Synthesis characterization and antibacterial studies of 4-aminoantipyrine schiff’s bases

Aim: To synthesize and evaluate 4-aminoantipyrine related schiff’s bases as antibacterial agents. Objective: To synthesize, purify, characterize and evaluate 4-aminoantipyrine. Method: Schiff bases derived from 4-aminoantipyrine play a vital role in biological and pharmacological activities. Knowing the importance of 4-aminoatipyrine schiff bases and their analogues wide varieties of bioactivities like analgesic, antiviral, antipyretic, anti-rheumatic, antimicrobial and anti-inflammatory activities have been widely studied. 4-aminoantipyrine compounds C1 (anisaldehyde), C2 (p-hydroxybenzaldehyde) and C3(vanillin) were prepared by condensation between 4-amino antipyrine and substituted aromatic benzaldehydes. The products were purified by recrystallization by using ethanol, characterized by IR spectroscopy. The N-H stretching in 4-aminoantipyrine is shown at 3430 cm&-3325 cm. The -HC=Nstretching is observed in the range of 1508-1504 cm The –OCH3 stretching is found at 1888 cm . 4-amino antipyrine related schiff’s bases evaluated their activity as antimicrobials in-vitro by spread plate method against E.coli. Schiff bases have potent antibacterial activity with gram negative bacteria E.coli. Results: Synthesis and characterization of a schiff bases derived from substituted benzaldehydes and 4-aminoantipyrine was evaluated and characterized with the IR spectroscopic techniques and schiff bases have shown potent antibacterial activity against E.Coli. International Journal of Applied Pharmaceutical Sciences and Research International Journal of Applied Pharmaceutical Sciences and Research 2017; 2(1):8-14 K Vinay et al/International Journal of Applied Pharmaceutical Sciences and Research 2017; 2(1):8-14 Copyright © 2017 Author. This is an open access article under the CC BY 4.0 license 9 Table 1: Structures showing biological activity


Introduction
4-Aminoantipyrine (4-Amino-2,3-dimethyl-1-phenyl-3pyrazolin-5-one) is a heterocyclic compound containing pyrazole ring. Its broad bioactivities are anticancer (Sigroha et   4-aminoantipyrine has an N phenyl group and a -CH 2 group on either side of a polar carbonyl group, thus resembles to N-substituted amides. The carbonyl group in 4-aminoantipyrine is a potential donor due to the large dipole moment and strong basic characters. Generally, the electron withdrawing and electron releasing nature and the position of substituents present in the phenyl ring affect the antimicrobial activities (Bondock et al., 2008); the presence of substituents at the o-position lowers the antimicrobial activity whereas the substituents at the pposition give higher antimicrobial activity. Inhibition is enhanced with the introduction of an electron withdrawing nitro group in the phenyl ring.

Schiff bases
A Schiff base is a nitrogen analog of an aldehyde or ketone in which the C=O group is replaced by C=N-R group. It is usually formed by condensation of an aldehyde or ketone with a primary amine according to the following scheme: Where R, may be an alkyl or an aryl group. Schiff bases that contain aryl substituents are substantially more stable and more readily synthesized, while those which contain alkyl substituents are relatively unstable. Schiff bases of aliphatic aldehydes are relatively unstable and readily polymerizable while those of aromatic aldehydes having effective conjugation are more stable. The formation of a Schiff base from an aldehydes or ketones is a reversible reaction and generally takes place under acid or base catalysis, or upon heating.
The formation is generally driven to the completion by separation of the product or removal of water, or both. Many Schiff bases can be hydrolyzed back to their aldehydes or ketones and amines by aqueous acid or base. The mechanism of Schiff base formation is another variation on the theme of nucleophilic addition to the carbonyl group. In this case, the nucleophile is the amine.
In the first part of the mechanism, the amine reacts with the aldehyde or ketone to give an unstable addition compound called carbinolamine. The carbinolamine loses water by either acid or base catalyzed pathways. Since the carbinolamine is an alcohol, it undergoes acid catalyzed dehydration.
Typically the dehydration of the carbinolamine is the rate-determining step of schiff base formation and that is why the reaction is catalyzed by acids. Yet the acid concentration cannot be too high because amines are basic compounds. If the amine is protonated and becomes non-nucleophilic, equilibrium is pulled to the left and carbinolamine formation cannot occur. Therefore, many schiff bases synthesis are best carried out at mildly acidic pH. The dehydration of carbinolamines is also catalyzed by base.This reaction is somewhat analogous to the E 2 elimination of alkyl halides except that it is not a concerted reaction. It proceeds in two steps through an anionic intermediate. The

Chemicals & Reagents:
The chemicals and reagents of Analytical and Laboratory grade from Asha Chemicals, Seth Chemicals, Prince trading company, Hyderabad.

II. Thin Layer Chromatography:
Purity of the compounds was ascertained by thin layer chromatography using silica gel-G as stationary phase and appropriate mixtures of the following Solvents as mobile phase Methanol and chloroform. The spots resolved were visualized using iodine chamber and UV chamber (Lawrence et al., 1976).

Preparation of Schiff's bases
Reaction:

Chemicals used:
Anisaladehyde-1.36g, Para hydroxybenzaldehyde-1.22g, Vanillin-1.5 g, Ethanol-10ml. Procedure: 2.03g of 4-amino antipyrine was dissolved in 10ml of ethanol in a beaker. 1.36g of aryl benzaldehyde was dissolved in 10ml of ethanol in a round bottomed flask. These two mixtures were mixed together and kept for reflex for 5hrs with stirring. The mixture was cooled and pour into crushed ice and the precipitate obtained was filtered, dried and recrystallized with ethanol.  Suspend 28 grams in 1000 ml distilled water. Heat to boiling to dissolve the medium completely. Dispense as desired and sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Mix well before pouring.

IR Spectra of compound C3
3.4 Antibacterial Activity:

Discussion
Results of our study demonstrated that Schiff bases were synthesized and characterized. Schiff bases derived from 4-aminoantipyrine have potent antibacterial activity. Compounds C 1, C2 and C 3 were prepared by condensation between 4-aminoantipyrine and substituted aromatic benzaldehydes. The products were purified by recrystallization by using ethanol, characterized by IR spectroscopy. The N-H stretching in 4-aminoantipyrine is shown at 3430 cm -1 &-3325 cm -1 . The -HC=N-stretching is observed in the range of 1508-1504 cm -1 The -OCH 3 stretching is found at 1888 cm -1 . In the view of synthesizing new antimicrobials, the synthesized Schiff bases from 4-aminoantipyrine having antimicrobial activity through in-vitro by spread plate method against E.coli (gram negative) bacteria.

Conclusion
In this work the synthesis and characterization of a Schiff bases derived from substituted benzaldehydes and 4aminoantipyrine is reported. The synthesized Schiff's bases were characterized by IR spectroscopic techniques.
The antibacterial studies are also reported.The yield of the products ranged from 80-85%. The purity of the compounds was checked by TLC. With these encouraging results, all the synthesized compounds can be further explored for structural modification and detailed microbiological investigations to arrive at possibly newer potent antibacterial agent with various other activities.