BIOSCIENCES BIOTECHNOLOGY RESEARCH ASIA,December 2013.
Vol. 10(2), 891-896 An Antibacterial, Antifungal and Anthelmintic Evaluations of Some Synthesized Chalcone Derived Benzimidazoles I. Sudheer Babu and S. Selvakumar*
Department of Pharmaceutical Chemistry, Sir.C.R.Reddy College of Pharmaceutical Sciences,
West Godavari (Dist), Eluru - 534 007, India.
DOI: http://dx.doi.org/10.13005/bbra/1213
(Received: 15 July 2013; accepted: 20 September 2013)
The Chalcone nucleus based natural plant products have various biological activities due to their highly reactive a, b unsaturated carbonyl group. If these medicinal plants not traceable in nature we must go through new synthetic drugs as a source of chalcone analogues. So we synthesized a series of chalcone derived benzimidazoles by condensation of 2-acetyl benzimidazole in alkali with various aromatic aldehydes. The synthesized chalcones were screened for their in-vitro antimicrobial activity using disc diffusion and broth micro-dilution assays. The synthesized chalcones shows good activity against the tested fungal species. They have better activity against gram positive bacteria but shows poor activity against gram negative bacteria. The In-vitro anthelmintic screening of all chalcones exhibited significant potency when compared to standard drug albendazole. Key words: Chalcones, Benzimidazolyl chalcones, Antibacterial, Antifungal & anthelmintic.
antimalarial, inhibiteosinophilia (asthma),
nucleus of various natural plant products such
antiseptical 6, analgesic/anti-inflammatory 7,
as flavonoids, isoflavonoids, aurones, tetralones,
cyclooxygenase inhibitors 8, anti ulcerogenic,
aziridines and clavicin etc.This nucleus analogue
prostaglandin binding, antiallergic, anaesthetic,
is an integral part of various natural medicinal plant
antiplasmodial 9, hypotensive, antifibrogenic ,
constitutions such as terpeneoids, dicoumarol,
immuno suppression,antineoplastic, cytotoxicity,
flavokawain, digitalis glycosides 1 and vitamin
anticancer 10, antiproliferative 11, antileukemic,
K etc. However in recent years the introduction
antitumor 12 ,trypsin inhibitor, anxiolytic 13 and
of new synthetic chalcone derived drugs has out
placed that of natural products such as warfarin
for dicoumarol. The Chalcone analogues are a
related to purine nucleoside bases and it is found
chemical class that has depicted antioxidant2,
in some natural products, such as vitamin B ,
antiviral, antibacterial 3, antifungal 4, insecticidal,
marine natural product namely makaluvamins
antitrichomonal, antitubercular 5,antileishmanial,
etc. The literature survey reports have been revealed that the 2- substituted 1H-benzimidazole compounds has reported to possess antibacterial 15, antifungal 16, antitubercular , antiviral 17, antiulcer and anthelminitic 18,19 activities . The benzimidazolyl chalcones also reported to have potent antimicrobial 20 properties. So we planned to merge the chalcone nucleus with benzimidazole at 2nd position to exhibit some better bioloical activity,
* To whom all correspondence should be addressed. E-mail: [email protected]
mainly to screen for their in-vitro antimicrobial and anthelminitic activities.
BaBu & SelvaKumar, Biosci., Biotech. Res. Asia, vol. 10(2), 891-896 (2013) ExpErimEntal antimicrobial activity micro-organisms Synthesis of 1-(1H-benzoimidazol-2-yl) ethanol
Klebsiella aerogenes mTCC-39,and Escherichia coli mTCC 1302. Three fungal species were
diamine (2) were refluxed for one and half an hour.
used, these being Aspergillus niger mTCC 2425,
The mixture was cooled, 25% potassium hydroxide
Candida albicans mTCC 183 andthe Penicillium
solution was added until the product (3) was just
citrinum mTCC 1256. all bacterial strains were
cultivated in mueller Hinton agar (mHa) media
Synthesis of 1-(1H-benzoimidazol-2-yl)ethanone
and fungi species were cultivated in Sabouraud
Dextrose agar (SDa) media. The stock culture was
maintained on agar slant at 4 °C. These microbial
50% sulphuric acid and 20% potassium dichromate
strains were subculture on a fresh appropriate agar
mixture, refluxed for one hour and allowed to cool
plate 24 hrs prior to any antimicrobial test.
at room temperature and poured, in to a ice cold
agar diffusion assay
water with stirring to get a product(4).
Synthesis of benzimidazolyl chalcones (6a-j)
out by using 100 µl of suspension of the tested
The 0.01 molar (4) in 10ml 30% potassium
microorganisms containing 2.0 × 106 CFu/ml for
hydroxide with 0.012 molar of various aromatic
bacteria and 2.0 ×105 CFu /ml spores for fungal
aldehydes namely, para-anisaldehyde (5a) ,
strains. This microbial suspension was used to
benzaldehyde (5b) , cinnamaldehyde (5c), ortho-
inoculate by flooding the surface of mHa and
chloro benzaldehyde (5d), para-(dimethyl amino)
SDa plates for bacteria and fungi respectively.
benzaldehyde (5e), para-fluorobenzaldehyde
Then sterilized discs were prepared at 30µg/disc for
(5f), ortho-nitro benzaldehyde (5g), para-nitro
synthesized chalcones and 10µg/disc for standard
benzaldehyde (5h) , ortho-hydroxybenzaldehyde
antibiotics. a discs have synthesized chalcones
(5i) and 4-hydroxy 3-methoxybenzaldehyde
were prepared with only the corresponding volume
(5j) separately,then refluxed for 2 hours
of dimethylsulphoxide was used as negative
with water bath, allow cooling to the room
control. The petri plates were then incubated at
temperature and pouring the mixture in to a
37°C for bacteria and 28°C for fungi species. The
beaker containing ice cold water, with stirring to
antimicrobial activity was evaluated by measuring
get a product namely, 1-(1H-benzoimidazol-2-
the diameter of the zones of inhibition around the
yl)-3-(4-methoxyphenyl) propenone (6a),1-(1H-
benzoimidazol-2-yl)-3-Phenyl Propenone (6b),
Broth micro-dilution assay
1-(1H-benzoimidazol-2-yl)-5-Phenyl Pentadienone
(6c), 1-(1H-benzoimidazol-2-yl)-3-(2-Chloro
(mIC) were determined by twofold serial micro
Phenyl) Propenone (6d), 1-(1H-benzoimidazol-2-
broth dilution method in mueller Hinton or
yl)-3-(4-(dimethyl amino) Phenyl) Propenone (6e),
Sabouraud dextrose broth media. The synthesized
1-(1H-benzoimidazol-2-yl)-3-(4-fluoro Phenyl
chalcones and standard antibiotics were dissolved
) Propenone (6f), 1-(1H-benzoimidazol-2-yl)-
in 50% dimethylsulphoxide aqueous solution. all
3-(2-nitrophenyl) Propenone (6g), 1-(1H-benzo
the compounds were diluted two fold concentration
imidazol-2-yl)-3-(4-nitrophenyl) Propenone (6h),
from 0.2 to 204 µg and the starting inoculums of
1-(1H-benzoimidazol-2-yl)-3-(2-hydroxy phenyl)
2.0 ×107 CFu/ ml were used. The test tubes were
propenone (6i) and1-(1H-benzoimidazol-2-yl)-3-
incubated at 37°C for bacteria and 28°C for fungi.
(4-hydroxy-3-methoxy phenyl) propenone (6j).
The lowest concentration of the drug displaying no
all the above products were collected by filtration
visible growth was considered as the mIC.
with ice cold water, dried and recrystallised from
anthelmintic investigation
90%ethanol. The structures of the synthesized
compounds were verified by Ir,1H-Nmr, 13C-
Pheretima posthuma of 7-9cm in length and
Nmrand mass spectral analysis.
0.2-0.3 cm in width were selected for the invitro anthelminitic activity due to its anatomical
BaBu & SelvaKumar, Biosci., Biotech. Res. Asia, vol. 10(2), 891-896 (2013)
and physiological resemblance with the gastro
bacteria, Klebsiella except the 6b and 6i. The most
intestinal worm parasites of human beings. The
of the chalcones exhibited better activity against
earth worms washed with normal saline solution to
Candida than the Aspergillus and Penicillium
remove all fecal and adhering soil materials before
strains. Only chalcone 6f have a potent activity
they were released in to petridishes. The standard drug albendazole and tested benzimidazoles were
prepared at a doses level of 10, 30,50 mg by
dissolving in, about 0.5ml of dimethylsulphoxide,
the volume was made-up to 15 ml with normal
saline, then poured into petridishes. The five earth
worms were taken in each petridishes. Then, the time taken for the induction of complete paralysis
and time taken for death of individual earthworms
were observed. The control group was observed
that the worms were still alive up to 48 hours.
rESultS and diScuSSion
benzimidazolyl chalcones were prepared and
evaluated for their antimicrobial activities using
disc diffusion and micro broth dilution assays, the
results are displayed in Table 2. The chalcones 6d, 6f, 6g and 6h were showed effective zone of inhibition against Klebsiella. all the chalcones
displayed less effective zone of inhibition against E. coli except 6f. The chalcones 6d, 6f, 6g and 6h
exerted potent invitro antifungal activity against
Aspergillus, Penicilliumand Candida species. Observations showed that chalcones 6a, 6c, 6e
and 6j had better activity against Aspergillus,
Penicilliumand Candida species respectively.
all the tested chalcones showed good zone of
inhibition against fungi species and gram positive
Scheme 1: table 1. Physical analysis of synthesised benzimidazolyl Chalcones
Solvent system (TlC): chloroform: 90% ethanol (8:2)
BaBu & SelvaKumar, Biosci., Biotech. Res. Asia, vol. 10(2), 891-896 (2013)
-N(CH ) or OCH groups as substituents at para or
When structure activity relationship studies
meta (r or r ) position on the benzene ring, both
are concerned, the antimicrobial activity might
enhanced the activity. It was observed that para
be increased by the presence of electronegative
substituted analogues are more potent than ortho
substituents such as NO , fluoro and chloro
or meta substituted chalcones. moreover extended
groups at ortho or para (r or r ) position on
conjugated analogue (6c) also slightly stimulates
the chalcone benzene ring, while polar electron
donating substituent OH group at ortho or para (r
In vitro anthelminitic screening results in
or r ) position decreases activity. Furthermore,
the Table 3, data displays chalcone 6a, 6c, 6d, 6g, 6h
compounds bearing nonpolar electron donating
and 6i showed appreciable activity. It indicates that
table 2. antimicrobial activity & minimum inhibition concentration of
the synthesized benzimidazolyl chalcones 6 a-j and reference antibiotics
Inhibition zone diameters in (mm) minimum inhibition concentration (µg)
values are given an average mean, (n = 3). anti-microbial activity synthesized chalcones 6a-j (30 µg D disc) and standard
antibiotics (10 µg D disc). K a - Klebsiella aerogenes, e C- escherichia coli, a N- aspergillus niger,C a-Candida albicans, P C- Penicillium Citrinum, CIPN- Ciprofloxacin, ClOe- Clotrimazole. table 3. In vitro anthelminitic activity of the synthesized benzimidazolyl chalcones (6a-j)
each average value represents the mean ± Sem (n=5). Significance levels *P<0.5, **P<0.01 and ***P<0.001 as compared with the respective standard drug (alZ- albendazole).
BaBu & SelvaKumar, Biosci., Biotech. Res. Asia, vol. 10(2), 891-896 (2013)
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