INTRODUCTION:
The
present work deals with the synthesis of 4-(Piperazin-1-ylcarbonyl)aniline from
PABA and study of its antibacterial and antifungal activities. PABA is an
essential nutrient for some bacteria and is sometimes called as Vitamin Bx or
Vitamin H. It is an intermediate in bacterial synthesis of folate. PABA is used
in sunscreen preparations since it can help protect the skin against
UV-radiation. People suffering from vitiligo, over-pigmentation of skin, or
without pigment in some spots have reported an improvement of the skin after
more PABA was ingested1-2. The various compounds related to PABA
have been found to possess useful pharmaceutical activities like antibacterial,
antifungal3-4, antitubercular5-7, anthelmintic8-9,
antitumor10-13. Being encouraged
by these observations work was planned to synthesize and study the
antimicrobial activity of the given amide derivative of PABA.
MATERIAL AND
METHODS:
Method
for Synthesis:
p-aminobenzoic acid (5 g, 0.025 mol) was boiled in
concentrated hydrochloric acid (50 ml) to prepare the hydrochloride salt of p-aminobenzoic
acid. It was dried on calcium chloride in dessicator. Hydrochloride salt of p-aminobenzoic
acid was dissolved in dry pyridine(10 ml) in a conical flask. This solution was
allowed to stand at 00 to 50 C for about 30 mins. Thionyl
chloride (3ml) was added dropwise (Solution A).
Simultaneously;
in another conical flask the solution of amine to be substituted was prepared
(B).
Solution
(B) and (A) was added equimole. The mixture was allowed to stand for 30 mins at
room temperature and then poured into acidic (HCl) crushed ice. The separated
dye was filtered using suction and dried at room temperature. The dye was
recrystallized from Dimethylsulfoxide and stored over calcium chloride in a
dessicator.
Yield:
69%
General
Features of One Pot Synthesis:
1)
It requires lesser time.
2)
In this process, hydrochloride salt
of PABA is converted into its corresponding acid chloride and then substituted
with desired amines.
3)
The reaction is temperature
specific. The ideal temperature condition should be 0-5o c.
4)
Pyridine is used as a solvent
medium which acts as a base to drive the equilibrium in the formation of amide
from amine and acid chloride.
Following one pot synthetic method
of amide synthesis was executed.
Mechanism
of Reaction:
Schotten-Baumann
Reaction:
The
use of added base is to drive the equilibrium in the formation of amides from
amines and acid chlorides. The acylation of amines with carboxylic acid
chlorides leads to the production of one equivalent acid, which will form a
salt with unreacted amine and diminish the yield. The addition of an additional
equivalent of base to neutralise this acid is a way to optimise the conditions.
In
general, the use of biphasic aqueous basic conditions is often named
"Schotten-Baumann conditions".
PROPOSED
STRUCTURE OF THE COMPOUND
4-(PIPERAZIN-I-YLCARBONYL)ANILINE
CHARACTERIZATION:
1.
Melting Point (mp):
401-404
0 C
2.
Thin Layer Chromatography (TLC):
Solvent
system used – DMSO: benzene: water in the concentration of 7:2:1.
|
Compound
|
Rf value
|
|
Test
|
0.56
|
3.
Ultraviolet-Visible(Uv) Spectroscopy:
The
synthesized compound was analysed using dimethyl sulfoxide as a solvent on
shimadzu 1700 UV-Visible Spectrophotometer.
4. Rotational And Vibrational (IR) Spectroscopy:
IR spectra of the compound was recorded using KBr
pellets on FTIR –8100 S.
PEAK TABLE
|
Sr. No.
|
Wave Number
(cm-1)
|
Characteristic Absorption Peak
Assignment
|
|
A.
|
3346
1505-1596
|
Hydrogen Chromophore:
• Aromatic Stretching
• C-C multiple bond stretching (aromatic)
|
|
B.
|
2580-2840
|
Carbonyl (C=O amide) Stretching
|
|
C.
|
3058
|
N-H Stretching (Primary amide)
|
|
D.
|
763
|
C-Cl Stretching (Aromatic)
|
5. Nuclear magnetic resonance (NMR) spectroscopy:
Spectra of the compound was
recorded using chloroform as a solvent on Varian Mercury YH-300
spectrophotometer at National Chemical Laboratory, Pune.
BIOLOGICAL SCREENING:
1. ANTIBACTERIAL ACTIVITY (in vitro):
The preliminary in vitro antibacterial activity of compound
was studied against four different species viz. Escherichia coli, Staphylococcus
aureus, Pseudomonas aeruginosa and Bacillus subtilis by cylinder
plate or cup-plate method. The method depends on the diffusion of drug from cup
through the solidified agar layer of a petridish to an extent such that growth
of the inoculated microorganism is prevented entirely in a circular area (known
as zone of inhibition) around the cup containing solution of the compound under
the test.
PROCEDURE:
Method : Cup Plate Method,
Media : Nutrient agar media,
Solvent : 70% DMSO,
Concentration: 100µg/ml,
Condition: 24 h at 32- 38° (depending on the bacterial
species)
Standard: Tetracycline (100μg/ml).
CONCLUSION:
The
results of characterization parameters were in conformity with the structure
assigned. Structural similarity of the compound with the existing drugs is
responsible for the above mentioned activities. More derivatives can be prepared using amino acids, alcohols by this
method and can be tested for antiviral, antifungal, antimalarial and other
relevant pharmacological activities.
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From PABA the test compound was synthesized as per the
given scheme and FTIR, NMR studies were carried out. The successful synthesis
of the compound was achieved with 69% yield. The purity and homogeneity of the
compound was checked and ascertained by TLC as the compound was found to give
single spot. According to the results obtained, the compound was found to
possess significant antibacterial and antifungal activities as compared to the
standards.