Antioxidant intestinal absorption

Diabetic patients have reduced antioxidant defences and suffer from an increased risk of free radical-mediated diseases such as coronary heart disease. EC has a pronounced insulin-like effect on erythrocyte membrane-bound acetylcholinesterase in type II diabetic patients (Rizvi and Zaid, 2001). Tea polyphenols were shown to possess anti-diabetic activity and to be effective both in the prevention and treatment of diabetes (Choi et al, 1998 Yang et al, 1999). The main mechanism by which tea polyphenols appear to lower serum glucose levels is via the inhibition of the activity of the starch digesting enzyme, amylase. Tea inhibits both salivary and intestinal amylase, so that starch is broken down more slowly and the rise in serum glucose is thus reduced. In addition, tea may affect the intestinal absorption of glucose. 

Murota K, Terao J. 2003. Antioxidative flavonoid quercetin implication of its intestinal absorption and metabolism. Arch Biochem Biophys 417 12-17. 

B18. Bohm, V., and Bitsch, R., Intestinal absorption of lycopene from different matrices and interactions to other carotenoids, the lipid status, and the antioxidant capacity of human plasma. Ear. J.Nutr. 38,118-125 (1999). 

D-lso-ascorbic acid (erythorbic acid see Figure 13.1) also has vitamin activity. in vivo and in cell culmre, it has only about 5% of the biological activity of ascorbate, but this seems to be from poor intestinal absorption and tissue uptake. In vitro with purified enzymes, it has the same cofactor activity as ascorbate. Although it is not a namrally occurring compound, erythorbic acid is widely used interchangeably with ascorbic acid, in cured meats and as an antioxidant in a variety of foods. 

Water-soluble vitamins such as vitamin C are present in large amount in sea lettuces. The levels of vitamin C in sea lettuces average from 500 to 3000 mg/kg of dry matter. These levels of vitamin C are comparable with that of parsley, blackcurrant, and peppers. In sea lettuces, the highest level of vitamin C were found in Ulvafasciata (22 mg/100 g) (McDermid and Stuercke, 2003). Vitamin C is of interest for many reasons. First, it strengthens the immime defense system, activates the intestinal absorption of iron, as a reversible reductant and antioxidant in the aqueous fluid and tissue compartments. Further, this vitamin is specifically required for the activity of eight human enzymes involved in collagen, hormone, amino acid, and carnitine synthesis or metabolism (Jacob and Sotoudeh, 2002). 

Curcumin possesses strong antioxidant capacities, which may explain its effects against degenerative diseases in which oxidative stress plays a major role. As previously described for flavonoids, it is unlikely that curcumin acts as a direct antioxidant outside the digestive tract since its concentration in peripheral blood and organs is very low (near or below 1 pM, even after acute or long-term supplementation). Indeed, it has been shown that the intestinal epithelium limits its entry into the body, as reflected by absorption studies in various models (portal blood perfusion, everted bags). ... 

Considerable efforts have also been made toward the development of novel compounds with superior antioxidant properties. Some attempts were also made to introduce new synthetic polymeric compounds which are non-absorbable and non-toxic. These are generally hydroxyaromatic polymers with various alkyl and alkoxyl substitutions. Such compounds are usually very large molecules and their absorption from the intestinal tract is practically nil. In addition to their reportedly high antioxidant activity, they are non-volatile under deep-fat frying conditions, which result in nearly quantitative carry-through to the fried items, but they have not yet received FDA approval. 

Vitamin C Perhaps the most famous role of vitamin C is its functioning in the conversion of collagen proline to collagen hydroxyproline. Vitamin C acts as an antioxidant that protects a variety of molecules from oxidation. As a reducing agent, it facilitates the absorption of iron in the intestines by reducing it to the more absorbable Fe" " form. Examples ... 

The distillate obtained from sunflower oil may be sold to pharmaceutical companies for tocopherol and sterol isolation. Tocopherols may be used as natural antioxidants or may be converted to vitamin E by methylating the heterocyclic ring. The interest in phytosterols is caused by the high potential of some of them to inhibit intestinal cholesterol absorption. 

Nowadays saponins have been studied because different beneficial properties to health have been described. Saponins possess a broad variety of biological effects analgesic, antiinflammatory, antimicrobial, antioxidant, antiviral, and cytotoxic activity, effect on the absorption of minerals and vitamins and on animal growth, hemolytic and immunosti-mulatory effects, increased permeability of the intestinal mucosa neuro-protective action, and reduction of fat absorption (Gu lii-Ustundag and Mazza, 2007). However, the biological properties of quinoa saponins require further study. 

Sauerkraut enhances intestinal health, promotes the growth of beneficial intestinal organisms, and improves nutrient absorption. It s also high in antioxidants—especially vitamin C. 

Vitamin D is not an antioxidant. It is a fat-soluble vitamin that has a major role in regulating calcium and phosphorus metabolism and is needed for calcium absorption from the intestines. 

Phytosterols are nonnutrient bioactive substances and act as a structural component in the cell membranes, a role which in mammalian cells is played by cholesterol. The methyl or ethyl group at C-24 location makes them different from cholesterol [58]. They include plant sterols (unsaturated form) and plant stanols (saturated form). Both sterols and stanols are effective in lowering plasma total and LDL cholesterols and inhibit the absorption of cholesterol from the small intestine [59]. A wide spectrum of other biological activities in animals and humans has been reported, including anti-inflammatory [60], antibacterial [61], antioxidative [62], and anticancer activities [63]. P-Sitosterol, campesterol, stigmasterol, A -avenasterol, sitostanol, and campestanol are the most common representative members in this series. P-Sitosterol, campesterol, and stigmasterol are the major identified phytosterols in Brazil nut, with sitostanol, campestanol, and A -avenasterol present in trace amounts. 

There is a growing body of evidence suggesting that nut consumption may be heart-healthy. In addition to their MUFA, fiber and phytochemical antioxidants, pistachios are rich sources of phytosterols, which promote heart health by inhibiting the absorption of cholesterol from the intestine through direct competition with uptake mechanisms. 

---