purified to produce a polyphenolic-rich extract. Standardized grape seed extracts
contain 74–78% oligomeric proanthocyanidins and less than approximately 6% of
free flavanol monomers on a dry-weight basis. The red color and astringent taste of
the GSE can be attributed to polyphenol-rich compounds, especially proanthocyanidins. It also has well-documented antioxidant, antimicrobial, and antiinflammatory properties. Proanthocyanidins in GSE exhibit protective properties
against free radicals and oxidative stress, making it an excellent anti-oxidant in
addition to other beneficial biological functions such as cardio- and neuroprotection and antibacterial activity [45].
2 Biological Roles of Phytochemicals
Dietary polyphenols have become potential therapeutic and chemopreventive
agents, and chemoprevention of cancer through the use these natural agents
has received an increasing interest. Chemoprevention, by definition, is a means
of therapy for precancerous lesions, which are called preinvasive neoplasia,
dysplasia, or intraepithelial neoplasia, depending on the organ system [8, 46].
Polyphenols have been demonstrated to act on multiple key elements in intracellular signal transduction pathways related to cell proliferation, differentiation,
apoptosis, inflammation, angiogenesis, and metastasis. Phytochemicals possess
favorable potential therapeutic effects including anti-oxidant, antiviral, antimicrobial, anti-inflammatory, anticancer, cardioprotective, and neuroprotective
effects [13, 14, 40, 45]. Many of these phytochemicals exert their biological
properties via common mechanisms and this section describes the actions that
are very specific. Figure 2 summarizes the major biological properties (antioxidant, anti-inflammatory, and anticancer) of these phytochemicals, with their
mechanisms.
2.1 Antioxidant Effect
Phytochemicals exert antioxidant activity and support redox homeostasis in several
in vitro and in vivo models. The antioxidant properties of the polyphenols come by
virtue of their chemical structure.
The curcuminoids consist of two methoxylated phenols connected by two
a,b-unsaturated carbonyl groups that exist in a stable enol form [47]. Curcumin
promotes neutralization of the lipid radicals and acts as a chain breaking antioxidant
at the 3
0 position, resulting in an intramolecular Diels–Alder reaction [48]. Curcumin
possesses free-radical scavenging activity. Using rat peritoneal macrophages as
a model, studies demonstrated that curcumin scavenged macrophage-generated
reactive oxygen species (ROS) both in vitro and in vivo [49, 50]. Curcumin
208
S. Maya et al.
contain 74–78% oligomeric proanthocyanidins and less than approximately 6% of
free flavanol monomers on a dry-weight basis. The red color and astringent taste of
the GSE can be attributed to polyphenol-rich compounds, especially proanthocyanidins. It also has well-documented antioxidant, antimicrobial, and antiinflammatory properties. Proanthocyanidins in GSE exhibit protective properties
against free radicals and oxidative stress, making it an excellent anti-oxidant in
addition to other beneficial biological functions such as cardio- and neuroprotection and antibacterial activity [45].
2 Biological Roles of Phytochemicals
Dietary polyphenols have become potential therapeutic and chemopreventive
agents, and chemoprevention of cancer through the use these natural agents
has received an increasing interest. Chemoprevention, by definition, is a means
of therapy for precancerous lesions, which are called preinvasive neoplasia,
dysplasia, or intraepithelial neoplasia, depending on the organ system [8, 46].
Polyphenols have been demonstrated to act on multiple key elements in intracellular signal transduction pathways related to cell proliferation, differentiation,
apoptosis, inflammation, angiogenesis, and metastasis. Phytochemicals possess
favorable potential therapeutic effects including anti-oxidant, antiviral, antimicrobial, anti-inflammatory, anticancer, cardioprotective, and neuroprotective
effects [13, 14, 40, 45]. Many of these phytochemicals exert their biological
properties via common mechanisms and this section describes the actions that
are very specific. Figure 2 summarizes the major biological properties (antioxidant, anti-inflammatory, and anticancer) of these phytochemicals, with their
mechanisms.
2.1 Antioxidant Effect
Phytochemicals exert antioxidant activity and support redox homeostasis in several
in vitro and in vivo models. The antioxidant properties of the polyphenols come by
virtue of their chemical structure.
The curcuminoids consist of two methoxylated phenols connected by two
a,b-unsaturated carbonyl groups that exist in a stable enol form [47]. Curcumin
promotes neutralization of the lipid radicals and acts as a chain breaking antioxidant
at the 3
0 position, resulting in an intramolecular Diels–Alder reaction [48]. Curcumin
possesses free-radical scavenging activity. Using rat peritoneal macrophages as
a model, studies demonstrated that curcumin scavenged macrophage-generated
reactive oxygen species (ROS) both in vitro and in vivo [49, 50]. Curcumin
208
S. Maya et al.