Figure 3. Dihydrocaffeic acid biosynthesis—proposed simplified pathway (adapted and modified from [34,35,36,37,38,39]). Explanations: ( Dihydrocaffeic acid biosynthesis—proposed simplified pathway (adapted and modified from [19][20][21][22][23][24]). Explanations: ( a
)–(
r
)—compounds, A–R—enzymes, i.e., (
a
)—D-Erythrose 4-phosphate, (
b
)—Phosphoenolpyruvate, (
c
)—7-phospho-2-dehydro-3-deoxy-D-arabino-heptonate, (
d
)—3-Dehydroquinate, (
e
)—3-Dehydroshikimate, (
f
)—Shikimate, (
g
)—Shikimate-3-phosphate, (
h
)—5-
O
-(1-carboxyvinyl)-3-phosphoshikimate, (
i
)—Chorismate, (
j
)—Prephenate, (
k
)—L-Arogenate, (
l
)—Phenylalanine, (
m
)—Tyrosine, (
n
)—
trans
-Cinnamic acid, (
o
)—
p
-Coumaric acid, (
p
)—Caffeic acid, (
q
)—3,4-Dihydroxy-L-phenylalanine (L-Dopa), (
r
)—Dihydrocaffeic acid, (
A
)—3-deoxy-7-phosphoheptulonate synthase (EC 2.5.1.54), (
B
)—3-dehydroquinate synthase (EC 4.2.3.4), (
C
)—3-dehydroquinate dehydratase I (EC 4.2.1.10), (
D
)—shikimate dehydrogenase (EC 1.1.1.25), (
E
)—shikimate kinase (EC 2.7.1.71), (
F
)—3-phosphoshikimate 1-carboxyvinyltransferase (EC 2.5.1.19), (
G
)—chorismate synthase (EC 4.2.3.5), (
H
)—chorismate mutase (EC 5.4.99.5), (
I
)—bifunctional aspartate aminotransferase and glutamate/aspartate-prephenate aminotransferase (EC 2.6.1.1, EC 2.6.1.78, EC 2.6.1.79), (
J
)—arogenate/prephenate dehydratase (EC 4.2.1.91, EC 4.2.1.51), (
K
)—arogenate dehydrogenase (NADP
+
) (EC 1.3.1.78), (
L
)—phenylalanine ammonia-lyase (EC 4.3.1.24), (
M
)—phenylalanine/tyrosine ammonia-lyase (EC 4.3.1.25), (
N
)—
trans
-cinnamate 4-monooxygenase (EC 1.14.14.91), (
O
)—
p
-coumarate 3-hydroxylase (EC 1.14.13.-), (
P
)—tyrosine 3-monooxygenase (EC 1.14.16.2), (
Q
)—3,4-dihydroxy-L-phenylalanine ammonia-lyase (EC 4.3.1.22), and (
R
)—double bond reductase (EC 1.3.1.-).