This article reports one-pot synthesis of ten novel spirooxindoles using 5-methyl-2-thiohydantoin, isatin derivatives, and malononitrile in good to high yields (65-90%). The structures of the synthesized compounds were deduced by 1H NMR, 13C NMR, FT-IR, and Mass spectral data. The antibacterial activity of the compounds was evaluated against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) based on the Kirby-Bauer method. According to the obtained data, the synthesized compounds show more activity against Gram-positive bacteria than Gram-negative bacteria. Also, the antioxidant activity of these compounds was measured using the DPPH radical scavenging test method, which showed good to excellent activity (59.65-94.03%). Among them, the chlorinated derivatives (4f-j) exhibited more antioxidant activity (84.85-94.03%) than the other compounds (4a-e) (56.65-74.4%) and even ascorbic acid as a standard antioxidant compound (82.3%)
