Synthesis of New Bis-Triazole Compounds Including Schiff Bases and Enzyme Inhibition and Antioxidant Activities 

Research Article

Synthesis of New Bis-Triazole Compounds Including Schiff Bases and Enzyme Inhibition
and Antioxidant Activities 

Corresponding author:  Dr. Yasemin Ünver, Department of Chemistry, Faculty of Sciences, Karadeniz Technical University, 61080 Trabzon, Turkey, Tel: +90 462 377 2485; Fax: +90 462 325 3196; Email:
Compounds 1 and 2 possessing bis-triazole rings were reacted with four aromatic aldehydes and compounds 3-4(a-d) carrying Schiff bases were synthesized. All newly compounds well characterized by spectroscopic data such as FT-IR, 1H NMR, 13C NMR, LC-MS/MS, and elemental analyses. All the newly synthesized compounds were screened for their enzyme and antioxidant activities. This study was explained the acetylcholinesterase/butyrcholinesterase and tyrosinase inhibitory effects, and 2,2-diphenyl1-picrylhydrazyl (DPPH) radical scavenging and phosphomolydenum reducing antioxidant power of the newly synthesized compounds for the first time. While compound 4a might be effective neurological agent, compounds 3c and 4c have antioxidant potential.

Keywords: Bis-Triazole; Schiff Base; Antioxidant; Enzyme Activities

Antioxidants have capacity to protect organisms and cells from damage caused by oxidative stress during metabolism. For this reason, the synthetic compounds are extensively studied for their antioxidant activities using different methodologies. The search for active components that prevent or reduce the impact of oxidative stress on cells is a quite contemporary field. Exogenous chemicals involved in food systems and endogenous compounds involved in metabolic processes in human body produce highly reactive free radicals, particularly oxygen derived ones. They have the potential to oxidize biomolecules and cause cell death, consequently causing tissue damage. It is known that free radical oxidative processes also play a significant pathological role in causing many human diseases together with aging [1-2]. As oxidative stress plays an important role in Parkinson, Alzheimer, heart failure and cancer, the use of antioxidants is intensively studied in medicinal chemistry, particularly as a means for the treatment of these widespread diseases [3-7].

Heterocyclic compounds have an increasing importance in medicinal chemistry among the five membered heterocyclics. Especially various 1,2,4-triazole derivatives have been investigated as therapeutically interesting drug candidates because of their properties as esterase, antimicrobial and antimycotic agents, anti-inflammatory, anti-tubercular, antioxidant, anticancer, antimicrobial activity [8-14]. Some of the modern day drugs with triazole ring are Fluconazole, Itraconazole (antifungal agent), Ribavirin (antiviral agent), Rizatriptan (antimigrane agent) and Alprazolam (anxiolytic agent) Schiff bases obtained from various heterocycles have a wide range of biological activities including antifungal, antibacterial, antimalarial, antimycobacterial, antimicrobial, anti-inflammatory, antiviral, cytotoxic, anticonvulsant, antiproliferative, anticancer, antifungal and antipyretic activities [15-22]. On the basis of these observations, we thought of designing and synthesizing a new class of bis-heterocycles which possess triazole-schiff base. Additionally, we reported the investigation results of antioxidant with five different methods and enzymeinhibition activities of all newly synthesized compounds in this



The 1H-, and 13C-Nuclear Magnetic Resonance spectra were recorded on an Agilent 400 MHz spectrometer, where tetramethylsilane (TMS) as an internal standard and Dimethyl sulfoxide d6 (DMSO-d6) as solvent are used. IR spectra were recorded on a Perkin-Elmer Spectrum one FT-IR spectrometer (resolution 4) in KBr pellets. The MS spectra were measured with an Micromass Quattro LC-MS/MS spectrometer with methanol as solvent. Elemental analyses were carried out on a C,H, N-O rapid elemental analyzer Hewlett-Packard 185 for C, H and N and results are with in 0.4 % of the therotical values. Melting points were measured on an electro thermal apparatus and are uncorrected.

Synthesis of the Compounds 3-4
0.01 mol compounds 1-2 and 0.02 mol aromatic aldehydes was heated in oil bath dry to dry for 2-3 h. at 160-180 0C. After cooling it to room temperature, the solids 3-4 were obtained and recrystallized from a mixture of dimethyl formamide (DMF) and ethanol.
2,2’-(4,4’-(butane-1,4-,diyl) bis (3-methy1-5-oxo-1H-1,2,4-triazole 4,1(4H,5H)-diyl))bis(N’-(thiophen-2-ylmethylene)acetohydrazide (3a). Yield: 86.40 %, m.p. 286-287 oC. IR (KBr, cm-1): 3052 (aromatic CH), 1695 (C=O), 1624 (C=N), 1575 (C=C); 1H NMR (400 MHz, DMSO-d6) δ: 1.57 (s, 4H, 2N-CH2-CH2), 2.17 (s, 6H, 2CH3), 3.60 (s, 4H, 2N-CH2), 4.33 (s, 4H, N-CH2-C=O), 7.12-8.86 (m, 6H, Arom.H), 8.86 (s, 2H, 2N=CH), 10.17 (s, 2H, 2NH);13C NMR (100 MHz, DMSO-d6) δ :11.66 (CH3), 25.92 (N-CH2-CH2), 40.57 (N-CH2), 46.60 (N-CH2-C=O), thiophene C [127.29 (CH), 128.37 (CH), 131.44 (CH), 136.63(C)], 143.06 (C=N), 154.18 (triazole C=O), 156.25 (N=CH), 169.85 (C=O); LC-MS (m/z): 721.41 (M++2+Na, 60%). Analysis (% Calculated/ found) for C26H28N14S4O2: C:44.81/44.56, H:4.05 /3.90, N:28.14/28.68.
2,2’-(4,4’-(hexane-1,6-,diyl) bis (3-methy1-5-oxo-1H-1,2,4-triazole 4,1(4H,5H)-diyl))bis(N’-(thiophen-2-ylmethylene)acetohydrazide (4a). Yield: 90.45 %, m.p. 215-216 oC. IR (KBr, cm 1): 3060 (aromatic CH), 1730 (C=O), 1644 (C=N), 1584 (C=C); 1H NMR (400 MHz, DMSO-d6) δ: 1.27 (s, 4H, 2N-CH2-CH2-CH2), 1.53 (s, 4H, 2N-CH2-CH2), 2.15(s, 6H, 2CH3), 3.50 (s, 4H, 2NCH2), 4.07 (s, 4H, 2N-CH2-C=O), 7.00-8.81 (m, 6H, Arom.H), 8.70 (s, 2H, 2N=CH), 10.01 (s, 2H, 2NH); 13C NMR (100MHz, DMSO d6) δ :11.68 (CH3), 25.86 (N-CH2-CH2-CH2), 28.70 (N-CHCH2), 41.02 (N-CH2), 46.55 (N-CH2-C=O), thiophene C [126.56 (CH), 128.68 (CH), 130.78 (CH), 136.00 (C)], 144.10 (C=N), 154.40 (triazole C=O), 155.85 (N=CH), 169.00 (C=O); LC-MS (m/z): 721.20 (M+, 60%). Analysis (% Calculated/found) for C28H32N14S4O2 C:46.39/46.16, H:4.45/4.07, N:27.05/27.80.
2,2’-(4,4’-(butane-1,4-diyl) bis (3-methy1-5-oxo-1H-1,2,4-triazole 4,1(4H,5H)-diyl))bis(N’-benzylideneacetohydrazide) (3b).
Yield: 80.10 %, m.p. 160-161 oC. IR (KBr, cm-1): 3101 (aromatic CH), 1736 (C=O), 1657 (C=N), 1608 (C=C); 1H NMR (400 MHz,
DMSO-d6) δ:1.56 (s, 4H, 2N-CH2-CH2), 2.18 (s, 6H, 2CH3), 3.60 (s, 4H, 2N-CH2), 4.37 (s, 4H, N-CH2-C=O), 7.12-8.7.65 (m, 10H, Arom.H), 8.85 (s, 2H, 2N=CH), 10.15 (s, 2H, 2NH); 13C NMR (100 MHz, DMSO-d6) δ :11.67 (CH3), 25.93 (N-CH2-CH2), 40.56 (N-CH2), 47.10 (N-CH2-C=O), Arom C [128.32 (CH), 128.39 (CH), 129.11 (CH), 131.08 (CH), 131.66 (CH), 134.26(C)], 143.90 (C=N), 154.40 (triazole C=O), 160.52 (N=CH), 169.86 (C=O); LC-MS (m/z): 685.50 (M++1, 60%). Analysis (% Calculated/ found) for C30H32N14S2O2 C:52.62/53.25, H:4.71/4.00, N:28.64/28.30.
2,2’-(4,4’-(hexane-1,6-,diyl) bis (3-methy1-5-oxo-1H-1,2,4-triazole-
4,1(4H,5H)-diyl))bis(N’-benzylideneacetohydrazide) (4b). Yield: 80.65 %, m.p. 220-221 oC. IR (KBr, cm-1): 3076 (aromatic CH), 1732 (C=O), 1645 (C=N), 1625 (C=C); 1H NMR (400 MHz, DMSO-d6) δ: 1.27 (s, 4H, 2N-CH2-CH2-CH2), 1.56 (s, 4H, 2N-CH2-CH2), 2.18 (s, 6H, 2CH3), 3.60 (s, 4H, 2N-CH2), 4.38 (s, 4H, 2N-CH2-C=O), 7.52-7.89 (m, 10 H, Arom.H), 8.73 (s, 2H,
2N=CH), 10.06 (s, 2H, 2NH); 13C NMR (100MHz, DMSO-d6) δ :11.68 (CH3), 25.86 (N-CH2-CH2-CH2), 28.71 (N-CH2-CH2), 41.01
(N-CH2), 46.56 (N-CH2-C=O), Arom C [128.83 (CH), 129.38 (CH), 131.56 (CH), 131.83 (CH), 134.26 (C)], 144.06 (C=N), 154.18 (triazole C=O), 161.94 (N=CH), 169.86 (C=O); LC-MS (m/z): 635.40 (M++Na, 60%). Analysis (%Calculated/found) for C32H36N14S2O2 C:53.92/54.05, H:5.09/4.90, N:27.51/27.50.

2,2’-(4,4’-(butane-1,4-,diyl) bis (3-methy1-5-oxo-1H-1,2,4-triazole 4,1(4H,5H)-diyl))bis(N’-(4-metoxybenzylidene)acetohydrazide) (3c). Yield: 81.50 %, m.p. 275-276 oC. IR (KBr, cm-1): 3068 (aromatic CH), 1733 (C=O), 1655 (C=N), 1582 (C=C); 1H NMR (400 MHz, DMSO-d6) δ:1.56 (s, 4H, 2N-CH2-CH2), 2.18 (s, 6H, 2CH3), 3.60 (s, 4H, 2N-CH2), 3.83 (s, 6H, 2 OCH3), 4.37 (s, 4H, N-CH2-C=O), 7.05-7.07 (m, 4H, Arom.H), 7.64-7.94 (m,4H, Arom.H) 8.64 (s, 2H, 2N=CH), 10.16 (s, 2H, 2NH); 13C NMR (100 MHz, DMSO-d6) δ :11.67 (CH3), 25.93 (N-CH2-CH2), 40.61 (N-CH2), 46.59 (N-CH2-C=O), 55.86 (OCH3), Arom C [114.87 (CH), 127.04 (C), 130.45 (CH), 162.14 (C)], 144.06 (C=N), 154.18 (triazole C=O), 160.96 (N=CH), 169.85 (C=O); LC-MS (m/z): 744.25 (M+, 60%). Analysis (% Calculated/found) for C32H36N14S2O4C:51.60/52.20, H:4.87/4.75, N:26.33/26.02.

2,2’-(4,4’-(hexane-1,6-,diyl) bis (3-methy1-5-oxo-1H-1,2,4-triazole 4,1(4H,5H)-diyl))bis(N’-(4-metoxybenzylidene)acetohydrazide) (4c). Yield: 81.50 %, m.p.170-171 oC. IR (KBr, cm-1): 3093 (aromatic CH), 1692 (C=O), 1619 (C=N), 1601 (C=C); 1H NMR (400 MHz, DMSO-d6) δ: 1.25 (s, 4H, 2N-CH2-CH2-CH2), 1.54 (s, 4H, 2N-CH2-CH2), 2.19 (s, 6H, 2CH3), 3.68 (s, 4H, 2NCH 2), 3.83 (s, 6H, 2OCH3), 4.38 (s, 4H, 2N-CH2-C=O), 6.86- 7.07 (m, 4H, Arom.H), 7.81-7.83 (m, 4H, Arom.H), 8.84 (s, 2H, 2N=CH), 9.87 (s, 2H, 2NH); 13C NMR (100MHz, DMSO-d6) δ :11.69 (CH3), 25.91 (N-CH2-CH2-CH2), 28.75 (N-CH2-CH2), 40.98 (N-CH2), 46.01 (N-CH2-C=O), 55.85 (OCH3), Arom C [114.86 (CH), 127.05 (C), 130.44 (CH), 162.14(C)], 144.09 (C=N), 154.30 (triazole C=O), 160.95 (N=CH), 169.60 (C=O);LC-MS (m /z): 772.12 (M+, 60%). Analysis (% Calculated/found) for C32H36N14S2O4 C:51.60/52.20, H:4.87/4.75, N:26.33/26.02.

2,2’-(4,4’-(butane-1,4-,diyl) bis (3-methy1-5-oxo-1H-1,2,4-triazole 4,1(4H,5H)-diyl))bis(N’-(2-hydroxybenzylidene)acetohydrazide) (3d). Yield: 78.90 %, m.p. 246-247 oC. IR (KBr, cm-1): 3085 (aromatic CH), 1734 (C=O), 1659 (C=N), 1582 (C=C); 1H NMR (400 MHz, DMSO-d6) δ: 1.56 (s, 4H, 2N-CH2– CH2), 2.18 (s, 6H, 2CH3), 3.60 (s, 4H, 2N-CH2), 4.37 (s, 4H, 2N-CH2-C=O), 4.98 (s, 2H, 2OH), 7.12-8.43 (m, 8H, Arom. H), 8.86 (s, 2H, N=CH), 10.15 (s, 2H, 2NH); 13C NMR (100 MHz, DMSO-d6) δ :11.67 (CH3), 25.92 (N-CH2-CH2), 40.56 (N-CH2), 46.58 (N-CH2-C=O), Arom.C [127.30 (CH), 128.83 (CH), 131.07 (CH), 131.47 (CH), 132.34 (C), 138.67 (C)], 144.06 (C=N), 150. 78 (triazole C=O), 159.28 (N=CH), 169.84 (C=O); LC-MS (m/z): 739.51 (M++Na, 60%). Analysis (% Calculated/found) for C30H32N14S2O4 C:50.27/50.98, H:4.50/4.20, N:27.36/26.97.

2,2’-(4,4’-(hexane-1,6-,diyl) bis (3-methy1-5-oxo-1H-1,2,4-triazole 4,1(4H,5H)-diyl))bis(N’-(2-hydroxybenzylidene)acetohydrazide) (4d). Yield: 75.48 %, m.p. 221-222 oC. IR (KBr, cm-1): 3097 (aromatic CH), 1687 (C=O), 1621 (C=N), 1584 (C=C); 1H NMR (400 MHz, DMSO-d6) δ: 1.26 (s, 4H, 2N-CH2– CH2-CH2), 1.55 (s, 4H, 2N-CH2-CH2), 2.17(s, 6H, 2CH3), 3.38 (s, 4H, 2N-CH2), 4.30 (s, 4H, 2N-CH2-C=O), 4.29 (s, 2H, 2OH), 7.14-8.78 (m, 6H, Arom.H), 8.88 (s, 2H, 2N=CH), 9.97 (s, 2H, 2NH); 13C NMR (100 MHz, DMSO-d6) δ : 11.86 (CH3), 25.80 (N-CH2-CH2-CH2), 28.88 (N-CH2-CH2), 40.30 (N-CH2), 47.11 (N-CH2-C=O), Arom.C [127.35 (CH), 128.76 (CH), 131.12 (CH), 131.48 (CH), 132.67 (C), 144.01 (C)], 144.39 (C=N), 150.81 (triazole C=O), 158.59 (N=CH), 169.70 (C=O); LC-MS (m/z): 767.61 (M++Na,60%). Analysis (%Calculated/found) for C32H36N14S2O4 C:51.60/51.40, H:4.87/4.33, N:26.33/26.30.
Materials and Methods for Biological Activities

Chemicals and Reagents

Acetylcholinesterase enzyme (AChE) from electric eel, acetylthiocholine iodide, 5,5-dithio-bis(2-nitrobenzoic) acid (DTNB), galantamine, Trisma-base, tyrosinase from mushroom, L-DOPA, kojic acid, 2,2-diphenyl-1-picrylhydrazyl (DPPH), gallic acid (GA), methanol, ethanol, phoshomolybdic acid, and quercetin (QE) were purchased from Sigma-Aldrich.

Enzyme Inhibitions

Acetylcholinesterase/Butyrylcholinesterase(AChE/BChE) Inhibition

Acetylcholinesterase/Butyrylcholinesterase (AChE/BChE) inhibiton was determined by Ingkaninan et al. [23] colorimetric method. Galantamine was used as the reference drug. First of all, the stock solutions (2.5 mg/mL) were prepared from the all of the compounds in 25% DMSO and then five different concentrations made from stock solutions in the buffer (Tris- HCI pH 8.00) for the experiments. 50 mM Tris-HCl buffer (pH 8.00), 3 mM DTNB (in buffer), 0.2 U/mL AChE/ BChE and the compounds at different concentrations were added in a 96- well microplate. The mixtures were incubated for 15 min at 25˚C. After incubation, 15 mM acetylthiocholine iodide/butyrylcholine chloride were added in the microplate and incubated 5 min at room temperature. The absorbance was measured at 412 nm using a 96-well microplate reader.

Inhibition of AChE/BChE was calculated by using the formula 1 and IC50 values obtained plotting the inhibition percentage against the compounds or reference drug. Acontrol is the activity of enzyme without the compounds (solvent in buffer pH= 8) and Asample is the activity of enzyme with the compounds at different concentrations. The experiments were carried out in
triplicate and results were expressed as the mean ± standard deviation (SD).

Formula 1.
Tyrosinase Inhibition

Tyrosinase inhibiton was determined using the method described by Masuda et al. [24]. Kojic acid was used as the reference drug. Firstly, the stock solutions (2.5 mg/mL) were prepared from the all of the compounds in 25% DMSO. Then five different concentrations were prepared from the stock solution in the phosphate buffer (pH 6.8). 20 μL of the compounds at different concentrations 20 μL of 250 U/mL tyrosinase and 100 μL of 100 mM pH 6.8 phosphate buffer solutions were added in a 96-well microplate. The reaction was initiated with addition of 20 μL of 3 mM L-DOPA and the absorbance was measured at 475 nm using a 96-well microplate reader. Inhibition of tyrosinase was calculated by using the formula 1 and IC50 values obtained plotting the inhibition percentage against the compounds or reference compound. The experiments were carried out in triplicate and results were expressed as the mean ± standard deviation (SD).

Antioxidant Activities

DPPH Radical Scavenging Assay

The DPPH radical scavenging activities were examined using the method described by Blois et al [25] compared to gallic acid and as the reference compound. Total volume of assay mixture which was 1 mL, contained methanolic DPPH solution (0.4 mM) and different concentrations of the compounds. The mixtures were incubated for 30 min at room temperature in the dark. After incubation, the absorbance of the compound (Acompound) was measured at 517 nm. Assay mixture without

samples was used as a control (Acontrol). DPPH scavenging was calculated by using the formula 2 and IC50 values obtained plotting the inhibition percentage against the compounds or reference drug. The experiments were carried out in triplicate and results were expressed as the mean ± standard deviation (SD).
Formula 2. 
Phosphomolibdenum-Reducing Antioxidant Power (PRAP) Assay

Phosphomolibdenum-reducing antioxidant power assay of the compounds were determined using phosphomolybdic acid compared to QE as the reference compound [26]. Total volume of assay mixture which was 1 mL, contained 10% phoshomolybdic acid solution in ethanol (w/v) and different concentrations (250 μg/mL, 500 μg/mL, and 1000 μg/mL) of the compounds. The mixtures were incubated for 30 min at 80 oC. After incubation, the absorbance was measured at 600 nm and compared to reference compound. The experiments were carried out in triplicate and results were expressed as the mean ± standard deviation (SD).

Results and Discussion

Scheme1. Synthetic pathway for the preparation of compounds 3-4(a-d)

The synthesis of bis-triazole compounds was performed following the steps shown in reaction the Scheme 1. The synthesis of known compounds 1 and 2 was performed according to previously reported procedure [8]. The reaction of compounds 1 and 2 with several aromatic aldehydes gave the bis triazoles 3-4(a-d) including Schiff bases respectively. NH2 peaks belonging to compounds 1 and 2 disappeared and the imine N=CH protons resonated as singlet at 8.64-8.88 ppm integrating f or 2 protons (there are two N=CH groups in the structure) in the 1H-NMR spectra of compounds 3-4(a-d). In addition, imine N=CH appeared 155.85-161.94 ppm in the 13C NMR spectra of compounds 3-4(a-d). 13C and 1H NMR spectra of compounds 3-4 exhibited additional signals due to aromatic group moiety at the related chemical shift values. Morever, compounds 3-4 gave relatively stable molecular ion peaks in the Mass spectra.

Enzyme Inhibition

Alzheimer Disease (AD), described to dementia, has become a major health issue in countries because of expected number of patients increased to 25 million by 2025 [27]. This disease is related to shortage of acetycholine and butyrycholine which are hydrolyzed by acetylcholinesterase and butyrcholinesterase [28]. Therefore, acetylcholinesterase and butyrcholinesterase inhibitors are currently used for this disease. In this work, the AChE/BChE inhibiton of the compounds were examined by Ingkaninan’s [23] assay with galantamine as a standard drug. AChE/BChE inhibition rates of the compounds were measured at different concentrations and the results of AChE/ BChE of the compounds in this study were summarized in Table 1, Figure 1 and Figure 2 as IC50 values. In this work, the lowest IC50 values of the compounds indicate a higher inhibition effectiveness. IC50 values of the compounds were determined lower than 0.25 mg/mL. Compounds 4c and 4a were exhibited the lowest IC50 values of AChE with 0.113 ± 0.03 mg/mL and 4a (0.113 ± 0.01 mg/mL) respectively, followed by compound 4d (0.116 ±0.03 mg/mL). At the same time, compound 4d was

Table1. Acetylcholinesterase, butyrylcholinesterase, tyrosinase and DPPH radical scavenging IC50 values (mg/mL) of the compounds(3-4)

Figure1. Acetylcholinesterase IC50 values (mg/mL)of the compounds (3-4).
Figure2. Butyrylcholinesterase IC50 values (mg/mL) of the compounds  (3-4).
showed lowest IC50 values of BChE with 0.094 ± 0.08 mg/mL followed by compound 3d (0.100 ± 0.08 mg/mL) and compound 4b (0.110 ± 0.03 mg/mL) respectively.

Tyrosinase enzyme plays a role formation of neuromelanin and damaged neurons related to Parkinson disease [28]. Therefore, researcher have aimed to find new tyrosinase enzyme inhibitor for against this disease. In this study, IC50 values of the compounds and reference drug on tyrosinase enzyme were summarized in Table 1. Compounds 3a and 4a inhibited tyrosinase enzyme and determined IC50 values among the all of the compounds. Compound 4a gave the lowest IC50value with 0.144 ± 0.008 mg/mL, at the same time IC50 value of compound 3a was determined 0.160 ± 0.01 mg/mL. The other compounds had no activity against tyrosinase enzyme. All of the data of enzyme inhibition indicated that, compound 4a might be effective neurological agent.

Figure3. DPPH radical scavenging activities IC50 values (mg/mL) of the compounds(3-4).

Antioxidant Activities

DPPH is a stable free radical that accepts an electron or hydrogen radical to become a stable diamagnetic molecule [29]. DPPH radical scavenging assay is a fast and simple method. DPPH radical scavenging activities of the compounds were examined based on reduction of absorbance at 517 nm compared to GA as reference compound [30]. The IC50 values for the DPPH radical scavenging activities of the compounds were presented in Table 1 and Figure 3. In this study, the lowest IC50 values of the compounds indicate a higher scavenging activities. All of the compounds exhibited radical scavenging activitites ranging from 0.781 ± 0.01 mg/mL to 0.988 ± 0.08 mg/ mL. Compound 3c showed the lowest IC50 value with 0.781 ± 0.01 mg/mL followed by compound 3b (0.845 ± 0.03 mg/mL) and compound 4c (0.886 ± 0.009 mg/mL), respectively. This results showed that, all of the newly synthesized compounds gave moderate scavenging activities to compare reference compound.

The reducing power activities of newly synthesized compounds were investigated by Phosphomolydenum reducing antioxidant power (PRAP). PRAP assay was based on the reduction of Mo(IV) to Mo(V) by the tested compounds [31]. PRAP was examined using phosphomolybdic acid compared to QE as the standard compound at 600 nm in this work. Absorbance of PRAP assay of the compounds and standard compound were summarized in Table 2. The highest absorbance values of the compounds showed a higher reducing antioxidant power. At 1 mg/mL, compound 3c gave the highest value with 2.0279 ± 0.049 followed by compound 4c as the DPPH scavenging assay. On the other hand, compound 4a showed the lowest value with 1.3191 ± 0.035. In this study, results of the antioxidant methods showed that compounds 3c and 4c have antioxidant potential.

Table2. Absorbance of PRAP assay of the compounds at 600 nm.
In this study, the synthesis of new bis-1,2,4-triazole compounds possessing Schiff bases were reported. The structures of all the compounds were confirmed by recording their elemental analyses, IR, 1H NMR, 13C NMR and mass spectra. All the newly synthesized compounds were screened for their enzym and antioxidant activities. This study was explained the acetylcholinesterase/butyrcholinesterase and tyrosinase inhibitory effects, and DPPH radical scavenging and phosphomolydenum
reducing antioxidant power of the newly synthesized compounds for the first time. While compound 4a might be effective neurological agent, compounds 3c and 4c have antioxidant potential.


This study was supported by grants from Karadeniz Technical University.


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