Synthesis, Characterization, and Antifungal Activity of Amide Derivatives of Piperic Acid, an Analog of Piperine from Piper nigrum

Piperine, a natural alkaloid isolated from black pepper ( Piper nigrum ), was subjected to alkaline hydrolysis to yield piperic acid. A series of amides were synthesized by treatment of piperic acid with piperidine-4-carboxylic acid derivatives via different routes. The synthesized amides were characterized by various spectral techniques like FT-IR, 1 H NMR, and 13 C NMR spectroscopy and evaluated for their antifungal activity against pathogenic fungal species, viz. Fusarium , Penicillium , and Aspergillus , using poison food technique. All derivatives showed a significant activity against various fungal species in a dose-dependent manner. The results revealed that among various amide derivatives, compound 7a is more effective against Fusarium and Penicillium species, and compound 9b is more effective against Aspergillus species. It was observed that the mycelial growth of test fungi decreases with increasing the concentration of amide derivatives.