Novel Schiff Bases Derived From Isothiocyanates: Synthesis, Characterization, and Antioxidant Activity

Abstract

A series of novel thiosemicarbazones including Schiff bases were synthesized by treatment of various aryl-substituted aldehydes with thiosemicarbazides in ethanol containing one drop of hydrochloric acid at reflux for 3-5 h. For this, thiosemicarbazides were obtained from hydrazine monohydrate and isothiocyanates in cold dry ethanol at 0 degrees C for 1 h. FT-IR,H-1 NMR,C-13 NMR, and LC-MS/MS spectroscopic methods and elemental analysis were used to characterize the identification of the synthesized products. The in vitro antioxidant activity of these compounds was tested by the 1,1-diphenyl-2-picryl hydrazyl (DPPH) free radical trapping method. All of the synthesized compounds showed lower antioxidant activity than the ascorbic acid standard and followed the sequenceI > VII > X > VI > IV > IX > XI > II > V > III > VIII.