Nutritional supplements containing conjugated linoleic acid (CLA) isomers, widely used to improve body composition and inhibit fat storage, should be thoroughly analyzed, as CLA effects are isomer specific. In this research, an improvement of silver-ion high performance liquid chromatography (Ag+-HPLC) was obtained by using a single-column instead of the most commonly used multi-columns. To develop the procedure, a standard CLA mixture has been derivatized with different chain length alcohols (from methanol to hexanol). Hexyl CLA showed better separation between CLA isomer pairs, in particular the resolution of t10,c12 : c9,t11 pair increased from 0.3 (methyl esters) to 0.8 (hexyl esters). Therefore, the CLA isomer composition of some commercial CLA products was determined by Ag+-HPLC analysis of hexyl esters. The main isomers in all supplements resulted to be c9,t11-CLA and t10,c12-CLA, the most antiadipogenic isomer. t8,c10- and c11,t13-CLA were not detected. The nutritional supplements were also analyzed by high resolution gas chromatography (HRGC) of methyl esters to evaluate the fatty acid % composition and total CLA % content. Total CLA ranged from 79.4% to 94.4%, and the t,t isomer from 1.4% to 7.3%.
Analysis of CLA isomer distribution in nutritional supplements by single column silver-ion HPLC
COSSIGNANI, Lina;SIMONETTI, Maria Stella;DAMIANI, Pietro;BLASI, FRANCESCA
2013
Abstract
Nutritional supplements containing conjugated linoleic acid (CLA) isomers, widely used to improve body composition and inhibit fat storage, should be thoroughly analyzed, as CLA effects are isomer specific. In this research, an improvement of silver-ion high performance liquid chromatography (Ag+-HPLC) was obtained by using a single-column instead of the most commonly used multi-columns. To develop the procedure, a standard CLA mixture has been derivatized with different chain length alcohols (from methanol to hexanol). Hexyl CLA showed better separation between CLA isomer pairs, in particular the resolution of t10,c12 : c9,t11 pair increased from 0.3 (methyl esters) to 0.8 (hexyl esters). Therefore, the CLA isomer composition of some commercial CLA products was determined by Ag+-HPLC analysis of hexyl esters. The main isomers in all supplements resulted to be c9,t11-CLA and t10,c12-CLA, the most antiadipogenic isomer. t8,c10- and c11,t13-CLA were not detected. The nutritional supplements were also analyzed by high resolution gas chromatography (HRGC) of methyl esters to evaluate the fatty acid % composition and total CLA % content. Total CLA ranged from 79.4% to 94.4%, and the t,t isomer from 1.4% to 7.3%.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
