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Review Article

Coumarin carbonic anhydrase inhibitors from natural sources

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Pages 1462-1470 | Received 27 May 2020, Accepted 21 Jun 2020, Published online: 11 Aug 2020

Abstract

Coumarins constitute a relatively new class of inhibitors of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), possessing a unique inhibition mechanism, acting as “prodrug inhibitors.” They undergo the hydrolysis of the lactone ring mediated by the esterase activity of CA. The formed 2-hydroxy-cinnamic acids thereafter bind within a very particular part of the enzyme active site, at its entrance, where a high variability of amino acid residues among the different mammalian CA isoforms is present, and where other inhibitors classes were not seen bound earlier. This explains why coumarins are among the most isoform-selective CA inhibitors known to date among the many chemotypes endowed with such biological activity. As coumarins are widespread secondary metabolites in some bacteria, plants, fungi, and ascidians, many such compounds from various natural sources have been investigated for their CA inhibitory properties and for possible biomedical applications, mainly as anticancer agents targeting hypoxic tumours.

1. Introduction

Coumarins are bicyclic aromatic compounds incorporating two oxygen atoms, an endocyclic and an exocyclic one, forming thus a cyclic lactone, as shown in for the simplest such derivative 1. Due to the presence of the lactone moiety, coumarins are easily hydrolysed, mainly in alkaline conditions, to the corresponding 2-hydroxy-cinnamic acid 2 – as sodium salts (usually as a trans isomer), which in turn, easily recyclizes (in acidic medium) with the formation of the initial coumarin and loss of a water moleculeCitation1–5. The chemistry of this well-known class of organic compounds was extensively reviewed and will be not discussed in detail hereCitation1–4.

Figure 1. The simplest coumarin, compound 1, its hydrolysis product 2, and the natural product coumarin 3 (and its hydrolysis product 4) for which the CA inhibitory activity was first reportedCitation6.

Figure 1. The simplest coumarin, compound 1, its hydrolysis product 2, and the natural product coumarin 3 (and its hydrolysis product 4) for which the CA inhibitory activity was first reportedCitation6.

Coumarins are widespread natural products, being present as secondary metabolites in many species of bacteria, plants, fungi, and marine organisms (such as the ascidians)Citation3–10. They also possess a range of biological activities, the best-known one being that of anticoagulantsCitation11, although for many representatives (natural or synthetic coumarin derivatives) other pharmacological activities were reported. They include inhibition of the enzyme monoamine oxidase (MAO)Citation4,Citation5, anti-infective activity (as antibacterial, antifungal, and antiviral agents)Citation8, antioxidantsCitation2,Citation8, antitumorCitation2,Citation4, and anti-inflammatory actionCitation2,Citation4,Citation8, among others. In many cases (except the anticoagulant effectsCitation11 and MAO inhibitionCitation4,Citation5) the precise mechanism of action or the real biological targets of the coumarins, active against so many different diseases/conditions, are not clearly understood. A rather different situation on the other hand is encountered for the enzyme carbonic anhydrase (CA, EC 4.2.1.1), for which the inhibitory activity of this class of compounds has been reported a decade agoCitation6,Citation7. Indeed, the first report that a natural product coumarin (compound 3, ) acts as an inhibitor of this enzyme came from Quinn’s groupCitation7 who reported a high-throughput screening assay of a large library of natural products of Australasian origin and detected just one active hit, compound 3. However, as coumarins were not among the classical chemotypes known to inhibit these enzymesCitation12,Citation13, only a subsequent detailed studyCitation6 demonstrated that coumarin 3 present in the Australian pant Leionema ellipticum (and coumarins more generallyCitation6,Citation10) are indeed a new class of CA inhibitors (CAIs) with a definitely unique inhibition mechanism, the real inhibitor being, in fact, the hydrolysed coumarin derivative, 4 (. In the following part of this review, I will examine the natural product coumarins reported to date to possess significant CA inhibitory properties and their potential use as pharmacological agents, after briefly introducing CAs and their inhibition/activation mechanisms.

2. Carbonic anhydrase inhibition/activation

CAs are widespread metalloenzymes in all life kingdoms, with eight diverse genetic families encoding themCitation12,Citation14–19. They catalyse the interconversion of carbon dioxide and bicarbonate, a simple but crucial reaction for a host of physiological processes in all types of organisms, since two neutral molecules, CO2 and water, are transformed into a weak base, bicarbonate, and H+ ions, a strong acidCitation12,Citation14–19. The nucleophile for achieving this transformation is a metal hydroxide species of the enzymeCitation12,Citation14–19. Thus, this reaction is fundamental for pH regulation processes in all types of cells and organisms, in healthy or diseased tissues, whereas the metabolic role of these enzymes started to be recognised only in the last periodCitation20,Citation21. As a consequence, the modulation of CA activity has pharmacological applications for the management of a multitude of human diseases. Indeed, CAIs started to be used in therapy as diuretics in the 50 sCitation22,Citation23, whereas nowadays they are still used for such applicationsCitation24, but also as anti-glaucoma agentsCitation25,Citation26, antiepilepticsCitation27,Citation28, and antiobesity drugsCitation29,Citation30. Furthermore, some CAIs are in various stages of clinical development for the management of metastatic, hypoxic tumoursCitation31–34. It should be also noted that recently, some types of CAIs showed promising activity for the management of conditions such as neuropathic painCitation35,Citation36, cerebral ischaemiaCitation37, arthritisCitation38–40, idiopathic intracranial hypertensionCitation41, and some neurodegenerative disordersCitation42,Citation43. On the other hand, the CA activators (CAAs) show pharmacological applications for memory therapyCitation44 and in the modulation of emotional memory, which opens the possibility to apply them in areas with few therapeutic options at this moment, such as phobias, post-traumatic stress, generalised anxiety, and obsessive-compulsive disordersCitation45,Citation46.

There are at least four CA inhibition mechanisms reported to dateCitation12,Citation47–50, which together with the CA activation mechanism are schematically shown in for α-CAs which incorporate a catalytically crucial zinc ion at their active siteCitation12,Citation14. They can be classified as follows:

  1. Inhibitors acting as zinc binders (). These chemotypes possess a zinc-binding group (ZBG) which is coordinated to the metal ion, whereas the remaining part of their molecule interacts either with the hydrophobic, hydrophilic, or both halves of the active siteCitation12,Citation47–50. Some ZBGs (sulphonamides, sulfamates, sulfamides, carboxylates, hydroxamates, benzoxaboroles, etc.) also participate in hydrogen bond interactions with two amino acid residues conserved in all α-CAs, the so-called gatekeepers, Thr199-Glu106Citation12. Their scaffold can be aromatic, heterocyclic, aliphatic, or carbohydrate-basedCitation47–50.

  2. Inhibitors anchoring to the zinc-coordinated water molecule (). These inhibitors incorporate an anchoring group (AG) in which hydrogen bonds with the water coordinated to the metal ion (acting as a nucleophile in the catalytic reaction), as well as with the OH of Thr199 from the gatekeeper dyadCitation47–50. Phenols, polyamines, sulfocoumarins, and some other compounds inhibit CAs by this mechanismCitation51,Citation52. So, AG is usually an OH, NH2, or SO3H moietiesCitation47–52.

  3. Inhibitors which occlude the entrance to the active site (). Coumarins, which will shortly be discussed in detail, are the compounds that bind in this wayCitation6,Citation10,Citation53–55, rather far away from the metal centre, at the entrance of the cavity. AG is here a COOH or phenolic OH moiety ().

  4. Inhibitors binding out of the active site (). Only one example of such a derivative is known at the moment (2-benzylsulfonyl-benzoic acid), which binds in an adjacent hydrophobic pocket to the entrance to the active site cavity, blocking the proton shuttle of the enzyme, residue His64 in its out conformation, which leads to the collapse of the catalytic cycleCitation56.

  5. CA activators (). These modulators of CA activity do not abolish but enhance the catalytic efficiency of these enzymes, which are already highly effective catalysts for the CO2 hydration reactionCitation12,Citation14,Citation46. The CA activators incorporate proton-shuttling moieties (PSMs) in their molecules, which most of the time are of the amino, carboxylate, or imidazole typeCitation57–60 and bind at the entrance of the active site cavity. Thus, the activator binding site is superimposable with the coumarin-binding site shown in .

Figure 2. CA inhibition mechanisms (A–D) and the CA activation mechanism (E). The CA modulators of activity incorporate various scaffolds and tails in their molecule, as well as characteristic functionalities for all category: (A) the zinc binders possess a zinc-binding group (ZBG) which is coordinated to the metal ion; (B) the compounds which anchor to the zinc-coordinated water incorporate an anchoring group (AG) which hydrogen bonds with the water coordinated to the metal and the OH of Thr199; (C) AGs are also present in compounds which occlude the entrance of the active site cavity; (D) some inhibitors which bind out of the active site; (E) the activators incorporate proton-shuttling moieties (PSMs) and bind in the same active site region as the inhibitors shown at (C). Only α-class CAs are considered here (as they are the enzymes present in mammals, including humansCitation12,Citation14) although these mechanisms may be valid to other CA classes.

Figure 2. CA inhibition mechanisms (A–D) and the CA activation mechanism (E). The CA modulators of activity incorporate various scaffolds and tails in their molecule, as well as characteristic functionalities for all category: (A) the zinc binders possess a zinc-binding group (ZBG) which is coordinated to the metal ion; (B) the compounds which anchor to the zinc-coordinated water incorporate an anchoring group (AG) which hydrogen bonds with the water coordinated to the metal and the OH of Thr199; (C) AGs are also present in compounds which occlude the entrance of the active site cavity; (D) some inhibitors which bind out of the active site; (E) the activators incorporate proton-shuttling moieties (PSMs) and bind in the same active site region as the inhibitors shown at (C). Only α-class CAs are considered here (as they are the enzymes present in mammals, including humansCitation12,Citation14) although these mechanisms may be valid to other CA classes.

Nowadays, a huge number of various chemotypes are associated with the inhibition and activation of CAs, and as mentioned above some of these compounds are clinically used as drugs for the management of a variety of disordersCitation12,Citation14,Citation15,Citation21–29,Citation33. However, as in humans, there are 15 CA isoforms which are rather similar from the structural viewpointCitation12,Citation14, for a very long period it was considered impossible to obtain isoform-selective CAIsCitation12. In fact, the quite large number of disorders in which inhibitors and activators of CAs show pharmacological effects is in fact due to the large number of isoforms, their diverse sub-cellular and tissue distributions, which leads to very different functions of the many CA isoforms present in various cells/tissues/organsCitation12,Citation14,Citation15,Citation21–29,Citation33. Thus, the first and second generation CAIs, which all belong to the zinc binders and are sulphonamides, sulfamates, and sulfamides, are in fact still in clinical use, but they are associated with relevant side effects due to their non-isoform selective profiles and off-target inhibitionCitation12,Citation14,Citation15,Citation21–29,Citation33,Citation61. Only the discovery of coumarins as CAIsCitation6,Citation7 allowed for the first time the rational drug design of isoform-selective inhibitors for all the catalytically active human(h) CA isoforms (12 of the 15 hCA isoforms possess catalytic activity, whereas hCA VIII, X, and XI are devoid of itCitation12,Citation14) As shown in , these compounds, the coumarins, bind at the entrance of the hCA active site, which is the region most variable between the different isoformsCitation12,Citation14. For this reason, compounds which can bind and interact with amino acid residues in this part of the active site are generally characterised by an enhanced isoform-selectivity compared with compounds which bind deep within the active site, where a large number of the amino acid residues are conserved among the various CA isoformsCitation12,Citation14,Citation16.

3. Coumarins as CAIs

Detailed kinetic and X-ray crystallographic techniques allowed us to unravel the CA inhibition mechanism with coumarinsCitation6,Citation10. The first crystal structure was that of the natural product coumarin 3Citation6 bound to human (h) isoform hCA II, followed shortly thereafter by the crystal structure of the simple coumarin 1 () bound to the same isoformCitation10. These two X-ray crystallographic structures are superimposed in .

Figure 3. X-ray crystal structure of adducts of coumarins 1Citation10 and 3Citation6 bound to hCA II. The hydrolysis products of the two coumarins, cis-2-hydroxycinnamic acid 2 (in yellow) and trans-2-hydroxy-cinnamic acid 4 (in magenta) were observed bound wat the entrance of the CA active site. The catalytic Zn(II) ion is the central violet sphere, its three protein ligands (His94, 96 and 119, CPK colors) and the proton shuttle residue His64 (in red) are evidenced. The hCA II backbone is shown as the green ribbon, with its various α-helices, β-sheets, and loops represented in a canonical manner.

Figure 3. X-ray crystal structure of adducts of coumarins 1Citation10 and 3Citation6 bound to hCA II. The hydrolysis products of the two coumarins, cis-2-hydroxycinnamic acid 2 (in yellow) and trans-2-hydroxy-cinnamic acid 4 (in magenta) were observed bound wat the entrance of the CA active site. The catalytic Zn(II) ion is the central violet sphere, its three protein ligands (His94, 96 and 119, CPK colors) and the proton shuttle residue His64 (in red) are evidenced. The hCA II backbone is shown as the green ribbon, with its various α-helices, β-sheets, and loops represented in a canonical manner.

Coumarins possess unique characteristics as CAIs, as determined from kinetic, mass spectrometric, and crystallographic experimentsCitation6,Citation10. Unlike sulphonamides or other small molecule inhibitors, the formation of the enzyme-inhibitor complex is not a rapid processCitation16, but it takes several hoursCitation6. Indeed, all experiments for determining the inhibition constants of these compounds are done by incubating the enzyme and the coumarins for 6 hCitation6,Citation10, whereas for other classes of CAIs the incubation period is 15 minCitation10,Citation14. This was the first indication that probably the coumarins are suicide inhibitors, which in fact was confirmed by the crystallographic experimentsCitation6,Citation10. As seen from , the coumarin ring is not present in the enzyme-inhibitor complexes formed between hCA II and the coumarins 1 and 3, respectively. Instead, the corresponding hydrolysis products, 2-hydroxy-cinnamic acids 2 and 4 are observed bound at the entrance of the active site. This can only be achieved by the hydrolysis of the lactone ring of the coumarins through the esterase activity of hCAs, which in fact has been well documented earlierCitation62–64. It is interesting to note that the unsubstituted 2-hydroxy-cinnamic acid 2 binds to the enzyme in its trans geometry, whereas the much bulkier derivative 4 obtained from the natural product coumarin 3 was observed in the generally less stable cis geometry (. But the most relevant finding was that these compounds bind at the entrance of the active site cavity at around 8–10 Å from the zinc ionCitation6,Citation10. In this active site region, no other inhibitors were observed bound previously, confirming the uniqueness of the coumarin inhibition mechanism. Thus, coumarins are indeed suicided CAIs, which undergo hydrolysis through the esterase CA activity and bind in a region of the active site not exploited by other classes of inhibitors, but which is in fact the same binding site of the CA activatorsCitation46,Citation59,Citation60. This discovery led to a large number of studies of coumarins as CAIs, both synthetic and naturally occurring derivatives.

4. Natural product coumarins investigated as CAIs

The most extensive study of natural product coumarins (NPCs) acting as CAIs was reported by Davis et al.Citation9 who investigated a series of such derivatives () isolated from plants and ascidians, of types 5–35, for the inhibition of six hCAs (). Isoforms hCA I, II, VII, IX, XII, and XIII were investigated. The first three of them and hCA XIII are cytosolic enzymes, whereas hCA IX and XII are transmembrane, tumour-associated isoforms, present in few normal tissuesCitation12,Citation14,Citation16 and validated as antitumor drug targetsCitation21. The NPCs incorporate a variety of scaffolds, as shown in , ranging from very simple coumarins with compact substituents, such as those present in 11, 12, 14, 17, 33, etc., to rather complex/bulky substituents in various positions, or condensation with other ring systems, such as in 5–7, 19, 20, 24, 25, 26, 34, 35, etc.

Figure 4. Natural product coumarins 5–35 investigated as CAIs.

Figure 4. Natural product coumarins 5–35 investigated as CAIs.

Table 1. Inhibition data against six CA isoforms (hCA I, II, VII, IX, XII, and XIII) with coumarins 5–35Citation9.

As seen from data of , all types of activities were observed with coumarins 5–35, but most of the derivatives were inactive or showed poor activity against the house-keeping and most diffuse isoform, hCA II, whereas they acted as efficient, micro- or submicromolar inhibitors against the other isoforms, such as hCA I, VII, IX, XII and XIII. One compound (17) was a low nanomolar inhibitor of hCA I (). Generally, hCA IX and XII showed better inhibition with these NPCs compared to the other isoformsCitation9. As for all other coumarins investigated to dateCitation6,Citation10, nature and position (number) of substituents on the coumarin ring were the most important factors influencing the enzyme inhibitory properties of these compoundsCitation9.

Another, more recent study, by Fois et al.Citation65 reported coumarins from the Sardinian plant Magydaris pastinacea () acting as efficient inhibitors of the tumour-associated isoforms hCA IX and XII whereas their activity for the cytosolic isoforms hCA I and II was found to be very weak ().

Figure 5. NPCs from the Sardinian plant Magydaris pastinacea investigated as CAIs.

Figure 5. NPCs from the Sardinian plant Magydaris pastinacea investigated as CAIs.

Table 2. hCA I, II, IX, and XII inhibition with NPCs 3650.

Some of these compounds (36–45) are in fact variously substituted furo-coumarins (psoralens), with a tricyclic ring system incorporating the furan heterocycle, and this class of NPs is well known in nature, being present in many other plantsCitation65. The remaining derivatives incorporate isoprenyl-, hydrated isoprenyl- or polyprenylated moieties, also typical for many NPsCitation65. It is interesting to note that all coumarins/furocoumarins 36–45 were ineffective as hCA I and II inhibitors, whereas they showed a rather good, high nanomolar inhibitory action against the tumour-associated isoforms hCA IX and XII ()Citation65.

In another study, by Melis et al.Citation66, several other NP coumarins and psoralen derivatives (51–58), this time incorporating carboxylic acid or ester moieties, were investigated as CAIs against isoforms hCA I, II, IX, and XII (). There is a continuous interest in this class of derivatives for their potential applications as anti-fungal agentsCitation67 or photo-activatable antitumor drugs, due to the photochemical properties of the psoralen ring systemCitation68.

Table 3. Coumarins and psoralens 51–58 and their hCA I, II, IX, and XII inhibitory action.

As for the derivatives from Magydaris pastinacea, also these investigated coumarins/psoralens 51–58 showed no inhibitory action towards the cytosolic hCA I and II isoforms, which is a positive feature, as these are house-keeping enzymes in most cells/tissues, but they were effective, in some cases as low nanomolar inhibitors against the tumour associated isoforms hCA IX and XII; making them of interest for anticancer studies. In fact, already in 2011, our group demonstratedCitation69 that some synthetic (not NP) coumarins incorporating glycosyl moieties show very effective in vitro CA IX/XII inhibitory action (with no inhibition of the off-target isoforms hCA I and II) and also a significant antitumor and antimetastatic effects in an in vivo animal model of hypoxic, metastatic tumoursCitation70.

5. Conclusions

Due to their unique CA inhibition mechanism, coumarins, and related compounds afforded for the first time the advent of highly isoform-selective CAIs for all human isoforms among the 12 catalytically active ones. The NP coumarins were essential for unravelling the inhibition mechanism and also for understanding in detail the structure-activity relationship for this class of enzyme inhibitors. Due to their particular inhibition mechanism, the presence of bulky moieties in the 3 position of the coumarin ring is associated with very poor or no CA inhibition. As a consequence, all the anticoagulant coumarins, which do possess very bulky moieties in position 3, do not act as CAIs, which is a positive feature both for the coumarin CAIs eventually designed for various pharmacological applications, as well as for the anticoagulants.

Apart from their highly interesting features as isoform-selective inhibitors, the discovery of coumarins as CAIs stimulated the research for the discovery of new chemotypes possessing such properties or similar inhibition mechanisms. Indeed, the monocyclic 5- and 6-ring lactones and thiolactones were reported to possess CA inhibitory effectsCitation71, as well as thio- and 2-thioxo-coumarinsCitation72, quinoline-2-onesCitation73, sulfocoumarinsCitation74, homosulfocoumarinsCitation75,Citation76 and various hetero-coumarins incorporating selenium, tellurium and other elementsCitation77. More recently, this type of prodrug CAI inspired also other groups to investigate this type of suicide inhibitor, such as for example aspirin, reported by McKenna’s groupCitation78. The huge number of synthetic studies of non-NP coumarins which have been reported in the last decade are not mentioned here, but many such compounds have been designed and showed a relevant biological activity. Overall, the very interesting moieties present in the NP coumarins make them a source of inspiration for medicinal chemists and pharmacologists in the search of new drugs with a safer profile and specific action in a variety of disorders, starting from the infective onesCitation79 and ending with tumoursCitation80 and inflammatory diseasesCitation81. For the moment, only the human α-CAs were investigated for their inhibition profile with coumarins, but such enzymes are also present in other organisms, such as pathogenic bacteria, protozoans, and fungiCitation82–85. Investigation of coumarin derivatives (including NPCs) against these enzymes may thus lead to interesting developments in the fight of infections produced by such pathogens.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was funded by the Italian Ministry for University and Research (MIUR), grant [PRIN: rot. 2017XYBP2R] (to CTS).

References

  • Sethna SM, Shah NM. The chemistry of coumarins. Chem Rev 1945;36:1–62.
  • Riveiro ME, De Kimpe N, Moglioni A, et al. Coumarins: old compounds with novel promising therapeutic perspectives. Curr Med Chem 2010;17:1325–38.
  • Pereira TM, Franco DP, Vitorio F, Kummerle AE. Coumarin compounds in medicinal chemistry: some important examples from the last years. Curr Top Med Chem 2018;18:124–48.
  • Stefanachi A, Leonetti F, Pisani L, et al. Coumarin: a natural, privileged and versatile scaffold for bioactive compounds. Molecules 2018;23:E250.
  • Carradori S, Secci D, Petzer JP. MAO inhibitors and their wider applications: a patent review. Expert Opin Ther Pat 2018;28:211–26.
  • Maresca A, Temperini C, Vu H, et al. Non-zinc mediated inhibition of carbonic anhydrases: coumarins are a new class of suicide inhibitors. J Am Chem Soc 2009;131:3057–62.
  • Vu H, Pham NB, Quinn RJ. Direct screening of natural product extracts using mass spectrometry. J Biomol Screen 2008;13:265–75.
  • Menezes JC, Diederich M. Translational role of natural coumarins and their derivatives as anticancer agents. Future Med Chem 2019;11:1057–82.
  • Davis RA, Vullo D, Maresca A, et al. Natural product coumarins that inhibit human carbonic anhydrases. Bioorg Med Chem 2013;21:1539–43.
  • Maresca A, Temperini C, Pochet L, et al. Deciphering the mechanism of carbonic anhydrase inhibition with coumarins and thiocoumarins. J Med Chem 2010;53:335–44.
  • Lippi G, Gosselin R, Favaloro EJ. Current and emerging direct oral anticoagulants: state-of-the-art. Semin Thromb Hemost 2019;45:490–501.
  • Supuran CT. Carbonic anhydrases: novel therapeutic applications for inhibitors and activators. Nat Rev Drug Discov 2008;7:168–81.
  • (a) De Simone G, Supuran CT. (In)organic anions as carbonic anhydrase inhibitors. J Inorg Biochem 2012;111:117–29. (b) Supuran CT. Carbon- versus sulphur-based zinc binding groups for carbonic anhydrase inhibitors? J Enzyme Inhib Med Chem 2018;33:485–95.
  • Supuran CT. Structure and function of carbonic anhydrases. Biochem J 2016;473:2023–32.
  • Supuran CT, Capasso C. Biomedical applications of prokaryotic carbonic anhydrases. Expert Opin Ther Pat 2018;28:745–54.
  • Nocentini A, Supuran CT. Advances in the structural annotation of human carbonic anhydrases and impact on future drug discovery. Expert Opin Drug Discov 2019;14:1175–97.
  • Zimmerman SA, Ferry JG, Supuran CT. Inhibition of the archaeal beta-class (Cab) and gamma-class (Cam) carbonic anhydrases. Curr Top Med Chem 2007;7:901–8.
  • (a) Supuran CT, Capasso C. An overview of the bacterial carbonic anhydrases. Metabolites 2017;7:56. (b) Capasso C, Supuran CT. An overview of the alpha-, beta- and gamma-carbonic anhydrases from bacteria: can bacterial carbonic anhydrases shed new light on evolution of bacteria? J Enzyme Inhib Med Chem 2015;30:325–32.
  • Del Prete S, Nocentini A, Supuran CT, Capasso C. Bacterial ι-carbonic anhydrase: a new active class of carbonic anhydrase identified in the genome of the Gram-negative bacterium Burkholderia territorii. J Enzyme Inhib Med Chem 2020;35:1060–8.
  • Supuran CT. Carbonic anhydrases and metabolism. Metabolites 2018;8:25.
  • (a) Supuran CT, Carbonic anhydrase inhibitors as emerging agents for the treatment and imaging of hypoxic tumors. Expert Opin Investig Drugs 2018;27:963–70. (b) Neri D, Supuran CT. Interfering with pH regulation in tumours as a therapeutic strategy. Nat Rev Drug Discov 2011;10:767–77. (c) Supuran CT, Vullo D, Manole G, et al. Designing of novel carbonic anhydrase inhibitors and activators. Curr Med Chem Cardiovasc Hematol Agents 2004;2:49–68.
  • (a) Supuran CT. Applications of carbonic anhydrases inhibitors in renal and central nervous system diseases. Expert Opin Ther Pat 2018;28:713–21. (b) Milite C, Amendola G, Nocentini A, et al. Novel 2-substituted-benzimidazole-6-sulfonamides as carbonic anhydrase inhibitors: synthesis, biological evaluation against isoforms I, II, IX and XII and molecular docking studies. J Enzyme Inhib Med Chem 2019;34:1697–710. (c) Distinto S, Meleddu R, Ortuso F, et al. Exploring new structural features of the 4-[(3-methyl-4-aryl-2,3-dihydro-1,3-thiazol-2-ylidene)amino]benzenesulphonamide scaffold for the inhibition of human carbonic anhydrases. J Enzyme Inhib Med Chem 2019;34:1526–33.
  • (a) Supuran CT. Drug interaction considerations in the therapeutic use of carbonic anhydrase inhibitors. Expert Opin Drug Metab Toxicol 2016;12:423–31. (b) Köhler K, Hillebrecht A, Schulze Wischeler J, et al. Saccharin inhibits carbonic anhydrases: possible explanation for its unpleasant metallic aftertaste. Angew Chem Int Ed Engl 2007;46:7697–9.
  • Supuran CT. Carbonic anhydrase inhibitors and their potential in a range of therapeutic areas. Expert Opin Ther Pat 2018;28:709–12.
  • Supuran CT. The management of glaucoma and macular degeneration. Expert Opin Ther Pat 2019;29:745–7.
  • Supuran CT, Altamimi ASA, Carta F. Carbonic anhydrase inhibition and the management of glaucoma: a literature and patent review 2013-2019. Expert Opin Ther Pat 2019;29:781–92.
  • Di Fiore A, De Simone G, Alterio V, et al. The anticonvulsant sulfamide JNJ-26990990 and its S,S-dioxide analog strongly inhibit carbonic anhydrases: solution and X-ray crystallographic studies. Org Biomol Chem 2016;14:4853–8.
  • Aggarwal M, Kondeti B, McKenna R. Anticonvulsant/antiepileptic carbonic anhydrase inhibitors: a patent review. Expert Opin Ther Pat 2013;23:717–24.
  • Scozzafava A, Supuran CT, Carta F. Antiobesity carbonic anhydrase inhibitors: a literature and patent review. Expert Opin Ther Pat 2013;23:725–35.
  • Poli G, Bozdag M, Berrino E, et al. N-aryl-N′-ureido-O-sulfamates as potent and selective inhibitors of hCA VB over hCA VA: deciphering the binding mode of new potential agents in mitochondrial dysfunctions. Bioorg Chem 2020;100:103896.
  • Supuran CT, Alterio V, Di Fiore A, et al. Inhibition of carbonic anhydrase IX targets primary tumors, metastases, and cancer stem cells: three for the price of one. Med Res Rev 2018;38:1799–836.
  • McDonald PC, Chia S, Bedard PL, et al. A phase 1 study of SLC-0111, a novel inhibitor of carbonic anhydrase IX, in patients with advanced solid tumors. Am J Clin Oncol 2020;43:484–490.
  • Nocentini A, Supuran CT. Carbonic anhydrase inhibitors as antitumor/antimetastatic agents: a patent review (2008–2018). Expert Opin Ther Pat 2018;28:729–40.
  • McDonald PC, Chafe SC, Brown WS, et al. Regulation of pH by carbonic anhydrase 9 mediates survival of pancreatic cancer cells with activated KRAS in response to hypoxia. Gastroenterology 2019;157:823–37.
  • Supuran CT. Carbonic anhydrase inhibition and the management of neuropathic pain. Expert Rev Neurother 2016;16:961–8.
  • Carta F, Di Cesare Mannelli L, Pinard M, et al. A class of sulfonamide carbonic anhydrase inhibitors with neuropathic pain modulating effects. Bioorg Med Chem 2015;23:1828–40.
  • Di Cesare Mannelli L, Micheli L, Carta F, et al. Carbonic anhydrase inhibition for the management of cerebral ischemia: in vivo evaluation of sulfonamide and coumarin inhibitors. J Enzyme Inhib Med Chem 2016;31:894–9.
  • Margheri F, Ceruso M, Carta F, et al. Overexpression of the transmembrane carbonic anhydrase isoforms IX and XII in the inflamed synovium. J Enzyme Inhib Med Chem 2016;31:60–3.
  • Bua S, Di Cesare Mannelli L, Vullo D, et al. Design and synthesis of novel nonsteroidal anti-inflammatory drugs and carbonic anhydrase inhibitors hybrids (NSAIDs-CAIs) for the treatment of rheumatoid arthritis. J Med Chem 2017;60:1159–70.
  • Akgul O, Di Cesare Mannelli L, Vullo D, et al. Discovery of novel nonsteroidal anti-inflammatory drugs and carbonic anhydrase inhibitors hybrids (NSAIDs-CAIs) for the management of rheumatoid arthritis. J Med Chem 2018;61:4961–77.
  • Supuran CT. Acetazolamide for the treatment of idiopathic intracranial hypertension. Expert Rev Neurother 2015;15:851–6.
  • Fossati S, Giannoni P, Solesio ME, et al. The carbonic anhydrase inhibitor methazolamide prevents amyloid beta-induced mitochondrial dysfunction and caspase activation protecting neuronal and glial cells in vitro and in the mouse brain. Neurobiol Dis 2016;86:29–40.
  • Provensi G, Carta F, Nocentini A, et al. A new kid on the block? Carbonic anhydrases as possible new targets in Alzheimer’s disease. Int J Mol Sci 2019;20:4724.
  • Canto de Souza L, Provensi G, Vullo D, et al. Carbonic anhydrase activation enhances object recognition memory in mice through phosphorylation of the extracellular signal-regulated kinase in the cortex and the hippocampus. Neuropharmacology 2017;118:148–56.
  • Blandina P, Provensi G, Passsani MB, et al. Carbonic anhydrase modulation of emotional memory. Implications for the treatment of cognitive disorders. J Enzyme Inhib Med Chem 2020;35:1206–14.
  • (a) Supuran CT. Carbonic anhydrase activators. Future Med Chem 2018;10:561–73. (b) Akocak S, Supuran CT. Activation of α-, β-, γ- δ-, ζ- and η- class of carbonic anhydrases with amines and amino acids: a review. J Enzyme Inhib Med Chem 2019;34:1652–9.
  • Supuran CT. Advances in structure-based drug discovery of carbonic anhydrase inhibitors. Expert Opin Drug Discov 2017;12:61–88.
  • Supuran CT. How many carbonic anhydrase inhibition mechanisms exist? J Enzyme Inhib Med Chem 2016;31:345–60.
  • De Simone G, Alterio V, Supuran CT. Exploiting the hydrophobic and hydrophilic binding sites for designing carbonic anhydrase inhibitors. Expert Opin Drug Discov 2013;8:793–810.
  • Supuran CT. Exploring the multiple binding modes of inhibitors to carbonic anhydrases for novel drug discovery. Expert Opin Drug Discov 2020;15:671–686.
  • (a) Innocenti A, Vullo D, Scozzafava A, Supuran CT. Carbonic anhydrase inhibitors: interactions of phenols with the 12 catalytically active mammalian isoforms (CA I-XIV)). Bioorg Med Chem Lett 2008;18:1583–7. (b) Boztaş M, Çetinkaya Y, Topal M, et al. Synthesis and carbonic anhydrase isoenzymes I, II, IX, and XII inhibitory effects of dimethoxybromophenol derivatives incorporating cyclopropane moieties. J Med Chem 2015;58:640–50.
  • (a) Innocenti A, Vullo D, Scozzafava A, Supuran CT. Carbonic anhydrase inhibitors: inhibition of mammalian isoforms I-XIV with a series of substituted phenols including paracetamol and salicylic acid. Bioorg Med Chem 2008;16:7424–8. (b) Nocentini A, Bonardi A, Gratteri P, et al. Steroids interfere with human carbonic anhydrase activity by using alternative binding mechanisms. J Enzyme Inhib Med Chem 2018;33:1453–9.
  • Maresca A, Supuran CT. Coumarins incorporating hydroxy- and chloro-moieties selectively inhibit the transmembrane, tumor-associated carbonic anhydrase isoforms IX and XII over the cytosolic ones I and II. Bioorg Med Chem Lett 2010;20:4511–4.
  • Maresca A, Scozzafava A, Supuran CT. 7,8-Disubstituted- but not 6,7-disubstituted coumarins selectively inhibit the transmembrane, tumor-associated carbonic anhydrase isoforms IX and XII over the cytosolic ones I and II in the low nanomolar/subnanomolar range. Bioorg Med Chem Lett 2010;20:7255–8.
  • Sharma A, Tiwari M, Supuran CT. Novel coumarins and benzocoumarins acting as isoform-selective inhibitors against the tumor-associated carbonic anhydrase IX. J Enzyme Inhib Med Chem 2014;29:292–6.
  • D’Ambrosio K, Carradori S, Monti SM, et al. Out of the active site binding pocket for carbonic anhydrase inhibitors. Chem Commun 2015;51:302–5.
  • Chiaramonte N, Maach S, Biliotti C, et al. Synthesis and carbonic anhydrase activating properties of a series of 2-amino-imidazolines structurally related to clonidine1. J Enzyme Inhib Med Chem 2020;35:1003–10.
  • Angeli A, Vaiano F, Mari F, et al. Psychoactive substances belonging to the amphetamine class potently activate brain carbonic anhydrase isoforms VA, VB, VII, and XII. J Enzyme Inhib Med Chem 2017;32:1253–9.
  • Vistoli G, Aldini G, Fumagalli L, et al. Activation effects of carnosine- and histidine-containing dipeptides on human carbonic anhydrases: a comprehensive study. Int J Mol Sci 2020;21:1761.
  • Temperini C, Innocenti A, Scozzafava A, et al. The coumarin-binding site in carbonic anhydrase accommodates structurally diverse inhibitors: the antiepileptic lacosamide as an example and lead molecule for novel classes of carbonic anhydrase inhibitors. J Med Chem 2010;53:850–4.
  • Supuran CT. An update on drug interaction considerations in the therapeutic use of carbonic anhydrase inhibitors. Expert Opin Drug Metab Toxicol 2020;16:297–307.
  • Innocenti A, Supuran CT. Paraoxon, 4-nitrophenyl phosphate and acetate are substrates of α- but not of β-, γ- and ζ-carbonic anhydrases. Bioorg Med Chem Lett 2010;20:6208–12.
  • Innocenti A, Scozzafava A, Parkkila S, et al. Investigations of the esterase, phosphatase, and sulfatase activities of the cytosolic mammalian carbonic anhydrase isoforms I, II, and XIII with 4-nitrophenyl esters as substrates. Bioorg Med Chem Lett 2008;18:2267–71.
  • Tanc M, Carta F, Scozzafava A, Supuran CT. α-carbonic anhydrases possess thioesterase activity. ACS Med Chem Lett 2015;6:292–5.
  • Fois B, Distinto S, Meleddu R, et al. Coumarins from Magydaris pastinacea as inhibitors of the tumour-associated carbonic anhydrases IX and XII: isolation, biological studies and in silico evaluation. J Enzyme Inhib Med Chem 2020;35:539–48.
  • Melis C, Distinto S, Bianco G, et al. Targeting tumor associated carbonic anhydrases IX and XII: highly isozyme selective coumarin and psoralen inhibitors. ACS Med Chem Lett 2018;9:725–9.
  • Mercer DK, Robertson J, Wright K, et al. A prodrug approach to the use of coumarins as potential therapeutics for superficial mycoses. PLoS One 2013;8:e80760.
  • Xia W, Gooden D, Liu L, et al. Photo-activated psoralen binds the ErbB2 catalytic kinase domain, blocking ErbB2 signaling and triggering tumor cell apoptosis. PLoS One 2014;9:e88983.
  • Touisni N, Maresca A, McDonald PC, et al. Glycosyl coumarin carbonic anhydrase IX and XII inhibitors strongly attenuate the growth of primary breast tumors. J Med Chem 2011;54:8271–7.
  • Lou Y, McDonald PC, Oloumi A, et al. Targeting tumor hypoxia: suppression of breast tumor growth and metastasis by novel carbonic anhydrase IX inhibitors. Cancer Res 2011;71:3364–76.
  • Carta F, Maresca A, Scozzafava A, et al. 5- And 6-membered (thio)lactones are prodrug type carbonic anhydrase inhibitors. Bioorg Med Chem Lett 2012;22:267–70.
  • Ferraroni M, Carta F, Scozzafava A, Supuran CT. Thioxocoumarins show an alternative carbonic anhydrase inhibition mechanism compared to coumarins. J Med Chem 2016;59:462–73.
  • Isik S, Vullo D, Bozdag M, et al. 7-Amino-3,4-dihydro-1H-quinolin-2-one, a compound similar to the substituted coumarins, inhibits α-carbonic anhydrases without hydrolysis of the lactam ring. J Enzyme Inhib Med Chem 2015;30:773–7.
  • Tars K, Vullo D, Kazaks A, et al. Sulfocoumarins (1,2-benzoxathiine-2,2-dioxides): a class of potent and isoform-selective inhibitors of tumor-associated carbonic anhydrases. J Med Chem 2013;56:293–300.
  • Pustenko A, Stepanovs D, Žalubovskis R, et al. 3H-1,2-benzoxathiepine 2,2-dioxides: a new class of isoform-selective carbonic anhydrase inhibitors. J Enzyme Inhib Med Chem 2017;32:767–75.
  • Krasavin M, Žalubovskis R, Grandāne A, et al. Sulfocoumarins as dual inhibitors of human carbonic anhydrase isoforms IX/XII and of human thioredoxin reductase. J Enzyme Inhib Med Chem 2020;35:506–10.
  • Angeli A, Trallori E, Carta F, et al. Heterocoumarins are selective carbonic anhydrase IX and XII inhibitors with cytotoxic effects against cancer cells lines. ACS Med Chem Lett 2018;9:947–51.
  • Andring J, Combs J, McKenna R. Aspirin: a suicide inhibitor of carbonic anhydrase II. Biomolecules 2020;10:527.
  • Mori M, Capasso C, Carta F, et al. A deadly spillover: SARS-CoV-2 outbreak. Expert Opin Ther Pat 2020;1–5. DOI:10.1080/13543776.2020.1760838
  • Peppicelli S, Andreucci E, Ruzzolini J, et al. The carbonic anhydrase IX inhibitor SLC-0111 as emerging agent against the mesenchymal stem cell-derived pro-survival effects on melanoma cells. J Enzyme Inhib Med Chem 2020;35:1185–93.
  • Dogné JM, Hanson J, Supuran C, Pratico D. Coxibs and cardiovascular side-effects: from light to shadow. Curr Pharm Des 2006;12:971–5.
  • (a) Modak JK, Tikhomirova A, Gorrell RJ, et al. Anti-Helicobacter pylori activity of ethoxzolamide. J Enzyme Inhib Med Chem 2019;34:1660–7. (b) Vullo D, Kumar RSS, Scozzafava A, et al. Sulphonamide inhibition studies of the β-carbonic anhydrase from the bacterial pathogen Clostridium perfringens. J Enzyme Inhib Med Chem 2018;33:31–6. (c) Rahman MM, Tikhomirova A, Modak JK, et al. Antibacterial activity of ethoxzolamide against Helicobacter pylori strains SS1 and 26695. Gut Pathog 2020;12:20. (d) Angeli A, Del Prete S, Pinteala M, et al. The first activation study of the β-carbonic anhydrases from the pathogenic bacteria Brucella suis and Francisella tularensis with amines and amino acids. J Enzyme Inhib Med Chem. 2019;34:1178–85.
  • (a) Vermelho AB, Rodrigues GC, Supuran CT. Why hasn’t there been more progress in new Chagas disease drug discovery? Expert Opin Drug Discov 2020;15:145–58. (b) Supuran CT, Capasso C. The eta-class carbonic anhydrases as drug targets for antimalarial agents. Expert Opin Ther Targets 2015;19:551–63. (c) Capasso C, Supuran CT. Bacterial, fungal and protozoan carbonic anhydrases as drug targets. Expert Opin Ther Targets 2015;19:1689–704.
  • Nocentini A, Osman SM, Almeida IA, et al. Appraisal of anti-protozoan activity of nitroaromatic benzenesulfonamides inhibiting carbonic anhydrases from Trypanosoma cruzi and Leishmania donovani. J Enzyme Inhib Med Chem 2019;34:1164–71.
  • Da’dara AA, Angeli A, Ferraroni M, et al. Crystal structure and chemical inhibition of essential schistosome host-interactive virulence factor carbonic anhydrase SmCA. Commun Biol 2019;2:333.