Publisher Summary This chapter discusses that the knowledge of phytic acid had its beginning in the discovery by Hartig, who isolated small particles or grains (which were not starch grains) from the seeds of various plants. Phytic acid has been generally regarded as the primary storage form of both phosphate and inositol in almost all seeds. The amount of phytic acid varies from 0.50% to 1.89% in cereals (except polished rice), from 0.40% to 2.06% in legumes, from 2.00% to 5.20% in oil seeds except soybeans and peanuts (grouped under legumes), and from 0.40% to 7.50% in protein products. Many foods and seeds contain myo-inositol hexaphosphate as an important source of phosphorus, and accurate methods for its determination are needed. Phytase (meso-inositol hexaphosphate phosphohydrolase, EC 3.1.3.8) is widely distributed in plants, animals, and fungi. In mature cereal grains, legumes, and oil seeds, the major portion of the total phosphorus is present in the form of phytic acid (phytate). Experiments with animals have suggested that phytic acid in plant foods complexes with dietary essential minerals such as calcium, zinc, iron, and magnesium and makes them biologically unavailable for absorption. The correlation of phytate with the cooking quality of peas was first suggested by Mattson. Phytic acid, myo-inositol 1,2,3,4,5,6-hexakis dihydrogen phosphate serves as the main phosphorus store in mature seeds and grains. In cereals and legumes, phytic acid content ranges from 0.14% to 2.05%, which accounts for 18 to 88% of the total phosphorus.

Phytates in Legumes and Cereals

Phytic acid is present in many plant systems, constituting about 1 to 5% by weight of many cereals and legumes. Concern about its presence in food arises from evidence that it decreases the bioavailability of many essential minerals by interacting with multivalent cations and/or proteins to form complexes that may be insoluble or otherwise unavailable under physiologic conditions. The precise structure of phytic acid and its salts is still a matter of controversy and lack of a good method of analysis is also a problem. It forms fairly stable chelates with almost all multivalent cations which are insoluble above pH 6 to 7, although pH, type, and concentration of cation have a tremendous influence on their solubility characteristics. In addition, at low pH and low cation concentration, phytate‐protein complexes are formed due to direct electrostatic interaction, while at pH >6 to 7, a ternary phytic acid‐mineral‐protein complex is formed which dissociates at high Na concentrations. These complexes appear to...

Phytic acid interactions in food systems

The protein quantity and quality, caloric value, and overall nutrient content of oilseeds are quite good. However, oilseeds are high in phytic acid and contain fiber and perhaps other binding agents which reduce mineral bioavailability from the seeds. Phytic acid, the hexaphosphate of myoinositol, functions as the chief storage form of phosphate and inositol in mature seeds. On a dry basis, whole oilseeds contain about 1.5% while some oilseed protein concentrates can contain over 7.0% of the compound. Phytic acid is a strong chelating agent that can bind mono- and divalent metal ions to form the complex phytate. Published results from numerous animal feeding trials suggest poor bioavailability of minerals such as zinc, calcium, magnesium, phosphorus and possibly iron from diets containing high phytate foods. Recent studies involving the feeding of soy products to rats suggest that zinc is the mineral of most concern as its bioavailability from some soy products is quite low. Prediction of mineral bioavailability from phytate-containing foods is complicated by the complex interactions between the minerals and phytic acid contained in the foods, intestinal and the meal phytase activities, previous food processing conditions (especially pH), digestibility of the foods as well as the physiological status of the consumer of the foods. Very little is known about the chemistry of such interactions. Therefore, most of the emphasis in controlling or reducing mineral binding in oilseed products has been placed upon development of methodology for phytate removal.

Oilseed phytates: Nutritional implications

The excretion of large amounts of P in effluent from intensive pig and poultry units is indicative of the poor availability of phytate-bound P in plant-derived feed ingredients. This environmental problem prompted the development and acceptance of microbial phytase feed enzymes for single-stomached animals. Their introduction led to an increasing recognition that phytate may have adverse effects on protein utilisation in addition to P. Consequently, the nutritional relevance of protein-phytate interactions for pigs and poultry is considered in the present review. Since the current understanding of the effects of protein-phytate interactions comes mainly from responses obtained to added phytase, literature on the influence of microbial phytases on amino acid digestibility and utilisation is summarised, followed by a discussion of possible mechanisms contributing to the negative effects of phytate. However, the rationale for the protein responses to added phytase remains largely speculative, and several modes of action are probably involved. It may be that the release of protein from protein-phytate complexes occurring naturally in feed ingredients, the prevention of formation of binary and ternary protein-phytate complexes within the gut, the alleviation of the negative impact of phytate on digestive enzymes and the reduction in endogenous amino acid losses are all contributing factors. A better understanding of the mechanisms of protein-phytate interactions and the modes of action of exogenous phytase enzymes is clearly desirable. Studies are also needed to identify and quantify the factors that contribute to the variable amino acid responses to added phytase. It appears that the relative solubilities of phytate salts and proteins from different feed ingredients and their effects on the extent of protein-phytate complex formation, coupled with variations in the effectiveness of phytase in different dietary contexts, may be the major factors responsible.

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Phytate and phytase: consequences for protein utilisation.

Tomatoes, a major food source for humans, accumulate a variety of secondary metabolites including phenolic compounds, phytoalexins, protease inhibitors, and glycoalkaloids. These metabolites protect against adverse effects of hosts of predators including fungi, bacteria, viruses, and insects. Because glycoalkaloids are reported to be involved in host-plant resistance, on the one hand, and to have a variety of pharmacological and nutritional properties in animals and humans, on the other, a need exists to develop a better understanding of the role of these compounds both in the plant and in the diet. To contribute to this effort, this integrated review presents data on the history, composition, and nutrition of tomatoes, with special focus on the assessment of the chemistry, analysis, composition, nutrition, microbiology, and pharmacology of the tomato glycoalkaloids comprising alpha-tomatine and dehydrotomatine; their content in different parts of the tomato plant, in processed tomato products, and in wild and transgenic tomatoes; their biosynthesis, inheritance, metabolism, and catabolism; plant-microbe relationships with fungi, bacteria, viruses, insects, and worms; interactions with ergosterol and cholesterol; disruption of cell membranes; tomatine-induced tomatinases, pantothenate synthetase, steroid hydroxylases, and cytokines; and inhibition of acetylcholinesterase. Also covered are tomato-human pathogen relationships and tomatine-induced lowering of plasma cholesterol and triglycerides and enhancement of the immune system. Further research needs in each of these areas are suggested. The overlapping aspects are discussed in terms of general concepts for a better understanding of the impact of tomato glycoalkaloids in the plant in general and in food in particular. Such an understanding can lead to the creation of improved tomatoes and to improved practices on the farm and in the consumption of tomatoes.

Tomato glycoalkaloids: role in the plant and in the diet.

Protein-phytic acid relationship in peanuts and cottonseed

The clinical attractiveness of antibiotic agents, as typified by penicillin and streptomycin, lies in their ability to effect striking and specific bacteriostatic action in vivo without the simultaneous production of severe toxic symptoms. However, since penicillin and streptomycin are limited in their usefulness because of their ineffectiveness against certain important groups of pathogenic organisms, the search for new antibiotic agents continues in the hope that additional substances having sufficiently low toxicity will be found whose high antibiotic activity against the penicillinand streptomycin-resistant organisms will permit their therapeutic use in the conquest of the diseases caused by these pathogens. Although the fungi, including Actinomyces and related forms, and bacteria have been the most fruitful sources of antibiotic agents, antibiotic activity has also been attributed to the juices of certain green plants. Many plant families have been examined for antibiotic activity (Osborn, 1943; Huddleson et al., 1944; Lucas and Lewis, 1944; Seegal and Holden, 1945), and several plant constituents that possess antibiotic activity have been isolated in crystalline form. Among these antibiotic agents are a substance from garlic (Allium sativum) that has been tentatively identified as the sulfoxide of diallyl disulfide (Cavallito, Buck, and Suter, 1945); a substance from common burdock (Arctium minus) that has not been identified but which appears to be a lactone having the empirical formula C15H2006 (Cavallito, Bailey, and Kirchner, 1945); and a substance designated "crepin" from Crepis taraxacifolia that has the empirical formula C14H1604 (Heatley, 1944). It is the purpose of this paper to describe some of the antibiotic properties of what is believed to be a new antibiotic agent from a plant source. This substance occurs in the tomato plant and has been designated "tomatin." Tomatin has not yet been crystallized, but preparations of sufficient potency have been obtained to warrant a preliminary investigation of its antibiotic spectrum. Because of the probable impurity of the tomatin preparation used in the present investigation, the data to be presented have only qualitative or, at best, semi-

George W. Irving

Papers

Protein-phytic acid relationship in peanuts and cottonseed

Partial Antibiotic Spectrum of Tomatin, an Antibiotic Agent from the Tomato Plant.

Lycopersicin, a Fungistatic Agent from the Tomato Plant

Translocation of a Radioactive Plant-Growth Regulator in Bean and Barley Plants.

Agricultural pest control and the environment.