Chemoselective Preparation of New Families of Phenolic-Organoselenium Hybrids—A Biological Assessment

Being aware of the enormous biological potential of organoselenium and polyphenolic compounds, we have accomplished the preparation of novel hybrids, combining both pharma-cophores in order to obtain new antioxidant and antiproliferative agents. Three different families have been accessed in a straightforward and chemoselective fashion: carbohydrate-containing N-acylisoselenoureas, N-arylisoselenocarbamates and N-arylselenocarbamates. The nature of the organoselenium framework, number and position of phenolic hydroxyl groups and substituents on the aromatic scaffolds afforded valuable structure–activity relationships for the biological as-says accomplished: antioxidant properties (antiradical activity, DNA-protective effects, Glutathione peroxidase (GPx) mimicry) and antiproliferative activity. Regarding the antioxidant activity, selenocar-bamates 24–27 behaved as excellent mimetics of GPx in the substoichiometric elimination of H2O2 as a Reactive Oxygen Species (ROS) model. Isoselenocarbamates and particularly their selenocarbamate isomers exhibited potent antiproliferative activity against non-small lung cell lines (A549, SW1573) in the low micromolar range, with similar potency to that shown by the chemotherapeutic agent cisplatin (cis-diaminodichloroplatin, CDDP) and occasionally with more potency than etoposide (VP-16).Ministerio de Ciencia e Innovación PID2020-116460RB-I00Junta de Andalucía FQM134Gobierno de las Islas Canarias ProID202001010

Identification of an acetyl esterase in the supernatant of the environmental strain Bacillus sp. HR21-6

Bacillus sp. HR21-6 is capable of the chemo- and regioselective synthesis of lipophilic partially acetylated phenolic compounds derived from olive polyphenols, which are powerful antioxidants important in the formulation of functional foods. In this work, an acetyl esterase was identified in the secretome of this strain by non-targeted proteomics, and classified in the GDSL family (superfamily SGNH). The recombinant protein was expressed and purified from Escherichia coli in the soluble form, and biochemically characterized. Site-directed mutagenesis was performed to understand the role of different amino acids that are conserved among GDSL superfamily of esterases. Mutation of Ser-10, Gly-45 or His-185 abolished the enzyme activity, while mutation of Asn-77 or Thr-184 altered the substrate specificity of the enzyme. This new enzyme is able to perform chemoselective conversions of olive phenolic compounds with great interest in the food industry, such as hydroxytyrosol, 3,4-dihydroxyphenylglycol, and oleuropein.Junta de Andalucía P11-CVI-7427 M

Masked Phenolic-Selenium Conjugates: Potent and Selective Antiproliferative Agents Overcoming P-gp Resistance

Cancer accounts for one of the most complex diseases nowadays due to its multifactorial nature. Despite the vast number of cytotoxic agents developed so far, good therapeutic approaches are not always reached. In recent years, multitarget drugs are gaining great attention against multifactorial diseases in contraposition to polypharmacy. Herein we have accomplished the conjugation of phenolic derivatives with an ample number of organochalcogen motifs with the aim of developing novel antiproliferative agents. Their antioxidant, and antiproliferative properties (against six tumour and one non-tumour cell lines) were analysed. Moreover, in order to predict P-gp-mediated chemoresistance, the P-glycoprotein assay was also conducted in order to determine whether compounds prepared herein could behave as substrates of that glycoprotein. Selenium derivatives were found to be significantly stronger antiproliferative agents than their sulfur isosters. Moreover, the length and the nature of the tether, together with the nature of the organoselenium scaffold were also found to be crucial features in the observed bioactivities. The lead compound, bearing a methylenedioxyphenyl moiety, and a diselenide functionality, showed a good activity (GI50 = 0.88-2.0 µM) and selectivity towards tumour cell lines (selectivity index: 14-32); moreover, compounds considered herein were not substrates for the P-gp efflux pump, thus avoiding the development of chemoresistance coming from such mechanism, commonly found for widely-used chemotherapeutic agents

Conformationally Restricted Glycoconjugates Derived from Arylsulfonamides and Coumarins: New Families of Tumour-Associated Carbonic Anhydrase Inhibitors

The involvement of carbonic anhydrases (CAs) in a myriad of biological events makes the development of new inhibitors of these metalloenzymes a hot topic in current Medicinal Chemistry. In particular, CA IX and XII are membrane-bound enzymes, responsible for tumour survival and chemoresistance. Herein, a bicyclic carbohydrate-based hydrophilic tail (imidazolidine-2-thione) has been appended to a CA-targeting pharmacophore (arylsulfonamide, coumarin) with the aim of studying the influence of the conformational restriction of the tail on the CA inhibition. For this purpose, the coupling of sulfonamido- or coumarin-based isothiocyanates with reducing 2-aminosugars, followed by the sequential acid-promoted intramolecular cyclization of the corresponding thiourea and dehydration reactions, afforded the corresponding bicyclic imidazoline-2-thiones in good overall yield. The effects of the carbohydrate configuration, the position of the sulfonamido motif on the aryl fragment, and the tether length and substitution pattern on the coumarin were analysed in the in vitro inhibition of human CAs. Regarding sulfonamido-based inhibitors, the best template turned out to be a d-galacto-configured carbohydrate residue, meta-substitution on the aryl moiety (9b), with Ki against CA XII within the low nM range (5.1 nM), and remarkable selectivity indexes (1531 for CA I and 181.9 for CA II); this provided an enhanced profile in terms of potency and selectivity compared to more flexible linear thioureas 1–4 and the drug acetazolamide (AAZ), used herein as a reference compound. For coumarins, the strongest activities were found for substituents devoid of steric hindrance (Me, Cl), and short linkages; derivatives 24h and 24a were found to be the most potent inhibitors against CA IX and XII, respectively (Ki = 6.8, 10.1 nM), and also endowed with outstanding selectivity (Ki > 100 µM against CA I, II, as off-target enzymes). Docking simulations were conducted on 9b and 24h to gain more insight into the key inhibitor–enzyme interactions.Ministerio de Ciencia e Innovación PID2020-116460RB-I00, PID2021-123059OB-I00Junta de Andalucía FQM134Italian Ministry for University and Research (MIUR) 2017XYBP2