Identification and characterization of selenium species in enriched green onion (Allium fistulosum) by HPLC-ICP-MS and ESI-ITMS

SHAH, MONIKA; KANNAMKUMARATH, SASI S.; ALTAMIRANO, JORGELINA C.; WUILLOUD, RODOLFO G.; CARUSO, JOSEPH A.

Fort Lauderdale, Florida

Conferencia; 2004 WINTER CONFERENCE ON PLASMA SPECTROCHEMISTRY; 2004

WINTER CONFERENCE ON PLASMA SPECTROCHEMISTRY

Selenium is a key trace element required in small amounts in humans and animals. The key nutritional roles and chemopreventive properties of selenium have been suggested by various studies. The critical metabolite responsible for anticancer activity is methylselenol (CH3SeH), which is generated in body tissues by chemical transformation of various selenoamino acids. Selenium is not an essential element for plants but they can incorporate selenium in their tissues following sulfur assimilatory pathway if grown in soil enriched with different forms of inorganic and organic selenium.In this work selenium speciation of selenium-enriched green onions (Allium fistulosum) was done by applying size-exclusion and ion-pairing chromatographic techniques coupled on-line to ICP-MS and further characterization by ESI-ITMS detection. Green onions were grown to maturity in a green house in two commercially available media: potting mix enriched with selenium (IV) concentrations ranging from 1 to 15 mg/kg of potting medium. The small bulbs and leaves of the plants were separated from the roots, cleaned using doubly deionized water, ground in liquid nitrogen and freeze dried together. The sodium hydroxide extracts were analyzed by size exclusion chromatography (SEC) coupled to ICP-MS detection. Selenium was found to be associated to high molecular weight compounds into a great extent. Speciation of selenium was done on enzymatic and HCl extracts by ion pairing high performance chromatography. The identification of the amino acids was done by both retention time matching with selenoamino acids standards and characterization by ESI-ITMS detection.