p-Coumaroyl Amides from the Plant Kingdom: A Comprehensive Review of Natural Sources, Biosynthesis, and Biological Activities

Hydroxycinnamic acids are widely distributed in the plant kingdom, both as free compounds and as conjugates with other molecules, such as amino acids, carbohydrates, alcohols or amines, and polyamines, forming different derivatives, such as amides, esters, thioesters, or ethers. Among the different hydroxycinnamic acids, p-coumaric acid has a high bioavailability and its amide derivatives, also known as phenolamides (PAs) and hydroxycinnamic acid amides (HCAAs), play specific roles in plant development and defense. They are also involved in several biological activities that affect human health. The present review collected data and described secondary and tertiary amides of p-coumaric acids found in plants, from their natural sources to their biosynthesis. The review also described the acyl-transferase mechanisms involved in their formation, their roles in plants, as well as studies of their biological activities in humans.