Abstract. – OBJECTIVE: A series of ten novel derivatives of 3-substituted-2-thioxoquinazolin- 4(3H)-ones have been synthesized from an- thranilic acid via Mannich reaction with various secondary amines in presence of formaldehyde in ice cold condition. MATERIALS AND METHODS: The structure of these compounds have been elucidated by spectral (FTIR, 1H-NMR and mass) analysis. The titled compounds were evaluated for antimicro- bial and anticonvulsant activities. Antimicrobial activities were determined by cup plate method and MIC values using the micro dilution broth method against two Gram positive bacteria Staphylococcus aureus and Streptococcus aureus, two Gram negative bacteria Escherichia coli and Proteus vulgaris and against two fungi Candida albicans and Aspergillus niger. Amikacin and flu- conazole were used as standard antibacterial and antifungal agents in the concentration of 10 μg/disc 20 μg/disc respectively. RESULTS AND CONCLUSIONS: Amongst the compounds tested, compound 2-(2,3-di- methylphenyl) (3-(4-ethoxyphenyl)-4-oxo-2- thioxo-3,4-dihydroquinazolin-1-2H)-1ylmethyl amino)benzoic acid (PTQ-03) and 2-((2,3-di- methylphenyl)((3-(4-ethoxyphenyl)-4-oxo-2- thioxo-3,4-dihydroquinazolin-1(2H)- yl)methyl)amino)benzoic acid (ETQ-03) showed broad spectrum of activity against all the tested Gram positive bacteria, Gram negative bacteria and the fungi. Anti-convulsant activity of the compounds was evaluated by maximal electro shock (MES) convulsion method. The com- pounds sodium 2-(2-((2,6-Dichlorophenyl)(3-(4- oxo-2-thioxo-3,4-dihydroquinazolin-1(2H)- yl)methyl)amino) phenyl acetate (PTQ-04) and N- (4-Hydroxyphenyl)-N-((3-naphthalen-2-yl)-4-oxo- 2-thioxo-3,4-dihydorquinazolin-1(2H)-yl- methyl)acetamide (NTQ-01) showed potent anti- convulsant activity. Key Words: Thioxoquinazolinone, Drug likeness, Antibacterial, Antifungal, Anti-convulsant. European Review for Medical and Pharmacological Sciences Synthesis of some new thioxoquinazolinone derivatives and a study on their anticonvulsant and antimicrobial activities A. RAJASEKARAN 1 , V. RAJAMANICKAM 2 , S. DARLINQUINE 3 1 KMCH College of Pharmacy, Coimbatore, Tamilnadu, India 2 Research Scholar, Sastra University, Tanjore, Tamilnadu, India 3 Sastra University, Tanjore, Tamilnadu, India Corresponding Author: Aiyalu Rajasekaran, Ph.D; e-mail: rsekaran2001in@yahoo.co.in 95 Introduction Quinazoline and quinazolinone derivatives have continued to attract a widespread interest for a long time due to their diverse pharmacological ac- tivities like anti-parkinsonism 1 , anticonvulsant 2,3 , hypoglycemic 4 , anti-HIV 5 , antimicrobial 6-11 , anti- cancer 12,13 and analgesic 14 activity. Literature sur- vey revealed that the presence of substituted aro- matic ring at position 3 and methyl or thiol group at position 2 are essential for the anticonvulsant 15,16 and antimicrobial activities 17 . Based on this fact, more than hundreds of 2-methyl-3-O-tolyl-4(3H)- quinazolinone and its analogues have been synthe- sized and tested for central nervous system depres- sion and anticonvulsant activities 18-21 . Hence, we have undertaken the synthesis, characterization, antimicrobial and anticonvulsant evaluation of medicinally important and promising pharma- cophore, 4(3H)-quinazolinone ring system for our study. Materials and Methods Melting points were determined in open capil- laries in the electrical melting point apparatus and are uncorrected. Purity of the compounds was checked on silica gel coated Merck-TLC plates using water, chloroform, acetone and ben- zene as mobile phase. The structure of the syn- thesized compounds was elucidated by FT-IR (Shizamadu-8400 series, Shizamadu Scientific Instruments, Nakagyo-ku, Kyoto, Japan) in KBr disc, 1 H-NMR (Brucker AMX-400 MHz, Bruck- er Biospin International, Ag, Aegeristrasse, Switzerland) in dimethylsulfoxide-d 6 (DMSO-d 6 ) and mass spectra using Jeol JMS-DX 303 double focusing mass spectrophotometer (Jeol Ltd, Ak- ishima, Tokyo, Japan). The agar medium and 2013; 17: 95-104