548
Phospholipids Phospholipids are diglycerides in which two fatty–acid molecules
are attached to the glycerol backbone while the third hydroxyl function of glycerol
backbone is attached to a phosphate moiety coupled with a nitrogen–containing
group. This unique structure makes phospholipids water soluble. The phospholipids
are thus amphiphilic lipids wherein the fatty–acid sides are hydrophobic (dislike
water) while the phosphate group is hydrophilic (likes water) in nature. In blood and
other body fluids, phospholipids form structures in which fat is enclosed and transported throughout the blood stream. In the body, amphiphilic nature of phospholipid
binds together to form a double layer in cell membranes. This layer effectively not
only protects the inside of the cell from the outside environment, but also allows
transport of fat and water through the membrane. For example, lecithin (phosphatidylcholine), found in egg yolk, honey, and mustard, is a popular food emulsifier that
does not allow the separation of fat and water. Another example is mayonnaise that
demonstrates similar ability to blend vinegar and oil to create the stable, spreadable
condiment. Phospholipids thus play an important role in making the appearance of
sauces, creams and other foods fresher and appetizing (Mairrino et al. 1991; Gibney
et al. 2009).
Phytosterols Phytosterols (sterols and stanol esters) are naturally occurring compounds that are found in plant cell membranes. Some examples of phytosterols are
β–sitosterol, campesterol, stigmasterol, and ergosterol while the most abundant is
sitosterol and campesterol. These are structurally similar to the cholesterol found in
the human body. When consumed, phytosterols compete with cholesterol for absorption in the digestive system. As a result, cholesterol absorption is hindered and blood
cholesterol levels reduced (Gibney et al. 2009; Mahan and Raymond 2016; Titchenal
et al. 2018). Cholesterol has specific beneficial functions and is present in all body
cells as it is an important substance in cell membrane structure. Approximately 25%
of cholesterol in the body is localized in brain tissue. From cholesterol, body synthesizes vitamin D, glucocorticoids, and the sex hormones progesterone, testosterone,
and estrogens. Stanols are also present in plants, but they form about 10% of total
dietary phytosterols. Cycloartenol, stigmastanol, and campestanol are some examples of stanols (Gylling and Simonen 2015). Phytosterols perform several biological
activities that promote the health of humans, animals, and micro–organisms by
playing an important role in cholesterol absorption and lipoprotein metabolism, testosterone metabolism, alterations in cell membrane properties, induction of apoptosis in cancer cells, reduction of total and LDL cholesterol levels thereby reducing
the risk of cardiovascular diseases, as well as prevention and treatment of colon,
breast and prostate cancers (Ling and Jones 1995; Ogbe et al. 2015).
25.2.1.2 Carbohydrates
Carbohydrates are one of the most abundant substances found in green plants as a
result of the photosynthesis process. They serve as energy source for humans and
other living organisms. They are classified into four groups namely monosaccharides,
K. Sharma et al.
Phospholipids Phospholipids are diglycerides in which two fatty–acid molecules
are attached to the glycerol backbone while the third hydroxyl function of glycerol
backbone is attached to a phosphate moiety coupled with a nitrogen–containing
group. This unique structure makes phospholipids water soluble. The phospholipids
are thus amphiphilic lipids wherein the fatty–acid sides are hydrophobic (dislike
water) while the phosphate group is hydrophilic (likes water) in nature. In blood and
other body fluids, phospholipids form structures in which fat is enclosed and transported throughout the blood stream. In the body, amphiphilic nature of phospholipid
binds together to form a double layer in cell membranes. This layer effectively not
only protects the inside of the cell from the outside environment, but also allows
transport of fat and water through the membrane. For example, lecithin (phosphatidylcholine), found in egg yolk, honey, and mustard, is a popular food emulsifier that
does not allow the separation of fat and water. Another example is mayonnaise that
demonstrates similar ability to blend vinegar and oil to create the stable, spreadable
condiment. Phospholipids thus play an important role in making the appearance of
sauces, creams and other foods fresher and appetizing (Mairrino et al. 1991; Gibney
et al. 2009).
Phytosterols Phytosterols (sterols and stanol esters) are naturally occurring compounds that are found in plant cell membranes. Some examples of phytosterols are
β–sitosterol, campesterol, stigmasterol, and ergosterol while the most abundant is
sitosterol and campesterol. These are structurally similar to the cholesterol found in
the human body. When consumed, phytosterols compete with cholesterol for absorption in the digestive system. As a result, cholesterol absorption is hindered and blood
cholesterol levels reduced (Gibney et al. 2009; Mahan and Raymond 2016; Titchenal
et al. 2018). Cholesterol has specific beneficial functions and is present in all body
cells as it is an important substance in cell membrane structure. Approximately 25%
of cholesterol in the body is localized in brain tissue. From cholesterol, body synthesizes vitamin D, glucocorticoids, and the sex hormones progesterone, testosterone,
and estrogens. Stanols are also present in plants, but they form about 10% of total
dietary phytosterols. Cycloartenol, stigmastanol, and campestanol are some examples of stanols (Gylling and Simonen 2015). Phytosterols perform several biological
activities that promote the health of humans, animals, and micro–organisms by
playing an important role in cholesterol absorption and lipoprotein metabolism, testosterone metabolism, alterations in cell membrane properties, induction of apoptosis in cancer cells, reduction of total and LDL cholesterol levels thereby reducing
the risk of cardiovascular diseases, as well as prevention and treatment of colon,
breast and prostate cancers (Ling and Jones 1995; Ogbe et al. 2015).
25.2.1.2 Carbohydrates
Carbohydrates are one of the most abundant substances found in green plants as a
result of the photosynthesis process. They serve as energy source for humans and
other living organisms. They are classified into four groups namely monosaccharides,
K. Sharma et al.