OBJECTIVE: A series of ten novel derivatives of 3-substituted-2-thioxoquinazolin-4(3H)-ones have been synthesized from anthranilic 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 antimicrobial 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 fluconazole 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-dimethylphenyl) (3-(4-ethoxyphenyl)-4-oxo-2-thioxo-3,4-dihydroquinazolin-1-2H)-1ylmethyl amino)benzoic acid (PTQ-03) and 2-((2,3-dimethylphenyl)((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 compounds 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)-ylmethyl) acetamide (NTQ-01) showed potent anticonvulsant activity. [ABSTRACT FROM AUTHOR]