plant secondary metabolite oxygen molecular entity organic molecular entity flavonoids Any organic molecular entity whose stucture is based on derivatives of a phenyl-substituted 1-phenylpropane possessing a C<small>₁₅</small> or C<small>₁₆</small> skeleton, or such a structure which is condensed with a C<small>₆</small>-C<small>₃</small> lignan precursors. The term is a 'superclass' comprising all members of the classes of flavonoid, isoflavonoid, neoflavonoid, chalcones, dihydrochalcones, aurones, pterocarpan, coumestans, rotenoid, flavonolignan, homoflavonoid and flavonoid oligomers. Originally restricted to natural products, the term is also applied to synthetic compounds related to them. Any organic molecular entity whose stucture is based on derivatives of a phenyl-substituted 1-phenylpropane possessing a C15 or C16 skeleton, or such a structure which is condensed with a C6-C3 lignan precursors. The term is a 'superclass' comprising all members of the classes of flavonoid, isoflavonoid, neoflavonoid, chalcones, dihydrochalcones, aurones, pterocarpan, coumestans, rotenoid, flavonolignan, homoflavonoid and flavonoid oligomers. Originally restricted to natural products, the term is also applied to synthetic compounds related to them.