Mineral absorption effects

Increased levels of nitrogen and phosphorous reduced the Inhibition of barley (Hordeum vulgare L.) growth caused by -coumaric and vanillic acids (8a). Although other explanations are possible, these effects of fertilizers suggest that Inhibition of mineral absorption was responsible for the observed Inhibition of growth. 

Table I. Effects of naturally-occurring phenolic compounds on mineral absorption in excised roots.

Two studies have used single cells to study the effect of phenolic acids on mineral absorption. In sterile cell cultures of Paul s Scarlet rose, 100 pM ferulic acid inhibited Rb+ absorption in about 10 min when the cells were 4-5 days old (37). Uptake from 0.2 mM RbCl was inhibited about 25% and absorption from 5.0 mM RbCl was inhibited 45%. Absorption by 10-day-old cells was affected little. Salicylic acid at 10 pM inhibited PO - absorption by Scenedesmus, a unicellular green alga (38). These studies show that allelochemicals inhibit mineral absorption in cellular systems as well as tissue systems (Table I). 

Benzoic acid derivatives also altered the electrical potential across the cell membrane in neurons of the marine mollusk Navanax lnermls (46). Salicylic acid (1-30 mM) caused a depolarization very rapidly (1-2 min) and decreased the ionic resistance across the membrane. As pH was decreased, more salicylic acid was required to reverse the effect of pH on the membrane potential (47). This result is contradictory to the influence of pH on the amount of salicylic acid required to affect mineral absorption in roots (32). The ability of a series of salicylic and benzoic acid derivatives to increase PD correlated with their octanol/water partition coefficients and pKa values (48). The authors proposed that the organic acid anions bound directly to membranes to produce the observed results. 

Effects of Allelochemlcals on ATPases. Several flavonoid compounds inhibit ATPase activity that is associated with mineral absorption. Phloretin and quercetin (100 pM) inhibited the plasma membrane ATPase Isolated from oat roots (33). The naphthoquinone juglone was inhibitory also. However, neither ferulic acid nor salicylic acid inhibited the ATPase. Additional research has shown that even at 10 mM salicylic acid inhibits ATPase activity only 10-15% (49). This lack of activity by salicylic acid was substantiated with the plasma membrane ATPase Isolated from Neurospora crassa (50) however, the flavonols fisetln, morin, myricetin, quercetin, and rutin were inhibitory to the Neurospora ATPase. Flavonoids inhibited the transport ATPases of several animal systems also (51-53). Thus, it appears that flavonoids but not phenolic acids might affect mineral transport by inhibiting ATPase enzymes. 

Effects of Allelochemlcals on ATP Supply. Allelochemlcals might decrease the ATP content of tissue by either increasing ATP utilization or decreasing ATP production. Some allelochemlcals that inhibit mineral absorption decrease ATP content of plant tissues. Salicylic acid decreased the ATP content of oat roots in a pH dependent manner (Figure 3). This result suggested that mitochondrial production of ATP was decreased in the tissue. On the other hand, Tillberg (38) found that salicylic acid and cinnamic acid increased the ATP content of Scenedesmus. Various flavonoids inhibited ATP production by mitochondria Isolated from cucumber (Cucumls satlvus L.) hypocotyls (54). Flavones such as kaempferol were more inhibitory than the corresponding flavanones. Substituted cinnamic acids such as caffeic acid were not inhibitory. 

It is quite possible that phenolic acids may produce more than one effect on the cellular processes responsible for mineral absorption. The potential sites of action discussed above all involve cellular membranes in some way. Which mechanism of action is predominant in a given situation may depend upon the concentration of allelochemicals present and the conditions (e.g. pH) of the plant/chemical interaction. 

Asvarujanon, P., Ishizuka, S., and Hara, H. (2004). Inhibitory effects of psyllium on rat mineral absorption were abolished by reduction of viscosity with partial hydrolysis. Biosci. Biotechnol. Biochem. 68,1737-1742. 

Singer, R. B. Roush, T. L. (1985) Effects of temperature on remotely sensed mineral absorption features. J. Geophys. Res., 90,12434-44. 

Several studies have been performed during the last two decades on CPPs which may function as carriers for different minerals, especially calcium. Published data on the effect of CPP/casein on mineral solubility and absorption are inconsistent, partly due to the diversity of the experimental approaches. Most of the findings in the literature that deal with the mineral absorption-stimulating effect of CPP are based on in vitro, in situ, cell culture or single meal studies. Majority of the studies have been done with rats and have provided considerable evidence for the potential effect of casein-derived phosphopeptides to improve mineral absorption. This potential is not limited to calcium but is also valid for zinc and iron, and possibly other elements that have not been investigated so far (FitzGerald, 1998). Furthermore, CPPs have been shown to have anticariogenic properties, based on their ability to localise amorphous phosphate in dental plaque (Reynolds, 1998). 

The divalent mineral-binding effect of CPPs can be put in use in applications where one wants to increase the availability for absorption of these minerals in the gut. Drinks with calcium and iron are examples for commercial uses of CPPs examples can be found especially in the Japanese market. Products for children that incorporate calcium or milk minerals and CPPs in sweets or cookies are found in the South Asian market. As mineral accretion is high during early childhood, incorporation of CPPs provides good solubility and availability for absorption of calcium or zinc and thus is worth considering for infant nutrition. Other possible uses are in calcium-enriched dairy products and natural calcium supplements. In addition, dental applications are obvious, since complexes of calcium, CPPs and phosphate may reduce caries in a dose-dependent fashion. 

Sun, Y. and Pignatello, J.J. (1993) Photochemical reactions involved in the total mineralization of 2,4-D by iron(3+)/hydrogen peroxide/UV. Environ. Sci. Technol. 27, 304-310 Toepfer, B., Gora, A. and Li Puma, G. (2006) Photocatalytic oxidation of multicomponent solutions of herbicides Reaction kinetics analysis with explicit photon absorption effects. Appl. Catal. B Environ. 68,171-180... 

The behavior of minerals is often influenced by the presence of other food constituents. The recent interest in the beneficial effect of dietary fiber has led to studies of the role fiber plays in the absorption of minerals. It has been shown (Toma and Curtis 1986) that mineral absorption is decreased by fiber. A study of the behavior of iron, zinc, and calcium showed that interactions occur with phytate, which is present in fiber. Phytates can form insoluble complexes with iron and zinc and may interfere with the... 

Antibiotics. Long-term administration of antibiotics could lead to vitamin B6 deficiency, If symptoms of peripheral neuropathy develop (numbness and tingling of the extremities), administer vitamin B6. Sulfasalazine can decrease the absorption of folic acid, and trimethoprim can cause folate deficiency, hence the need to administer folic acid if there is evidence of deficiency. Rifampicin can cause disturbances in vitamin D metabolism and lead to osteomalacia. The absorption of tetracyclines can be reduced by calcium, magnesium, iron and zinc, while this antibiotic could also decrease the absorption of these minerals. This effect is probably least with minocycline and is not confirmed with doxycycline. Doses of minerals and antibiotic should be separated by at least 2 hours. The absorption of quinolones is reduced by cationic and anionic supplements. 

Another important consideration in designing mineral absorption experiments is the effect of adaptation to a specific type of diet or level of mineral. Iii mineral absorption studies conducted to date, increasing periods of adaptation to a diet or to a level of nutrient results in decreased variability between subjects. Absorption determined from a diet which is fed only at one meal or on one day may be very different from absorption studied after a period of adaptation to the diet is allowed. 

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