INTRODUCTION:

Several antimicrobial drugs have been synthesized to prevent infections of several pathogenic microorganisms. Most of the researches have been carried out to develop therapeutically active phenothiazine derivatives. Phenothiazine nucleus containing drugs have been reported to possess anti-microbial and CNS effects.¹ Replacement of one aromatic nucleus of phenothiazine by pyridine ring has been reported to possess more prominent biological activity². Nitrogen containing heterocyclic compound like aza-phenothiazine have received considerable attention in recent years due to their biological activities like antihypertensive³ anti-histaminic⁴, anti-microbial⁵, sedative⁶ and anti-allergic⁶ activities. Since azaphenothiazin is bioisosteric isomer of phenothiazine, it is expected to have biological activities similar to phenothiazine. The present work reports the synthesis of alkyl substituted azaphenothiazine by condensation of 2-chloro-1-(10H-azaphenothiazin-10yl) ethanone with various amines (3a-j). The structures of the synthesized compounds were confirmed by their IR, ¹HNMR and Mass spectral datas.The synthesized compounds were screened for anti-microbial and sedative activities.

EXPERIMENTAL:

Melting points were determined in open capillary tube and are uncorrected. IR spectra were recorded in Perkin- Elmer FTIR spectrophotometer using KBr disc. ¹HNMR spectra were recorded on Varian 300 MHZ spectrometer with TMS as internal standard Mass spectra were recorded on LCMS-2010 using CDCl₃ as solvent. The completion of reaction was tested by TLC using precoated TLC plate with varying composition of mobile phase. [chloroform: methanol: acetic acid]

General procedure for the preparation of azaphenothiazine derivatives 3a-j:

Azaphenothiazine was synthesized by the condensation of 2-amino thiophenol and 2-chloropyridine in presence of iodine as reported in the litrature⁵

Synthesis of 2-Chloro-1-(10H-azaphenothiazine-10-yl-) ethanone (2):

To a solution of chloroacetylchloride (0.2mol) in ethanol azaphenothiazine (0.2mol) was added drop wise and the solution was refluxed for one hour. The content was poured into cold water and the solid obtained was filtred, dried and recrystallized from ethanol to give a compound 2

Synthesis of 2-(amino substituted)-1-(10H- azaphenothiazine-10-yl-) ethanone (3a-j):

To the compound 2 (0.01mole), various amines (0.01mole) were added and dissolved in acetone .It was refluxed for 2 hours. Then, poured over crushed ice, solid thus obtained was recrystallized by methanol.

The physical characterization data of the synthesized compounds is given in Table 1. The spectral analysis has been reported in Table 2

BIOAVAILABILITY:

The bioavailability of the synthesized compounds was determined by Lipinski rule ⁷of 5 using customized software and data is described in Table 1.

ANTIMICROBIAL ACTIVITY:

All the compounds (3a-j) were screened for invitro antibacterial activity against Bacillus spharicus, Enterococcus feacalis, Vibrio cholerae and Salmonella typhi by disc diffusion technique⁸ at a concentration of 500µg/ml by measuring the zone of inhibition in mm and reported in Table 3.Amoxicillin was used as standard drug. Nutrient agar and DMF were used as culture medium and solvent control respectively.

Table 1. Physical characterization and bioavailability of compounds 3a-j

Physical Characterization				Lipinski Rule of 5
Compound	R	M.P (^oC)	Yield (%)	Log P	M.W	No of H bond		No of violation
Compound	R	M.P (^oC)	Yield (%)	Log P	M.W	Acceptor	Donor	No of violation
3Ia	Morpholinyl	81	53	2.37	327.409	5	0	0
3b	N-methyl Piperazinyl	79	86	2.42	340.452	4	0	0
3c	Pyrrolyl	89	45	3.66	307.378	4	0	0
3d	Pyrrolidinyl	75	60	2.93	311.411	4	0	0
3e	Piperazinyl	80	75	1.82	326.425	5	1	0
3f	Diethyl aminyl	87	46	3.28	313.462	4	0	0
3g	Imidazolyl	85	60	2.73	308.366	5	0	0
3h	Indolyl	82	46	4.92	357.438	4	0	0
3i	Dimethyl aminyl	78	47	2.08	285.372	4	0	0
3j	2-amino pyridinyl	84	31	1.80	334.425	5	0	0

Table 2. Spectral analysis of 3a-j

Compds	IR (Cm^-1, KBr)	1H NMR/ CDCl₃/DMSO-d₆ ppm	MS(m/z)
3a	1597(C=O), 1429(C=C), 1384(C-N), 739(C-S)	(s,2H,CH₂)3.40,(m,7H,ArH)6.53-.8.04	330
3b	1596(C=O), 1429(C=C), 1388(C-N), 739(C-S)	(s,2H,CH₂)3.40,(m,7H,ArH)6.52-8.04	339
3c	1639(C=O), 1478(C=C), 1384(C-N), 703(C-S)	(s,2H,CH₂)1.15,(m,7H,ArH)7.03-8.23	306
3d	1594(C=O), 1446(C=C), 749(C-S)	(s,2H,CH₂)3.84,(m,7H,ArH)6.53-7.84	311
3e	3449(N-H), 1630(C=O), 1431(C=C), 1384(C-N), 740(C-S)	(s,2H,CH₂)3.40,(m,7H,ArH)6.53-7.84	326
3f	1597(C=O), 1429(C=C), 1384(C-N), 739(C-S)	(s,2H,CH₂)3.4,(m,7H,ArH) 6.53-7.84	307
3g	1597(C=O), 1429(C=C), 1384(C-N), 739(C-S)	(s,2H,CH₂)3.48,(m,7H,ArH)6.53-7.84	309
h	1596(C=O), 1429(C=C), 1310(C-N), 741(C-S)	(s,2H,CH₂)1.90,(m,7H,ArH)6.49-8.23	350
3i	1596(C=O), 1430(C=C), 1308(C-N), 750(C-S)	(s,2H,CH₂)3.30,(m,7H,ArH)6.53-7.84	285
3j	3443(N-H), 1596(C=O), 1427(C=C), 1384(C-N), 739(C-S)	(s,2H,CH₂)1.15,(m,7H,ArH)7.03-8.23	334

SCHEME 1. Synthesis of Azaphenothiazine derivatives.

Table 3: Antimicrobial activity of compounds 3a-j

Compounds	Zone of inhibition( in mm)
Compounds	Vibrio cholerae	Bacillus spharicus	Salmonella typhi	Enterococcus feacalis
3a	7	8	10	8
3b	14	6	11	5
3c	7	11	6	5
3d	10	4	10	8
3e	15	7	11	5
3f	7	8	6	9
3g	8	10	12	6
3h	7	11	14	7
3i	9	7	7	6
3j	7	12	5	7
Amoxicillin	18	16	18	20

SEDATIVE ACTIVITY:

Sedative activity⁹ of compounds 3a-j was measured for locomotor activity,motor co-ordination test and Phenobarbitone hypnosis. Swiss albino mice of either sex weighing 25-30g were used for this study. Locomotor activity and motor co-ordination test were performed using Diazepam as standard drugs. Phenobarbitone was used as standard drug for Phenobarbitone hypnosis the standard and test compounds were administered i.p. (1mg/ml). Time of onset of action, duration of action and percentage decrease in activities were recorded and tabulated in Table 4.

Table 4: Sedative activity of compounds 3a-j

Compounds	Phenobarbitone hypnosis		Locomotor activity	Motor co-ordination test
Compounds	Onset of sleep	Duration of action	%decrease in activity	%decrease in activity
3a	5.42±0.32	36.12±0.32	.40.9±0.22	56. ±0.45
3b	6.42±0.94	30.15±0.33	45.4±0.15	62.4±0.62
3c	4.42±0.90	37.94±0.47	47.7±0.57	76.3±0.59
3d	5.11±0.16	40.15±0.49	54.5±0.58	82.3±0.32
3e	5.37±0.22	29.31±0.36	39.2±0.24	70.8±0.77
3f	4.31±0.72	42.37±0.22	51.5±0.27	78.3±0.31
3g	4.16±0.21	34.31±0.72	35.9±0.55	61.2±0.22
3h	4.40±0.94	37.52±0.33	39.7±0.32	75.3±0.73
3i	6.33±0.42	32.74±0.46	56.2±0.54	71.5±0.61
3j	5.82±0.01	33.16±0.21	31.6±0.29	62.5±0.49
Phenobarbitone	3.56±0.41	40.16±0.35	-	-
Diazepam	-	-	58.90±0.64	74.16±0.11

CONCLUSION:

According to Lipinski rule of 5 no violation is seen in any of the compounds. Hence, all the titled compounds assumed to have good bioavailability.From the antimicrobial screening it was observed that the new azaphenothiazine derivatives show mild antimicrobial activity against all the organisms employed. From sedative studies it is clear that the compounds with amino substitution like dimethyl amine, diethyl amine and pyrolidine show significant sedative activity. It reveals that as the basicity of the compound increases the sedative activity of the compound also increases.

ACKNOWLEDGEMENT:

Authors are thankful to The Dean Dr. K. S. Lakshmi, SRM College of Pharmacy, for her constant encouragement and providing necessary facilities to carryout this work

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Received on 24.04.2009 Modified on 23.06.2009

Asian J. Research Chem. 2(4):Oct.-Dec. 2009 page 411-413

P. Valentina*, K. Ilango, Deepak Jain and Prerna Shukla