Nine 2,4-disubstituted 6H-5,1,3-benzothiadiazocines have been tested for antibacterial and cytoto- xic efficacy. None of the tested compounds showed any significant antibacterial activity in compa- rison with ampicillin. The most cytotoxic effect was manifested by those derivatives which have morpholine or phenyl in position 2 and benzimidazole, imidazole or 1,2,4-triazole in position 4. The highest concentrations of derivatives I, VII, IX induced an acute cytotoxic effect which was manifested by cell lysis after 24 h of culturing. Derivative VII, concentration 30.5 mmol/L, and derivative IX, concentration 13.3 mmol/L, exhibited a delayed cytotoxic effect on L1210 cells. While during the first 24 and 48 h a certain part of cell population proliferated, during further 24 h a total inhibition of cell division was found. The cytotoxic concentration of derivative IX induced damage to the integrity of the cytoplasmic membrane. Benzothiadiazocines I, VII and IX induced a two-phase unbalanced growth. Based on these results, benzothiodiazocines I, VII and IX could be considered new potential anticancer drugs which are appropriate for further research.

        Key words: benzothiadiazocine derivatives – antibacterial activity – inhibition of tumour cell proliferation – cytotoxicity – damage of cytoplasmic membrane – unbalanced growth