Synthesis of Isatin Derivatives Exhibiting Antibacterial, Antifungal and Cytotoxic Activities

The current objective was to synthesize biologically active Isatin derivatives. For this purpose, six (06) chemical entities of Isatin derivatives such as 3a-3c and 4a-4c were synthesized from Isatin substrate.

The pure compounds were characterized with the help of ¹H-NMR, FT-IR, EIMS spectroscopic techniques. The synthesized amines 3a-3c and hydrazones 4a-4c were evaluated for their toxicity potential with the help of brine shrimp bioassay.

The obtained results revealed that 3c exhibited promising toxicity (LD₅₀ = 1.03 × 10^-5 M) against Artemia salina. The pure chemical entities such as compounds 3a-3c and 4a-4c were evaluated against four Gram-negative (E. coli, P. aeruginosa, S. typhi, S. flexneri) and two Gram-positive (B. subtilis, S. aureus) bacteriae. The compound 3a displayed significant activity against two bacterial strains; i.e. P. aeruginosa, S. typhi, compound 3c demonstrated significant activity against P. aeruginosa. Compound 4b was the most active against S. typhi, displaying a greater diameter of the growth of inhibition zone (GIZ) than the standard drug. Compound 4c exhibited significant activity against P. aeruginosa and S. typhi. Compounds 3a-3c and 4a-4c exhibited moderate to significant antibacterial activity against three out of five strains. Only Compound 3c revealed promising toxicity (LD₅₀ = 1.03 × 10^-5 M) against Artemia salina. Antifungal studies of the compounds 3a-3c and 4a-4c against six fungal cultures; T. longifusus, C. albicans, A. flavus, M. canis, F. solani, and C. glabrata. All the compounds were active against one or more pathogens having inhibition (10- 90 %). Compound 3a exhibited significant inhibition i.e. 90 % against M. canis, 70 % against T. longifusus, compound 4b further displayed significant inhibition (90 %) against A. flavus and thus proved to be the most active member of the series.

All compounds showed better antibacterial, antifungal and cytotoxic activities, which may provide a ground to prepare enhanced molecules with much higher antibacterial activities.