[kjc]

Biotin, also known as vitamin H or B7, is a water-soluble B-complex vitamin which is composed of an ureido (tetrahydroimidizalone) ring fused with a tetrahydrothiophene ring. A valeric acid substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring. Biotin is a cofactor in the metabolism of fatty acids and leucine, and it plays a role in gluconeogenesis.

Sodium selenite is a salt, a colourless solid, and the most common water-soluble selenium compound. It has the formulas Na2SeO3 and Na2SeO3(H2O)5 (CAS#26970-82-1). Respectively, these are the anhydrous salt and its pentahydrate. This hydrated salt is the more common one. The hydrated and anhydrous salts behave identically for most purposes, although their molar masses differ.
Because selenium is an essential element, sodium selenite is an ingredient in some food supplements

or Vitamins and minerals?