Relationship between Physical Parameters of Various Metal Ions and Binding Affinity for Alginate

Abstract

Key words alginate; toxic metal; binding mechanism; affinity Metal ions absorbed via the intestinal tract, respiratory system or skin can cause serious damage to various internal organs, depending on their type and amount. For example, lead (Pb) causes acute damage to the central nervous system, and chronic damage to the kidney and hematopoetic and nervous systems.1,2) Long-term, low-dose exposure to cadmium (Cd) damages the lung (chronic bronchitis, fibrosis, emphysema), kidney (renal tubular degeneration, interstitial inflammation, fibrosis, diabetes, proteinuria), and bone (fake fracture, osteomalacia).3) Cadmium is well known to induce itai-itai disease (kidney tubular damage and osteomalacia), 4) and moreover, it is carcinogenic. 3,5) In addition, aluminum (Al) causes encephalopathy and osteodystrophy, 6,7) and copper (Cu) causes hemolytic anemia and gastroenteritis. 8) In the case of acute oral exposure, damage can be reduced by immediate treatments such as induction of vomiting and/or the use of a laxative to promote excretion of the metal. In addition, chelating agents can be administered; for example, ethylenediaminetetraacetic acid and dimercaptopropionylsulfonate are used as antidotes for Pb poisoning, 9-11) and dimercaprol is used for detoxification of Pb and Cu.11,12) However, in the case of chronic exposure, it is essential to use intrinsically safe absorption inhibitors and/or excretion accelerators that are suitable for long-term administration.Alginate (Alg), an intercellular polysaccharide found in brown algae, is used as a health food and food additive to reduce cholesterol in the blood and to inhibit weight gain. [13][14][15] It also protects the gastric mucous membrane.16) Moreover, it was reported that accumulation of strontium (Sr) in the human body decreased when sodium alginate (Na-Alg) was ingested before exposure to Sr. 17) Further, when rats pre-fed with NaAlg for ten days were administered Sr, the cumulative amount of Sr in the body was markedly reduced, compared with the control group.18) Consequently, it has been suggested that daily intake of Na-Alg would offer protection against radiation damage from radioactive fall-out by decreasing the absorption of radioactive Sr. Accordingly, the International Atomic Energy Agency (IAEA) has recommended Na-Alg intake for persons exposed to large amounts of radioactive Sr. 19)We have compared the effects of Na-Alg and Ca-Alg in promoting excretion and decreasing absorption of Sr and cesium (Cs) in rats. 20) Both additives increased the excretion of Sr, though Cs concentration was significantly reduced only in the Ca-Alg group. There have been some reports describing the capacity of Alg for metal binding and the order of affinity between Alg and metals. 21,22) However, there is little information about the relationship between the physical parameters of various metal ions and the binding affinity of these metal ions for Alg. Therefore we performed range and limitation tests of the adapting metals by evaluating the binding constants and the b...

Mechanism of Suppression of Blood Glucose Level by Calcium Alginate in Rats

“…However, our results indicate that it acts predominantly by inhibiting α-glucosidase. We ruled out a substantial contribution of direct binding, because the Km value of Ca-Alg and glucose was 201.6 mM, suggesting only weak binding compared to the binding constants of Alg and metals reported previously 26) . In addition, Ca-Alg did not affect the membrane transport of glucose.…”

Reduction Effect of Calcium Alginate on Blood Triglyceride Levels Causing the Inhibition of Hepatic and Total Body Accumulation of Fat in Rats

“…Recently, we reported that Ca-Alg reduces absorption and promotes excretion of both strontium (Sr) and cesium (Cs), whereas Na-Alg is effective only for Sr. 20) In addition, we investigated the relationship between the physical parameters of various metal ions and the binding affinity of these metal ions for Alg. 21) Moreover, we found that Ca-Alg suppressed the elevation of blood glucose levels after ingestion of starch in rats and humans by inhibiting the degradation of maltose to glucose by α-glucosidase.…”

Pharmacological Effects and Utility as a Food Additive of Calcium Alginate

“…It is well established that Alg forms a cross-linked structure with divalent or trivalent metal ions, resulting in gel formation. These results might indicate that metal ions with an ionic radius of about 90-120 pm form more robust and water-insoluble gels (Figure 2) [11].…”

“…Although the effect of Alg on Sr or Cs absorption and excretion has already been reported, there is little information about its effect on other metals. Therefore, we investigated the relationship between the physical parameters of various metal ions, including toxic metal ions, and the binding affinity of these metal ions for Alg [11]. For this purpose, the binding constants (K, mM −1 ) and the binding amount with Alg were evaluated for Sr, Pb, Tb, Dy, Ca, Cd, Mg, Fe(II), Fe(III), Co, Al, Ni, Cs, Cu, Ag, Li, and K. Aqueous solutions of each metal salt and an equivalent amount of Na-Alg were mixed, and the amount of unbound metal remaining in the filtrate was determined using an atomic absorption photometer.…”

“…In the group fed the 2% Ca-Alg diet, the portal plasma concentration of bile acid was significantly decreased, compared to that in the high-Cho diet group. Furthermore, the portal Relationships between K value, charge number and ionic radius of metal ions [11].…”