The Paradise nut - a natural Selenium source You may drive out nature with a fork - it will HOOC-CH(NH2)-CH2-CH2-Se-CH2-CH(NH2)-COOH always revert". In our time the sentence of the Latin poet is more appreciated than ever. The advantage of this compound is that it (like the "Naturalness" is an attractive feature of any sulphur analog cystathionine) is not incorporated product, especially if it is to be used as food. metabolism at a precursor of the seleno amino acids, into proteins. Thus, proteins cannot be damaged. Vitamins and trace elements are considered to namely selenocystathionine (ARONOW, 1965): Rather, the uncommon amino acid is "compart- be more valuable if they come from a natural Caption for pix mentalized" in certain parts of the plant in the free source. form rendering these parts less attractive to browsing For the important trace element animals. Selenium is thus used as a selenium a natural source exists in the form protective agent. And the selenium of the seeds of the paradise nut tree. accumulator plants can thrive on selenif- The name Paradise nut or Sapucaia nut erous soils unlike all other plants. is used for the genus Lecythis of which 26 Paradise or Brazil nuts can be species have been described (MORI 1990). used as sources for nutritional Together with the genus Bertholettia (only selenium provided they do contain one species: B. excelsa, the Brazil nut) it sufficient selenium to make the forms the subfamily of the Lecythidoideae processing economical. This is rarely of the family Lecythidaceae. Many the case with Brazil nuts: Bertholettia members of the Lecythidaceae have an excelsa cannot be cultivated (in pure interesting characteristic: They accumu- stands the trees do not bear seeds), the late selenium in the seeds if they grow in nuts are collected from the wild and the seleniferous soil. Selenium accumulation provenance of individual lots is usually has been found in the Brazil nut unknown. And this provenance can be any (PALMER, 1982), in the species Lecythis location of the entire Amazonian region ollaria (KERDEL-VEGAS, 1966), Lecythis where soils are often free of selenium. minor (DICKSON, 1969), Lecythis Individual Brazil nuts may have a very high pisonis (ANDRADE 1999) and Lecythis selenium content, but the average tuyrana (BEHR, 2002). It is likely that concentration in commercial lots is fairly low selenium accumulation is a common (SECOR 1989, CHANG 1995). characteristic of the entire genus Lecythis, In contrast, paradise nut species (in or, to include the Brazil nut, of the entire particular L. ollaria and L. minor) have more subfamily Lecythidoideae. narrow distribution ranges. Provenances can thus be selected in view of the occurrence of Why and how does Selenium selenium. Paradise nuts too are collected from present in the soil end up in the the wild. Their cultivation has often been seeds of paradise and Brazil nut recommended ("Frutales de Venezuela" trees? (HOYOS, 1989), "Some Fruits and Nuts for the Tropics" (KENNARD, 1960), "Edible Nuts Selenium is actually an element which of the World" (MENNINGER, 1977) and is detrimental to most plants. They absorb "Tropische Nutzpflanzen " (BRUECHER, the selenium from the soil as selenate and 1977). But so far the cultivation was not a process it in analogy to the common success. It should be stressed that biochemical pathway of sulphur. Most plants common nut species (walnut, almond, cannot differentiate between selenium and pecan) do not accumulate selenium in sulphur and therefore incorporate selenium at the seeds (CARLSON), it is an exclu- random instead of sulphur into amino acids: sive characteristic of the They synthesise instead of cysteine to a Lecythidoideae subfamily of the certain degree selenocysteine and instead Lecithidaceae. of methionine selenomethionine. Most plants By pressing shelled paradise do also not differentiate between normal nuts a meal is obtained which sulphur containing amino acids and these may contain as much as several seleno analogs and thus incorporate them in thousand milligrams selenium random substitution of the sulphur analogs per kilogram. For practical into proteins (DAWSON, 1988). There are certain purposes it is blended with a differences between sulphur amino acids and carrier to obtain a standard selenium selenium amino acids: The selenium atom is concentration of 1000 mg/kg. While the Se larger and - more important - it behaves concentration in the pure nut meal varies, it chemically somewhat differently. The Se- is fairly constant (and low) in the oil: H bond in selenocysteine is more acidic (that Around 4 mg Se/kg. This is explained by the is, it ionises at lower pH) than the S-H bond; fact that the selenium in paradise nut is also it is more prone to oxidation. predominantly present as Thus, in proteins Se-H groups form selenocystathionine which is water readily -Se-Se- crosslinking bridges. These, soluble and has a correspondingly low together with the higher degree of ionisa- solubility in oil. The high molecular weight tion contorts proteins and makes them and low volatility of Selenocystathionine has -from a certain Se concentration on also the consequence that paradise nut -dysfunctional: The organism - be it plant or meal does not have the offensive odour animal - dies if it has absorbed too much commonly associated with organic selenium selenium (HUBER, 1967). Selenium accumulator compounds. plants have found a solution for this dilemma. The importance of an adequate They interrupt the normal biochemical nutritional selenium intake is generally known pathway of selenium and therefore shall be summarized only shortly here. Selenium is essential for human and animal nutrition. It occurs in the body in appr. 35 proteins, generally in the form of seleno- cysteine. Many of the proteins are enzymes (glutathione peroxidases, iodothyronine deiodinases, thioredoxine reductase), the function of others selenium group, the blinded phase was stopped Cancer Prevention (Selenoprotein P, Selenoprotein W) is unknown, they in Patients With Carcinoma of the Skin. JAMA, December 25, early". Crucial for the prevention effect seem to 1996, vol 276, No. may simply be storage forms. Non-proteinaceous be certain selenium metabolites, e.g. seleno- 24,1957-1963 selenium occurs in form of certain metabolites (e.g. diglutathione. This compound does not harm COMBS, G.F.; COMBS, St.B., 1986: The role of Selenium in selenodiglutathione) which do also have an normal cells but causes apoptosis of tumor cells by Nutrition, Academic important function. Selenium is further found in low Press 1986, S. 511 inducing the tumor suppressor protein, p53 DAWSON, J.C.; ANDERSON, J.W., 1988: Incorporation of cysteine concentration in all (e.g. muscle) proteins where (LANFEAR 1994). and selenosysteine into cystathionine and selenocystathionine by methionine (and probably also cysteine) is randomly "Selenium modulates immunity: Se deficiency crude extracts of spinach. Phytochemistry 27, 3453-3460 substituted by the seleno analogs selenomethionine impairs immunity, Se intakes above those habitually DICKSON, J. D., 1969): Notes on Hair and Nail Loss After Ingesting (and selenocysteine). Sapucaia consumed in many Western countries boost Nuts (Lecythis elliptica). Econ. Bot., 23,133-134 Selenium is not evenly distributed in the body. In immunity and high Se intakes lead to toxic effects HOYOS, J. F., 1989: Frutales en Venezuela. Soc. de Cienc. Nat. La times of deficiency the element is rapidly lost from and suppression of immunity" (McKENZIE 2002, p. Salle, muscle and liver and retained in brain, endocrine 229). The influence of selenium on the immune Monografia No. 36, Caracas, 1989, S. 124 and reproductive organs, apparently because it is HUBER, R.E., CRIDDLE, R.S. 1967: Comparison of the Chemical system has many facets which cannot be discussed Properties of essential for the functioning of these organs. Even in detail here. Only one function shall be mentioned, Selenocysteine and Selenocystine with Their Sulfur Analogs. Arch. within organs certain selenoenzymes are expressed the role of selenium, or rather the selenoenzyme Biochem. with preference over others in periods of under- glutathione peroxidase in the so-called "respiratory Biophys. 122,164 (1967). supply (McKENZIE, 2002, p. 234). HUTTUNEN, J.K., 1997: Selenium and cardiovascular diseases - burst". The respiratory burst is a rapid generation of an update. Biomed.l and Environm.l Science 10, 220-226 reactive oxygen species (ROS), most of all superoxide KARDINAAL, A.F. et al., 1997: Association between toenail How much selenium intake is sufficient? (O2-.) which certain lymphocytes direct against selenium and risk of acute myocardial infarction in European men: The Euramic Study: European invading microorganisms to destroy them. For the Antioxidant Myocardial Infarction and Breast Cancer.American LEVANDER and MORRIS (1984) determined optimal function of the respiratory burst a sufficient Journal of the dietary selenium requirement to maintain a concentration of the glutathione peroxidase is Epidemiology 145, 373-379. balance to be 80 mcg per person per day for men decisive and indispensible. Hydrogen peroxide KENNARD; WINTERS, 1960: Some Fruits and Nuts for the Tropics, and 57 mcg for women or 1 mcg/kg body weight in p.78, generated in the process threatens to damage other Miscellaneous Publication No. 801, US Dept. of Agriculture general. At equilibrium, excretion equals intake. Is this cell functions and most of all it blocks the enzyme KERDEL-VEGAS, F., 1966: The Depilatory and Cytotoxic Action of balance requirement an optimal value? It is rather a which provides the superoxide in the first place. The "Coco de Mono" minimum value, if the results of certain intervention respiratory burst cannot start unless the hydrogen (Lecythis ollaria). Econ. Bot. 20,187-195 studies are considered, e.g. of CLARK (1996). KIEM, J.; KOSLOWSKI, G., 1987: Platelet and erythrocyte kinetics peroxide is removed. The removal of the hydrogen studied with Selenium-74. Trace Element - Anal. Chem. in Med. Cancer incidence reduction was observed at supple- peroxide is effected by glutathione peroxidase which and Biol.