392
Kampferol
Kaempferol is a 3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one
flavonoid that is present in a wide variety of edible plants including cabbage, beans,
tomato, grapes and strawberries (Calderón-Montaño et al. 2011). They are similarly
found in Moringa oleifera, Ginkgo biloba and Sophora japonica. Kaempferol and
their glycosides exhibit wide biological activities including analgesic, antiallergic,
anticancer, antidiabetic, anti-inflammatory, antimicrobial, anti-osteoporotic, antioxidant, cardioprotective, and neuroprotective activities (Calderón-Montaño et al.
2011). The chemical structure of kaempferol, which include the double bound at
C2-C3 link with an oxo group at C4 and the presence of an hydroxyl groups at C3,
C5 and C4’ are reported to be important in its antioxidant activities (van Acker et al.
1996; Rice-Evans 2001).
Myricetin
Myricetin is a flavonoid that is structurally related to quercetin and kaempferol
(Semwal et al. 2016). Just like kaempferol, myricetin may occur in its free and
glycosidically-bound forms. Its found in beverages including teas, vegetables and
fruits. Myricetin is a strong iron-chelating compound (Ong and Khoo 1997) with
anticancer, antidiabetic, anti-inflammatory and anti-oxidant properties (Ong and
Khoo 1997; Semwal et al. 2016).
19.2 Classifications of Polyphenols
Plant metabolites are classified into primary or secondary metabolites depending on
the functions they play in the plant system. While primary metabolites play important roles in plants growth and their survival (Tijjani et al. 2018), secondary metabolites are synthesized as defense system against disease and herbivores (Mazid et al.
2011). These secondary metabolites are bioactive compounds, which are very useful as functional foods (Carović-StanKo et al. 2016). Polyphenols are among the
largest group of secondary metabolites found in plants. Over 8000 structurally variants of polyphenols exist which are characterized by aromatic rings with one or
more hydroxyl groups (Han et al. 2007). They are majorly classified into groups and
subgroups based on the numbers of phenolic rings and structural elements attached
to the rings (Butterfield et al. 2002). The major classes are phenolics, flavonoids,
stilbenes and lignans (Fig. 19.2) (Pietta et al. 2003). Phenolic acids are subclassified
into hydroxybenzoic acids including gallic acid or hydroxycinnamic acid and ferulic, coumaric, caffeic acid. The flavonoid subclass include anthocyanidins, flavanols, flavanones, flavones, flavonols and isoflavones.
Polyphenols are similarly classified into their various sources of origin, major
biological functions and based on their chemical structures (Tsao 2010). Majority
of these polyphenols that exist in plants are glycosylated with different carbohydrate units and acylated sugars at various positions on their basic polyphenol skeletons (Tsao 2010).
H. Tijjani et al.
Kampferol
Kaempferol is a 3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one
flavonoid that is present in a wide variety of edible plants including cabbage, beans,
tomato, grapes and strawberries (Calderón-Montaño et al. 2011). They are similarly
found in Moringa oleifera, Ginkgo biloba and Sophora japonica. Kaempferol and
their glycosides exhibit wide biological activities including analgesic, antiallergic,
anticancer, antidiabetic, anti-inflammatory, antimicrobial, anti-osteoporotic, antioxidant, cardioprotective, and neuroprotective activities (Calderón-Montaño et al.
2011). The chemical structure of kaempferol, which include the double bound at
C2-C3 link with an oxo group at C4 and the presence of an hydroxyl groups at C3,
C5 and C4’ are reported to be important in its antioxidant activities (van Acker et al.
1996; Rice-Evans 2001).
Myricetin
Myricetin is a flavonoid that is structurally related to quercetin and kaempferol
(Semwal et al. 2016). Just like kaempferol, myricetin may occur in its free and
glycosidically-bound forms. Its found in beverages including teas, vegetables and
fruits. Myricetin is a strong iron-chelating compound (Ong and Khoo 1997) with
anticancer, antidiabetic, anti-inflammatory and anti-oxidant properties (Ong and
Khoo 1997; Semwal et al. 2016).
19.2 Classifications of Polyphenols
Plant metabolites are classified into primary or secondary metabolites depending on
the functions they play in the plant system. While primary metabolites play important roles in plants growth and their survival (Tijjani et al. 2018), secondary metabolites are synthesized as defense system against disease and herbivores (Mazid et al.
2011). These secondary metabolites are bioactive compounds, which are very useful as functional foods (Carović-StanKo et al. 2016). Polyphenols are among the
largest group of secondary metabolites found in plants. Over 8000 structurally variants of polyphenols exist which are characterized by aromatic rings with one or
more hydroxyl groups (Han et al. 2007). They are majorly classified into groups and
subgroups based on the numbers of phenolic rings and structural elements attached
to the rings (Butterfield et al. 2002). The major classes are phenolics, flavonoids,
stilbenes and lignans (Fig. 19.2) (Pietta et al. 2003). Phenolic acids are subclassified
into hydroxybenzoic acids including gallic acid or hydroxycinnamic acid and ferulic, coumaric, caffeic acid. The flavonoid subclass include anthocyanidins, flavanols, flavanones, flavones, flavonols and isoflavones.
Polyphenols are similarly classified into their various sources of origin, major
biological functions and based on their chemical structures (Tsao 2010). Majority
of these polyphenols that exist in plants are glycosylated with different carbohydrate units and acylated sugars at various positions on their basic polyphenol skeletons (Tsao 2010).
H. Tijjani et al.