Antinutritional effects

MAWSON R, HEANEY R K, ZDUNCZYK z and KOZLOwsKA H (1994) Rapeseed meal-glucosinolates and their antinutritional effects. Part 3. Animal growth and performance , Nahrung, 38 167-77. 

Blytt, H. J., Guscar, T. K., and Butler, L. G. (1988). Antinutritional effects and ecological significance of dietary condensed tannins may not be due to binding and inhibiting digestive enzymes. Journal ofChemicalEcology 14,1455. 

Pusztai, A., et al. 1993. Antinutritive effects of wheat-germ agglutinin and other iV-acetylglycosa-mine-specific lectins. Br J Nutr 70 313. 

Nutritional Effects Due to the Presence of the Maillard Products. Many physiological or antinutritional effects have been attributed to the Maillard products. Specific effects have been attributed to the Amadori products deoxyfructosylphenylalanine (a model substance not likely to be present in large quantities in foods) appears to depress the rate of protein synthesis in chicks (32) and to partially inhibit in vitro and in vivo the absorption of tryptophan in rats (33). The compound e-deoxyfructosyllysine inhibits the intestinal absorption of threonine, proline, and glycine and induces cytomegaly of the tubular cells of the rat kidneys (34) as does lysinoalanine. In parenteral nutrition the infusion of the various Amadori compounds formed during sterilization of the amino acid mixture with glucose is associated with milk dehydration in infants and excessive excretion of zinc and other trace metals in both infants and adults (35,36,37). 

Our results have been recapitulated with other proteins of varying nutritional value to S. exigua and H. zea they include soy protein, tomato foliar protein, corn gluten and zein. In all cases, more than 2.5% dietary protein was required to alleviate antinutritional effects, because these proteins are less nutritious than casein (Table III). The ability of a protein to alleviate the toxicity of o-quinones is proportional to its nutritional value to the insect (Table III). The proteins ability to function as an alkylatable sink (alleviation of antinutritive effects) is correlated with the relative amounts of alkylatable amino acids (e.g., lysine, cysteine, histidine, methionine Felton and Duffey, unpublished data). 

Toxicologic and Antinutritional Effect of Maillard Browned Protein... 

We have the least information about the antinutritive effects of lipoxygenase (LOX). Experiments (Table IV) show that the nutritive value of protein to H. zea is reduced by treatment with LOX and linoleic acid (52% reduction in growth). Tomato foliage contains significant quantities of LOX activity and linoleic acid has been shown to be covalently bound to protein both in vitro and in planta (unpubl. data). Studies are underway to determine which amino acids are preferentially destroyed. Also, preliminary studies with foliage demonstrate that copious quantities of malondialdehyde are generated in crushed foliage the antinutritional effects of this Schiff base former are as yet undetermined. 

Currently we are determining if the joint antinutritional effects of POP, POD, and LOX activity are additive or synergistic. If these activities are found to differentially destroy amino acids, then their battery of effects may be synergistic. If their effects are equal (same amino acids destroyed), then perhaps only one enzyme, say PPO (with high phenolic levels) requires amplification to prove a sufficient antinutritive defense. We are also determining if various oxidized phenolics (e.g., caffeic acid, chlorogenic acid, coumaric acid, and rutin) are equivalent in their ability to alkylate and impair protein quality. 

Several methods have been attempted to overcome the antinutritional effects of tannins in the diet. The most common are summarized by Price and Butler (1980) along the following lines. 

Native ovoflavoprotein (49 kDa, pf=5.1) has, as does ovomucoid, certain antinutritional effects, as it inhibits serine proteases (trypsin, chymotrypsin and also microbial proteases) and has antiviral activity. Ovomacroglobulin (ovostatin) is an inhibitor of serine, cysteine, thiol and metalloproteases and shows antimicrobial activity. Some antinutritional effects are also seen in the basic glycoprotein avidin in raw egg white (relative molecular weight of the monomer is 15.6 kDa). It contains four identical subunits (pf = 9.5), each of which binds one molecule of biotin to give an unavailable complex. However, the denatured avidin, for example in hard-boiled eggs, does not interact with biotin. The interaction of riboflavin with flavoprotein (32 kDa, pf = 4.0) has, on the contrary, a positive influence on vitamin stability. Cystatin acts as cysteine protease inhibitor, and shows antimicrobial, antitumor and immunomodulating activities. 

Glucosinolates are another group of bioactive compounds found in canola/oilseed rape. They are not toxic until hydrolysed and then are associated with goitrogenicity and antinutritional effects in animals which consume the meal as feed. In humans, the glucosinolates may have a positive health benefit due to anticarcinogenic activity. As mentioned earlier, in order to be classified as canola, the dry meal must contain <30 pg glucosinolates/g. 

Butler, L.G. 1992. Antinutritional effects of condensed, and hydrolysable tannins. Pages 693-698 in Plant Phenols Synthesis, Properties, and Significance, L.W. Heminway and RE. Laks (eds.). Plenum Press, New York. 

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