2H-chromene and 7H-furo-chromene derivatives selectively inhibit tumour associated human carbonic anhydrase IX and XII isoforms

Tumour associated carbonic anhydrases (CAs) IX and XII have been recognised as potential targets for the treatment of hypoxic tumours. Therefore, considering the high pharmacological potential of the chromene scaffold as selective ligand of the IX and XII isoforms, two libraries of compounds, namely 2H-chromene and 7H-furo-chromene derivatives, with diverse substitution patterns were designed and synthesised. The structure of the newly synthesised compounds was characterised and their inhibitory potency and selectivity towards human CA off target isoforms I, II and cancer-associated CA isoforms IX and XII were evaluated. Most of the compounds inhibit CA isoforms IX and XII with no activity against the I and II isozymes. Thus, while the potency was influenced by the substitution pattern along the chromene scaffold, the selectivity was conserved along the series, confirming the high potential of both 2H-chromene and 7H-furo-chromene scaffolds for the design of isozyme selective inhibitors.

A Multitarget Approach against Neuroinflammation: Alkyl Substituted Coumarins as Inhibitors of Enzymes Involved in Neurodegeneration

Neurodegenerative disorders (NDs) include a large range of diseases characterized by neural dysfunction with a multifactorial etiology. The most common NDs are Alzheimer's disease and Parkinson's disease, in which cholinergic and dopaminergic systems are impaired, respectively. Despite different brain regions being affected, oxidative stress and inflammation were found to be common triggers in the pathogenesis and progression of both diseases. By taking advantage of a multi-target approach, in this work we explored alkyl substituted coumarins as neuroprotective agents, capable to reduce oxidative stress and inflammation by inhibiting enzymes involved in neurodegeneration, among which are Carbonic Anhydrases (CAs), Monoamine Oxidases (MAOs), and Cholinesterases (ChEs). The compounds were synthesized and profiled against the three targeted enzymes. The binding mode of the most promising compounds (7 and 9) within MAO-A and -B was analyzed through molecular modeling studies, providing and explanation for the different selectivities observed for the MAO isoforms. In vitro biological studies using LPS-stimulated rat astrocytes showed that some compounds were able to counteract the oxidative stress-induced neuroinflammation and hamper interleukin-6 secretion, confirming the success of this multitarget approach.

Kinetic Study on the Base-Catalyzed Imine-Enamine Tautomerism of a Chiral Biologically Active Isoxazoline Derivative by HPLC on Amylose Tris(3,5-dimethylphenylcarbamate) Chiral Stationary Phase

Isoxazoline is a nitrogen- and oxygen-containing five-membered heterocyclic scaffold with diverse biological profiles such as antimicrobial, fungicidal, anticancer, antiviral, analgesic and anti-inflammatory activity. Accordingly, the use of this peculiar structural framework in drug discovery is a successful strategy for the development of new drug candidates. Here, a chiral saccharin/isoxazoline hybrid was considered to investigate the tendency of the imine moiety of the heterocyclic ring to tautomerize to the enamine form in the presence of a basic catalyst. The pseudo-first-order rate constants for the base-catalyzed tautomerization process were measured in different solvents and at different temperatures by off-column kinetic experiments based on the amylose (3,5-dimethylphenylcarbamate)-type chiral stationary phase. The kinetic results obtained in this study may be a useful aid in the perspective of designing experimental conditions to control the stereointegrity of these types of pharmacologically active compounds and drive their synthesis toward the preferred, imine or enamine, tautomer.

Novel Insights on CAI-CORM Hybrids: Evaluation of the CO Releasing Properties and Pain-Relieving Activity of Differently Substituted Coumarins for the Treatment of Rheumatoid Arthritis

Pain control is among the most important healthcare services in patients affected by rheumatoid arthritis (RA), but the current therapeutic options (i.e., disease-modifying anti-rheumatic drugs) are limited by the risk of the side effects. In this context, we proposed an innovative approach based on the hybridization between carbonic anhydrase inhibitors (CAIs) and CO releasing molecules (CORMs). The resulting CAI-CORM hybrids were revealed to possess strong anti-inflammatory effects in in vitro models of diseases and to relieve ache symptoms in an in vivo RA rat model. In this work, we have deepened the study of these promising hybrids, designing a library of coumarin-based compounds, also including internal dicobalt hexacarbonyl systems. The results obtained from the CO releasing study, the CA inhibitory activity, and the in vivo pain-relief efficacy evaluation in the RA rat model confirmed the success of this strategy, allowing us to consider CAI-CORM hybrids promising anti-nociceptive agents against arthritis.

Discovery and Hit-to-Lead Optimization of Benzothiazole Scaffold-Based DNA Gyrase Inhibitors with Potent Activity against Acinetobacter baumannii and Pseudomonas aeruginosa

We have developed compounds with a promising activity against Acinetobacter baumannii and Pseudomonas aeruginosa, which are both on the WHO priority list of antibiotic-resistant bacteria. Starting from DNA gyrase inhibitor 1, we identified compound 27, featuring a 10-fold improved aqueous solubility, a 10-fold improved inhibition of topoisomerase IV from A. baumannii and P. aeruginosa, a 10-fold decreased inhibition of human topoisomerase IIα, and no cross-resistance to novobiocin. Cocrystal structures of 1 in complex with Escherichia coli GyrB24 and (S)-27 in complex with A. baumannii GyrB23 and P. aeruginosa GyrB24 revealed their binding to the ATP-binding pocket of the GyrB subunit. In further optimization steps, solubility, plasma free fraction, and other ADME properties of 27 were improved by fine-tuning of lipophilicity. In particular, analogs of 27 with retained anti-Gram-negative activity and improved plasma free fraction were identified. The series was found to be nongenotoxic, nonmutagenic, devoid of mitochondrial toxicity, and possessed no ion channel liabilities.

An innovative spectroscopic approach for qualitative and quantitative evaluation of Mb-CO from myoglobin carbonylation reaction through chemometrics methods

In this work, an innovative approach using K-means and multivariate curve resolution-purity based algorithm (MCR-Purity) for the evaluation and quantification of carboxymyoglobin (Mb-CO) formation from Deoxy-Myoglobin (Deoxy-Mb) was presented. Through a multilevel multifactor experimental design, samples with different concentrations of Mb-CO were created. The UV-Vis spectra of these samples were submitted to K-means analysis, finding 3 clusters. The mean spectra of the clusters were extracted and it was possible to detect 2 totally differentiable groups through peaks 423 and 434 nm, which are wavelengths related to the Mb-CO and Deoxy-Mb components, respectively. The spectral data were subjected to MCR-Purity analysis. The MCR-Purity result successfully described the analyzed reaction, explaining more than 99.9% of the variance (R²) with a LOF of 1.43%. Then, a predictive model of MbCO was created through the linear relationship between MCR-Purity contributions and known concentrations of MbCO. The performance parameters of the created predictive model were R²CV = 0.98, RMSECV = 0.58 and RPDcv = 7.8 for the training set, and R²P = 0.98, RMSEP = 0.7 and RPDp = 6.8 for the test set. Thus, the predictive model presented an excellent performance considering that the Mb-CO variation is comprised between 0 and 21 µM. Therefore, these results demonstrate that the application of the proposed strategy to the analysis of spectral data presenting overlapping bands is feasible and robust.

Selective inhibition of carbonic anhydrase IX and XII by coumarin and psoralen derivatives

A small library of coumarin and their psoralen analogues EMAC10157a-b-d-g and EMAC10160a-b-d-g has been designed and synthesised to investigate the effect of structural modifications on their inhibition ability and selectivity profile towards carbonic anhydrase isoforms I, II, IX, and XII. None of the new compounds exhibited activity towards hCA I and II isozymes. Conversely, both coumarin and psoralen derivatives were active against tumour associated isoforms IX and XII in the low micromolar or nanomolar range of concentration. These data further corroborate our previous findings on analogous derivatives, confirming that both coumarins and psoralens are interesting scaffolds for the design of isozyme selective hCA inhibitors.

Exploring New Scaffolds for the Dual Inhibition of HIV-1 RT Polymerase and Ribonuclease Associated Functions

Current therapeutic protocols for the treatment of HIV infection consist of the combination of diverse anti-retroviral drugs in order to reduce the selection of resistant mutants and to allow for the use of lower doses of each single agent to reduce toxicity. However, avoiding drugs interactions and patient compliance are issues not fully accomplished so far. Pursuing on our investigation on potential anti HIV multi-target agents we have designed and synthesized a small library of biphenylhydrazo 4-arylthiazoles derivatives and evaluated to investigate the ability of the new derivatives to simultaneously inhibit both associated functions of HIV reverse transcriptase. All compounds were active towards the two functions, although at different concentrations. The substitution pattern on the biphenyl moiety appears relevant to determine the activity. In particular, compound 2-{3-[(2-{4-[4-(hydroxynitroso)phenyl]-1,3-thiazol-2-yl} hydrazin-1-ylidene) methyl]-4-methoxyphenyl} benzamide bromide (EMAC2063) was the most potent towards RNaseH (IC₅₀ = 4.5 mM)- and RDDP (IC₅₀ = 8.0 mM) HIV RT-associated functions.

Novel insights on saccharin- and acesulfame-based carbonic anhydrase inhibitors: design, synthesis, modelling investigations and biological activity evaluation

A large library of saccharin and acesulfame derivatives has been synthesised and evaluated against four isoforms of human carbonic anhydrase, the two off-targets hCA I/II and the tumour related isoforms hCA IX/XII. Different strategies of scaffold modification have been attempted on both saccharin as well as acesulfame core leading to the obtainment of 60 compounds. Some of them exhibited inhibitory activity in the nanomolar range, albeit some of the performed changes led to either micromolar activity or to its absence, against hCA IX/XII. Molecular modelling studies focused the attention on the binding mode of these compounds to the enzyme. The proposed inhibition mechanism is the anchoring to zinc-bound water molecule. Docking studies along with molecular dynamics also underlined the importance of the compounds flexibility (e.g. achieved through the insertion of methylene group) which favoured potent and selective hCA inhibition.

Practical Synthesis and Application of Halogen-Doped Pyrrole Building Blocks

A practical access to four new halogen-substituted pyrrole building blocks was realized in two to five synthetic steps from commercially available starting materials. The target compounds were prepared on a 50 mg to 1 g scale, and their conversion to nanomolar inhibitors of bacterial DNA gyrase B was demonstrated for three of the prepared building blocks to showcase the usefulness of such chemical motifs in medicinal chemistry.

Synthesis and Evaluation of Thymol-Based Synthetic Derivatives as Dual-Action Inhibitors against Different Strains of H. pylori and AGS Cell Line

Following a similar approach on carvacrol-based derivatives, we investigated the synthesis and the microbiological screening against eight strains of H. pylori, and the cytotoxic activity against human gastric adenocarcinoma (AGS) cells of a new series of ether compounds based on the structure of thymol. Structural analysis comprehended elemental analysis and ¹H/¹³C/¹⁹F NMR spectra. The analysis of structure–activity relationships within this molecular library of 38 structurally-related compounds reported that some chemical modifications of the OH group of thymol led to broad-spectrum growth inhibition on all isolates. Preferred substitutions were benzyl groups compared to alkyl chains, and the specific presence of functional groups at para position of the benzyl moiety such as 4-CN and 4-Ph endowed the most anti-H. pylori activity toward all the strains with minimum inhibitory concentration (MIC) values up to 4 µg/mL. Poly-substitution on the benzyl ring was not essential. Moreover, several compounds characterized by the lowest minimum inhibitory concentration/minimum bactericidal concentration (MIC/MBC) values against H. pylori were also tested in order to verify a cytotoxic effect against AGS cells with respect to 5-fluorouracil and carvacrol. Three derivatives can be considered as new lead compounds alternative to current therapy to manage H. pylori infection, preventing the occurrence of severe gastric diseases. The present work confirms the possibility to use natural compounds as templates for the medicinal semi-synthesis.

Synthesis and evaluation of a large library of nitroxoline derivatives as pancreatic cancer antiproliferative agents

Pancreatic cancer (PC) is one of the deadliest carcinomas and in most cases, which are diagnosed with locally advanced or metastatic disease, current therapeutic options are highly unsatisfactory. Based on the anti-proliferative effects shown by nitroxoline, an old urinary antibacterial agent, we explored a large library of newly synthesised derivatives to unravel the importance of the OH moiety and pyridine ring of the parent compound. The new derivatives showed a valuable anti-proliferative effect and some displayed a greater effect as compared to nitroxoline against three pancreatic cancer cell lines with different genetic profiles. In particular, in silico pharmacokinetic data, clonogenicity assays and selectivity indexes of the most promising compounds showed several advantages for such derivatives, as compared to nitroxoline. Moreover, some of these novel compounds had stronger effects on cell viability and/or clonogenic capacity in PC cells as compared to erlotinib, a targeted agent approved for PC treatment.

Synthesis and Biological Evaluation of Carvacrol-Based Derivatives as Dual Inhibitors of H. pylori Strains and AGS Cell Proliferation

This study reports on the synthesis, structural assessment, microbiological screening against several strains of H. pylori and antiproliferative activity against human gastric adenocarcinoma (AGS) cells of a large series of carvacrol-based compounds. Structural analyses consisted of elemental analysis, 1H/13C/19F NMR spectra and crystallographic studies. The structure-activity relationships evidenced that among ether derivatives the substitution with specific electron-withdrawing groups (CF3 and NO2) especially in the para position of the benzyl ring led to an improvement of the antimicrobial activity, whereas electron-donating groups on the benzyl ring and ethereal alkyl chains were not tolerated with respect to the parent compound (MIC/MBC = 64/64 µg/mL). Ester derivatives (coumarin-carvacrol hybrids) displayed a slight enhancement of the inhibitory activity up to MIC values of 8-16 µg/mL. The most interesting compounds exhibiting the lowest MIC/MBC activity against H. pylori (among others, compounds 16 and 39 endowed with MIC/MBC values ranging between 2/2 to 32/32 µg/mL against all the evaluated strains) were also assayed for their ability to reduce AGS cell growth with respect to 5-Fluorouracil. Some derivatives can be regarded as new lead compounds able to reduce H. pylori growth and to counteract the proliferation of AGS cells, both contributing to the occurrence of gastric cancer.

Metabolic profiling of different wild and cultivated Allium species based on high-resolution mass spectrometry, high-performance liquid chromatography-photodiode array detector, and color analysis

Many plants of the genus Allium are widely cultivated and consumed for their nutraceutical and health-enhancing bioactive components effective in many metabolic and infectious diseases. In particular, Allium sativum L. (garlic), the most economically important Allium species, is known to present volatile, comparatively polar sulfur-containing compounds responsible for both the typical garlic aroma and antimicrobial property. More recently, the (moderately) polar portion of garlic metabolome, rich of polyphenols and amino acids, is gaining increasing interest as a source of antioxidants and primary nutrients. In this study, we have explored the chemical diversity of eight different hydroalcoholic extracts obtained by microwave-assisted extraction of white and red crop A. sativum and wild Allium triquetrum, Allium roseum, and Allium ampeloprasum, all originating from the Mediterranean Basin. The aim is to appraise their potential dietetic and healing value through an in-depth chemical characterization and contribute to preserve and exploit natural resources. The multimethodological method applied here is based on an untargeted metabolic profiling by means of high-resolution electrospray ionization Fourier-transform ion cyclotron resonance (ESI FT-ICR) mass spectrometry. More than 850 by ESI(+) and 450 by ESI(-) putative metabolites have been annotated covering all main classes of primary and secondary metabolites, including amino acids, alkaloids, organic and fatty acids, nucleotides, vitamins, organosulfur compounds, and flavonoids. The pigment and polyphenol components have been separated and quantified by a targeted chromatographic high-performance liquid chromatography-photodiode array detector (HPLC-PDA) and CIEL*a*b* colorimetric assay, showing characteristic yellow and red components in each extract, related to a different milieu of anthocyanins and flavonoids as assigned by high-resolution mass spectrometry (MS).

Inhibition of lysine acetyltransferases impairs tumor angiogenesis acting on both endothelial and tumor cells

Background

Understanding the signalling pathways involved in angiogenesis, and developing anti-angiogenic drugs are one of the major focuses on cancer research. Herein, we assessed the effect of CPTH6, a lysine acetyltransferase inhibitor and anti-tumoral compound, on angiogenesis-related properties of both endothelial and cancer cells.

Methods

The in vitro effect of CPTH6 on protein acetylation and anti-angiogenic properties on endothelial and lung cancer cells was evaluated via wound healing, trans-well invasion and migration, tube formation, immunoblotting and immunofluorescence. Matrigel plug assay, zebrafish embryo and mouse xenograft models were used to evaluate in vivo anti-angiogenic effect of CPTH6.

Results

CPTH6 impaired in vitro endothelial angiogenesis-related functions, and decreased the in vivo vascularization both in mice xenografts and zebrafish embryos. Mechanistically, CPTH6 reduced α-tubulin acetylation and induced accumulation of acetylated microtubules in the perinuclear region of endothelial cells. Interestingly, CPTH6 also affected the angiogenesis-related properties of lung cancer cells, and conditioned media derived from CPTH6-treated lung cancer cells impaired endothelial cells morphogenesis. CPTH6 also modulated the VEGF/VEGFR2 pathway, and reshaped cytoskeletal organization of lung cancer cells. Finally, anti-migratory effect of CPTH6, dependent on α-tubulin acetylation, was also demonstrated by genetic approaches in lung cancer cells.

Conclusion

Overall, this study indicates that α-tubulin acetylation could play a role in the anti-angiogenic effect of CPTH6 and, more in general, it adds information to the role of histone acetyltransferases in tumor angiogenesis, and proposes the inhibition of these enzymes as an antiangiogenic therapy of cancer.

Synthesis, Antiproliferative Effect, and Topoisomerase II Inhibitory Activity of 3-Methyl-2-phenyl-1H-indoles

A series of 3-methyl-2-phenyl-1H-indoles was prepared and investigated for antiproliferative activity on three human tumor cell lines, HeLa, A2780, and MSTO-211H, and some structure-activity relationships were drawn up. The GI₅₀ values of the most potent compounds (32 and 33) were lower than 5 μM in all tested cell lines. For the most biologically relevant derivatives, the effect on human DNA topoisomerase II relaxation activity was investigated, which highlighted the good correlation between the antiproliferative effect and topoisomerase II inhibition. The most potent derivative, 32, was shown to induce the apoptosis pathway. The obtained results highlight 3-methyl-2-phenyl-1H-indole as a promising scaffold for further optimization of compounds with potent antiproliferative and antitopoisomerase II activities.

Benzo[b]tiophen-3-ol derivatives as effective inhibitors of human monoamine oxidase: design, synthesis, and biological activity

A series of benzo[b]thiophen-3-ols were synthesised and investigated as potential human monoamine oxidase (hMAO) inhibitors in vitro as well as ex vivo in rat cortex synaptosomes by means of evaluation of 3,4-dihydroxyphenylacetic acid/dopamine (DOPAC/DA) ratio and lactate dehydrogenase (LDH) activity. Most of these compounds possessed high selectivity for the MAO-B isoform and a discrete antioxidant and chelating potential. Molecular docking studies of all the compounds underscored potential binding site interactions suitable for MAO inhibition activity, and suggested structural requirements to further improve the activity of this scaffold by chemical modification of the aryl substituents. Starting from this heterocyclic nucleus, novel lead compounds for the treatment of neurodegenerative disease could be developed.

High-performance liquid chromatography enantioseparation of chiral 2-(benzylsulfinyl)benzamide derivatives on cellulose tris(3,5-dichlorophenylcarbamate) chiral stationary phase

Recently it has been reported that immobilized chlorinated-type chiral stationary phases based on cellulose tris(3,5-dichlorophenylcarbamate) are able to express an outstanding enantioselectivity towards the structure of 2-(benzylsulfinyl)benzamide. We now introduce two homologue series of chiral sulfoxides based on the same 2-(sulfinyl)benzoyl core as the prototype of new selectands for HPLC, whose enantioselectivity could be modulable through the replacement of the benzyl group with an unbranched alkyl chain varying in length from 1 to 5 carbon atoms. HPLC parameters such as mobile phase composition and column temperature have been carefully evaluated in order to get pertinent structure-enantioselectivity relationships. The enantiomer elution order was unambiguously determined by a combined strategy involving theoretical and experimental procedures. Two cases of temperature-dependent inversion of the elution order of enantiomers in the operative temperature range of chiral chromatographic support were observed.

Design, synthesis and biological activity of selective hCAs inhibitors based on 2-(benzylsulfinyl)benzoic acid scaffold

A large library of derivatives based on the scaffold of 2-(benzylsulfinyl)benzoic acid were synthesised and tested as atypical inhibitors against four different isoforms of human carbonic anhydrase (hCA I, II, IX and XII, EC 4.2.1.1). The exploration of the chemical space around the main functional groups led to the discovery of selective hCA IX inhibitors in the micromolar/nanomolar range, thus establishing robust structure-activity relationships within this versatile scaffold. HPLC separation of some selected chiral compounds and biological evaluation of the corresponding enantiomers was performed along with molecular modelling studies on the most active derivatives.

Novel approaches to the discovery of selective human monoamine oxidase-B inhibitors: is there room for improvement?

Introduction: Selective monoamine oxidase-B (MAO-B) inhibitors are currently used as coadjuvants for the treatment of early motor symptoms in Parkinson's disease. They can, based on their chemical structure and mechanism of inhibition, be categorized into reversible and irreversible agents. Areas covered: This review provides a comprehensive update on the development state of selective MAO-B inhibitors describing the results, structures, structure-activity relationships (SARs) and Medicinal chemistry strategies as well as the related shortcomings over the past five years. Expert opinion: Researchers have explored and implemented new and old chemical scaffolds achieving high inhibitory potencies and isoform selectivity. Most of them were characterized and proposed as multitarget agents able to act at different levels (including AChE inhibition, H3R or A_2AR antagonism, antioxidant and chelating properties, Aβ_1-42 aggregation reduction) in the network of aetiologies of neurodegenerative disorders. These results can also be used to avoid 'cheese-reaction' effects and the occurrence of serotonergic syndrome in patients.

Investigation on the Stability of New Biologically Active Thiosemicarbazone- Derived Compounds by a Validated HPLC-PDA Method

Background:

New Chemical Entities (NCEs) could be generally exposed to several stress conditions of hydrolysis, oxidation, photolysis and thermal degradation in order to better characterize the compounds and to know if the degradation processes lead to generate undesired (or toxic) products.

Objective:

This paper reports the development and validation of an HPLC-PDA method for the qualiquantitative profiles determination and chemical-physical stability evaluation after forced decomposition studies of thiosemicarbazone-derived compounds endowed with interesting pharmacological activities.

Methods:

All compounds and two possible degradation products were resolved by using a Grace® C-18 (ODS) column (250 mm × 4.6 mm; 5 mm particle size) in gradient elution mode. The chromatographic analysis was run in 28 min. The analytical method was correctly validated using weighted-matrix matched standard curves in the following ranges: 1-100 µg mL-1 for the lead compounds, and 0.1-8 μg mL-1 for the two possible degradation products showing a good correlation coefficients (≥0.9756). Precision and trueness comply with International Guidelines on method validation.

Results:

The obtained results demonstrated an excellent stability of the thiosemicarbazone-derived products following the treatment with UV set at 254 nm and heat (at 80°C). In solution, however, the compounds showed different stability profiles.

Conclusion:

The results obtained through the forced degradation studies provided important information not only for handling, formulation and storage of the substances, but also for the possible chemical changes in order to increase the stability. Given the importance of the non-conventional dosage forms, the stability of the substances was also analyzed in the presence of widely used surfactants.

4-(3-Nitrophenyl)thiazol-2-ylhydrazone derivatives as antioxidants and selective hMAO-B inhibitors: synthesis, biological activity and computational analysis

A new series of 4-(3-nitrophenyl)thiazol-2-ylhydrazone derivatives were designed, synthesised, and evaluated to assess their inhibitory effect on the human monoamine oxidase (hMAO) A and B isoforms. Different (un)substituted (hetero)aromatic substituents were linked to N1 of the hydrazone in order to establish robust structure–activity relationships. The results of the biological testing demonstrated that the presence of the hydrazothiazole nucleus bearing at C4 a phenyl ring functionalised at the meta position with a nitro group represents an important pharmacophoric feature to obtain selective and reversible human MAO-B inhibition for the treatment of neurodegenerative disorders. In addition, the most potent and selective MAO-B inhibitors were evaluated in silico as potential cholinesterase (AChE/BuChE) inhibitors and in vitro for antioxidant activities. The results obtained from molecular modelling studies provided insight into the multiple interactions and structural requirements for the reported MAO inhibitory properties.

Design, Synthesis, Docking Studies and Monoamine Oxidase Inhibition of a Small Library of 1-acetyl- and 1-thiocarbamoyl-3,5-diphenyl-4,5-dihydro-(1H)-pyrazoles

New N-acetyl/N-thiocarbamoylpyrazoline derivatives were designed and synthesized in high yields to assess their inhibitory activity and selectivity against human monoamine oxidase A and B. The most important chiral compounds were separated into their single enantiomers and tested. The impact of the substituents at N1, C3 and C5 positions as well the influence of the configuration of the C5 on the biological activity were analyzed. Bulky aromatic groups at C5 were not tolerated. p-Prenyloxyaryl moiety at C3 oriented the selectivity toward the B isoform. The results were also corroborated by molecular modelling studies providing new suggestions for the synthesis of privileged structures to serve as lead compounds for the treatment of mood disorders and neurodegenerative diseases.