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. 2022 Dec 9;11(12):2427. doi: 10.3390/antiox11122427

Figure 2.

Figure 2

Pathways for the biosynthesis of HCQAs in plants. The four main routes of phenylpropanoid metabolism are highlighted in different colors: green, shikimate shunt; red, quinate shunt; blue and pink, direct conversion and cinnamoyl glucosides pathway. Dashed arrows show the suggested enzymatic reactions. Abbreviations: PAL, L-phenylalanine ammonia-lyase; C4H, cinnamate 4-hydroxylase; 4CL, p-coumaroyl-CoA ligase; HCT/HQT, 4-hydroxycinnamoyl CoA - shikimate/quinate hydroxycinnamoyl transferase; C3’H, p-coumaroyl shikimate/quinate 3’-hydroxylase, CSE - caffeoyl shikimate esterase, ICS isochlorogenate synthase, HCT - hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyltransferase; HQT, hydroxycinnamoyl-CoA quinate hydroxycinnamoyl transferase; CSE, caffeoyl shikimate esterase; FSE, feruoyl shikimate esterase; SSE, sinapoyl shikimate esterase; COMT, caffeic/5-hydroxyferulic acid O-methyltransferase; C3H, p-coumarate 3-hydroxylase (ascorbate peroxidase); CCoAOMT, caffeoyl-CoA 3-O-methyltransferase; UGT84, UDP-glucoside transferase; HCGQT, hydroxycinnamoyl D-glucose:quinate hydroxycinnamoyl transferase; F5’H—ferulic acid 5-hydroxylase.