Milan Čačić

Synthesis and Antioxidant Activity of Some New Coumarinyl-1,3-Thiazolidine-4-ones

A series of Schiff’s bases (E)-N-2-aryliden-2-(4-methyl-2-oxo-2H-chromen-7-yloxy)acetohydrazides 2a-l and N-(2-(substituted phenyl)-4-oxo-thiazolidin-3-yl)-2-(4-methyl-2-oxo-2H-chromen-7-yloxy)acetamides 3a-l were synthesized and evaluated for their antioxidant activity by the phosphomolybdenum method. Most of the Schiff’s bases and thiazolidine-4-ones bearing two hydroxyl groups on the phenyl ring showed excellent antioxidant activity in comparison with ascorbic acid. Preliminary investigation on cytotoxic and antifungal activity was done on some representative samples.

4-Methyl-7-hydroxycoumarin antifungal and antioxidant activity enhancement by substitution with thiosemicarbazide and thiazolidinone moieties

According to literature data, thiosemicarbazide and thiazolidinone moieties should enhance biological properties of coumarin. Antioxidant, metal-chelating and antifungal activities of all compounds were investigated and compared to the activity of the starting material, 7-hydroxy-4-methylcoumarin, and were proven to possess potent antioxidant and antifungal activity. In general, thiosemicarbazides showed higher scavenging activity towards DPPH and galvinoxyl radicals than did 4-thiazolidinones and some of them had the same or even better activity than had ascorbic acid itself, depending on the free radical used. In antifungal activity tests towards four foodborne mycotoxigenic fungi, Aspergillus flavus, Aspergillus ochraceus. Fusarium graminearum and Fusarium verticillioides, coumarin derivatives were proven to possess a very high activity in terms of growth inhibition, depending on the fungi investigated. In general, 4-thiazolidinones showed better antifungal activity than did thiosemicarbazides. F. graminearum was the most susceptible to the compounds investigated and F. verticillioides was proven to be the most resistant. Two compounds, both coumarinyl thiosemicarbazides, were found to possess both antifungal and antioxidant activity which could be useful for applications in medicine, food industry and agriculture.

Design and Synthesis of Some New 1,3,4-Thiadiazines with Coumarin Moieties and Their Antioxidative and Antifungal Activity

A series of newly disubstituted (compounds 4a,b) and trisubstituted 1,3,4-thiadiazines 5a–l with various substituents was prepared utilizing different thiosemicarbazides and 3-α-bromoacetylcoumarins as starting compounds. The structures of the synthesized 1,3,4-thiadiazines are elucidated and confirmed utilizing the corresponding analytical and spectroscopic data. All of the new thiadiazine derivatives were tested for their antioxidant activity, employing different antioxidant assays (DPPH scavenging activity, iron chelating activity, power reducing activity). Compounds 5b, 5f, 5j and 4b were proven to be the best DPPH radical scavengers, while compounds 5h and 5j have shown the best iron chelating activity. Thiadiazine derivatives were also tested on their antifungal activity against four mycotoxicogenic fungi, Aspergillus flavus, A. ochraceus, Fusarium graminearum and F. verticillioides. The best antifungal against A. flavus was proven to be compound 5e, while compounds 4a and 5c were the best antifungals on A. ochraceus, and compound 5g showed the best antifungal activity on F. verticillioides.

Design and Synthesis of Some Thiazolidin-4-ones Based on (7-Hydroxy-2-oxo-2H-chromen-4-yl) Acetic Acid

(7-Hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid methyl ester (1) upon reaction with ethyl bromoacetate furnishes (7-ethoxycarbonylmethoxy-2-oxo-2H-chromen-4-yl)-acetic acid methylester (2), which on treatment with 100% hydrazine hydrate yields (7-hydrazinocarbonylmethoxy-2-oxo-2H-chromen-4-yl)-acetic acid hydrazide (3). The condensation of compound 3 with different aromatic aldehydes afforded a series of [7-(arylidenehydrazinocarbonylmethoxy)-2-oxo-2H-chromen-4-yl]-acetic acid arylidene-hydrazide Schiff’s bases 4a-k. Cyclo-condensation of compounds 4a-k with 2-mercapto-acetic acid in N,N-dimethylformamide in the presence of anhydrous ZnCl2 affords N-(2-aryl-4-oxothiazolidin-3-yl)-2-(4-(2-aryl-4-oxothiazolidin-3-ylcarbamoyl)-methyl)-2-oxo-2H-chromen-7-yloxy)-acetamides 5a-k. Structure elucidation of the products has been accomplished on the basis of elemental analysis, IR, 1H-NMR and 13C-NMR data. Compounds 4a-k and 5a-k will be screened for their antibacterial activity against both Gram-positive and Gram-negative bacteria and the results reported elsewhere in due course.

Design, Synthesis and Characterization of Some Novel 3-Coumarinyl- 5-aryliden-1, 3-thiazolidine-2, 4-diones and Their Antioxidant Activity

In our effort to obtain biologically active compounds, new 3,5-disubstituted 1,3-thiazolidine-2,4- diones (5a - r) were synthesized. A series of 5-arylmethylidene-1,3-thiazolidine-2,4-diones (3a - r) were prepared by Knoevenagel reaction from 1,3-thiazolidine-2,4-dione (2) and appropriate aromatic aldehydes. Condensation of 3a - r with 7-hydroxy-4-bromomethyl-2-oxo-2H-chromene (1) afforded novel 3-(7-hydroxy-2-oxo-2H-chromen-4-ylmethyl)-5-arylidene-1,3-thiazolidine-2,4-diones 5a - r. Compounds 3a - r and 5a - r were evaluated for their antioxidant activity (DPPH free radical scavenging activity). Graphical Abstract Design, Synthesis and Characterization of Some Novel 3-Coumarinyl- 5-aryliden-1,3-thiazolidine-2,4-diones and Their Antioxidant Activity

Mono- and bis-dipicolinic acid heterocyclic derivatives – thiosemicarbazides, triazoles, oxadiazoles and thiazolidinones as antifungal and antioxidant agents

Abstract A series of dipicolinic acid derivatives was synthesized and investigated for antimicrobial and antioxidant activity. Mono and bis derivatives of ethyl dipicolinate were utilized as starting materials for synthesis of mono- and bis-hydrazides. Thiosemicarbazides were obtained by reaction of hydrazides with isothiocyanates and cyclized into triazoles, thiadiazoles, oxadiazoles and thiazolidinones. Some of these products, especially those incorporating a thiazolidinone moiety in their structure, are excellent antioxidants, DPPH scavengers and antifungal agents.

Synthesis and Antioxidant Evaluation of Schiff Bases Derived from 2,6- Pyridinedicarboxylic Acid

A series of novel Schiff bases derived from dipicolinic acid was synthesized and evaluated for antioxidant and iron chelating activity. In most cases Schiff bases derived from di-hydrazide showed higher antioxidant activity than the ones derived from mono-hydrazide and some of them are very promising considering the fact of being better antioxidants than the standards used in the investigation. For iron chelating activity substituents had a greater impact on the activity than mono or di-hydrazide skeleton.

Synthesis and biological evaluation of a novel series of 1, 3-dicoumarinyl-5-aryl-2-pyrazolines

In the present paper novel 1, 3, 5-trisubstituted 2-pyrazolines (4a-q) were synthesized via condensation of different substituted 3-cinnamoyl-2-oxo-2H-chromenes (2a-q) with 2-(4-methyl-2-oxo-2H-chromen-7- yloxy)acetohydrazide (3). Chalcones were prepared via Claisen-Schmidt condensation by refluxing 3-acetyl-2-oxo-2H-chromen (1) with corresponding aldehydes in ethanol, in the presence of piperidine. All of these compounds were characterized by means of their IR, 1H NMR and LC/MS/MS spectroscopic data and elemental microanalysis. Chalcones and pyrazolines were screened for their antioxidant and iron chelating activity.