397
properties, which showed their importance in the field of medicine. Many scientific
studies have revealed that people who focused on specific diet, especially polyphenolic rich diets are at low risk of certain chronic diseases such as heart disease,
diabetes, obesity, and cancer. Studies on plant polyphenols has been carried out with
the intention of discovering protective compounds against certain diseases including their antioxidant, anti-inflammatory and anti-microbial properties. Their blood
pressure reducing effects, immune response, skin protection and nutraceuticals have
also been reported.
19.5.1 Antioxidant Properties of Polyphenols
The production of reactive oxygen species (ROS) and reactive nitrogen species
(RNS) are deleterious to the body system. If the ROS and the RNS produced from
cellular reactions are at balanced levels, they serve as beneficial compounds for cellular functions. However, if they are produced at unbalanced levels, which sometimes occur, they lead to oxidative stress, which can cause degenerative disorders,
especially to the vital organs in the organism (Valko et al. 2006; Pham-Huy et al.
2008). Many scientist have advocated for the use of antioxidant compounds, which
are found in plant based food substances, some of which are polyphenolic compounds. The use of these naturally occurring antioxidant compounds have significantly increased and they’ve been employed in medical usage as well as in
pharmaceutical companies, which serve as substitute for the artificial ones which
have been suspected to be one of the major causes of cancer (Carocho et al. 2014).
Heim et al. (2002) stated that the arrangement of functional groups, their configuration, substitution and the number of hydroxyl groups also influence the antioxidant
activity of flavonoids such as the radical scavenging activity and or metal ion chelation ability. Flavonoids and phenolic compounds have been described by many scientists as phytochemicals with the highest antioxidant properties from plants (Ryu
et al. 2006; Okpuzor et al. 2009; Mishra et al. 2013; Wang et al. 2016; Andreu et al.
2018; Zahoor et al. 2018).
Oki et al. (2002) examined the antioxidant capacity of anthocyanins and other
phenolics from different cultivars of purple-fleshed sweet potato (Ipomea batatas
L.) which is an edible and economic medicinal specie in Japan. Their assessment of
the antioxidant activity using diphenyl-2-picrylhydrazyl (DPPH) radical scavenging
activity shows that a positive antioxidant activity exist the cultivars used for their
study. Similarly, they observed that chlorogenic acid showed a dominant DPPH
radical scavenging activity in Miyanou-36 cultivar and Bise cultivar in the sweet
potato. The other two cultivars; Ayamurasaki and kyushy-132 also showed antioxidant activities but anthocyanins were rather observed to show the DPPH radical
scavenging activity in them (Oki et al. 2002).
Mishra et al. (2013) observed that leaf extracts of Bauhinia variegate contained
flavonoid compounds which showed a great antioxidant ability against oxidative
stress through ion binding ability, reducing power ability as well as radical
19 Polyphenols: Classifications, Biosynthesis and Bioactivities
properties, which showed their importance in the field of medicine. Many scientific
studies have revealed that people who focused on specific diet, especially polyphenolic rich diets are at low risk of certain chronic diseases such as heart disease,
diabetes, obesity, and cancer. Studies on plant polyphenols has been carried out with
the intention of discovering protective compounds against certain diseases including their antioxidant, anti-inflammatory and anti-microbial properties. Their blood
pressure reducing effects, immune response, skin protection and nutraceuticals have
also been reported.
19.5.1 Antioxidant Properties of Polyphenols
The production of reactive oxygen species (ROS) and reactive nitrogen species
(RNS) are deleterious to the body system. If the ROS and the RNS produced from
cellular reactions are at balanced levels, they serve as beneficial compounds for cellular functions. However, if they are produced at unbalanced levels, which sometimes occur, they lead to oxidative stress, which can cause degenerative disorders,
especially to the vital organs in the organism (Valko et al. 2006; Pham-Huy et al.
2008). Many scientist have advocated for the use of antioxidant compounds, which
are found in plant based food substances, some of which are polyphenolic compounds. The use of these naturally occurring antioxidant compounds have significantly increased and they’ve been employed in medical usage as well as in
pharmaceutical companies, which serve as substitute for the artificial ones which
have been suspected to be one of the major causes of cancer (Carocho et al. 2014).
Heim et al. (2002) stated that the arrangement of functional groups, their configuration, substitution and the number of hydroxyl groups also influence the antioxidant
activity of flavonoids such as the radical scavenging activity and or metal ion chelation ability. Flavonoids and phenolic compounds have been described by many scientists as phytochemicals with the highest antioxidant properties from plants (Ryu
et al. 2006; Okpuzor et al. 2009; Mishra et al. 2013; Wang et al. 2016; Andreu et al.
2018; Zahoor et al. 2018).
Oki et al. (2002) examined the antioxidant capacity of anthocyanins and other
phenolics from different cultivars of purple-fleshed sweet potato (Ipomea batatas
L.) which is an edible and economic medicinal specie in Japan. Their assessment of
the antioxidant activity using diphenyl-2-picrylhydrazyl (DPPH) radical scavenging
activity shows that a positive antioxidant activity exist the cultivars used for their
study. Similarly, they observed that chlorogenic acid showed a dominant DPPH
radical scavenging activity in Miyanou-36 cultivar and Bise cultivar in the sweet
potato. The other two cultivars; Ayamurasaki and kyushy-132 also showed antioxidant activities but anthocyanins were rather observed to show the DPPH radical
scavenging activity in them (Oki et al. 2002).
Mishra et al. (2013) observed that leaf extracts of Bauhinia variegate contained
flavonoid compounds which showed a great antioxidant ability against oxidative
stress through ion binding ability, reducing power ability as well as radical
19 Polyphenols: Classifications, Biosynthesis and Bioactivities