Antiultraviolet, Antioxidant, and Antimicrobial Properties and Anticancer Potential of Novel Environmentally Friendly Amide-Modified Gallic Acid Derivatives

Polyphenols and amides isolated from natural products have various biological functions, such as antioxidant, antimicrobial, anticancer, and antiviral activities, and they are widely used in the fields of food and medicine. In this work, four novel and environmentally friendly amide-modified gallic acid derivatives (AMGADs), which were prepared by using different amides to modify gallic acid (GA) from Polygonaceae plants, displayed good antiultraviolet (anti-UV), antioxidant, antimicrobial, and anticancer effects. Significantly, the anti-UV capability of compounds n1 and n2 was notably superior to that of the UV absorber GA. Moreover, compound n2 possessed better 2,2-diphenyl-1-picrylhydrazyl radical (DPPH^•) scavenging ability and ferric reducing antioxidant power than vitamin C. The antibacterial activities of all AMGADs, with inhibition rates of more than 96.00 and 79.00% for Escherichia coli and Staphylococcus aureus, respectively, were better than those of GA. Compound n1 had broad-spectrum anticancer activity, and its inhibitory effect on HepG2 cells exceeded that of 5-fluorouracil. The good and rich bioactivities of these AMGADs revealed that combining GA with amides is conducive to improving the activity of GA, and this study laid a good foundation for their scientific application in the fields of food and medicine.