Iron-ascorbic acid interaction

Flavonoids exhibit protective action against LDL oxidation. It has been shown [145] that the pretreatment of macrophages and endothelial cells with tea flavonoids such as theaflavin digallate diminished cell-mediated LDL oxidation probably due to the interaction with superoxide and the chelation of iron ions. Quercetin and epicatechin inhibited LDL oxidation catalyzed by mammalian 15-lipoxygenase, and are much more effective antioxidants than ascorbic acid and a-tocopherol [146], Luteolin, rutin, quercetin, and catechin suppressed copper-stimulated LDL oxidation and protected endogenous urate from oxidative degradation [147]. Quercetin was also able to suppress peroxynitrite-induced oxidative modification of LDL [148],... 

Interactions. Antacids inhibit iron absorption. Combination with ascorbic acid (Vitamin C), for protecting Fe + from oxidation to Fe +, is theoretically sound, but practically is not needed. 

There is a danger of creating new imbalances by careless use of supplements of vitamins and trace minerals, hormones and drugs. Examples of interaction between trace elements and vitamins include the following vitamin C (ascorbic acid) enhances the biological availability of iron, de-... 

In the diet and at the tissue level, ascorbic acid can interact with mineral nutrients. In the intestine, ascorbic acid enhances the absorption of dietary iron and selenium reduces the absorption of copper, nickel, and manganese but apparently has little effect on zinc or cobalt. Ascorbic acid fails to affect the intestinal absorption of two toxic minerals studied, cadmium and mercury. At the tissue level, iron overload enhances the oxidative catabolism of ascorbic acid. Thus, the level of dietary vitamin C can have important nutritional consequences through a wide range of inhibitory and enhancing interactions with mineral nutrients. 

Within the body, ascorbic acid and minerals have two additional levels of important interaction in the tissue storage and turnover of ascorbic acid and in the synthesis of tissues and organs. The apparent decrease in the half-life of ascorbic acid in the presence of excess iron is an example of the former interaction, whereas the simultaneous participation of vitamin C, calcium, and phosphorus in the formation of growing bone is an example of the latter. 

The possibility of an important interaction of ascorbic acid and iron in the human intestine was first suggested in 1940 (2). Since then, research with experimental animals and human subjects has extended and elucidated the biology of the interaction. 

The uptake of iron by the human intestine is governed not only by its dietary form and companion consituents, but also by the iron condition of the individual. Iron-depleted subjects absorb all forms of iron with greater avidity than do iron-replete individuals. In human dietetics, therefore, the ascorbic content of a diet can be included in the equation for describing the bioavailability of iron from a mixed diet (35). The interaction of iron nutrition and graded intakes of ascorbic acid (< 25 mg > 25 but < 75 mg and > 75 mg) as a prediction of iron availability from a mixed North American diet is plotted in Figure 1. 

Mechanistic Aspects of the Ascorbic Acid—Iron Interaction in the Intestine. Studies of the mechanism of the interaction of ascorbic acid and iron at the molecular and cellular levels have yielded a variety of theories. An acidic pH in the lumen of the intestine favors the absorption... 

Given the eflFects of ascorbic acid on the absorption of iron and copper, investigators have been interested in possibly significant interactions with zinc. The absorption of zinc and other divalent mineral ions was studied using an isolated, filled duodenal loop in situ in the rat (58). A lO -M zinc solution was infused in the presence or absence of 10" M ascorbate or dehydroascorbate. A two-thirds reduction in the... 

Clinically important, potentially hazardous interactions with aluminum hydroxide, antacids, ascorbic acid, bone marrow suppressants, chloroquine, cytotoxic agents, food, gold, hydroxychloroquine, iron, magnesium, primaquine, probenecid... 

No discussion of complexation of iron would be complete without mentioning ascorbic acid. Studies too numerous to list have clearly defined the positive effects of ascorbic acid on increasing the bioavailability of non-heme iron to both animals and humans. The interactions of Vitamin C and iron have recently been reviewed by lynch and Cook (31) However, upon examination it would seem that the effects of ascorbic are due to factors which include, but are not limited to, complex formation. 

Ascorbic acid has also been shown to interact with therapeutic iron. Derman, et al., have reported that ascorbic acid increases absorption of various iron fortification compounds in infant formulas in cereals this three-fold increase in iron absorption induced by ascorbic acid was observed in multiparous women (16). El-Hawary, et al., studied 97 infants and young children and observed that ascorbic acid increased absorption from a four mg iron supplement as ferrous sulfate (17). 

The Importance of iron in nutritional status has been recognized for centuries. In an effort to dissolve iron and make it more available numerous therapies have been devised including such rarities as syrups of sherry in which iron wire has been soaked for 30 days, slices of apple into which iron nails have been imbedded, and solutions of vinegar into which iron filings have been placed weeks earlier. The interaction of ascorbic acid and iron has been recognized more recently (30). It may be that the most useful and readily found therapy for iron deficiency will be dietary ascorbic acid which has the capability of increasing the rate of nonheme iron absorption several fold. 

The main absorption band of benzoquinones appears around 260 nm in nonpolar solvents and at 280 nm iu water. Extinction coefficients are 1.3-1.5 x 10 M Upon reduction to hydroquinones, a four times smaller band at 290 nm is found. The most important property of quinones and related molecules is the relative stability of their one-electron reduction products, the semiquinone radicals. The parent compound 1,4-benzoquinone is reduced by FeCl, ascorbic acid, and many other reductants to the semiquinone anion radical which becomes protonated in aqueous media (pk = 5.1). Comparisons of the benzaldehyde reduction potential with some of the model quinones given below show that carbonyl anion radicals are much stronger reductants than semiquinone radicals and that ortho- and para-benzoquinones themselves are even relatively strong oxidants comparable to iron(III) ions in water (Table 7.2.1). This is presumably caused by the repulsive interactions between two electropositive keto oxygen atms, which are separated only by a carbon-carbon double bond. When this positive charge can be distributed into neighboring n systems, the oxidation potential drops significantly (Lenaz, 1985). 

There are numerous reports of interactions of dietary elements that cause variation in the absorption of chromium. Amino acids, which chelate chromium, prevent precipitation at the basic pH in the small intestine, which increases its absorption [13]. Other chelating agents have mixed effects. Phytates significantly decrease absorption whereas oxalates lead to increased absorption [15]. Certain vitamins such as nicotinic acid and ascorbic acid have been shown to increase absorption [16]. Starch has also been shown to increase absorption to a greater degree than glucose, fructose, and sucrose. Some metals can compete with chromium and decrease its absorption. Studies show that zinc, vanadium, and iron have a common intestinal transport mechanism with chromium and can decrease the absorption of chromium [9]. 

Various carbonyl compounds and decomposition products of methyl linolenate hydroperoxides were tested for their interaction with DNA by measuring fluorescence in the presence of ferric chloride and ascorbic acid. 2,4-Alkadienals and 2,4,7-decatrienals were among the most active decomposition products of linolenate hydroperoxides (Table 5.8). To determine the type of reactive species involved in fluorescence formation with DNA, the effect of free radical antioxidants and a singlet oxygen quencher were examined. )3-Carotene, a-tocopherol and phenolic antioxidants strongly inhibited DNA fluorescence formed by decomposition of linolenate hydroperoxides in the presence of ferric chloride and ascorbic acid (Table 5.9). These results indicate that singlet oxygen and free radical species are important intermediates in the interaction of linolenate hydroperoxides with DNA in the presence of iron and ascorbic acid. 

El-Shobaki, F. A., and Sprour, M. G., 1989, The influence of ascorbic acid and lactose on the interaction of iron with each of cobalt and zinc during intestinal absorption, Z. Erndhrungswiss. 28 310-315. 

As E vitamers are easily oxidizable, the use of an antioxidant during sample pretreatment would seem to be warranted. However, the effect of this practice on analyte recovery varies. There appears to be none for human plasma, unlike, e.g., for rat plasma and buccal mucosal cells. In contrast, the addition of an antioxidant is essential in connection with the analysis of erythrocytes to prevent dramatic losses of tocopherols due to their interaction with coextracted, iron-containing pigments. Likewise, the harsh conditions of saponification (alkaline pH, high temperature) do require this protective measure. As antioxidants, pyrogallol, ascorbic acid, and butylated hydroxytoluene are most commonly used. 

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