There are many phenolic compounds in the plant kingdom. They are so ever present and unavoidable in the American diet. You can get your phenolic compounds from fruits, vegetables, grains, cereals, seeds, beans, and most spices. The highest concentration of phenolics in the diet are in the foods that most individuals consume the least which as spices and herbs. I feel we consume most phenolic compounds in beverages such as tea and coffee while others consume it in beer and wine.
I even found out that there is a phenolic database on the Internet where you can find the foods with the most phenolic compounds.
There are also studies to suggest that the high concentration of polyphenols are associated with better cognitive function. Polyphenols play a major role in assisting the prevention of chronic disease such as coronary artery diseases, diabetes, Alzheimer's and Parkinson's disease.