Selenized garlic

Fish, shellbsh, red meat, wheat, liver, and some vegetables (e.g., garlic and broccoli) are all good dietary sources of Se, but speciation studies published so far have mainly focused on vegetables and selenized yeast-based food supplements. 

The exclusion of selenium from the proteins of accumulator plants is thought to be the basis for their selenium tolerance. Their selenium metabolism is based mainly on water-soluble nonprotein forms such as selenium methylselenomethionine (Jacobs, 1989). The garlic odor characteristic of selenium-accumulator plants reflects the volatile organic compounds dimethylselenide and dime-thyldiselenide. Plants can suffer selenium toxicity as a result of selenium competition with essential metabolites for biochemical sites, replacement of essential ions by selenium, mainly major cations, selenate occupation of the sites of essential groups such as phosphate and nitrate, or selenium substimtion in essential sulfur compounds. 

Humans accidentally exposed to high levels of selenium have been reported to have a noticeable garlic odor of the breath, probably as a result of excretion of dimethyl selenide in expired air (Bopp et al. 1982 Wilbur 1980). Garlic odor of the breath has been noted in humans following ingestion of toxic levels of sodium selenate (Civil and McDonald 1978) and following inhalation of elemental selenium dust or selenium dioxide (Glover 1970). 

B. Chronic ingestion of elemental selenium, sodium selenite, sodium selenate, or selenium dioxide may cause pallor, stomach disorders, nervousness, metallic taste, and garlic breath. 

Electrospray MS that allows a precise ( lDa) determination of molecular mass is an invaluable tool for the identification and a prerequisite for further characterization of compounds in speciation analysis. ESTMS has been applied mostly to commercial standards or synthetic preparations. Pneumatically assisted ESTMS is used to identify Se-adenosylhomocysteine in an extract of selenized yeast. Selenium in garlic has been speciated by parallel ICP-MS and electrospray tandem MS. A novel selenium metabolite in rat mine, the selenosugar di-asteriomer Se-methyl-N-acetylhexosamine, has been identified by this method. It should be emphasized that when authentic standards are not available the use of tandem MS is vital to confirm selenium speciation indicated by means of hyphenated seleni-mn-specific detection. 

---