Selenomethionine (L-Selenomethionine)

L-Selenomethionine (CAS 3211-76-5, C5H11NO2Se, molecular weight 196.11) is the selenium analogue of L-methionine, in which the sulphur atom in the amino acid side chain is replaced by selenium. It is a white to off-white crystalline powder, soluble in water at roughly 50 mg/mL, melting at about 265 degrees C with decomposition, with a specific rotation of approximately +18 degrees (c = 1 in 1 M hydrochloric acid) that distinguishes the L-form from the DL racemate, CAS 1464-42-2. One selenium atom in a molecule of 196.11 gives a theoretical elemental selenium content of 40.3 per cent, and that is the figure formulators work back from when setting an inclusion rate. Selenomethionine is the predominant form in which selenium occurs in the food chain, arising because plants and micro-organisms do not reliably distinguish selenium from sulphur during methionine synthesis; it is the main selenium species in cereal grains, soybeans, grassland legumes and Brazil nuts. Selenium itself is an essential trace element and a constituent of selenoproteins such as glutathione peroxidase and thioredoxin reductase. Buyers should be explicit about which of the three commercial selenium formats they are specifying, because they are not interchangeable on a certificate: isolated L-selenomethionine is a single defined chemical assaying 98 per cent or better; selenium-enriched yeast is a fermentation biomass in which selenomethionine sits protein-bound inside a yeast matrix at 1,000 to 2,000 ppm total selenium; and sodium selenite or sodium selenate are inorganic salts. This listing is the isolated amino acid. Thovek lists selenium yeast and sodium selenite separately for buyers who need those forms. At 40.3 per cent selenium the neat powder is far too potent to dose directly into a blend, so Thovek supplies standardised triturations at 0.5, 1 and 2 per cent selenium on a food-grade carrier alongside the 98 per cent material; that is what most tablet, capsule and premix lines actually need to hold content uniformity at microgram inclusion. National maximum levels for selenium in food supplements differ by market, and the buyer should confirm the destination limit before fixing a dose. The synthetic amino acid is vegan and vegetarian with no animal, dairy, egg, soy, fish, crustacean, gluten, nut or yeast input — a real distinction from selenium yeast for yeast-free and low-allergen lines, and one worth stating explicitly on the label even though the natural dietary form is associated with Brazil nuts and cereals. Every batch is certified for assay by HPLC, total selenium by ICP-MS, inorganic selenium species, related substances, optical purity, loss on drying, heavy metals and microbiology, and ships with CoA, MSDS, Certificate of Origin and allergen, GMO and BSE/TSE statements.