(IJIRSE) International Journal of Innovative Research in Science & Engineering ISSN (Online) 2347-3207 Synthesis, Spectral and Antioxidant Studies of Indole-2,3-dione derivatives L.F. Flarlin Sheeja, J. Margaret Marie* Department of Chemistry, Women’s Christian College,Chennai -600006, India. *Corresponding author email id: margaretxavier@gmail.com Abstract The changes in lifestyle, food habits and climate have significantly influenced the biology of human beings. Stress has become one of the major illnesses in today’s world. Oxidative stress leads to the formation of free radicals in the body which becomes a major cause for diseases. Hence, over the last decade, there is an increased interest to find effective free radical scavengers that could address this issue. Compounds that have potential antioxidant activity from plant sources are on being explored. 1H-Indole-2,3-dione derivatives are one such class of compounds that show potential antioxidant activities. In the present work new potent molecules having indolin moiety with enhanced free radical scavenging properties have been synthesized. The synthesized indole-2,3-dione derivatives were characterized by Fourier transform infrared, 1 H nuclear magnetic resonance, 13 C nuclear magnetic resonance and mass spectroscopy techniques. The in vitro antioxidant activity was evaluated using hydrogen peroxide scavenging activity and total antioxidant capacity by a phosphomolybdenum assay and their reducing power ability. The results show that the synthesized indole-2,3-dione derivatives have remarkable antioxidant activity and are suitable candidates for development into drug for oxidative stress and other diseases. Keywords: indole-2,3-dione, antioxidant, free radical scavengers I. INTRODUCTION Antioxidants play a significant role in several important biological processes such as immunity, protection against tissue damage, reproduction and growth or development. They reduce damage to cells and biochemicals caused by free radicals, which are normal products of metabolism[1]. Isatin and its derivatives are among an extensive diversity of heterocycles that have been explored for developing pharmaceutically important lead compounds. They are biologically active and have significant importance in medicinal chemistry. Several isatin derivatives are in the development phase as potential new drugs for various diseases[2] which includes antifungal, antihistaminics, antiemetics, neuroleptics, tranquilizers[3], analgesic, anticonvulsant[4], anti- inflammatory[5], antiplasmoidal[6], anti HIV[7], anthelmintic[8], antidepressant, antimicrobial[9], anticancer[10], antiviral[11], antitubercular[12], antibacterial[13], especially with antioxidant activity[14]. The presence of the keto groups at carbonyl positions 2 and 3 can either enter into addition reaction at the C-O bond or form condensation products with release of water. Through the NH group, compounds of the isatin series are capable of entering into N-alkylation and N-acylation[15]. In present work, we have synthesized isatin derivatives, exploiting the above possibilities. The two isatin derivatives namely, 1-benzoyl indole-2, 3-dione (S1) and 1-benzoyl-3-(4-bromophenylimino)indolin-2-one (S3) were studied for their potential antioxidant activity and reducing power ability. II. MATERIALS AND METHODS A. Materials and physical measurements All the chemicals and solvents were used as such without any further purification. Infrared spectra were recorded on a Perkin-Elmer FT-IR Spectrometer in the range of 4000-500 cm -1 , using KBr pellets. The proton and carbon-13 NMR spectra were recorded using Bruker 1 H NMR having a frequency of 500 MHz and 13 C NMR having frequency of 125 MHz. The solvents used were CDCl 3 and C 6 D 6 with reference TMS. Mass spectra were recorded by Thermoscientific LT2 X2 model ESI of m/z range 100-1000. The solvent used was chloroform. The electronic absorption for various antioxidant studies were recorded on a Systronics UV-Visible