Phytochemicals As Nutraceuticals

1. Fatty Acids

Conjugated linoleic acids (CLA) are geometrical and positional isomers of linoleic acid. The effects include inhibition of tumor growth, reduction of atherosclerotic risk, and reduction of body fat. y-Linolenic acid (GLA) is used for suppression of inflammation and in the treatment of diabetic neuropathy, atopic eczema, and certain cancers, such as malignant human brain glioma. a-Linolenic acid (ALA) has a broad range of health benefits; it inhibits the production of eicosanoids, alters the production of several prosanoids, reduces blood pressure in hypertensive patients, and lowers triglycerides and cholesterol. Diets containing ALA inhibit lymphocyte proliferation, retard tumor growth, and may also play a role in metastasis.8

2. Inulin and Oligofructose

These carbohydrates were first isolated from chicory root and are unique storage carbohydrates that occur naturally in numerous common fruits and vegetables and, thus, have always been part of the human diet. The average consumption in the United States is 1 to 4 g, whereas at Europe is 3 to 11 g/day. Onion is an important source; a typical onions soup contains 6 to 18 g of inulin and oligofructose per serving. Other sources are garlic, wheat, bananas, and artichokes. Today, industrial production is based on the synthesis starting with sucrose, or it is obtained as a natural extract from chicory roots. The roots of the Cichorium intybus plant contain approximately 15 to 20% inulin and 5 to 10% oligofructose. Inulin and oligofructose are not digested and have low caloric values; thus, they are suitable for use in diabetic foods.

The oligosaccharides are fermented by colonic microflora in the large intestine, a bifidogenic effect, and they are called "prebiotics." Organic acids are produced (lactate, proprionate, butyrate, and acetate) by the fermentation process, and two distinct effects are observed: (1) the local intestinal pH is lowered, which dissolves calcium-phosphate-magnesium complexes that have been formed during transit through the small intestine; and (2) intestinal concentration of ionized minerals is raised. Interestingly, improved absorption also leads to improved bone mineralization and an increased resistance against bone fracture and osteoporosis. Prebiotics induce the reduction of growth of harmful bacteria such as E. coli and Clostridium. Thus, the severity and incidence of diarrhea are diminished; in addition, relief of constipation and reduction of putrefactive substances in the colon have been observed.41,42

Cereals have been prepared with oligosaccharides, where oligofructose lends a sweetness profile similar to that of sucrose but with only 30% of the sweetness level. These oligofructoses are fibers that bring next-generation health benefits and better taste to the breakfast table.41,42

3. Flavonoids

Flavonoids are common components of natural products (e.g., grape, soybean, peanut) and historically have been used in remedies; today, more than a hundred preparations containing flavonoids are marketed in Switzerland and France. The biological activities of flavonoids are diverse (Table 10.7).43 Rutin and diosmin preparations are commonly used to increase vascular tone. Anthocyanins from Vac-cinium and Ribes (such as bilberry or black currants) are used to enhance vision and increase capillary resistance. The Labiatae family is a source of traditional remedies; within this family, which includes basil, mint, oregano, rosemary, sage, and thyme, flavonoids are one of the most important phytochemical components, although terpenes and saponins may have an active role as well. Quercetin inhibits oxidative cytotoxic activity and the macrophage oxidative modification of LDL by conserving the a-tocopherol content and delaying the onset of lipid peroxidation. Flavonoid content decreases the risk of coronary heart disease.44

Onions, apples, and grapefruit are rich sources of flavonoids, which may protect against certain forms of lung cancer. The effects are partially explained by decreased bioactivation of carcinogens by inhibition of cytochrome P-450 enzymes of the CYP1A family. In a case-control study developed in Hawaii, it was found that quercetin (onions and apples) and naringin (white grapefruit) have inverse associations with lung cancer. Additionally, a decreased bioactivation of polycyclic aromatic hydrocarbons (PAHs) and other carcinogens by inhibition of CYP1A (by quercetin) and CYP3A4 (by naringenin) has been demonstrated; this could be an important mechanism by which these foods may protect against lung cancer.45

4. Tannins

This term was originally coined to describe substances, present in vegetable extracts, responsible for converting animal skin into leather. The molecular weight of these compounds is in the range 500 to 3000 Da. Tannins are classified into two categories: hydrolyzable and nonhydrolyzable or condensed tannins. Hydrolyzable tannins contain a central core of polyhydric alcohol such as glucose, and a hydroxyl group, which are esterified partially or wholly by gallic acid (gallotannins) or hexahydrox-ydiphenic acid (ellagitannins). Hydrolyzable tannins occur in seed pods, bark and wood, fruits, and leaves or galls of plants belonging to the families Leguminosae, Fabaceae, Combretaceae, and Anacardiaceae. Condensed tannins are more complex than hydrolyzable tannins and their complete structures are yet to be determined; they are mainly the polymerized products of flavan-3-ols and flavan-3,4-diols or a mixture of the two. Condensed tannins are widely distributed in fruits, vegetables, forage, plants, cocoa, red wine, and certain food grains, such as sorghum, finger millets, and legumes.

Originally tannins were considered antinutritional factors; they form complexes with proteins and starch inhibiting their absorption. They also inhibit digestive enzymes. Further, tannins have shown an impressive range of beneficial biological activities (Table 10.8).46 Tannins have antimicrobial activity that may be associated with the inhibition of microbial enzymes such as cellulase, pectinase, and xylanase, among others; another explanation is related with toxicity by their action on the membranes of the microorganisms. Tannins accelerate bloodclotting and could be used to control hemorrhage in animals. Tannic acid reduces the venom-induced elevation of blood creatine kinase activity and prolongs the survival time of mice when injected immediately after the administration of venom. Additionally, tannin acid has been reported to reduce allergen levels in house dust and is marketed for that purpose as a 1 or 3% solution. It has also been reported that a significant number of plants show activity against HIV; 90% of the aqueous extracts are associated mainly with tannins or polysaccharides. Tannins and their related compounds may inhibit the metabolic enzymes of xenobiotics, which are involved in the endogenous

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