This paper reviews the chemistry and biochemistry of dietary polyphenols, focusing on their classification, extraction, separation, and analytical methods, as well as their occurrence and biosynthesis in plants. Polyphenols, a diverse group of natural compounds with phenolic structural features, have been linked to numerous health benefits, particularly in preventing degenerative diseases such as cancer, cardiovascular disease, and neurodegenerative diseases. They act as strong antioxidants, complementing the functions of antioxidant vitamins and enzymes by neutralizing reactive oxygen species (ROS). The review highlights the importance of polyphenols in cell signaling modulation and their potential roles beyond antioxidant functions. The paper also discusses the challenges in characterizing polyphenols, including their complex glycosylation and polymerization patterns, and the methods used for their extraction, separation, and analysis. Additionally, it explores the biosynthesis pathways of polyphenols and their biological activities, emphasizing the need for further research to understand their mechanisms of action and potential health benefits.This paper reviews the chemistry and biochemistry of dietary polyphenols, focusing on their classification, extraction, separation, and analytical methods, as well as their occurrence and biosynthesis in plants. Polyphenols, a diverse group of natural compounds with phenolic structural features, have been linked to numerous health benefits, particularly in preventing degenerative diseases such as cancer, cardiovascular disease, and neurodegenerative diseases. They act as strong antioxidants, complementing the functions of antioxidant vitamins and enzymes by neutralizing reactive oxygen species (ROS). The review highlights the importance of polyphenols in cell signaling modulation and their potential roles beyond antioxidant functions. The paper also discusses the challenges in characterizing polyphenols, including their complex glycosylation and polymerization patterns, and the methods used for their extraction, separation, and analysis. Additionally, it explores the biosynthesis pathways of polyphenols and their biological activities, emphasizing the need for further research to understand their mechanisms of action and potential health benefits.