Synthesis and Antioxidant Properties of Two New Derivatives of Indeno-Benzofuran

Ninhydrin reacts with poly-phenols in different ratios to produce tetracyclic adducts. Here, pyrogallol was used as a polyphenol compound. In the company of acidic ionic liquid (AIL), there was a selective reaction between the ortho-site of polyphenol and the ninhydrin’s carbonyl group. Mono-adduct (1:1) 3 and bis-adduct (2:1) 4 were prepared as a solvent and a catalyst for the reaction of ninhydrin with pyrogallol in 1-(carboxymethyl)-3-methyl-1H-imidazolium chloride (mcmimCl). Purity of the products was approved by 1H NMR, 13C NMR, IR and Mass Spectroscopy. Moreover, the antioxidant activity of novel derivatives investigated in this paper by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical assay and butylated hydroxytoluene (BHT) was considered to be standard. The results indicated that mono-adduct showed the strongest antioxidant activity (IC50 = 5.289µg/ml).