475
are being extensively used by the therapeutic drug industries, with high demands
in the market of herbal medicine.
Recent molecular and morphological evidence supports the fact that the Fabaceae
is a single monophyletic family (Lewis et al. 2005). The fact has been supported not
only by the degree of interrelation shown by different groups within the family, but
also by all the recent phylogenetic studies based on DNA sequences (Kajita et al.
2001). These studies confirm Leguminosae as a monophyletic group with close
relation to Polygonaceae, Surianaceae and Quillajaceae families. Many cereals, several fruits and tropical roots of Leguminosae family have been a staple human food
for millennia and their use is intertwined with human evolution (Burkart 1987). A
number are important agricultural and food plants, including Glycine max (soybean), Phaseolus (beans), Pisum sativum (pea), Cicer arietinum (chickpeas),
Medicago sativa (alfalfa), Arachis hypogaea (peanut), Ceratonia siliqua (carob),
and Glycyrrhiza glabra (liquorice). A number of species are also weedy pests in
different parts of the world, including: Cytisus scoparius (broom), Ulex europaeus
(gorse), Pueraria lobata (kudzu), and a number of Lupinus species (Sprent 2009;
Wojciechowski et al. 2004).
22.2 Isoflavones: Biosynthesis and Mode of Action
Isoflavones are group of secondary metabolite formed by a symbiotic relationship
with the rhizobium bacteria and the defence responses of leguminous plants (Yu
et al. 2000). Isoflavons are synthesized as part of the phenylpropanoid pathway,
the same biosynthetic pathway of flavonoid biosynthesis (Barnes 2010).
Phenylalanine converts 4-hydroxycinnamoyl CoA by reaction with malonyl
CoA. Chalcone synthase catalyzes the reaction of this intermediate to convert to
4,2,4′,6′-tetrahydrozychalcon (naringenin chalcone) and the combined enzyme
reaction of chalcon synthase and chalcone reductase convert this intermediate to
4,2′,4′-trihydrozychalcone (isoliquiritigenin). Then, chalcone isomerase catalyzes
the ring closure of the heterocyclic ring to form 7,4′-dihydrozyflavone (liquirintigenin) and 5,7,4′-trihydroxyflavone (naringenin). The B-ring is moved from the
2-position to 3-position by isoflavone synthase. Isoflavone dehydratase removed
water to generate the 2,3-double bond in the heterocyclinc ring. The products generated by this reaction were daidzein (7,4′-dihydroxyisoflavone) and genistein
(5,7,4′-trihydroxy isoflavone).
According to the xenohormesis theory, plants synthesize phytochemicals to
withstand and adapt under stress (Table 22.1). Indeed, isoflavone biosynthesis
depend on the environmental conditions in which the plant grows and is stimulated
by stress. The stress-induced plant compounds have the ability to upregulate stress
adaptive pathways in animals and humans. In the body, modulating pathways mediated by estrogen receptors (ERs) or various key enzymes involved in cellular signalling or metabolism and antioxidant potential exercise the precise biological effects
of isoflavones (Cederroth and Nef 2009).
22 Health Benefits of Isoflavones Found Exclusively of Plants of the Fabaceae Family
are being extensively used by the therapeutic drug industries, with high demands
in the market of herbal medicine.
Recent molecular and morphological evidence supports the fact that the Fabaceae
is a single monophyletic family (Lewis et al. 2005). The fact has been supported not
only by the degree of interrelation shown by different groups within the family, but
also by all the recent phylogenetic studies based on DNA sequences (Kajita et al.
2001). These studies confirm Leguminosae as a monophyletic group with close
relation to Polygonaceae, Surianaceae and Quillajaceae families. Many cereals, several fruits and tropical roots of Leguminosae family have been a staple human food
for millennia and their use is intertwined with human evolution (Burkart 1987). A
number are important agricultural and food plants, including Glycine max (soybean), Phaseolus (beans), Pisum sativum (pea), Cicer arietinum (chickpeas),
Medicago sativa (alfalfa), Arachis hypogaea (peanut), Ceratonia siliqua (carob),
and Glycyrrhiza glabra (liquorice). A number of species are also weedy pests in
different parts of the world, including: Cytisus scoparius (broom), Ulex europaeus
(gorse), Pueraria lobata (kudzu), and a number of Lupinus species (Sprent 2009;
Wojciechowski et al. 2004).
22.2 Isoflavones: Biosynthesis and Mode of Action
Isoflavones are group of secondary metabolite formed by a symbiotic relationship
with the rhizobium bacteria and the defence responses of leguminous plants (Yu
et al. 2000). Isoflavons are synthesized as part of the phenylpropanoid pathway,
the same biosynthetic pathway of flavonoid biosynthesis (Barnes 2010).
Phenylalanine converts 4-hydroxycinnamoyl CoA by reaction with malonyl
CoA. Chalcone synthase catalyzes the reaction of this intermediate to convert to
4,2,4′,6′-tetrahydrozychalcon (naringenin chalcone) and the combined enzyme
reaction of chalcon synthase and chalcone reductase convert this intermediate to
4,2′,4′-trihydrozychalcone (isoliquiritigenin). Then, chalcone isomerase catalyzes
the ring closure of the heterocyclic ring to form 7,4′-dihydrozyflavone (liquirintigenin) and 5,7,4′-trihydroxyflavone (naringenin). The B-ring is moved from the
2-position to 3-position by isoflavone synthase. Isoflavone dehydratase removed
water to generate the 2,3-double bond in the heterocyclinc ring. The products generated by this reaction were daidzein (7,4′-dihydroxyisoflavone) and genistein
(5,7,4′-trihydroxy isoflavone).
According to the xenohormesis theory, plants synthesize phytochemicals to
withstand and adapt under stress (Table 22.1). Indeed, isoflavone biosynthesis
depend on the environmental conditions in which the plant grows and is stimulated
by stress. The stress-induced plant compounds have the ability to upregulate stress
adaptive pathways in animals and humans. In the body, modulating pathways mediated by estrogen receptors (ERs) or various key enzymes involved in cellular signalling or metabolism and antioxidant potential exercise the precise biological effects
of isoflavones (Cederroth and Nef 2009).
22 Health Benefits of Isoflavones Found Exclusively of Plants of the Fabaceae Family