Chemical speciation influences comparative activity of selenium-enriched garlic and yeast in mammary cancer prevention.
A recent human intervention trial showed that daily supplementation with selenized yeast (Se-yeast) led to a decrease in the overall cancer morbidity and mortality by nearly 50%; past research has also demonstrated that selenized garlic (Se-garlic) is very effective in mammary cancer chemoprevention in the rat model. The goal of this study was to compare certain biological activities of Se-garlic and Se-yeast and to elucidate the differences based on the chemical forms of selenium found in these two natural products. Characterization of organic selenium compounds in yeast (1922 microg/g Se) and garlic (296 microg/g Se) was carried out by high-performance liquid chromatography with inductively coupled plasma mass spectrometry or with electrospray mass spectrometry. Analytical speciation studies showed that the bulk of the selenium in Se-garlic and Se-yeast is in the form of gamma-glutamyl-Se-methylselenocysteine (73%) and selenomethionine (85%), respectively. The above methodology has the sensitivity and capability to account for >90% of total selenium. In the rat feeding studies, supplementation of Se-garlic in the diet at different levels consistently caused a lower total tissue selenium accumulation when compared to Se-yeast. On the other hand, Se-garlic was significantly more effective in suppressing the development of premalignant lesions and the formation of adenocarcinomas in the mammary gland of carcinogen-treated rats. Given the present finding on the identity of selenomethionine and gamma-glutamyl-Se-methylselenocysteine as the major form of selenium in Se-yeast and Se-garlic, respectively, the metabolism of these two compounds is discussed in an attempt to elucidate how their disposition in tissues might account for the differences in cancer chemopreventive activity.
Ip
C
C
Department of Experimental Pathology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA. Clement.Ip@roswellpark.org
Birringer
M
M
Block
E
E
Kotrebai
M
M
Tyson
J F
JF
Uden
P C
PC
Lisk
D J
DJ
D000230:Adenocarcinoma / Q000139:chemically induced / Q000517:prevention & control; D000818:Animals; D016588:Anticarcinogenic Agents / Q000627:therapeutic use*; D002273:Carcinogens; D005260:Female; D005737:Garlic / Q000627:therapeutic use*; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000517:prevention & control*; D008517:Phytotherapy; D010946:Plants, Medicinal; D011230:Precancerous Conditions / Q000139:chemically induced / Q000517:prevention & control; D051381:Rats; D017207:Rats, Sprague-Dawley; D018036:Selenium Compounds / Q000627:therapeutic use*; D018038:Sodium Selenite / Q000627:therapeutic use; D015003:Yeasts
D016588:Anticarcinogenic Agents; D002273:Carcinogens; D018036:Selenium Compounds; D018038:Sodium Selenite