Synthesis and Biological Activity of some New Nitrogenous Heterocyclic Compounds Derived from Azachalcone

ABCTRACT A series of heterocyclic compounds containing oxygen and nitrogen atoms, isoxazoline ІI(a-d) and another containing two nitrogen atoms, pyrazolinesІII(a-d) and phenylpyrazolines IV(a-d) were prepared by the reaction of a proper azachalcones І(a-d) with hydroxylaminehydrochloride, hydrazine hydrate or phenylhydrazine. These heterocyclic compounds were characterized by H-NMR , CHN , IR and UV spectra in addition to their some physical properties. Also, these prepared compounds were screened for their biological activities and a theoretical calculation which shows that the product IVa obtained from 1,2 – rout was energetically more stable by 1.3967 kcal/mole than that came from 1,4 – rout, thus the reaction proceed via 1,2 – addition.


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INTRODUCTION Study for the improvement of novel biological activity agents is becoming the main importance in many investigate laboratories all over the world with the plan to find out newer, additional effective molecules, with elevated specificity and reduced toxicity than the existing ones (Shih et al., 2018). Five membered rings contain two nitrogen molecules or one nitrogen and other oxygen which were found to be a extremely significant pharmacophore in many therapeutic agents (Gunkara and Ocal, 2018;Rajanarendar et al., 2007). In addition, the incorporation of these moiety into a pharmacologicallyactive pyridyl molecule resulted in many cases in improving the therapeutic profile of the parent compound (Abedalazem et al., 2015). Hundreds or even thousands of isooxazoles and pyrazolines nitrogen-containing five-membered heterocyclic compounds have been prepared by many procedures (Gunkara et al., 2018;Patel et al., 2016;Sharma et al., 2014), while pyrazoline derivatives prepared by the addition of hydrazine hydrate or phenylhydrazine to azachalcones, isoxazolines were prepared by the addition of hydroxyl amine hydrochloride to these chalcones (Sharma et al., 2014;Patel et al., 2016;Bhimwal et al., 2011). These five membered ring nitrogenous or oxygenous heterocyclic derivatives have widespread potential biological activities such as, antimicrobial (Kotla et al., 2012;Hassan et al., 2013), antitumoractivites (Mntoya et al., 2014), antiinflammatory (Venkataraman et al., 2010), antibacterial (Bhimwal et al., 2011;Patel et al., 2016), anticancer agents (Gunkara et al., 2018) and antitubercular activity (Bishnoi et al., 2013). These titles of the heterocyclic compounds appeared of interest to synthesis using azachalcones derivatives as synthons.

EXPERIMENTAL
Melting points were determined on an electrothermal Stuart melting point SM P30 and were uncorrected. 1 H-NMR spectra of some synthesized compounds were recorded on NMReady 60 Pro-User Manual/Version 1.0 at central service laboratory, University of Baghdad. The chemical shifts are reported in δ values (ppm) relative to tetramethylsilane and quoted as s(singlet), d(doublet), t(triplet), br(broad) and m(multiplet). Infrared absorption spectra were recorded on Bruker spectrophotometer from college of Pharmacy, University of Mosul. Elemental analysis (CHN) obtained via EuroEA-3000/Italy Elemental analyzer from the central service laboratory, University of Baghdad. Ultra-Violet spectra (UV spectra) obtained via Spectro UV-Vis Auto,UV-2602, from college of Agriculture, University of Mosul. All heterocyclic products IІ(a-d), ІII(a-d) and IV(a-d) have been tested for their biological activity at college of Sciences-Mosul University, through agar diffusion method. The starting azachalcones (3-(pyridine-2-yl)-1-(p-tolyl,bromo, chloro or fluro)prop-2-en-1-one) I(a-d) were prepared according to a previous work (Raoof, 2005).

Synthesis of [3-(4-substituted phenyl )-5-(2`-pyridyl)]-4,5-dihydro pyrazolines ІII(a-d)
A mixture of a proper azachalcone (2.5mmol), hydrazine hydrate(5mmol, 0.25gm), either in pyridine to prepare compounds ІII(a and b)(method A), or in ethanol to prepare compounds ІII(c and d)(method B) was refluxed for 6-7 hrs. The mixture was poured into ice water, the precipitate formed washed with water, dried and crystallized with suitable solvent to afford amorphous solid of compounds IIІ(a-d). Tables (3 and 4) showed some physical properties and spectral data of these compounds respectively.

BIOLOGICAL ACTIVITY
The procedure followed for tested the titles heterocyclic products is simply that a filter disk impregnated with an antibiotic which is applied to the surface of anagar plate containing the organism to be tested and the plate is incubated at 37°C for 24-48 hours. AS the substance diffuses from the filter paper into the agar, the concentration decreases. At some particular distance from each disk, the antibiotic is diluted to the point that is no longer inhibits microbial growth. The effectiveness of particular antibiotic is shown by the presence of growth inhibition zones. These zones appear as clear areas surrounding the disk from the substances with antimicrobial activity. Measur the zone sizes to the nearest millimeter using a ruler and the results reported as (++), (+), (±) or (-), Table (7). Dimethyl sulfoxide (DMSO) was used as a solvent for the compounds, blank paper disk of DMSO also was used as control.

RESULS AND DISCUSSION
A suitable synthesis of aimed heterocyclic compounds were accomplished by the route outlined in Scheme (1) :

Scheme 1: Synthesis heterocyclic compounds containing N,O or N, N-atoms
In this work, the synthesis of isoxazolines II(a-d) from the cyclization of starting azachalcones and hydroxylamine hydrochloride was carried out as shown in Scheme (1). In order to achieve this aim, sodium acetate as a base was used.
Antimicrobial activity of the prepared compounds II, III, IV(a-d) was examined by the agar diffusion method used free different bacterial species, i.e. E-Coli, Staphylococcus aureus and Pseudomonas aeruginosa. The prepared compounds show higher activity towards E. coli and Staph. aureus compared to the pseudomonas aeruginosa, (Table 7) (Nowakowska et al., 2001).