Hydroxycinnamic acids on gut microbiota and health

Hydroxycinnamic acids (HCAs) are a major class of phenolic acids with the characteristic phenylpropanoid C₆-C₃ backbone. Its typically conjugated status with plant cell wall components and liberation by limited enzymes might be the reason for its neglect by researchers compared to flavonoid-type polyphenols. The polyphenol–gut microbiota interactions and their impact on human health have captured the interest of researchers recently. In addition, there has been a significant progress over the past few years in understanding the gut microbiota-modulating effect of HCA using animal model studies. This review discusses the metabolism of HCA in the digestive tract, HCA–gut microbiota interactions, and its link to colorectal cancer, inflammatory bowel diseases, mental-cognitive impairments, nonalcoholic liver disease, and obesity. The effects of food matrix and processing technologies on HCA bioavailability and HCA–gut microbiota interactions, and HCA safety concerns are also featured in this review. This paper has provided an in-depth insight on HCA–gut microbiota relationship and identified the current literature gaps for future research.