Objective:  The aim of present work is to synthesize a novel series of (Isatin) 1H-indole-2, 3-diones derivatives and evaluate its antioxidant activity. The structure of these compounds was established on basis of NMR data and IR data. Introduction: Isatin (1H-indole-2, 3-dione) is a synthetically versatile substrate, where it can be used for the synthesis of large variety of heterocyclic compounds, such as Indoles and quinolones. Isatin modify can considered as an important pharmacophore in the field of medicinal chemistry which can be used for conjugating it with other bioactive molecules such as antibacterial, antifungals, anticonvulsants and antiviral agents due to its potent pharmacological activity. Looking at the pharmacological potential of isatin we thought it worthwhile to synthesize and characterize some Schiff’s and Mannich bases of isatin.   Isatin and its derivatives undergo nucleophilic attack at position C-3. The chemo selectivity of these reactions depends on the nature of the substituents attached to the isatin nucleus, and especially of those bonded to the nitrogen atom, as well upon solvent and temperature employed. Chemistry:   Isonitrosoacetanilide was prepared from aniline by treating aniline with chloral hydrate and hydroxylamine hydrochloride and from Isonitrosoacetanilide, indole-2, 3-dione was prepared in presence of conc. Sulphuric acid. Then various derivatives of indole-2, 3-diones were prepared by treating indole-2, 3-dione with various amines in presence of glacial acetic acid and formaldehyde to yield Schiff’s and Mannich bases. The structure of synthesized compounds were confirmed by chromatographic and spectral analysis Antioxidant activity: The synthesized compounds were then evaluated for their Free radical scavenging activity by the DPPH assay method at 10, 20, 30, 40, 50 µg/ml concentrations of ligands & standard. Ascorbic acid was used as the standard. The data obtained were analyzed and results were expressed as mean absorbance ± standard error mean for each compound. The results of the pharmacological screening indicated that Compound ISS-2 shows more significant Free radical scavenging activity in comparison to other ligands and compounds ISS-1, ISS-5 shows moderate antioxidant activity and compounds ISS-4 and ISS-3 shows less antioxidant activity.  Conclusion: The compounds synthesized were then characterized using various spectroscopic techniques i.e.IR, 1H-NMR. The spectroscopic studies showed spectral data confirmed the formation of new compounds. The synthesized compound possesses significant antioxidant activity.

Keywords: Isatin, antioxidant, Manichh and Schiff base, DDPH assay, ascorbic acid.