Flavones 29 from Tetrahydroxychalcone

Tetrahydroxychalcone (18) was converted to naringenin (1) by chalcone iso-merase (CHI), and then to flavones (29) by flavone synthase I (FSI) and flavone synthase II (FSII), respectively (Fig. 6). 

UDPG-flavonoid glucosyl t ransf erase (UFGT) 

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A large number of phenolics are derived from the C15 flavonoid skeleton, which is synthesised via the chalcone synthase (CHS) catalysed condensation of p-coumaroyl-coenzyme A and three molecules of malonyl-CoA. In most plant families, the initial CHS product is a tetrahydroxychalcone, which is further converted to other flavonoid classes, such as flavones, flavonols, flavanones, flavan-3-ols, isoflavones and anthocyanins (Fig. 2). Structural diversity among the phenylpropanoids arises from a variety of modifications, including... 

The biosynthetic pathway for isoflavonoids in soybean and the relationship of the isoflavonoids to several other classes of phenylpropanoids is presented in Fig. 8.2. Production of /i-coumaryl-CoA from phenylalanine requires phenylalanine ammonia lyase to convert phenylalanine to cinnamate, cinnamic acid hydroxylase to convert cinnamate to /7-coumarate, and coumaraterCoA ligase to convert jt -coumarate to -coumaroyl-CoA. Lignins may be produced from j3-coumaroyl-CoA or from />-coumarate. Chalcone synthase catalyzes the condensation of three molecules of malonyl CoA with p-coumaroyl-CoA to form 4, 2 , 4 , 6 -tetrahydroxychalcone, which is subsequently isomerized in a reaction catalyzed by chalcone isomerase to naringenin, the precursor to genistein, flavones, flavonols, condensed tannins, anthocyanins, and others. 

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