Background: The MAO enzyme is presented in the brain and peripheral tissues and is a significant enzyme that is responsible for the deamination of biogenic amines and thus the regulation of neurotransmitter levels. The reaction of these neurotransmitters with the MAO enzyme produces aldehyde and free amine. MAO enzyme consists of two isoforms, MAO-A and MAO-B, which are characterized by amino acid sequence, three-dimensional structure, substrate preference, and inhibitor selectivity. Dopamine, tyramine, and tryptamine are substrates of both MAO isoforms and MAO inhibitors such as clorgiline and selegiline, which are used as medications in neurodegenerative and neurological diseases. In particular, MAO-A inhibitors are used in the treatment of depression, while MAO-B inhibitors are used in the treatment of Parkinson's disease. It is also investigated whether MAO-B inhibitors are effective in the treatment of Alzheimer's disease. Nowadays, life expectancy has increased, as a result, neurodegenerative diseases such as Parkinson's and Alzheimer's disease have started to occur more frequently. The elderly population is increasing day by day. As a result of these common diseases in elderly people, these people are unable to do their jobs and need care. Therefore, these diseases have become a significant health problem in society. Methods: In this study, review, inclusion, and exclusion criteria were used. Peer-reviewed research articles were searched. The quality of the examined articles was evaluated with standard tools. The information obtained was analyzed conceptually by using qualitative content analysis methodology. Results: One hundred and five papers were included in the review. The current MAO-B inhibitors and their usage areas are discussed together with the structures of the drugs; also, their possible effects in Alzheimer’s and Parkinson’s treatment are evaluated. In addition, different articles have been compiled in which structures such as arylalkylamines, chalcones, benzoquinone, benzoxazinone, and chromen are substituted with various functional groups and aromatic rings, along with thestructures of 44 different compounds that have recently been developed and their inhibitory effects on MAO-B enzyme. As a result, the structure required for MAO-B inhibition and SAR studies is discussed. Conclusion: Many studies demonstrate that MAO-B activity increases with age in brain tissue, cerebrospinal fluid (CSF), and platelets in Alzheimer's patients. This suggests that MAO-B inhibitor drugs, which may be effective in the treatment of Parkinson's disease, may also be effective in the treatment of Alzheimer's disease. This article was written to explain the multifaceted MAO-B inhibitor molecules.

Sixteen compounds (TR1–TR16) were synthesized and evaluated for their inhibitory activities against monoamine oxidase A and B (MAOs). Most of the derivatives showed potent and highly selective MAO-B inhibition. Compound TR16 was the most potent inhibitor against MAO-B with an IC₅₀ value of 0.17 μM, followed by TR2 (IC₅₀ = 0.27 μM). TR2 and TR16 selectivity index (SI) values for MAO-B versus MAO-A were 84.96 and higher than 235.29, respectively. Compared to the basic structures, the para-chloro substituent in TR2 and TR16 increased the inhibitory activity of MAO-B. TR2 and TR16 were reversible MAO-B inhibitors that were competitive, with K_i values of 0.230 ± 0.004 and 0.149 ± 0.016 µM, respectively. The PAMPA method indicated that compounds TR2 and TR16 had the tendency to traverse the blood–brain barrier. Docking investigations revealed that lead compounds were beneficial for MAO-B inhibition via association with key as well as selective E84 or Y326 residues, but not for MAO-A inhibition via interaction primarily driven by hydrophobic contacts. In conclusion, TR2 and TR16 are therapeutic prospects for the management of multiple neurodegenerative diseases.

Novel twenty-three 3(2H)-pyridazinone derivatives were designed and synthesized based on the chemical requirements related to the anti-proliferative effects previously demonstrated within this scaffold. The introduction of a piperazinyl linker between the pyridazinone nucleus and the additional (un)substituted phenyl group led to some compounds endowed with a limited cytotoxicity against human gingival fibroblasts (HGFs) and good anti-proliferative effects against gastric adenocarcinoma cells (AGS) as evaluated by MTT and LDH assays, using doxorubicin as a positive control. Successive analyses revealed that the two most promising representative compounds (12 and 22) could exert their effects by inducing oxidative stress as demonstrated by the hydrogen peroxide release and the morphological changes (cell blebbing) revealed by light microscopy analysis after the haematoxylin-eosin staining. Moreover, to further assess the apoptotic process induced by compounds 12 and 22, Bax expression was measured by flow cytometry. These findings enlarged our knowledge of the structural requirements in this scaffold to display valuable biological effects against cancerous cell lines.

The olive (Olea europaea L.) is one of the most important plants grown in many Mediterranean countries that has a high economic value. Olives, which are specific to each region, have different bioactive components. In this study, we investigated the phenolic/flavonoid contents, as well as antioxidant, antimicrobial, and antithrombotic activities of the fruit, leaf, and seed extracts obtained from the Halhalı olive grown in Arsuz district of Hatay, Turkey. Antioxidant activities of the phenolic compounds found in the olive fruit, seed, and leaf extracts were determined by employing established in vitro systems. Total phenolics were determined as gallic acid equivalents, while total flavonoids were determined as quercetin equivalents. Also, we evaluated a possible interaction between oleuropein and aggregation-related glycoproteins of the platelet surface via docking studies. The extracts showed effective antioxidant activity. The seed extract had the highest phenolic content of 317.24 μg GAE, while the fruit extract had the highest flavonoid content of 4.43 μg. The highest potential for metal chelating activity was found in the leaf extract, with an IC50 value of 13.33 mg/mL. Also, the leaf extract showed higher levels of antioxidant, antithrombotic, and antimicrobial activity, compared to the fruit and seed extracts. The docking scores of oleuropein against the target molecules GPVI, α2β1, and GPIbα were calculated as –3.798, –4.315, and –6.464 kcal/mol, respectively. The olive fruit, leaf, and seed extracts used as experimental material in our study have remarkable antioxidant, antimicrobial, and antithrombotic potential.