Monoamine oxidase inhibitions are considered as important targets for the treatment of depression, anxiety, and neurodegenerative disorders, including Alzheimer’s and Parkinson’s diseases. This has encouraged many medicinal chemistry research groups for the development of most promising selective monoamine oxidase (MAO) inhibitors. A large number of plant isolates also reported for significant MAO inhibition potential in recent years. Differently substituted flavonoids have been prepared and investigated as MAO-A and MAO-B inhibitors. Flavonoid scaffold showed notable antidepressant and neuroprotective properties as revealed by various and established preclinical trials. The current review made an attempt to summarizing and critically evaluating the new findings on the quercetin and related flavonoid derivatives functions as potent MAO isoform inhibitors.

Natural based inhibitors of monoamine oxidase are promising drug candidates for the treatment of several neurodegenerative and neuropsychological disorders including depression, anxiety, Parkinson’s disease and Alzheimer’s disease. In the present study we designed and synthesized the eugenol based derivatives and investigated them for human MAO inhibitory potential as promising candidates for therapeutics of neurological disorders. Moreover, radical scavenging activity of designed derivatives was tested by and H 2 O 2 and DPPH scavenging methods. Eugenol based derivatives were designed and synthesized for human MAO inhibitory action. The in silico and in vitro models were utilized for the evaluation of hMAO inhibition. The insight into molecular interactions among the compounds and both hMAO-A and hMAO-B active site was achieved by molecular docking studies. The two spectrophotometric titrations techniques were used to evaluate antioxidant potential. Compounds 5b and 16 were found as most active hMAO-A inhibitors with IC 50 values of 5.989 ± 0.007 µM and 7.348 ± 0.027 µM respectively, through an appreciable selectivity index value of 0.19 and 0.14 respectively. In case of hMAO-B inhibition compounds 13a and 13b were found as most active hMAO-B inhibitors with IC 50 values of 7.494 ± 0.014 µM and 9.183 ± 0.034 µM receptively and outstanding value of selectivity index of 5.14 and 5.72 respectively. Radical scavenging assay showed that compounds 5b , 5a , 9b , 9a were active antioxidants. The findings of present study indicated excellent correlation among dry lab and wet lab hMAO inhibitory experiments. Interestingly, the compounds exhibiting better MAO inhibition activity was also appeared as good antioxidant agents.

It is clear that, by this computational drug design approach, more particular, reversible and potent compounds can be proposed as MAO inhibitors by exact changes on the fundamental framework.

<P>Background: A large number of disorders and their symptoms emerge from deficiency or overproduction of specific metabolites has drawn the attention for the discovery of new therapeutic agents for the treatment of disorders. Various approaches such as computational drug design have provided the new methodology for the selection and evaluation of target protein and the lead compound mechanistically. For instance, the overproduction of xanthine oxidase causes the accumulation of uric acid which can prompt gout. </P><P> Objective: In the present study we critically discussed the various techniques such as 3-D QSAR and molecular docking for the study of the natural based xanthine oxidase inhibitors with their mechanistic insight into the interaction of xanthine oxidase and various natural leads. Conclusion: The computational studies of deferent natural compounds were discussed as a result the flavonoids, anthraquinones, xanthones shown the remarkable inhibitory potential for xanthine oxidase inhibition moreover the flavonoids such as hesperidin and rutin were found as promising candidates for further exploration.<P>

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The development of xanthine oxidase and monoamine oxidase inhibitors led to important breakthroughs in the therapy of oxidative damage, hyperuricemia, gout, neurological, neuropsychiatric disorders and management of reperfusion injury. Drugs obtained from natural sources play an important role in the treatment of various pathological disorders and act as a lead compound for the discovery of new synthetic drug substances. In this review, various pharmacological effects produced by the inhibition of xanthine oxidase and monoamine oxidase through natural and synthetic flavonoids as well as anthraquinones are discussed in detail. Several methods have been designed for monitoring enzymatic activity and its inhibitor screening of bioactive natural and synthetic flavonoids and anthraquinones. In this review, all the in-vitro and other computational approaches are critically discussed which provided the clue about structure activity requirements for further precise modifications on the basic scaffold.

Two new series of methyl 7-methyl-5-(substituted-phenyl)-3,5-dihydro-2H-substituted [3,2-a]pyrimidine-6-carboxylate derivatives of thiourea and guanidine were synthesized. These compounds were characterized and evaluated for their antibacterial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and antifungal Aspergillus niger and Candida albicans and free radical scavenging activity using DPPH reagent method. Compound 7f was found to be the most active antibacterial and antifungal agent comparable to the standard drugs ciprofloxacin and fluconazole. Further, the compounds 5e, 7g, and 7h were also found to have significant antimicrobial activity. Compound 5a was found to be the most active antioxidant among all the targeted compounds, while compounds 5b, 5g, 7b, and 7f also had significant antioxidant activity compared to standard ascorbic acid.

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