Synthesis, Spectral Characterization, and Biological Evaluation of a Novel Curcumin–L-Cystine Schiff Base Derivative

Khairi M. Hamza^{1 *}, Abdunaser Megrahi², Naeema Hafedha³

¹ Department of Chemistry, Faculty of Education, University of Zawia, Zawia, Libya,

² Department of Chemistry, Faculty of Education, University of Tripoli, Janzour, Libya ³Department of Chemistry, Faculty of Science, University of Zawia, Zawia, Libya

Dr.hamza.khairi@gmail.co¹  a.megrahi@uot.edu.ly²       Benamer151@gmail.com³

 https://orcid.org/0009-0007-4673-4666  ¹   https://orcid.org/0009-0005-6968-8522  ²https://orcid.org/0009-0008-1530-8653 ³

Abstract:

Curcumin, a natural polyphenolic compound derived from Curcuma longa, possesses diverse biological activities including antimicrobial and antioxidant effects. However, its clinical application is limited by poor aqueous solubility and low bioavailability [1–5]. In this study, a novel curcumin–L-cystine Schiff base derivative was synthesized via condensation under reflux conditions with a yield of 74%. The structure was confirmed using FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy. Antibacterial activity was evaluated against Gram-negative (Escherichia coli, Klebsiella pneumoniae) and Gram-positive (Staphylococcus aureus, Staphylococcus agalactiae) strains using the agar well diffusion method [19]. Antioxidant activity was assessed via the DPPH radical scavenging assay [10,11]. The derivative exhibited concentration-dependent moderate antibacterial activity, particularly against Gram-positive bacteria, while antioxidant activity was lower than that of ascorbic acid. These findings demonstrate that amino acid conjugation via Schiff base formation modifies curcumin’s biological profile and may serve as a promising strategy for further structural optimization.

Keywords: Curcumin; L-Cystine; Schiff Base; Antibacterial Activity; Antioxidant Activity; Spectral Characterization.