Benzothiazole (BTA) belongs to the heterocyclic class of bicyclic compounds. BTA derivatives possesses broad spectrum biological activities such as anticancer, antioxidant, anti-inflammatory, anti-tumour, antiviral, antibacterial, anti-proliferative, anti-diabetic, anti-convulsant, analgesic, anti-tubercular, antimalarial, anti-leishmanial, anti-histaminic and anti-fungal among others. The BTA scaffolds showed a crucial role in the inhibition of the metalloenzyme carbonic anhydrase (CA). In this review an extensive literature survey over the last decade discloses the role of BTA derivatives mainly as anticancer agents. Such compounds are effective against various types of cancer cell lines through a multitude of mechanisms, some of which are poorly studied or understood. The inhibition of tumour associated CAs by BTA derivatives is on the other hand better investigated and such compounds may serve as anticancer leads for the development of agents effective against hypoxic tumours.

Sulphonamides are biologically important compounds with low toxicity, many bioactivities and cost-effectiveness. Eight sulphonamide derivatives were synthesised and characterised by FT-IR, ¹³C NMR, ¹H NMR, LC-MS and elemental analysis. Their inhibitory effect on AChE, and carbonic anhydrase I and II enzyme activities was investigated. Their antioxidant activity was determined using different bioanalytical assays such as radical scavenging tests with ABTS^•+, and DPPH^•+ as well as metal-reducing abilities with CUPRAC, and FRAP assays. All compounds showed satisfactory enzyme inhibitory potency in nanomolar concentrations against AChE and CA isoforms with K_I values ranging from 10.14 ± 0.03 to 100.58 ± 1.90 nM. Amine group containing derivatives showed high metal reduction activity and about 70% ABTS radical scavenging activity. Due to their antioxidant activity and AChE inhibition, these novel compounds may be considered as leads for investigations in neurodegenerative diseases.

Carbonic anhydrases (CAs, EC 4.2.1.1) belonging to the α-, β-, γ-, δ- and ζ-CAs are ubiquitous metalloenzymes present in prokaryotes and eukaryotes. CAs started to be investigated in detail only recently in pathogenic bacteria, in the search for antibiotics with a novel mechanism of action, since it has been demonstrated that in many such organisms they are essential for the life cycle of the organism. CA inhibition leads to growth impairment or growth defects in several pathogenic bacteria. The microbiota of the human oral mucosa consists of a myriad of bacterial species, Porphyromonas gingivalis being one of them and the major pathogen responsible for the development of chronic periodontitis. The genome of P. gingivalis encodes for a β- and a γ-CAs. Recently, our group purified the recombinant γ-CA (named PgiCA) which was shown to possess a significant catalytic activity for the reaction that converts CO₂ to bicarbonate and protons, with a k_cat of 4.1 × 10⁵s⁻¹ and a k_cat/K_m of 5.4 × 10⁷M⁻¹× s⁻¹. We have also investigated its inhibition profile with a range of inorganic anions such as thiocyanate, cyanide, azide, hydrogen sulfide, sulfamate and trithiocarbonate. Here, we describe the cloning, purification and kinetic parameters of the other class of CA identified in the genome of P. gingivalis, the β-CA, named PgiCAb. This enzyme has a good catalytic activity, with a k_cat of 2.8 × 10⁵s⁻¹ and a k_cat/K_m of 1.5 × 10⁷M⁻¹× s⁻¹. PgiCAb was also inhibited by the clinically used sulfonamide acetazolamide, with an inhibition constant of 214 nM. The role of CAs as possible virulence factors of P. gingivalis is poorly understood at the moment but their good catalytic activity and the fact that they might be inhibited by a large number of compounds, which may pave the way for finding inhibitors with antibacterial activity that may elucidate these phenomena and lead to novel antibiotics.