Flavonoids are polyphenolic compounds with the C6-C3-C6 skeleton structure. Natural flavonoids, including their O-glycoside and C-glycoside forms, are synthesized as plant secondary metabolites and thus ubiquitously found in foods of plant origin. Because of the potential health benefits of dietary flavonoids, there has been much interest in characterizing the involvement of gut microbiome and identifying key metabolites and their interactions. For example, equol metabolized from soy products [MD:
M00966] is known to have estrogenic activity.