Synthesis and Application of Thiobarbituric Acid Derivatives as Antifungal Agents
Barbiturates are well known for their hypnotic effect and various methods have been worked out for their synthesis. Numerous barbiturate derivatives have been found to possess considerable biological activities, which stimulated the research activity in this field. They have several prominent effects, such as antimicrobial, anti-mycobacterial, antifungal, anticonvulsant, analgesic, antiviral, antidepressant and anticancer activities. They also possess Xanthine oxidase (XO) inhibitory activity along with inhibitory action against protein tyrosine phosphates (PTP) 1B. 2,4,6-Trioxohexahydropyrimidine seems to be the most frequently studied barbituric type compounds and a large no. of synthetic methods for their preparation have been described in the chemistry literature. In the present work, nine new substituted TBA derivatives were synthesized by Knoevenagel condensation of indole-3-carboxaldehyde, substituted pyrazole carboxaldehyde and 3,4,5-trimethoxy carboxaldehyde with substituted thiobarbituric acid. The synthetic route for the final compounds starts with the formation of substituted biphenyl thiourea from reaction of carbon disulfide and substituted aniline in ethanol. Then the cyclization of substituted biphenyl thiourea in the presence of malonic acid and acetyl chloride afforded substituted biphenyl thiobarbituric acid. The subsequent condensation of substituted TBA with different carboxaldehyde derivatives yielded final compounds. All the final compounds were characterized by IR, 1H NMR spectroscopy. They were screened for their antifungal activity against C. albicans, A. niger and P. citrinum. Newly synthesized compounds were evaluated for antifungal activity by cup plate method using Fluconazole as standard. The unsubstituted biphenyl thiobarbituric acid derivatives were found more active than the substituted biphenyl thiobarbituric acid derivatives.