Polyphenols (/ˌpɒliˈfiːnoʊl, -nɒl/) are a large family of naturally occurring phenols.[1] They are abundant in plants and structurally diverse.[1][2][3] Polyphenols include phenolic acids, flavonoids, tannic acid, and ellagitannin, some of which have been used historically as dyes and for tanning garments.