Synthesis, Characterization, and Antioxidant Activity of Thiosemicarbazide-Derived Schiff Base

Heng, Huai Yu (2025) Synthesis, Characterization, and Antioxidant Activity of Thiosemicarbazide-Derived Schiff Base. Final Year Project (Bachelor), Tunku Abdul Rahman of Management and Technology.

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Abstract

In this study, a novel thiosemicarbazide-derived Schiff base, 2-[(3-hydroxyphenyl)methylidene]-N-methylhydrazine-1-carbothioamide (MTHBA), was synthesised using a reflux method. The compound was characterised by melting point determination, DSC, TGA, FTIR, UV-Vis, ¹H/¹³C NMR, LC-ESI-MS and CHNS analysis. Structural analysis confirmed that MTHBA adopts the thione (C=S) form in both solid and liquid phases. The antioxidant activity of MTHBA and was assessed using DPPH assay. This assay revealed a consistent activity trend: MT > MTHBA > HBA. Overall, these findings indicate that coupling 4-methyl-3-thiosemicarbazide with 3-hydroxybenzaldehyde enhances the antioxidant capacity relative to 3-hydroxybenzaldehyde alone, but results in a markedly lower activity compared with 4-methyl-3-thiosemicarbazide.