Fig. 1.

Biochemical pathway and chemical structural information regarding selected flavonoid compounds in plants. (A) Schematic diagram of the biosynthetic pathways of the major flavonoids (Rausher et al., 2008; Wessinger and Rausher, 2012). Dashed arrows represent the unclear steps. The names and structures of three anthocyanidin compounds are indicated. The enzyme names in black boxes are as follows: CHS, chalcone synthase; CHI, chalcone isomerase; F3H, flavanone 3-hydroxylase; F3′H, flavonoid 3′-hydroxylase; F3′5′H, flavonoid 3′,5′-hydroxylase; DFR, dihydroflavonol 4-reductase; ANS, anthocyanidin synthase; FNS, flavones synthase; FLS, flavonol synthase; GT, glycosyltransferase; OMT, O-methyltransferase. (B) Chemical structures of anthocyanins, flavones, and flavonols in Paeonia flower petals (Wang et al., 2001; Li et al., 2009).