Synthesis, Characterization of Different Five-Membered Heterocyclic Derivatives, Evaluated Their as Antioxidant, and In Vitro Antimicrobial Agents

Objective: This study involved synthesis of a new series of different five-membered heterocyclic derivatives, testing their antioxidant activity, and examining their potential in vitro antimicrobial agents. Methods: The synthesis of the derivatives involved a three-step process. Initially, succinyl chloride was reacted with methanol, followed by a reaction with 80% hydrazine hydrate through a nucleophilic addition-elimination mechanism, resulting in the formation of succinohydrazide (I). This compound was then employed as a precursor for the synthesis of Schiff bases (II), and (III) by reacting it with m-nitro benzaldehyde and p-nitro benzaldehyde. Following this, a ring closure reaction was applied using thioglycolic acid, glycolic acid, and glycine, resulting in the synthesis of different five-membered heterocyclic rings (IV–IX). Results and Discussion: The formation of the prepared derivatives was confirmed by FT-IR, ¹H NMR, and ¹³C NMR spectroscopy. Comparative analysis with L-ascorbic acid as a standard revealed that all the prepared compounds exhibited excellent antioxidant activities. In terms of antimicrobial activity, the tested derivatives showed moderate activity against both positive and negative types of bacteria, when compared to the reference drug Ciprofloxacin. Additionally, the antifungal test showed moderate activity for all the tested compounds against a specific pathogenic fungus, with Clotrimazole being as the reference drug. The antimicrobial activity of the synthesized compounds was found to be dependent on the type of heterocyclic rings containing S, O, and N atoms. These atoms were observed to enhance antimicrobial activity by donating electrons and becoming active. Additionally, the presence of active functional groups such as C=O, NO₂, and C=N contributed to this observed result. Conclusions: All of the synthesized compounds have demonstrated excellent antioxidant agents. Most of them have shown promising antimicrobial activity against certain bacteria strains, and effectiveness against a pathogenic fungus.