Synthesis and anticonvulsant activity of some potent 5,6-bis aryl 1,2,4-triazines

Synthesis and anticonvulsant activity of some potent 5,6-bis aryl 1,2,4-triazines 1 first-author 1 †E-mail:gvsureshkumar@yahoo.com †E-mail:gvsureshkumar@yahoo.com gvsureshkumar@yahoo.com 2 3 4 Department of Medicinal Chemistry, St. Johns Pharmacy College, Bangalore-560040, Karnataka, India Department of Medicinal Chemistry, St. Johns Pharmacy College, Bangalore-560040, Karnataka, India Department of Pharmaceutical Sciences, Andhra University, Visakhapatnam-530002, Andhra Pradesh, India Department of Pharmaceutical Sciences, Andhra University, Visakhapatnam-530002, Andhra Pradesh, India Pharmacy Department, M.S. University, Baroda-390002, Gujarat, India Pharmacy Department, M.S. University, Baroda-390002, Gujarat, India Department of Pharmacognosy, Dr. H.L.T. College of Pharmacy, Bangalore-571502, Karnataka, India Department of Pharmacognosy, Dr. H.L.T. College of Pharmacy, Bangalore-571502, Karnataka, India In the present research, a series of 5,6-bis aryl 1,2,4-triazines 5a ~ 5f were synthesized by condensation of various benzils 4a ~ 4f with aminoguanidine bicarbonate and were screened in vivo, for their anticonvulsant and neurotoxicity studies. Compounds 5a , 5b and 5d were found to be potent molecules of this series, when compared with the reference drugs phenytoin sodium, diazepam and lamotrigine. The structures of these compounds were established by IR, 1 H NMR, 13 C NMR and mass spectroscopic data. 5,6-Bis aryl 1,2,4-triazines Synthesis Anticonvulsant activity INTRODUCTION 1 Epilepsy, characterized by the periodic and unpredictable occurrence of seizures is the most prevalent neurological disorder, affecting 0.5% to 1% of the worldwide population (45~100 million) (Chang and Lowenstein, 2003 2003 ; McNamara, 2001 2001 ). Conventional antiepileptic drugs (AEDs) though widely used by approximately 25% of epileptics (Sander, 1993 1993 ; Pastalos, 1999 1999 ) fail to adequately control seizures and exhibit unfavourable side effects such as ataxia, hepatotoxicity, gingival hyperplasia and megaloblastic anemia (Duncan, 2002 2002 ; Danny et al., 1992 1992 ). Phenytoin and carbamazepine prolong the inactive state of the voltage-dependent Na + channels. A similar action was found for felbamate and topiramate. Topiramate also affects chloride currents and increases the number of channel openings induced by GABA (gama amino butyric acid) (Petroff et al., 1995 1995 ). Contrary to this lamotrigine acts by prolonging inactivation of voltage-sensitive Na + channels. Selectivity differences for the α subunits of Na + channels might be responsible for the two different mechanisms (Taylor, 1996 1996 ). The 1,2,4-triazines seem to act by inhibition of the Na + channel in a frequency-dependent manner. As proposed previously, the pharmacophoric elements responsible for this mechanism are lipophilic aryl ring and hydrogen bonding to triazine moiety. The attachment of a second aryl ring to increase the van der Waal’s bonding at the binding site, substitutions by diverse electron rich groups on aryl ring has proven to increase potency in the maximal electroshock seizure (MES) screen (Pandeya et al., 2000 2000 ; Dimmock et al., 1995a 1995a ). These structural contemplations gave impetus to synthesize some novel and potent 1,2,4-triazines, with phenyl having substitutions at C-5 and C-6 with halogen groups (electron withdrawing), which were considered to have sufficient diverse electronic, steric and hydrophobic characters. CHEMISTRY 1 The synthesis of various 1,2,4-triazines was accomplished as shown in Fig. 1 1 , by condensation of aldehydes 1 and 2 to yield compounds 3a ~ 3f , which structures were confirmed by disappearance of a peak between δ 9.6 to 9.9 for −CHO proton (Erickson, 1952 1952 ). Compounds 3a ~ 3f on reacting with c-HNO 3 (concentrated HNO 3 ) yield corresponding benzils 4a ~ 4f , which were confirmed by disappearance of a singlet of −OH between δ 2.0 to 2.3 and CH proton between δ 6.0 to 6.2 in the 1 H NMR spectra (Sawyer and Copp, 1992 1992 ). Substituted benzil derivatives 4a ~ 4f on condensation with aminoguanidine bicarbonate yield corresponding 5,6-bis aryl 1,2,4-triazines 5a ~ 5f . The structures of 5a ~ 5f were established by the appearance of a singlet between δ 4.0 to 4.3 for 2 protons of −NH 2 in the 1 H NMR spectra and disappearance of the peak at δ 195.2 (C=O) which was present in 4a ~ 4f (Richard et al., 1972 1972 ). The spectral data of each compound was shown in the EXPERIMENTAL PROTOCOLS section and physical data was presented in Table 1 1 . MF: Molecular formula; MW: Molecular weight Partition coefficient values are calculated by biobyte interactive log P calculator Data are express as calculated (found) 2 Compounds 2 MF 3 Elemental analysis (%) # # 5 Substitutions 2 MW 2 Yield (%) 2 m.p. (°C) 2 CLOGP * * C H N R 1 R 2 R 3 R 4 R 5 5a C 17 H 16 N 4 73.89 (73.18) 5.84 (5.14) 20.27 (20.16) H CH 3 H CH 3 H 276.3357 80 132~134 3.5864 5b C 17 H 17 N 5 70.08 (70.11) 5.88 (5.16) 24.04 (24.23) H N(CH 3 ) 2 H H H 291.3504 78 94~96 3.0816 5c C 18 H 19 N 5 O 67.27 (67.17) 5.96 (5.91) 21.79 (21.11) H OCH 3 H N(CH 3 ) 2 H 321.3764 85 110~112 2.9987 5d C 16 H 13 ClN 4 O 61.26 (61.14) 4.19 (4.18) 17.91 (17.18) Cl H H OCH 3 H 312.7536 74 198~200 3.9706 5e C 17 H 15 ClN 4 O 2 59.57 (59.47) 4.41 (4.14) 16.34 (16.27) Cl H OCH 3 OCH 3 H 342.7796 70 212~214 3.0925 5f C 18 H 17 ClN 4 O 3 57.99 (57.23) 4.60 (4.16) 15.03 (15.34) Cl H OCH 3 OCH 3 OCH 3 372.8056 71 172~174 2.8105 PHARMACOLOGY 1 All the 5,6-bis aryl 1,2,4-triazines 5a ~ 5f , obtained from the reactional sequence were injected intraperitoneally into mice and evaluated for acute toxicity test, initial anticonvulsant screening and minimal motor impairment by the rotorod (neurotoxicity, NT) test, with three dose levels (30, 100 and 300 mg/kg) at two different time intervals. The profile of anticonvulsant activity was established by MES pattern test and subcutaneous pentylene tetrazole (ScPTZ) seizure threshold test. All the compounds 5a ~ 5f were evaluated for their CNS (central nervous system) behavioral activity in mice using actophotometer and Porsolt’s swim pool test with rats. RESULTS AND DISCUSSION 1 Compounds 5a ~ 5f were first tested for preliminary anticonvulsant evaluation (Table 2 2 ) as per testing procedures described in National Institute of Neurological Disorders, Stroke, NH, Bethesda, MD, USA, for Anticonvulsant Screening Project (ASP). Compounds rendering protection in the MES test may prove to be useful in treating generalized tonic-clonic and complex partial seizures, and activity in the ScPTZ screening is deemed to denote the agents of value in treating seizures. The data in Table 3 3 reveal that all the compounds were active in both MES and ScPTZ screening at 30 min, thus indicating that synthesized compounds are rapid acting anticonvulsants. Neurotoxicity in mice was measured by the rotorod apparatus, with compounds 5d and 5f exhibiting neurotoxicity at dose of 300 mg/kg, when compared to other compounds. The figures are the doses affording protection or causing neurotoxicity in 50% or more of the animals. The animals were examined 0.5 and 4 h after injections were made. The designation “−” indicates the absence of activity or toxicity at the maximum dose administered (300 mg/kg) 3 Compound 3 Acute toxicity, ALD 50 (mg/kg p.o.) 6 Intraperitoneal injection in mice a a (mg/kg) 2 MES screen 2 ScPTZ screen 2 NT screen 0.5 h 4 h 0.5 h 4 h 0.5 h 4 h 5a >1000 − − − − − − 5b >1000 − − − − − − 5c >1000 − − − − − − 5d >1000 − − − 300 − 300 5e >1000 − − − − − − 5f >1000 − − − − − 300 Phenytoin >1000 − − − − − − N =6 in each group The compounds 5a ~ 5f were tested at a dose of 10 mg/kg 0.5% methyl cellulose/water standard for control group Standard drug for MES pattern test Standard drug for ScPTZ seizure test 2 Drug/test compounds 2 Dose 2 MES model a a 3 ScPTZ model a a Duration of tonic hind limb extensor phase (s) Animals protected (%) Latency (s) (mean± SEM ) Duration of seizure (s) (mean± SEM ) Animals protected (%) Control b b 0.001 ml/g 13.43±0.32 0 135.8±2.18 248.19±2.56 0 5a 10 2.85±0.16 80 316.5±12.18 98.00±1.50 60 5b 10 4.56±0.19 76 3600 0 100 5c 10 3.25±0.38 67 234.67±5.61 126.89±1.29 49 5d 10 2.12±0.24 84 216.16±18.19 29.19±2.87 88 5e 10 9.48±0.36 30 3600 0 100 5f 10 12.46±0.13 8 373.7±13.39 126.33±0.28 50 Phenytoin c c 40 0 100 − − − Diazepam d d − − − 3600 0 100 In MES screening, all the compounds showed protection varying in the range of 8% to 84%, among them compounds 5a , 5b , and 5d showed excellent protection. The characteristic feature of these compounds is substitution of electron rich atom/group at different positions of aryl ring, which demonstrates potent anticonvulsant activity in comparison to other derivatives (Dimmock et al., 1995b 1995b ). The bioevaluation data of the synthesized compounds by ScPTZ induced seizures led to comprehending why compounds 5b and 5e were equipotent in protection to phenytoin. The assessment led to understanding the importance of methoxy substitution on aryl ring, i.e. with dimethoxy, the optimum electron donor guaranteed superior anticonvulsant activity in 5e . The introduction of 3rd methoxy group led to 5f , which was found to be inactive. This observation suggests that the additional methoxy group caused interference with alignment at binding site. The optimum log P values in both 5b and 5e ensure lipophilicity required by the compounds. Although the drug levels in cerebrospinal fluid (CSF) or in brain were not measured, higher log P values for the potent molecules suggest that there is a correlation between anticonvulsant activity and lipophilicity. In the locomotor study using actophotometer (Table 4 4 ), the compound 5a produced no behavioral despair effect when compared to phenytoin. Compound 5f exhibited decreased locomotor activity in the 30 min interval, but did not exhibit significant behavior despair in 1 h time period. All other compounds were found to decrease locomotor activity. In a similar study using swim pool test, the immobility time after administration of the test compounds was compared with carbamazepine. The compound 5d produced no significant CNS depression compared with control at P < 0.004. All other tested compounds were found to emerge as CNS depressants, as they increased the immobility time (Table 5 5 ). The compounds were tested at a dose of 10 mg/kg (i.p.) Each score represents the mean± SEM of six mice, significantly different from the control score at P < 0.0001 Each score represents the mean± SEM of six mice, significantly different from the control score at P < 0.008 Tested at 5 mg/kg 3 Compound a a 3 Activity score b b 2 Control (24 h prior) 2 Post-treatment 0.5 h after 1 h after 5a 345±21.13 303±12.76 * * 278±17.19 * * 5b 234±21.34 45±12.12 48±12.81 5c 412±31.62 67±17.89 89±3.67 5d 342±45.18 47±24.19 76±12.66 5e 212±22.07 89±12.11 112±45.18 5f 247±10.90 127±13.45 207±54.43 Phenytoin c c 265±21.37 54±12.78 58±12.55 The compounds were tested at a dose of 10 mg/kg (i.p.) Each value represents the mean± SEM of six rats, significantly different from the control at P < 0.004 and NS denotes not significant at P < 0.004 (Student’s t -test) 2 Compounds a a /drugs 2 Immobility time b b Control (24 h prior) Post treatment (60 min after) Control 173.67±13.69 178.67±22.3 NS 5a 123.56±11.49 189.58±55.5 5b 178.38±12.23 219.89±11.8 5c 138.78±10.39 256.88±19.9 NS 5d 108.78±10.19 161.89±10.3 5e 89.90±12.39 128.10±10.0 5f 119.76±11.18 157.89±16.7 Carbamazepine a a 148.58±11.12 219.77±18.0 EXPERIMENTAL PROTOCOLS 1 Chemistry 2 Melting points were determined in open capillary tubes with a Thomas Hoover melting point apparatus and were uncorrected. Infrared spectra were recorded in KBr on (Nicolet MX-1) FTIR instrument, 1 H NMR spectra (in CDCl 3 ) were recorded by Varian Gemini 200 (200 Hz) NMR spectrometer. Electron impact (EI) mass spectra were determined on AMD-604 mass spectrometer operating at 70 eV. 1. 2-Hydroxy-1,2-diphenylethanone derivatives 3a ~ 3f 3 The equimolar mixture of compounds 1 and 2 (0.47 mol), rectified spirit (65 ml) and sodium cyanide (0.1 mol) in 50 ml of water was refluxed for 2 h. Then the mixture was cooled in ice bath and filtered, the solid thus obtained was washed with water and recrystalized with hot ethanol to obtain compounds 3a ~ 3f . 2. Substituted benzil derivatives 4a ~ 4f 3 A mixture of 3a ~ 3f (0.014 mol) and c-HNO 3 (2 mol) were refluxed until the oxides of nitrogen ceased to evolve and poured into ice-cold water, the solid thus obtained was filtered off and washed with water and recrystalized with ethanol to yield compounds 4a ~ 4f . 3. 5,6-Diphenyl-1,2,4-triazin-3-amine derivatives 5a ~ 5f 3 The mixture of aminoguanidine bicarbonate (0.08 mol), 4a ~ 4f (0.035 mol) and 30.0 ml of rectified spirit was acidified to pH 3~4 with c-HCl and refluxed for 2 h. Mixture was made alkaline with aq. ammonia and the solid so obtained was further recrystalized with ethanol. Spectal data 2 1. 5,6-Dip-tolyl-1,2,4-triazin-3-amine 5a 3 FT-IR (KBr): 1620.5 cm −1 (C=C), 3305.0 cm −1 (−NH str ), 1528.2 cm −1 (C=N bend ), 1350.2 cm −1 (−CN str ). 1 H-NMR (CDCl 3 ): δ 4.01 (s, 2H, −NH 2 ), δ 7.36 (d, 4H, −Ar-H), δ 7.12 (d, 4H, −Ar-H), δ 2.35 (s, 6H, −2CH 3 ). 13 C-NMR (CDCl 3 125 MHz): 24.3 (2CH 3 ), 129.6 (4CH), 127.4 (4CH), 138.4 (2C), 130.1 (2C), 156.0 (C), 162.0 (C), 150.1 (C). Electron impact mass spectrum ( m / z ): 277.22 M + (32%), 206.09 (C 16 H 14 ) (base), 120.01 (C 9 H 11 ) (34.5%), 103.6 (C 9 H 11 ) (22.4%), 90.05 (C 7 H 7 ) (18.5%). 2. 5-(4-(Dimethylamino)phenyl)-6-phenyl-1,2,4-triazin-3-amine 5b 3 FT-IR (KBr): 1580.2 cm −1 (C=C), 3480.2 cm −1 (−NH str ), 1538.5 cm −1 (C=N bend ), 1348.2 cm −1 (−CN str ). 1 H-NMR (CDCl 3 ): δ 4.09 (s, 2H, −NH 2 ), δ 6.65 (d, 2H, −Ar-H), δ 2.85 (s, 6H, −CH 3 ), δ 7.32 (d, 2H, −Ar-H), δ 7.22 (d, 1H, −Ar-H), δ 7.30 (d, 1H, −Ar-H), δ 7.48 (d, 2H, −Ar-H). 13 C-NMR (CDCl 3 125 MHz): 114.8 (2CH), 128.4 (2CH), 129.3 (2CH), 127.5 (2CH), 128.8 (CH), 40.3 (2CH 3 ), 162.0 (C), 156.9 (C), 133.1 (C), 122.6 (C), 156.0 (C). Electron impact mass spectrum ( m / z ): 291.22 M + (base) (100%), 221 (C 16 H 15 N) (22%), 205.26 (C 14 H 17 N) (24.5%). 3. 6-(4-(Dimethylamino)phenyl)-5-(4-methoxyphenyl)-1,2,4-triazin-3-amine 5c 3 FT-IR (KBr): 1586.4 cm −1 (C=C), 3475.6 cm −1 (−NH str ), 1519.5 cm −1 (C=N bend ), 1317.6 cm −1 (−CN str ) 1260.5 cm −1 (−Ar-OCH 3str ), 2845.5 cm −1 (−CH-OCH 3str ). 1 H-NMR (CDCl 3 ): δ 4.02 (s, 2H, −NH 2 ), δ 7.37 (d, 2H, −Ar-H), δ 7.30 (d, 2H, −Ar-H), δ 6.65 (d, 2H, −Ar-H), δ 6.83 (d, 2H, −Ar-H), δ 3.73 (s, 3H, −OCH 3 ), δ 2.85 (s, 6H, −CH 3 ). 13 C-NMR (CDCl 3 125 MHz): 40.9 (2CH 3 ), 55.9 (CH 3 ), 114.8 (4CH), 128.4 (4CH), 149.6 (C), 160.7 (C), 125.4 (C), 122.6 (C), 156.1 (C), 162.0 (C), 150.9 (C). Electron impact mass spectrum ( m / z ): 321.15 M + (98.7%), 277.13 (C 17 H 15 N 3 O) (32%), 251.13 (C 16 H 15 N 3 ) (41.5%). 4. 5-(2-Chlorophenyl)-6-(4-methoxyphenyl)-1,2,4-triazin-3-amine 5d 3 FT-IR (KBr): 1603.6 cm −1 (C=C), 3470.8 cm −1 (−NH str ), 1508.7 cm −1 (C=N bend ), 1317.6 cm −1 (−CN str ) 1264.3 cm −1 (−Ar-OCH 3str ), 2861.3 cm −1 (−CH-OCH 3str ), 1087.6 cm −1 (−C-Cl str ). 1 H-NMR (CDCl 3 ): δ 4.23 (s, 2H, −NH 2 ), δ 3.73 (s, 3H, −OCH 3 ), δ 7.37 (d, 3H, −Ar-H), δ 6.83 (d, 2H, −Ar-H), δ 7.26 (m, 2H, −Ar-H), δ 7.49 (s, H, −Ar-H). 13 C-NMR (CDCl 3 125 MHz): 55.9 (−OCH 3 ), 128.9 (3CH), 114.8 (2CH), 125.6 (CH), 130.6 (CH), 12.4 (CH), 134.5 (2C), 160.7 (C), 125.4 (C), 150.1 (C), 162.1 (C), 156.0 (C). Electron impact mass spectrum ( m / z ): 312.07 M + (100%), 242.13 (C 15 H 11 ClO) (base) (69%), 200.21 (C 10 H 9 N 4 O) (13.16%). 5. 5-(2-Chlorophenyl)-6-(3,4-dimethoxyphenyl)-1,2,4-triazin-3-amine 5e 3 FT-IR (KBr): 1601.4 cm −1 (C=C), 3337.8 cm −1 (−NH str ), 1508.7 cm −1 (C=N bend ), 1326.6 cm −1 (−CN str ) 1276.3 cm −1 (−Ar-OCH 3str ), 2968.4 cm −1 (−CH-OCH 3str ), 1043.6 cm −1 (−C-Cl str ). 1 H-NMR (CDCl 3 ): δ 3.73 (s, 6H, −2OCH 3 ), δ 4.36 (s, 2H, −NH 2 ), δ 6.93 (d, 1H, −Ar-H), δ 6.88 (s, 1H, −Ar-H), δ 6.72 (d, 1H, −Ar-H), δ 7.49 (s, 1H, −Ar-H), δ 7.36 (d, 1H, −Ar-H), δ 7.23 (m, 2H, −Ar-H). 13 C-NMR (CDCl 3 125 MHz): 56.2 (−2OCH 3 ), 112.3 (CH), 115.8 (CH), 120.8 (CH), 127.4 (CH), 128.9 (CH), 127.4 (CH), 128.9 (CH), 130.7 (CH), 125.6 (CH), 134.9 (2C), 150.9 (C), 149.8 (C). Electron impact mass spectrum ( m / z ): 342.08 M + (C 17 H 15 ClN 4 O 2 ) (base) (100%), 307.13 (C 14 H 14 N 4 O 2 Cl) (69.2%), 272.13 (C 16 H 13 ClO 2 ) (86.5%). 6. 5-(2-Chlorophenyl)-6-(3,4,5-trimethoxyphenyl)-1,2,4-triazin-3-amine 5f 3 FT-IR (KBr): 1580.4 cm −1 (C=C), 3447.3 cm −1 (−NH str ), 1510.8 cm −1 (C=N bend ), 1329.7 cm −1 (−CN str ) 1254.2 cm −1 (−Ar-OCH 3str ), 2968.4 cm −1 (−CH-OCH 3str ), 1043.6 cm −1 (−C-Cl str ). 1 H-NMR (CDCl 3 ): δ 3.73 (s, 9H, −3OCH 3 ), δ 4.66 (s, 2H, −NH 2 ), δ 6.44 (s, 2H, −Ar-H), δ 7.49 (s, 1H, −Ar-H), δ 7.36 (d, 1H, −Ar-H), δ 7.26 (m, 2H, −Ar-H). 13 C-NMR (CDCl 3 125 MHz): 56.5 (−2OCH 3 ), 56.9 (−OCH 3 ), 104.6 (CH), 128.3 (CH), 137.4 (CH), 130.4 (CH), 126.3 (CH), 134.5 (C), 151.3 (C), 139.2 (C). Electron impact mass spectrum ( m / z ): 372.08 M + (32%), 337.28 (C 18 H 17 N 4 O 3 ) (base) (92%), 302.13 (C 17 H 15 ClO 3 ) (19.2%), 287.32 (C 14 H 11 ClN 4 O) (26.5%). Pharmacology 2 1. Acute toxicity test 3 The compounds were investigated for their acute toxicity (ALD 50 ) in albino mice by following the method of Smith ( 1960 1960 ). 2. Neurotoxicity screening (Grundmann and Kreutzberger, 1954 1954 ; Hosford and Wang, 1997 1997 ) 3 Minimal motor impairment was measured in mice by the rotorod apparatus. The mice were trained to stay on an accelerating rotorod rotating at 10 r/min with rod diameter being 3.2 cm. The trained animals were injected intraperitoneally with the test compounds 5a ~ 5f at doses 30, 100 and 300 mg/kg. Neurotoxicity was indicated by the inability of the animal to maintain equilibrilium on the rod for at least 1 min in each of the three trials. 3. Anticonvulsant activity 3 (1) MES test (Kubicki and Codding, 2001 2001 ; Stephani, 1989 1989 ) 4 This activity was performed according to the reported method on albino rats of either sex, weighing between 80 to 120 g. Rats were divided into 8 groups of 6 animals each. The rats were treated with compounds 5a ~ 5f at dose of 10 mg/kg or phenytoin 40 mg/kg i.p. After 1 h they were subjected to shock of 150 mA by convulsiometer through ear electrodes for 0.2 s, the duration of extensor phase response was noted and animals in which extensor response was abolished were taken as protected rats. (2) ScPTZ induced seizures test (Fisher, 1989 1989 ) 4 The test was performed using albino mice which were divided into eight groups of 6 each. Pentylenetetrazole (80 mg/kg) (convulsant), diazepam (standard drug) and test compounds 5a ~ 5f were dissolved in 0.5% methyl cellulose/water and injected intraperitoneally at volume of 0.01 ml/g. The time needed for the development of unequivocal sustained clonic seizure activity involving limbs (isolated myoclonic jerks or other preconclusive chewing behavior were not counted) and duration of seizure was carefully noted. Seizure free period of 1 h was considered as protection. The number of animals protected in each group was recorded and percentage of protection was calculated. 4. Locomotor activity (Stephani, 1989 1989 ) 3 The titlered compounds 5a ~ 5f at 10 mg/kg were screened for their behavioral effects using actophotometer at 30 min and 1 h after injection. The locomotor activity was recorded by photocell as a digital score, and increased scores suggest good behavioral activity. The control was administered 0.5% methyl cellulose/water in a volume of 0.01 ml/g. 5. CNS depressant study 3 The forced swim pool method described in Porsolt et al.( 1978 1978 ) was followed. Albino rats were placed in a chamber (diameter: 45 cm, height: 20 cm) containing water up to a height of 15 cm at (25±2) °C. Two swim sessions were conducted, an initial 15 min pre-test, followed by a 5 min test session 24 h later. The animals were treated with intraperitoneal injection of test compounds at dose of 10 mg/kg before 30 min of test session. The period of immobility (passive floating without struggling, making only those movements which are necessary to keep its head above the surface of water) during the 5 min test period was measured. CONCLUSION 1 In summary, this study highlights the importance of the structural features responsible for the anticonvulsant activity; p -methoxy derivative 5e was found to be most potent in both anticonvulsant activity-evaluating models, which serve as prototypic compounds for subsequent molecular modifications. References BS Chang , DH Lowenstein . Mechanisms of disease: epilepsy . N Eng J Med , 2003 . 349 ( 13 ): 1257 - 1262 . DOI: 10.1056/NEJMra022308 http://doi.org/10.1056/NEJMra022308 . Mechanisms of disease: epilepsy DS Danny , HL René , LS Jill , V Alan . Comparative anticonvulsant potency and pharmacokinetics of (+)- and (−)-enantiomers of stiripentol . Epilepsy Res , 1992 . 1 ( 11 ): 29 - 36 . . Comparative anticonvulsant potency and pharmacokinetics of (+)- and (−)-enantiomers of stiripentol JR Dimmock , KK Sidhu , DF Tumber . Some aryl semicarbazones possessing anticonvulsant activitie . Eur J Med Chem , 1995 . 30 ( 4 ): 287 - 301 . DOI: 10.1016/0223-5234(96)88237-7 http://doi.org/10.1016/0223-5234(96)88237-7 . Some aryl semicarbazones possessing anticonvulsant activitie JR Dimmock , SC Vashishtha , JP Stables . Evaluation of the semicarbazones, thiosemicarbazones and bis-carbohydrazones of some aryl alicycylic ketones for anticonvulsant and other biological propertie . Eur J Med Chem , 1995 . 30 ( 4 ): 303 - 314 . DOI: 10.1016/0223-5234(96)88238-9 http://doi.org/10.1016/0223-5234(96)88238-9 . Evaluation of the semicarbazones, thiosemicarbazones and bis-carbohydrazones of some aryl alicycylic ketones for anticonvulsant and other biological propertie JS Duncan . The promise of new antiepileptic drugs . Br J Clin Pharmacol , 2002 . 53 ( 2 ): 123 - 131 . 11851635 DOI: 10.1046/j.0306-5251.2001.01540.x http://doi.org/10.1046/j.0306-5251.2001.01540.x . The promise of new antiepileptic drugs JG Erickson . 3-Amino-as-triazines . J Am Chem Soc , 1952 . 74 ( 18 ): 4706 DOI: 10.1021/ja01138a506 http://doi.org/10.1021/ja01138a506 . 3-Amino-as-triazines RS Fisher . Animal models of the epilepsies . Brain Research Reviews , 1989 . 14 ( 3 ): 245 - 278 . 2679941 DOI: 10.1016/0165-0173(89)90003-9 http://doi.org/10.1016/0165-0173(89)90003-9 . Animal models of the epilepsies C Grundmann , A Kreutzberger . 1,3,5-Triazine . J Am Chem Soc , 1954 . 76 ( 2 ): 632 - 633 . DOI: 10.1021/ja01631a107 http://doi.org/10.1021/ja01631a107 . 1,3,5-Triazine DA Hosford , Y Wang . Utility of the lethargic ( lh / lh ) mouse model of absence seizures in predicting the effects of lamotrigine, vigabatrin, tiagabine, gabapentin, and topiramate against human absence seizures . Epilepsia , 1997 . 38 ( 4 ): 408 - 414 . 9118845 DOI: 10.1111/j.1528-1157.1997.tb01729.x http://doi.org/10.1111/j.1528-1157.1997.tb01729.x . Utility of the lethargic (lh/lh) mouse model of absence seizures in predicting the effects of lamotrigine, vigabatrin, tiagabine, gabapentin, and topiramate against human absence seizures M Kubicki , PW Codding . Hydrogen bonding patterns in 3,5-diamino-6-aryl triazines . Journal of Molecular Structure , 2001 . 570 ( 1-3 ): 53 - 60 . DOI: 10.1016/S0022-2860(01)00477-X http://doi.org/10.1016/S0022-2860(01)00477-X . Hydrogen bonding patterns in 3,5-diamino-6-aryl triazines JO McNamara . LG Hardman , LE Limbird . Drugs Effective in the Therapy of the Epliepsies . Goodman and Gilman’s the Pharmacological Basis of Therapeutics , 2001 . : New York McGraw Hill , 521 - 547 . . Drugs Effective in the Therapy of the Epliepsies SN Pandeya , P Yogeswari , JP Stables . Synthesis and anticonvulsant activity of 4-bromophenyl substituted aryl semicarbazones . Eur J Med Chem , 2000 . 35 ( 10 ): 879 - 886 . 11121613 DOI: 10.1016/S0223-5234(00)01169-7 http://doi.org/10.1016/S0223-5234(00)01169-7 . Synthesis and anticonvulsant activity of 4-bromophenyl substituted aryl semicarbazones PN Pastalos . Synthesis of some oxime ether derivatives of 1-(2-naphthyl)-2-(1,2,4-triazol-1-yl)ethanone and their anticonvulsant and antimicrobial activities . Curr Opin CPNS Invest Drugs , 1999 . 1 ( 64 ): 549 - 555 . . Synthesis of some oxime ether derivatives of 1-(2-naphthyl)-2-(1,2,4-triazol-1-yl)ethanone and their anticonvulsant and antimicrobial activities OA Petroff , DL Rothman , KL Behar , RH Mattson . Initial observations on effect of vigabatrin on in vivo 1 H spectroscopic measurements of γ-aminobutyric acid, glutamate, and glutamine in human brain . Epilepsia , 1995 . 36 ( 5 ): 457 - 464 . 7614922 DOI: 10.1111/j.1528-1157.1995.tb00486.x http://doi.org/10.1111/j.1528-1157.1995.tb00486.x . Initial observations on effect of vigabatrin on in vivo 1H spectroscopic measurements of γ-aminobutyric acid, glutamate, and glutamine in human brain RD Porsolt , G Anton , N Blavet , M Jalfre . Behavioural despair in rats: a new model sensitive to antidepressant treatments . Eur J Pharmacol , 1978 . 47 ( 4 ): 379 - 391 . 204499 DOI: 10.1016/0014-2999(78)90118-8 http://doi.org/10.1016/0014-2999(78)90118-8 . Behavioural despair in rats: a new model sensitive to antidepressant treatments WA Richard , BR Peter , JF Theodre . Antimalarial activities of some 3,5-diamino-as-triazine derivatives . J Med Chem , 1972 . 15 ( 4 ): 859 - 871 . 5044307 . Antimalarial activities of some 3,5-diamino-as-triazine derivatives JWAS Sander . Some aspects of prognosis in the epilepsies: a review . Epilepsia , 1993 . 34 ( 6 ): 1007 - 1016 . 8243349 DOI: 10.1111/j.1528-1157.1993.tb02126.x http://doi.org/10.1111/j.1528-1157.1993.tb02126.x . Some aspects of prognosis in the epilepsies: a review DA Sawyer , FC Copp . Synthesis of novel triazoles as potent anticonvulsants . Chem Abstr , 1992 . 108 1125 . Synthesis of novel triazoles as potent anticonvulsants QE Smith . Pharmacological Screening Tests Progress in Medicinal Chemistry.1: Butterworths. , 1960 . : London 1 - 33 . . Pharmacological Screening Tests Progress in Medicinal Chemistry.1: Butterworths. U Stephani . The natural history of myoclonic astatic epilepsy the natural history of myoclonic astatic epilepsy . Epilepsia , 1989 . 47 ( Suppl. 1 ): S53 - S55 . . The natural history of myoclonic astatic epilepsy the natural history of myoclonic astatic epilepsy CP Taylor . Voltage-gated Na + channels as targets for anticonvulsant, analgesic and neuroprotective drugs . Curr Pharm Des , 1996 . 2 ( 4 ): 375 - 379 . . Voltage-gated Na+ channels as targets for anticonvulsant, analgesic and neuroprotective drugs The authors are grateful to I.S.R. Nidya and Wilkin Einstein, Department of Pharmacology for statistical evaluation of pharmacological data and to management of St Johns Pharmacy College for providing essentials. 10.1631/jzus.2007.B0526 2007-02-05 2007-04-20 2022-01-05 Copyright © 2007, Journal of Zhejiang University Science 2007 Journal of Zhejiang University-SCIENCE B (Biomedicine and Biotechnology) 07 08