Kidney rhubarb

The potassium or calcium salt form of oxaUc acid is distributed widely ia the plant kingdom. Its name is derived from the Greek o>ys, meaning sharp or acidic, referring to the acidity common ia the foflage of certain plants (notably Oxalis and Mmex) from which it was first isolated. Other plants ia which oxahc acid is found are spinach, rhubarb, etc. Oxahc acid is a product of metabohsm of fungi or bacteria and also occurs ia human and animal urine the calcium salt is a principal constituent of kidney stones. 

Oxalic acid occurs in high concentrations in pineapple and rhubarb, among other plants, and is responsible for the sharpness of the fresh fruits. Ingestion of too much oxalic acid can cause gastroenteritis, commonly recognized as a stomach ache. A salt of oxalic acid, calcium oxalate, is the stuff of kidney stones. 

The ethylene glycol and methyl alcohol (see below), which is also sometimes found in antifreeze, are poisonous because they are converted into more toxic products. Once inside the body, the ethylene glycol in the antifreeze is changed by metabolism into first one, and then several other chemicals. This requires the same enzyme that metabolizes the alcohol we consume in alcoholic drinks (ethyl alcohol). The ethylene glycol is converted into oxalic acid which is poisonous, and other poisonous products are also produced. Oxalic acid is also found in rhubarb leaves, which is what makes them poisonous. The result of these metabolic conversions is that the acidity of the blood increases (the pH decreases) and normal metabolic processes are inhibited. The oxalic acid formed can crystallize in the brain and the kidneys, causing damage. The oxalic acid also reacts with calcium and removes it from the body. The reduction of calcium... 

There are many other foods that contain toxic chemicals from a particular part of a plant or at some stage of their processing, which it is beyond the scope of this book to cover. It is well known, for example, that rhubarb leaves are poisonous, as they contain oxalic acid which is toxic, especially to the kidney. Unripe, green potatoes are also poisonous because they produce a poison called solanine. Some foods, for example fava beans, are poisonous only to certain individuals. 

It is a white solid used in removal of certain kinds of stains, in removing calcium ions from solutions, and in tanning leather. It occurs naturally and is toxic. The potassium and calcium salts of oxalic acid are found naturally in cabbage, spinach, and rhubarb leaves, and are also found in the bark of some species of eucalyptus trees. The metabolism of sugar by many species of mold results in the production of oxalic acid. Ingestion of large amounts can cause kidney damage, convulsions, and death. 

From a knowledge of the solubility rules (see Section 4.2) and the solubility products listed in Table 16.2, we can predict whether a precipitate will form when we mix two solutions or add a soluble compound to a solution. This ability often has practical value. In industrial and laboratory preparations, we can adjust the concentrations of ions until the ion product exceeds K p in order to obtain a given compound (in the form of a precipitate). The ability to predict precipitation reactions is also useful in medicine. For example, kidney stones, which can be extremely painful, consist largely of calcium oxalate, CaC204 (K p = 2.3 X 10 ). The normal physiological concentration of calcium ions in blood plasma is about 5 mM (1 mM = 1 X 10 M). Oxalate ions ( 204 ), derived from oxalic acid present in many vegetables such as rhubarb and spinach, react with the calcium ions to form insoluble calcium oxalate, which can gradually build up in the kidneys. Proper adjustment of a patient s diet can help to reduce precipitate formation. Example 16.10 illustrates the steps involved in precipitation reactions. 

Although not used in medicine, the leaf blade of Chinese rhubarb contains oxalic acid, which can cause precipitation of calcium oxalate in the renal tubules, thus causing kidney failure (Bensky et al. 2004). 

Spinach and rhubarb contain oxalic acid (Table 14.7). Individuals prone to kidney stones composed of highly insoluble calcium oxalate must limit their intake of foods containing oxalic acid. 

The name oxalic acid is derived from one of its sources in the biological world, namely, plants of the genus Oxalis, one of which is rhubarb. Oxalic acid also occurs in human and animal urine, and calcium oxalate (the calcium salt of oxalic acid) is a major component of kidney stones. Adipic acid is one of the two monomers required for the synthesis of the polymer nylon 66. The U.S. chemical industry produces approximately 1.8 billion pounds of adipic acid annually, solely for the synthesis of nylon 66 (Section 16.4A). 

CI.9 Oxalic acid, an organic compound found in plants and vegetables such as rhubarb, has a mass percent composition of 26.7% C, 2.24% H, and 71.1% 0. Oxalic acid can interfere with respiration and cause kidney or bladder stones. If a large quantity of rhubarb leaves is ingested, the oxalic acid can be toxic. The lethal dose (LD50) in rats for oxalic acid is 375 mg/kg. Rhubarb leaves contain about 0.5% by mass of oxalic add. (2.7,7.4,7.5)... 

Rules 8 and 9 apply to the oxalate and chromate ions— C2O4 and Cr04, respectively— which are less common in nature than the ions in the preceding rules. Kidney stones are an example of an oxalate. Oxalic acid (H CjO ) occurs in certain foods Hke spinach and rhubarb. Calcium ions (Ca +) are an essential electrolyte in the body. Put Ca + and together in sufficient concentrations, and calcium oxalate (CaC O ) precipitates. 

Leaf blades of rhubarb are poisonous, and accidental ingestion will cause severe vomiting and may also cause liver and kidney damage. The toxic effect was formerly attributed to oxalates present in the leaves, but later data indicate it to be due to monoanthrones (see cascara) Many cases of renal failure in rats and chronic renal toxicity in humans have been reported. However, a recent report claims that extracts from Indian R. emodi have nephroprotective and renal function improving effects. ... 

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