Synthesis and biological evaluation of piperic acid amides as free radical scavengers and αglucosidase inhibitors

Abstract

A series of piperic acid amides (4-24, 29, 30) were synthesized and their 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and α-glucosidase inhibitory activities were evaluated. Among the synthesized compounds, the amides 11, 13 and 15, which contain o-methoxyphenol, catechol or 5-hydroxyindole moieties, showed potent DPPH free radical scavenging activity (11: EC50 140 μM; 13: EC50 28 μM; 15: EC50 20 μM). The amides 10, 18 and 23 showed higher inhibitory activity of α-glucosidase (10: IC50 21 μM; 18: IC50 21 μM; 23: IC50 12 μM). These data suggest that the hydrophobicity of the conjugated amines is an important determinant of α-glucosidase inhibitory activity. In addition, the amides 13 and 15 showed both potent DPPH free radical scavenging activity and α-glucosidase inhibitory activity (13: IC50 46 μM; 15: IC50 46 μM). This is the first report identifying the DPPH free radical scavenging and α-glucosidase inhibitory activities of piperic acid amides and suggests that these amides may serve as lead compounds for the development of novel αglucosidase inhibitors with antioxidant activity.