclooxigenases; it is also possible to identify acetazolamide (ACZ), a diuretic that acts by inhibiting the activity of carbonic anhydrase (CA). In this work, the effects of both single and combined effects of these drugs were assessed on the marine gastropod Phorcus lineatus, by measuring key enzymatic activities, namely carbonic anhydrase (CA) and cyclooxygenase (COX), under two different exposure periods (14 and 28 days). We observed no straightforward pattern of enzymatic response in all treatments of both pharmaceuticals, on both analyzed tissues (gut and gills), and for both exposure regimes. We assume that this species is not responsive to the hereby tested pharmaceuticals, a finding that may be due to general mechanisms of response to adverse conditions, such as reduction of metabolism, of heart rate, of filtration rates, and to the increase production of mucus. All these functional adaptations can mitigate the deleterious effects caused by adverse conditions, without triggering biochemical responses. In conclusion, the species P. lineatus seems not to be sensitive in terms of these specific enzymatic pathways to these contaminants, under the adopted conditions.

1,3,5-Triazine: A versatile pharmacophore with diverse biological activities

1,3,5-Triazine and its derivatives have been the epicenter of chemotherapeutic molecules due to their effective biological activities, such as antibacterial, fungicidal, antimalarial, anticancer, antiviral, antimicrobial, anti-inflammatory, antiamoebic, and antitubercular activities. The present review represents a summarized report of the crucial biological activities possessed by substituted 1,3,5-triazine derivatives, with special attention to the most potent compounds.

Preparation, carbonic anhydrase enzyme inhibition and antioxidant activity of novel 7-amino-3,4-dihydroquinolin-2(1H)-one derivatives incorporating mono or dipeptide moiety

New dipeptide–dihydroquinolinone derivatives were successfully synthesised by benzotriazole mediated nucleophilic acyl substitution reaction and their structures were elucidated by spectroscopic and analytic techniques. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of the new compounds was determined against four human (h) isoforms, hCA I, hCA II, hCA IX and hCA XII. While all compounds showed moderate to good in vitro CA inhibitory properties against hCA IX and hCA XII with inhibition constants in the micromolar level (37.7–86.8 and 2.0–8.6 µM, respectively), they did not show inhibitory activity against hCA I and hCA II up to 100 µM concentration. The antioxidant capacity of the peptide–dihydroquinolinone conjugates was determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method. Most of the synthesised compounds showed low antioxidant activities compared to the control antioxidant compounds BHA and α-tocopherol.

Relationship between zinc content and carbonic anhydrase activity in blood of anemic pregnant women in Turkey

AIMS

Carbonic anhydrase (CA) in pregnancy plays an important part in gaseous exchange across the placenta. The aim of our study was to determine the relationship between zinc content and the CA activity in blood of anemic and normal pregnant women in their third trimester, in Turkey.

METHODS

The patients with hemoglobin values below 11 g/dL were accepted as anemic. CA enzyme activity and zinc levels in erythrocyte of anemic and non-anemic pregnant women were carried out in 27 non-anemic pregnant women and 31 anemic pregnant women. Mean corpuscular volume (MCV) levels of the participants were also tested.

RESULTS

Zinc levels were lower in the anemic group compared to the non-anemic group (P = 0.049). Total CA enzyme activity was also lower in the anemic group (P = 0.044). MCV levels were found to be lower in the anemic group (P = 0.007). The decrease in these values was statistically significant (P < 0.05).

CONCLUSION

This is the first study to evaluate the zinc content in red blood cells of anemic pregnant women in the third trimester and its relationship with carbonic anhydrase activity. CA isoenzymes to work healthily, providing iron and zinc supports is important for fetal development.

Carbonic Anhydrase Inhibitors Targeting Metabolism and Tumor Microenvironment

The tumor microenvironment is crucial for the growth of cancer cells, triggering particular biochemical and physiological changes, which frequently influence the outcome of anticancer therapies. The biochemical rationale behind many of these phenomena resides in the activation of transcription factors such as hypoxia-inducible factor 1 and 2 (HIF-1/2). In turn, the HIF pathway activates a number of genes including those involved in glucose metabolism, angiogenesis, and pH regulation. Several carbonic anhydrase (CA, EC 4.2.1.1) isoforms, such as CA IX and XII, actively participate in these processes and were validated as antitumor/antimetastatic drug targets. Here, we review the field of CA inhibitors (CAIs), which selectively inhibit the cancer-associated CA isoforms. Particular focus was on the identification of lead compounds and various inhibitor classes, and the measurement of CA inhibitory on-/off-target effects. In addition, the preclinical data that resulted in the identification of SLC-0111, a sulfonamide in Phase Ib/II clinical trials for the treatment of hypoxic, advanced solid tumors, are detailed.

Single and combined effects of the drugs salicylic acid and acetazolamide: Adverse changes in physiological parameters of the freshwater macrophyte, Lemna gibba

Pharmaceutical drugs are among the most used chemicals, for human and veterinary medicines, aquaculture and agriculture. Pharmaceuticals are biologically active molecules, having also environmental persistence, thereby exerting biological effects on non-target species. Among the most used pharmaceuticals, one may find salicylic acid (SA), a non-steroid anti-inflammatory drugs (NSAIDs), and acetazolamide (ACZ), a diuretic drug that acts by inhibiting the activity of carbonic anhydrase (CA). In this work, single and combined effects of SA and ACZ were assessed in the aquatic macrophyte Lemna gibba L., focusing on physiological parameters, namely photosynthetic pigments, (chlorophyll a, b and total (Chl a, b and TChl) as well as carotenoids (Car)). In addition, chemical biomarkers, namely, glutathione S-transferases (GSTs), catalase (CAT) and carbonic anhydrase (CA) activities, were also determined. The highest concentrations of ACZ, caused a decrease in the contents of all chlorophylls; this effect was however reverted by SA exposure. Both ACZ and SA levels caused a decrease in CA activity. Nevertheless, when in combination, this inhibition was not observed in plants exposed to the lowest concentration of these drugs. In conclusion, both pharmaceuticals have the capacity to cause alterations in L. gibba enzymatic activity and photosynthetic pigments content. Additionally, SA seems to exert a protective effect on this species against deleterious effects caused by ACZ.

The Anticancer Activity for the Bumetanide-Based Analogs via Targeting the Tumor-Associated Membrane-Bound Human Carbonic Anhydrase-IX Enzyme

The membrane-bound human carbonic anhydrase (hCA) IX is widely recognized as a marker of tumor hypoxia and a prognostic factor within several human cancers. Being undetected in most normal tissues, hCA-IX implies the pharmacotherapeutic advent of reduced off-target adverse effects. We assessed the potential anticancer activity of bumetanide-based analogues to inhibit the hCA-IX enzymatic activity and cell proliferation of two solid cancer cell lines, namely kidney carcinoma (A-498) and bladder squamous cell carcinoma (SCaBER). Bumetanide analogues efficiently inhibit the target hCA-IX in low nanomolar activity (IC₅₀ = 4.4–23.7 nM) and have an excellent selectivity profile (SI = 14.5–804) relative to the ubiquitous hCA-II isoform. Additionally, molecular docking studies provided insights into the compounds’ structure–activity relationship and preferential binding of small-sized as well as selective bulky ligands towards the hCA-IX pocket. In particular, 2,4-dihydro-1,2,4-triazole-3-thione derivative 9c displayed pronounced hCA-IX inhibitory activity and impressive antiproliferative activity on oncogenic A-498 kidney carcinoma cells and is being considered as a promising anticancer candidate. Future studies will aim to optimize this compound to fine-tune its anticancer activity as well as explore its potential through in-vivo preclinical studies.

Design, Synthesis, and Biological Evaluation of 1,2,3-Triazole-Linked Triazino[5,6-B]Indole-Benzene Sulfonamide Conjugates as Potent Carbonic Anhydrase I, II, IX, and XIII Inhibitors

A series of 1,2,3-triazole-linked triazino[5,6-b]indole-benzene sulfonamide hybrids (6a-6o) was synthesized and evaluated for carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity against the human (h) isoforms hCA I, II, XIII (cytosolic isoforms), and hCA IX (transmembrane tumor-associated isoform). The results revealed that the compounds 6a-6o exhibited K_i values in the low to medium nanomolar range against hCA II and hCA IX (K_is ranging from 7.7 nM to 41.3 nM) and higher K_i values against hCA I and hCA XIII. Compound 6i showed potent inhibition of hCA II (K_i = 7.7nM), being more effective compared to the standard inhibitor acetazolamide (AAZ) (K_i = 12.1 nM). Compounds 6b and 6d showed moderate activity against hCA XIII (K_i= 69.8 and 65.8 nM). Hence, compound 6i could be consider as potential lead candidate for the design of potent and selective hCA II inhibitors.

Qualitative Phytochemical Fingerprint and Network Pharmacology Investigation of Achyranthes aspera Linn. Extracts

Achyranthes aspera Linn. (Amaranthaceae), commonly known as the Prickly Chaff flower, is used as herbal medicine in the Ivorian's culture, Africa. Nonetheless, there is currently a paucity of scientific information on A. aspera from the Ivory Coast. Herein, the antioxidant activity of A. aspera extracts (methanol, dichloromethane, ethyl acetate and infusion) as well as the enzymatic inhibitory potentials towards key enzymes in human diseases, namely Alzheimer's disease, (cholinesterases: AchE and BChE), type 2 diabetes (α-glucosidase and α-amylase) and hyperpigmentation (tyrosinase) were assessed. The total phenolic (TPC) and flavonoid (TFC) content was determined using colorimetric methods and the individual compounds were characterized using ultra-high performance liquid chromatography coupled with hybrid quadrupole-Orbitrap high resolution mass spectrometry (UHPLC-HRMS). Furthermore, a network pharmacology analysis was conducted to predict putative targets of identified phenolic compounds. The highest TPC was observed in the infused extract (28.86 ± 0.12 mg GAE/g), while the dichloromethane extract (38.48 ± 1.48 mg RE/g) showed the highest level of TFC. UHPLC-HRMS analysis has revealed an abundance of fatty acids, flavonoids, phenols and acylquinic acids. Among tested extracts, the infused extract displayed the highest free radical quenching, reducing and metal-chelating ability. The extracts (except infusion) were effective as enzyme inhibitors against AChE, while only methanolic and infused extracts showed noteworthy anti-BChE effects. The methanolic extract showed a remarkable antityrosinase effect (56.24 ± 5.05 mg KAE/g), as well. Modest to moderate inhibitory activity was observed against α-amylase (all extracts) and α-glucosidase (only dichloromethane extract). Finally, the network pharmacology analysis suggested the carbonic anhydrase II enzyme as a putative target for explaining, at least in part, the traditional use of A. aspera preparations as diuretic and blood clotting agent. Data amassed herein tend to validate the use of A. aspera in traditional medicine, as well as act as a stepping stone for further studies in the quest for novel phytopharmaceuticals. In this context, it is desirable that this study will contribute to the validation of the traditional uses of this plant in the African herbal medicine, and to the valorization of the whole chain production of A. aspera, as a local and sustainable botanical resource.

Exploring the multiple binding modes of inhibitors to carbonic anhydrases for novel drug discovery

INTRODUCTION

The spacious active site cavity of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) shows a great versatility for a variety of binding modes for modulators of activity, inhibitors, and activators, some of which are clinically used drugs.

AREAS COVERED

There are at least four well-documented CA inhibition mechanisms and the same number of binding modes for CA inhibitors (CAIs), one of which superposes with the binding of activators (CAAs). They include (i) coordination to the catalytic metal ion; (ii) anchoring to the water molecule coordinated to the metal ion; (iii) occlusion of the active site entrance; and (iv) binding outside the active site. A large number of chemical classes of CAIs show these binding modes explored in detail by kinetic, crystallographic, and other techniques. The tail approach was applied to all of them and allowed many classes of highly isoform-selective inhibitors. This is the subject of our review.

EXPERT OPINION

All active site regions of CAs accommodate inhibitors to bind, which is reflected in very different inhibition profiles for such compounds and the possibility to design drugs with effective action and new applications, such as for the management of hypoxic tumors, neuropathic pain, cerebral ischemia, arthritis, and degenerative disorders.

Inhibitory Effects and Kinetic-Docking Studies of Xanthohumol FromHumulus lupulusCones Against Carbonic Anhydrase, Acetylcholinesterase, and Butyrylcholinesterase

Xanthohumol is an essential prenyl flavonoid of Humulus lupulus L. cones, and the taste of beer is due to this compound. Lately, xanthohumol has earned significant interest due to its potential anticancer, antigenotoxic, and adipogenesis effects. In this paper, the inhibitory effects of xanthohumol on human carbonic anhydrase isozymes (hCAI and hCAII), acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) were studied. Also, molecular docking studies were used to investigate ligand interaction diagrams of xanthohumol at the binding cavities of hCAI and II. Xanthohumol was isolated from hop cones by silica gel column chromatography. Carbonic anhydrase enzyme activities were determined spectrophotometrically. In addition, molecular modeling approaches were used for the hCAI and hCAII isoenzymes. Ellman’s method was used for the inhibitor activities of AChE and BChE. The KIvalues of xanthohumol were detected as 0.085 µM for hCAI, 0.049 µM for hCAII, 95.5 nM for AChE, and 124.9 nM for BChE. In conclusion, xanthohumol can pleiotropically exert health promoting effects. It has antiglaucoma, anticonvulsant, antiepileptic, and anticancer activities due to its potent inhibitory effects on hCAI and hCAII. These findings may open new avenues for the design and development of novel hCAI, hCAII, AChE, and BChE inhibitors compared with sulfonamide/sulfamate.

Carbon- versus sulphur-based zinc binding groups for carbonic anhydrase inhibitors?

A set of compounds incorporating carbon-based zinc-binding groups (ZBGs), of the type PhX (X = COOH, CONH2, CONHNH2, CONHOH, CONHOMe), and the corresponding derivatives with sulphur(VI)-based ZBGs (X = SO3H, SO2NH2, SO2NHNH2, SO2NHOH, SO2NHOMe) were tested as inhibitors of all mammalian isoforms of carbonic anhydrase (CA, EC 4.2.1.1), CA I-XV. Three factors connected with the ZBG influenced the efficacy as CA inhibitor (CAI) of the investigated compounds: (i) the pKa of the ZBG; (ii) its geometry (tetrahedral, i.e. sulphur-based, versus trigonal, i.e. carbon-based ZBGs), and (iii) orientation of the organic scaffold induced by the nature of the ZBG. Benzenesulphonamide was the best inhibitor of all isoforms, but other ZBGs led to interesting inhibition profiles, although with an efficacy generally reduced when compared to the sulphonamide. The nature of the ZBG also influenced the CA inhibition mechanism. Most of these derivatives were zinc binders, but some of them (sulfonates, carboxylates) may interact with the enzyme by anchoring to the zinc-coordinated water molecule or by other inhibition mechanisms (occlusion of the active site entrance, out of the active site binding, etc.). Exploring structurally diverse ZBGs may lead to interesting new developments in the field of CAIs.

The Human Carbonic Anhydrase II in Platelets: An Underestimated Field of Its Activity

Carbonic anhydrases constitute a group of enzymes that catalyse reversible hydration of carbon dioxide leading to the formation of bicarbonate and proton. The platelet carbonic anhydrase II (CAII) was described for the first time in the '80s of the last century. Nevertheless, its direct role in platelet physiology and pathology still remains poorly understood. The modulation of platelet CAII action as a therapeutic approach holds promise as a novel strategy to reduce the impact of cardiovascular diseases. This short review paper summarises the current knowledge regarding the role of human CAII in regulating platelet function. The potential future directions considering this enzyme as a potential drug target and important pathophysiological chain in platelet-related disorders are described.

Designing, synthesis and bioactivities of 4-[3-(4-hydroxyphenyl)-5-aryl-4,5-dihydro-pyrazol-1-yl]benzenesulfonamides

In this study, 4-[3-(4-hydroxyphenyl)-5-aryl-4,5-dihydro-pyrazol-1-yl]benzenesulfonamide (1-9) types compounds were synthesized and their chemical structures were confirmed by 1H NMR, 13C NMR and HRMS spectra. Cytotoxic and carbonic anhydrase (CA) inhibitory effects of the compounds were investigated. Cytotoxicity experiments pointed out that compound 4, (4-[5-(4-chlorophenyl)-3-(4-hydroxyphenyl)-4,5-dihydro-pyrazol-1-yl]benzenesulfonamide), exerting the highest tumor selectivity (TS) and potency selectivity expression (PSE) values, can be considered as a lead compound of this study in terms of development of novel anticancer agents. All synthesized sulfonamides showed a good inhibition profile on hCA IX and XII in the range of 53.5-923 nM and 6.2-95 nM, respectively. These compounds were 2.5-13.4 times more selective for the inhibition of hCA XII versus hCA IX, except compound 2 which had similar inhibitory action towards both isoenzymes.

Synthesis and carbonic anhydrase inhibition of polycyclic imides incorporating N-benzenesulfonamide moieties

A series of polycyclic imides was prepared by reaction of the benzenesulfonamide with an appropriate polycyclic acid anhydride in refluxing glacial acetic acid. The synthesized mono- and bis-sulfonamides were evaluated as a carbonic anhydrase inhibitors (CA, EC 4.2.1.1), more precisely against the human (h) isoforms hCA I, II, IX and XII, some of which are involved in various pathologies, such as glaucoma, epilepsy and cancer. Several low nanomolar and isoform-selective hCA II, IX and XII inhibitors were detected, and the structure-activity relationship for CA inhibition with this class of compounds is discussed in details. Computational studies allowed us to explain the efficacy and isoform-selective behaviour for some of these enzyme inhiibtors.

Natural product inhibitors of carbonic anhydrase I and II isoenzymes: osajin and pomiferin

The aim of this study is to purify carbonic anhydrase I and II isoenzymes from human erythrocyte, isolate two natural products osajin (OSJ) and pomiferin (PMF) from Maclura pomifera fruits, and evaluate the in vitro effect of these natural metabolites on these isoenzymes. These natural products may be used as starting points for drug discovery (like drugs used in several therapeutic applications, including antiglaucoma activity). For the purification procedure, the Sepharose-4B-l-tyrosine-sulphonamide affinity chromatography was used. Column chromatography and thin layer chromatography methods were used for isolation of OSJ and PMF from M. pomifera fruits and their chemical structures were elucidated by IR, 1D, and 2D NMR methods. We compared inhibitory effects of these natural products with inhibitory effects of phenolic compounds and found that these products demonstrated average inhibition effects. We thought that this study will give inspiration to scientists interested in this issue.

An approach to clarify the effect mechanism of glyphosate on body malformations during embryonic development of zebrafish (Daino rerio)

In this study, it has been investigated that the effects of glyphosate, which is a herbicide within organophosphate and unselective widely used in agriculture on enzyme activity of carbonic anhydrase, production of reactive oxygen species, cell apoptosis and body morphology during the embryonic development of zebrafish. To this end, it has been treated embryo with 1, 5, 10 and 100 mg/L gyphosate at 96 h. The embryos treated with glyphosate from 4 hpf were evaluated by considering the survival rates, hatching rates, body malformations under the stereo microscope in 24, 48, 72 and 96th hours. In order to clarify the mechanism of the abnormalities ROS, enzyme activity of carbonic anhydrase and cellular death were detected end of the 96th hour. The data obtained in the present study have shown that glyphosate treatment inhibited CA activity, caused production of ROS especially branchial regions, triggered cellular apoptosis and caused several types of malformations including pericardial edema, yolk sac edema, spinal curvature and body malformation in a dose-dependent manner. As a conclusion, in light of present and previous studies, we can deduce that (1) the probable reason of ROS production was CA inhibition via decreasing of CO2 extraction and developing respiratory acidosis (however, one needs to clarify), (2) abundance of ROS triggered cellular apoptosis and (3) as a result of cellular apoptosis malformations increased. These data will enable us to further understand potential toxic mechanism of glyphosate on embryonic development stage of zebrafish and may be useful for assessment in the toxicology studies.

Activation of Two Different Drugs Used in Alzheimer's Disease Treatment on Human Carbonic Anhydrase Isozymes I and II Activity: an In Vitro Study

OBJECTIVES

Human carbonic anhydrase I and II (hCAI, II) isoenzymes were purified from human erythrocyte. Kinetic interactions between the enzymes and memantine and donepezil, two different drugs used in Alzheimer's disease (AD) treatment, were investigated.

MATERIALS AND METHODS

The purification procedure was composed of preparation of homogenate (or hemolysate) and affinity chromatography on Sepharose 4B-L-tyrosine-sulfanilamide.

RESULTS

Both drug exhibited in vitro activator effects on hCAI and II enzymes activity. Strong activations were found for these compounds: The CA values of memantine and donepezil against hCAI were 0.013 µM and 1.8 µM, respectively. The KA values of memantine and donepezil against hCAII were 0.045 µM and 3.7 µM, respectively.

CONCLUSION

Since the levels of CA isoenzymes are low in patients with AD or in the older population, increasing activities of these isoenzymes are important for these patients. The effect of these drugs used in AD treatment was thought to be caused by positive changes in the levels of carbonic anhydrase isoenzymes.

Synthesis and biological evaluation of cyclic imides incorporating benzenesulfonamide moieties as carbonic anhydrase I, II, IV and IX inhibitors

A group of cyclic imides was synthesized by reaction of amino-substituted benzenesulfonamides with a series of acid anhydrides such as succinic, maleic, tetrahydrophthalic, pyrazine-2,3-dicarboxylic acid anhydride, and substituted phthalic anhydrides. The synthesized sulfonamides were evaluated as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors against the human (h) isoforms hCA I, II, IV and IX, involved in a variety of diseases among which glaucoma, retinitis pigmentosa, etc. Some of these sulfonamides showed effective inhibitory action (in the nanomolar range) against the cytosolic isoform hCA II and the transmembrane, tumor-associated one hCA IX, making them interesting candidates for preclinical evaluation in glaucoma or various tumors in which the two enzymes are involved. hCA I and IV were on the other hand less inhibited by these sulfonamides, with inhibition constants in the micromolar range.

Carbonic Anhydrase and Urease Inhibitory Potential of Various Plant Phenolics Using in vitro and in silico Methods

Plant phenolics are known to display many pharmacological activities. In the current study, eight phenolic compounds, e.g., luteolin 5-O-β-glucoside (1), methyl rosmarinate (2), apigenin (3), vicenin 2 (4), lithospermic acid (5), soyasaponin II (6), rubiadin 3-O-β-primeveroside (7), and 4-(β-d-glucopyranosyloxy)benzyl 3,4-dihydroxybenzoate (8), isolated from various plant species were tested at 0.2 mm against carbonic anhydrase-II (CA-II) and urease using microtiter assays. Urease inhibition rate for compounds 1 - 8 ranged between 5.0 - 41.7%, while only compounds 1, 2, and 4 showed a considerable inhibition over 50% against CA-II with the IC₅₀ values of 73.5 ± 1.05, 39.5 ± 1.14, and 104.5 ± 2.50 μm, respectively, where IC₅₀ of the reference (acetazolamide) was 21.0 ± 0.12 μm. In silico experiments were also performed through two docking softwares (Autodock Vina and i-GEMDOCK) in order to find out interactions between the compounds and CA-II. Actually, compounds 6 (30.0%) and 7 (42.0%) possessed a better binding capability toward the active site of CA-II. According to our results obtained in this study, among the phenolic compounds screened, particularly 1, 2, and 4 appear to be the promising inhibitors of CA-II and may be further investigated as possible leads for diuretic, anti-glaucoma, and antiepileptic agents.

Synthesis, characterization and in vitro inhibition of metal complexes of pyrazole based sulfonamide on human erythrocyte carbonic anhydrase isozymes I and II

Sulfonamides represent an important class of biologically active compounds. A sulfonamide possessing carbonic anhydrase (CA) inhibitory properties obtained from a pyrazole based sulfonamide, ethyl 1-(3-nitrophenyl)-5-phenyl-3-((5-sulfamoyl-1,3,4-thiadiazol-2-yl)carbamoyl)-1H-pyrazole-4-carboxylate (1), and its metal complexes with the Ni(II) for (2), Cu(II) for (3) and Zn(II) for (4) have been synthesized. The structures of metal complexes (2-4) were established on the basis of their elemental analysis, ¹H NMR, IR, UV-Vis and MS spectral data. The inhibition of two human carbonic anhydrase (hCA, EC 4.2.1.1) isoenzymes I and II, with 1 and synthesized complexes (2-4) and acetazolamide (AAZ) as a control compound was investigated in vitro by using the hydratase and esterase assays. The complexes 2, 3 and 4 showed inhibition constant in the range 0.1460-0.3930 µM for hCA-I and 0.0740-0.0980 µM for hCA-II, and they had effective more inhibitory activity on hCA-I and hCA-II than corresponding free ligand 1 and than AAZ.

Dithiocarbamates effectively inhibit the β-carbonic anhydrase from the dandruff-producing fungus Malassezia globosa

A series of dithiocarbamates (DTCs) was investigated for the inhibition of the β-class carbonic anhydrase (CAs, EC 4.2.1.1) from the fungal parasite Malassezia globosa, MgCA, a validated anti-dandruff drug target. These DTCs incorporate various scaffold, among which those of N,N-dimethylaminoethylenediamine, the aminoalcohols with 3-5 carbon atoms in their molecule, 3-amino-quinuclidine, piperidine, morpholine and piperazine derivatives, as well as phenethylamine and its 4-sulfamoylated derivative. Several DTCs resulted more effective in inhibiting MgCA compared to the standard sulfonamide drug acetazolamide (K_I of 74μM), with K_Is ranging between 383 and 6235nM. A computational approach, involving a homology modeling of the enzyme and docking inhibitors within its active site, helped us rationalize the results. This study may contribute to better understand the inhibition profile of MgCA, and offer new ideas for the design of modulators of activity which belong to less investigated chemical classes, thus potentially useful to combat dandruff and other fungal infections.

Sulfonamide inhibition profile of the γ-carbonic anhydrase identified in the genome of the pathogenic bacterium Burkholderia pseudomallei the etiological agent responsible of melioidosis

A new γ-carbonic anhydrase (CA, EC 4.1.1.1) was cloned and characterized kinetically in the genome of the bacterial pathogen Burkholderia pseudomallei, the etiological agent of melioidosis, an endemic disease of tropical and sub-tropical regions of the world. The catalytic activity of this new enzyme, BpsCAγ, is significant with a k_cat of 5.3×10⁵s^-1 and k_cat/K_m of 2.5×10⁷M^-1×s^-1 for the physiologic CO₂ hydration reaction. The inhibition constant value for this enzyme for 39 sulfonamide inhibitors was obtained. Acetazolamide, benzolamide and metanilamide were the most effective (K_Is of 149-653nM) inhibitors of BpsCAγ activity, whereas other sulfonamides/sulfamates such as ethoxzolamide, topiramate, sulpiride, indisulam, sulthiame and saccharin were active in the micromolar range (K_Is of 1.27-9.56μM). As Burkholderia pseudomallei is resistant to many classical antibiotics, identifying compounds that interfere with crucial enzymes in the B. pseudomallei life cycle may lead to antibiotics with novel mechanisms of action.

Benzenesulfonamides Incorporating Flexible Triazole Moieties Are Highly Effective Carbonic Anhydrase Inhibitors: Synthesis and Kinetic, Crystallographic, Computational, and Intraocular Pressure Lowering Investigations

Herein we report the synthesis of two series of benzenesulfonamide containing compounds that incorporate the phenyl-1,2,3-triazole moieties. We explored the insertion of appropriate linkers, such as ether, thioether, and amino type, into the inner section of the molecules with the intent to confer additional flexibility. All obtained compounds were screened in vitro as inhibitors of the physiologically relevant human (h) isoforms of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). Many of them were low nanomolar or subnanomolar hCA II, IX, and XII inhibitors, whereas they did not potently inhibit hCA I. Computational and X-ray crystallographic studies of the enzyme-inhibitor adducts helped us to rationalize the obtained results. Some of the sulfonamides reported here showed significant intraocular pressure lowering activity in an animal model of glaucoma.

Discovery of 4-sulfamoyl-phenyl-β-lactams as a new class of potent carbonic anhydrase isoforms I, II, IV and VII inhibitors: The first example of subnanomolar CA IV inhibitors

A series of benzenesulfonamides incorporating 1,3,4-trisubstituted-β-lactam moieties was prepared from sulfanilamide Schiff bases and in situ obtained ketenes, by using the Staudinger cycloaddition reaction. The new compounds were assayed as inhibitors of four human isoforms of the metalloenzyme carbonic anhydrase (hCA, EC 4.2.1.1) involved in various physiological/pathological conditions, hCA I, II, IV and VII. Excellent inhibitory activity was observed against all these isoforms, as follows: hCA I, involved in some eye diseases was inhibited with K_Is in the range of 7.3-917nM; hCA II, an antiglaucoma drug target, with K_Is in the range of 0.76-163nM. hCA IV, an isoform involved in several pathological conditions such as glaucoma, retinitis pigmentosa and edema was potently inhibited by the lactam-sulfonamides, with K_Is in the range of 0.53-51.0nM, whereas hCA VII, a recently validated anti-neuropathic pain target was the most inhibited isoform by these derivatives, with K_Is in the range of 0.68-9.1nM. The structure-activity relationship for inhibiting these CAs with the new lactam-sulfonamides is discussed in detail.

Burkholderia pseudomallei γ-carbonic anhydrase is strongly activated by amino acids and amines

Activation of the γ-class carbonic anhydrase (CAs, EC 4.2.1.1) from the pathogenic bacterium Burkholderia pseudomallei (BpsγCA) with a series of natural and non-natural amino acids and aromatic/heterocyclic amines has been investigated. The best BpsγCA activators were d-His, l-DOPA, d-Trp, 4-amino-l-Phe, dopamine, 2-(2-aminoethyl)pyridine, 2-aminoethyl-piparazine/morpholine and l-adrenaline, which showed activation constants ranging between 9 and 86nM. The least effective activators were l-His, l-Phe and 2-pyridyl-methylamine, with K_As in the range of 1.73-24.7μM. As little is known about the role of γ-CAs in the lifecycle and virulence of this saprophytic bacterium, this study may shed some light on such phenomena. This is the first CA activation study of a γ-CA from a pathogenic bacterium, the only other such study being on the enzyme discovered in the archaeon Methanosarcina thermophila, Cam.

Advances in structure-based drug discovery of carbonic anhydrase inhibitors

INTRODUCTION

The enzyme carbonic anhydrase (CA, EC 4.2.1.1) is found in numerous organisms across the tree of life, with seven distinct classes known to date. CA inhibition can be exploited for the treatment of edema, glaucoma, seizures, obesity, cancer and infectious diseases. A myriad of CA inhibitor (CAI) classes and inhibition mechanisms have been identified over the past decade, mainly through structure-based drug design approaches. Five different CA inhibition mechanisms are presently known. Areas covered: Recent advances in structure-based CAI design are reviewed, with periodic table-based organization of inhibitor classes. Expert opinion: Various structure-based drug design studies have led to deep understanding of factors governing tight binding and selectivity for the various isoforms. Carboxylic acids, phenols, polyamines, diols, borols, boronic acids, coumarins and sulfonamides represent successful stories which led to an anti-tumor sulfonamide in Phase I clinical trials (SLC-0111). For many inhibitor classes, no detailed crystallographic data are available. Detailed structural characterization of all CAI classes may lead to further advances in the field with potential therapeutic implications in the management of indications including neuropathic pain, cerebral ischemia, arthritis and tumor imaging.