1. INTRODUCTION:
Many natural and synthetic derivatives of coumarin have been used as anticoagulants [4]. Coumarin including compounds were used as ligand with synthesis from coordination compounds [5]. Metal complexes of coumarin and their derivatives have found reported into function such as thermal constancy as well visual characteristics, but as well, they have the promising biological as well medicinal implementations consist of antiinflammatory, antitubercular, chemotherapeutic, anticoagulant, antibacterial, cycotoxicity as well as antioxidant [6]. Metal complexes of coumarins have been advanced medicinal and biological applications. It has been found that on some statuses the metal compounds acquired detected higher biological efficacy than ligands [7].
2. MATERIAL AND METHODS:
Every chemicals have been analytical grade as well utilized without any modulation. 1HNMR spectral have been acquired employing a Bruker 400 MHz as well d6 – dimethylsulphoxide as a solvent in University for Al-Albeit, Amman, Jordan. FTIR spectral have been registered as potassium bromide disc employing a Shimadzu 8400 FTIR spectrophotometer at range 4000-400 cm−1. Elemental analysis (C.H.N.S) with [L] has been executed at EuroEA-Element Analyzer model 3000. Mass spectra have been registered through electron effect mass spectrometry (EIMS) utilizing in the Direct Injection Probe in the a Shimadzu GCMS –QP5050A Spectrometer.
Preparation of (E)-1,1-dimethyl-3-((2-oxo-2H-chromen-3-yl) methylene) urea
The enamine derivative was prepared according to the modified procedure established in literature [8]. A solution of (0.01 mole, 1.88 g) of 3-actyl coumarin (25 ml) hot ethanol was added gradually to (0.011 mole, 5 ml) of N, N-dimethyl formamide dimethyl acetal then refluxed on water bath for two hours. A dark brown crude separated and filtered off, washed several times for ether as well recrystallized with hot methanol to afford pale brown precipitate, chemical formula: C13H12NO3 M. wt.=230, elemental analysis, Calc. (Obs.): C, 67.82 (67.91); H, 5.95 (5.22); N, 6.47 (6.80), O, 20.86 (20.44). Scheme (1).
Scheme (1). Synthesis of [A] enamine derivative
Preparation of the tested 3-(4-hydroxy-4H-benzo [4,5] thiazolo [3,2-a] pyrimidin-4-yl)-2H-chromen-2-one
To solution from [A] derivative (0.24 g, 1 mmol) on a mixture
for diethylene dioxide as well ethanoic acid mixture (20mL) 2-aminobenzothiazole
(0.15g, 1mmol) has been added. Reaction mixture has been refluxed until 10 hours
as well the performing solution has been cooled in room temperature as well poured
to the crushed ice. The solid acquired has been filtrated off, washed for water,
dried as well as crystallized of benzene/ethyl alchol mixture to bear [L] yellow
powder, yield: 78%, m.p: (296–298
). The chemical formula: C19H12N2O3S,
elemental analysis: C, 65.51 (64.34); H, 3.47 (3.11); N, 8.0 (7.22); S, 13.78 (13.00).
Scheme (2).
Scheme (2). Preparation of [L].
3. RESULTS AND DISCUSSION:
Infrared spectrum:
The product [L] exhibited bands in 1683, 1635, 1600, 1583 and 1288cm-1 assigning to the modes functional groups of phenolic υ (C=O) of coumarin, υ(C=N), υ(C=C) and υ (C-O) and these data supports the ring closure of the enamine intermediate in the first step of the reaction. However, band at 3284cm-1 could be attributed to υ (OH) [9,10].
Figure (1): IR spectrum of Schiff base, L in KBr disc
1H-NMR spectrum
Further evidence for the formation of the derivative [L] was explained from 1HNMR spectrum (Figure 2) whom supply diagnostic instrument with positional as well as illustration for protons. Assignment from signals concerning into resonance from aromatic protons have been noticed at region (δ=7.08-7.89) ppm, signal obtained at (δ=7.06) ppm lead to proton of phenol. The signals at (δ=3.45) ppm as well (δ=2.50) ppm may be specified into nuclear spin of solvent protons and the less amount of water originally present [10].
Figure (2): 1H-NMR spectrum of Schiff base, L in d6-DMSO
Mass spectra:
The mass spectra from compound [L] explained at figure (3) displayed a molecular ion peak on m/e = 348g/mole well consistent with the experiments formula of the compound, the base peak with relative I= 100% of the peak at m/e= 149 may be resulted from extreme stability from ion [m/e=C7H4N2S]+. As well as other molecular ion on m/e=205 and 176 due into fragmentation ring closure from enamine [A] with 2-aminobenzothiazole and the peak showed on m/e=76 due to the fragmentation [L-C6H4]+ respectively.
Figure (3): Mass spectrum of [L] compound.
In-Vitro Antioxidant determination:
Free radicals were a topic from critical concern among researchers at past decade. Broad range from free radical impacts at biological systems has garnered concern of many particularists. It was proved that free radicals. An antioxidant are molecules that prevent the oxidation from other compounds through hydrogen or electron donors as well neutralize free radicals [11,12]. A number from in-vitro checks have been sophisticated to deduce the antioxidant activities depend at diverse mechanisms, consist of ; Trolox equivalent antioxidant [13], oxygen radical absorption [14], ferric reducing capacity [15] antioxidant efficacy from tested coumarin derivatives has been estimated through DPPH radical scavenging efficacy assay [16], which was the most popular one , in which the steady free radical DPPH can accept an electron or a hydrogen atom of other molecule to become more steady . A 0.1 mL from synthesized compounds on condensation range (100- 1000)μg/mL or ascorbic acid as standard antioxidant has been mixed for1 mL from 0.2 mM DPPH [(2,2-diphenyl-1-picrylhydrazyl)] resolved at methanol, after the mixture has been brood at dark to 20 min on 28°C 20. The scavenging efficacy was specificed during absorbance measurement at 517 nm utilizing UV-VIS spectrophotometer. The percentage of DPPH radical scavenger was calculated using Equation 1.
Scavenging effect % = [(Ao−A)/Ao] × 100 …………..(1)
Ao = Control absorbance; A = Tested absorbance
Results of this current study showed that in vitro antioxidant efficacy of the synthesized coumarin derivative had good antioxidant activity through hydrogen-donating action, measured utilizing 2,2-diphenyl-1-picrylhydrazyl radicals as hydrogen acceptor, moreover, Fig.4 showed concentration -dependent association between the condensation from novel synthesized molecule as well the percentage from inhibition. On DPPH manner, the synthesized compounds possessing maximum scavenging activity about 80 % on condensation 1000μg/mL, compared to vitamin c as standard antioxidant reaching about 92% DPPH radical scavenging activity at the same concentration, moreover obtained results showed positive association between the scavenging impact which was increased for increasing condensation from check coumarin compound which was comparable to previous study by ( Ahmed A. Al-Amiery, et al 2015) [17] . The possible explanation to current study results is according to (Roussaki, M, et al 2010) [18], compounds from these substituents are predictabled to have antioxidant efficacy, since hydrogen donation leads up into forming from a steady intermediate -structure. It was notified that existence from hydroxyl groups substitution are necessary with antioxidant efficacy like numerous natural as well as synthetic organic compounds have stellar performance such as antioxidants [19,20].
Figure (4): Percentage inhibition from DPPH scavenging efficacy for synthesized compound at comparison into Vitamin C.
Moreover , Fig. 5 showed linear regression equation for both coumarin derivative and vitamin C standard antioxidant based on showed outcomes the synthesized coumarin compound can be categories as mild free radical scavenger exhibits An important dose inhibition dependent on DPPH activity for 50% from inhibition (IC50) within condensation of 591.68µg/m (Figure 5a ) and IC50 value of Vit.C was 391.25µg/m (Figure 5b). logically, a higher DPPH radical-scavenging efficacy is linked for a lower IC50 value.
There are many studies have been carried out to evaluate the antioxidant activity of some synthesized coumarin derivatives compounds using DPPH assay, whereby the present study proof that, the synthesized coumarin has good and comparable antioxidant activity to standard Vit. C antioxidant that is appropriate in future work , to evolve a drugs with coumarin substitution with prevention from human illness concerning in free radical mechanism.