Synthesis, characterization and biological evaluation of benzothiazole derivatives as potential antimicrobial and analgesic agents

 

Konda Ravi Kumar¹*, K.N.S. Karthik¹, P. Reshma Begum¹, Ch. M.M. Prasada Rao²

¹Department of Pharmaceutical Chemistry, Hindu College of Pharmacy, Amaravathi Road, Guntur.

²Department of Pharm. Chemistry, QIS College of Pharmacy, ongole-523272

 

ABSTRACT:

Five series of benzothiazole moieties were efficiently synthesized and evaluated for antimicrobial and anticancer activities. The results indicated that the compounds possessed a broad spectrum of activity against the tested microorganisms and showed higher activity against fungi than bacteria. Compounds BT-02 exhibited the greatest antimicrobial activity. Preliminary study of the structure–activity relationship revealed that electronic factors in benzothiazole rings had a great effect on the antimicrobial activity of these compounds. The analgesic activity of compounds performed by using tail immersion method. in this case, compound BT-02 shows activity at 100 mg/kg dose 46 ± 0.22, 51 ± 0.22,58 ± 0.43, 48 ± 0.27 at time interval of 30 min,1 hour,2 hour,3 hour respectively compare with the other compounds due to the greater electronic effects.

 

 

 

INTRODUCTION:

The development of new antimicrobial and anticancer therapeutic agents is one of the fundamental goals in medicinal chemistry. Cytotoxicity and genotoxicity of anticancer drugs to the normal cells are major problems in cancer therapy and engender the risk of inducing secondary malignancy[1]. A dose of anticancer drug sufficient to kill tumor cells is often toxic to the normal tissue and leads to many side effects, which in turn, limits its treatment efficacy. In recent years, there has been a concerned search for the discovery and development of novel selective anti-tumor agents, devoid of many of the unpleasant side effects of conventional antitumor agents.

 

In the efforts to develop drugs with such capabilities, scientists have focused upon many different aspects of cancer biology during their research.

 

Among the anti-tumor drugs discovered in the recent years, various benzothiazoles[2–4] as well as urea and thiourea derivatives[5–8] possess potent anticancer properties. The combinations of urea and thiourea derivatives with benzothiazoles have produced DNA topoisomerase[9,10] or HIV reverse transcriptase inhibitors[11,12]. Thiourea derivatives display a wide range of biological activity including antibacterial, anti-fungal, antitubercular, antithyroid, antihelmintic, rodenticidal, insecticidal, herbicidal, and plant growth regulator properties[13–18].

 

The importance of such work lies in the possibility that the next generation thiourea derivatives might be more efficacious as antimicrobial and anticancer agents. However, a thorough investigation relating the structure and the activity of the thiourea derivatives as well as their stability under biological conditions is required. These detailed investigations could be helpful in designing more potent antimicrobial and anticancer agents for the therapeutic use.

 

Since varying substituents is a common method for drug design in medicinal chemistry and a useful medical value of substituted thiourea derivatives containing benzothiazole moiety, we aimed to synthesize new thiourea derivatives and to investigate their antimicrobial and anti-tumor activities. Based on these reports, we herein report the synthesis, characterization, antibacterial, anti-fungal and in vitro evaluation of anti-tumor activity of five different series of novel thiourea derivatives bearing benzothiazole moiety.

 

MATERIALS AND METHODS:

Synthetic starting material, reagents and solvents were of analytical reagent grade or of the highest quality commercially available and were purchased from Aldrich Chemical Co., Merck Chemical Co. and were dried when necessary. Melting points were recorded on Electrothermal IA9000 series digital melting point apparatus. The proton NMR was recorded inDMSOd6 solvent 300 MHz spectrophotometer using tetramethylsilane as an internal reference. The apparent resonance multiplicity is described as s (singlet), br s (broad singlet), d (doublet), dd (doublet of doublets), t (triplet), q (quartet) and m (multiplet). Infrared measurements were recorded in the range 400–4000 cm_1 on spectrum 2000 by Perkin Elmer. Elemental analysis was carried out using Perkin Elmer CHNS/O 2400. Obtained results were within 0.4% of the theoretical values. Thin layer chromatography (TLC) analysis was carried out on 5×20 cm plate coated with silica gel GF 254 type 60 (25–250 mesh) using an ethyl acetate–petroleum ether mixture (1:2) as solvent.

 

General procedure for synthesis: [19-20]

To substituted aniline (25mL), concentrated hydrochloric acid (25mL) was added and the solution was warmed for 30 min. A saturated solution of ammonium thiocyanate in water (30g in 60mL) was added slowly in above solution. The mixture was boiled until the solution got turbid. The turbid solution was poured in cold water. The resulting precipitate was filtered and re-crystallized from aqueous ethanol (80%) to provide pure phenylthiourea. The substituted phenylthiourea (26 mmol) in chloroform (75mL) was brominated by using bromine solution in chloroform (5%) till the orange-yellow color appeared. The slurry was kept overnight. The precipitate obtained was filtered and washed with chloroform until the colour disappeared. The precipitate, as hydrobromide, was dissolved in rectified spirit (150mL) and basified with ammonia solution. The precipitated was filtered, washed with water, dried and re-crystallized using ethanol: dichloromethane mixture (1:2).

 

 

Table: 1 list of compounds

Biological evolution of compounds:

Based on the literature, chalcones were reported to possess antimicrobial activity, anti oxidant, anti inflammatory, analgesic, anti cancerous, etc. Therefore the present work performs the anti microbial, analgesic activities.

 

Antibacterial activity: [21-23]

The antibacterial activity was tested by determining inhibitory concentration by diffusion disc technique. The bacterial strains were obtained from National Chemical Laboratories (NCL), Pune and Microbial Type Culture Collection (MTCC), Chandigarh. The strains used for the present study were Staphylococcus aureus (MTCC 737) Bacillus subtilis (MTCC 441), Escherichia coli (MTCC 1687), P.vulgaris MTCC 1771

 

Procedure:

The antimicrobial activity of the compounds was assessed by disc diffusion method Nutrient agar medium was prepared and sterilized by an autoclave. In an aseptic room, they were poured into a petridishes to a uniform depth of 4 mm and then allowed to solidify at room temperature. After solidification, the test organisms, Staphylococcus aureus, Bacillus subtilis, Escherichia coli and P. vulgaris were spread over the media with the help of a sterile swab socked in bacterium and is used for antibacterial study. The synthesized compounds were dissolved in dimethyl sulfoxide (DMSO) to produce a concentration of 500 μg/disc, 1 mg/disc and used for the study. Streptomycin 5 μg/disc was used as the standard. Then the sterile filter paper discs (6mm) having a capacity to hold 10 μl of solution were immersed in definite concentration of compounds and placed over the solidified agar in such a way that there is no overlapping of the zone of inhibition. Plates were kept at room temperature for half an hour for the diffusion of the sample into the agar media. The organism inoculated petridishes were incubated at 37 °C for 24 hours. After the incubation period is over, the zone of inhibition produced by the samples and standard were measured. All tests were performed in triplicate. The results were tabulated in Table-4

 

 

Scheme

Analgesic activity:[24]

The analgesic activity was determined by tail immersion method.¹² Wistar albino mice (n = 6) of either sex selected by random sampling technique were used for the study. Paracetamol at (100 mg/kg) was administered as standard drug for comparison. The test compounds (100 mg/kg) were administered orally by intragastric tube. The animals were held in position by a suitable restrained with the tail extending out and the tail (up to 5 cm) was then dipped in a beaker of water maintained at 55 ± 5°C. The time in seconds taken to withdraw the tail clearly out of water was taken as the reaction time. The reading was recorded at 30, 60, 120 and 180 min after administration of compounds. A cut off point of 10 sec was observed to prevent the tail damage. The results were tabulated in Table-5

 

RESULTS AND DISCUSSION:

Table 2: Physical data of compounds:

 

Table: 3 Elemental Composition

 

Table 4: Spectral Data

 

Anti bacterial evolution

Table 4: anti bacterial evolution

 

Analgesic activity:

Table 5: Analgesic Results

 

DISCUSSION:

The above synthesized compounds anti microbial evolution were performed by using Diffusion method by the calculation of Zone of inhibition against the test organisms, the compounds shows that compound BT-01 shows maximum activity than compare with other compounds, the compound BT-02 (5-nitro-1,3-benzothiazol-2-amine) shows activity at concentration of Staphylococcus aureus zone of inhibition 16,24 mm at 50 µg/ml, 100 µg/ml with Pseudomonas vulgaris  zone of inhibition 13,26 mm at 50 µg/ml ,100 µg/ml with Escherichia coli the zone of inhibition 14,26 mm at 50 µg/ml ,100 µg/ml.. the compound BT-02 (5-nitro-1,3-benzothiazol-2-amine) shows activity at concentration of Staphylococcus aureus zone of inhibition 13,26 mm at 50 µg/ml ,100 µg/ml with Pseudomonas vulgaris  zone of inhibition 12,24 mm at 50 µg/ml, 100 µg/ml with Escherichia coli the zone of inhibition 12,24 mm at 50 µg/ml, 100 µg/ml.

 

The analgesic activity the compound the compound BT-02 (5-nitro-1,3-benzothiazol-2-amine) shows activity at 100 mg/kg dose 46 ± 0.22, 51 ± 0.22,58 ± 0.43, 48 ± 0.27 at time interval of 30 min,1 hour,2 hour,3 hour respectively.

 

CONCLUSION:

The above results we concluding the compound BT-02 was showing the better anti microbial activity against both gram positive and gram negative the organism. The reason is due that compound contain electron with drawing group than that of other compounds. In case of analgesic activity, compound BT-02 shows better analgesic than other compounds We concluding the compound BT-02(5-nitro-1,3-benzothiazol-2-amine) was be best fit molecule against microbes, anti-oxidant activity on the further exploration of the compound the statement may confirmed.

 

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Received on 08.04.2017       Accepted on 16.05.2017     

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