The reaction of ninhydrin with primary amino groups to form the purple dye now called Ruhemann's purple (RP) was discovered by Siegfried Ruhemann in 1910. In addition, imines such as pipecolic acid and proline, the guanidino group of arginine, the amide groups of asparagine, the indole ring of tryptophan, the sulfhydryl group of cysteine, amino groups of cytosine and guanine, and cyanide ions also react with ninhydrin to form various chromophores of analytical interest. Since its discovery, extensive efforts have been made to apply manual and automated ninhydrin reactions as well as ninhydrin spray reagents to the detection, isolation, and analysis of numerous compounds of interest across a broad spectrum of disciplines. These include agricultural, biochemical, clinical, environmental, food, forensic, histochemical, microbiological, medical, nutritional, plant, and protein sciences. This reaction is unique among chromogenic reactions in that at pH 5.5 it results in the formation of the same soluble chromophore by all primary amines which react, be they amines, amino acids, peptides, proteins, and even ammonia. Because the chromophore is not chemically bound to the protein or other insoluble material, it is not lost when the insoluble substrate is removed by centrifugation or filtration after the reaction is completed. The visible color of the chromophore is distinctive and is generally not affected by the yellow colors present in many food, plant, and tissue extracts. Adaptations of the classical ninhydrin reaction to specialized needs in analytical chemistry and biochemistry include the use of acid, alkaline, and fluorogenic ninhydrin reagents. To cross-fertilize information among several disciplines wherein an interest in the ninhydrin reaction has developed, and to enhance its utility, this review attempts to integrate and correlate the widely scattered literature on ninhydrin reactions of a variety of structurally different compounds. Specifically covered are the following aspects: historical perspective, chemistry and mechanisms, applications, and research needs. A better understanding of these multifaceted ninhydrin reactions provide a scientific basis for further improvements of this important analytical technique.

Applications of the Ninhydrin Reaction for Analysis of Amino Acids, Peptides, and Proteins to Agricultural and Biomedical Sciences

Potatoes, members of the Solanaceae plant family, serve as a major, inexpensive food source for both energy (starch) and good-quality protein, with worldwide production of about 350 million tons per year. U.S. per capita consumption of potatoes is about 61 kg/year. Potatoes also produce potentially toxic glycoalkaloids, both during growth and after harvest. Glycoalkaloids appear to be more toxic to man than to other animals. The toxicity may be due to anticholinesterase activity of the glycoalkaloids on the central nervous system and to disruptions of cell membranes affecting the digestive system and other organs. The possible contribution of glycoalkaloids to the multifactorial aspects of teratogenicity is inconclusive. Possible safe levels are controversial; guidelines limiting glycoalkaloid content of potato cultivars are currently being debated. This review presents an integrated, critical assessment of the multifaceted aspects of the role glycoalkaloids play in nutrition and food safety; che...

Potato glycoalkaloids: chemistry, analysis, safety, and plant physiology

Publisher Summary This chapter discusses the deamidation of glutaminyl and asparaginyl residues in peptides and proteins. The occurrence of glutaminyl and asparaginyl residues in peptides and proteins is so widespread that these residues have become known as 2 of the 20 most commonly occurring amino acid residues. It has been hypothesized that these residues play static roles in protein structure and also play dynamic roles as molecular timers of biological events. Deamidation of glutaminyl and asparaginyl residues has been responsible for artifacts in peptide and protein chemistry. The rate of deamidation of these residues has been shown to be dependent upon primary sequence, secondary and tertiary structure, temperature, pH, ionic strength, and special intermolecular interactions. Deamidation has been found to occur in a wide variety of different proteins and may be expected to occur in most proteins under physiological conditions. Many of the essential processes in living things may be timed by deamidation of glutaminyl and asparaginyl residues. These molecular timers are under simple genetic control, are adjustable to many different timed intervals, and are easily implementable by means of the important changes that they can effect in the proteins in which they are included.

Deamidation of Glutaminyl and Asparaginyl Residues in Peptides and Proteins

Potatoes, tomatoes, and aubergines are all species of the Solanum genus and contain a vast array of secondary metabolites including calystegine alkaloids, phenolic compounds, lectins, and glycoalkaloids. Glycoalkaloids have been the subject of many literature papers, occur widely in the human diet, and are known to induce toxicity. Therefore, from a food safety perspective further information is required regarding their analysis, toxicity, and bioavailability. This is especially important in crop cultivars derived from wild species to prevent glycoalkaloid-induced toxicity. A comprehensive review of the bioactivity of glycoalkaloids and their aglycones of the Solanum species, particularly focused on comparison of their bioactivities including their anticancer, anticholesterol, antimicrobial, anti-inflammatory, antinociceptive, and antipyretic effects, toxicity, and synergism of action of the principal Solanum glycoalkaloids, correlated to differences of their individual molecular structures is presented.

Bioactivities of glycoalkaloids and their aglycones from Solanum species.

(1981). Naturally Occurring Toxic Alkaloids in Foods. CRC Critical Reviews in Toxicology: Vol. 9, No. 1, pp. 21-104.

Naturally occurring toxic alkaloids in foods.

Specific gravity and total solids data were studied statistically to test the absolute reliability of the relationship in American potatoes. On a limited number of samples it is strongly indicated that studies should be instituted in the United States to establish a regression curve especially suited to American varieties and growing conditions. The variation in the relationship, due to tissue air space and perhaps other causes, indicates doubt as to the absolute reliability of individual total solids values determined by means of specific gravity. This is amply demonstrated by the 95% confidence limit of ± 1.5% total solids.

Studies of the relationship of specific gravity to total solids of potatoes

Enzymatic hydrolysis of α-chaconine and α-solanine

Prior to storage, Maine-grown Katahdin potatoes were sorted into five specific gravity classes Samples of three classes (high, intermediate, and low) were stored in individual boxes at 38 F for eight months, 45 F for one month, and 50 F for one month New York-grown Katahdins were sorted into specific gravity classes periodically after removal from storage Both lots were analyzed periodically for free amino acids (including the amides) In general, an inverse relationship was found between total solids and free amino acids calculated on a dry weight basis in Maine-grown and New York-grown Katahdin potatoes In most cases little difference was found on the fresh-weight basis Changes in the amino acids during storage were quite random The differences found in the amino acid values between samples due to sorting for specific gravity before and after placing in storage were minor

Chemical composition of potatoes. VII Relationship of the free amino acid concentrations to specific gravity and storage time

Non-nitrogenous ninhydrin-positive compounds in ion-exchange chromatography identification of levulinic in hydrolyzed plant fractions☆

Formation of Fumaramic Acid from Asparagine in Phosphate Buffer

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