Key Findings:
Enterolactone (EL) is an enterolignan produced by intestinal microbiota from several dietary plant lignans. EL is a chiral compound, and the enantiomers (one of two stereoisomers that are mirror images of each other) occurring are (8R, 8-R)-(−)EL and (8S, 8-S)-(+)EL. The results shows that the ratio of (+) and (−)EL in human serum varies significantly between individuals with their habitual diet. In this study, it was demonstrated that (+)EL dominates in human serum after the flaxseed ingestion. The use of immunoassay is not an optimal quantitation method for samples with very high EL concentrations or with significantly altered ratio of EL enantiomers such as following flaxseed ingestion and recommend the use pf chromatographic quantitation methods in flaxseed intervention studies.
ABSTRACT:
Enterolactone (EL) is an enterolignan found in human subjects. In this pilot study, the enantiomeric ratios of serum EL were determined in serum from healthy adults during consumption of habitual diet, and after an 8-day supplementation with flaxseed (25 g/day). (−)EL dominated in all serum samples collected during habitual diet consumption. However, the ratio of (−)EL and (+)EL enantiomers differed markedly between individuals. Flaxseed ingestion increased significantly the proportion of (+)EL in all subjects. Moreover, a small but significant increase in serum (−)EL concentration was measured. After flaxseed ingestion, (−)EL concentrations correlated with those of (+)EL suggesting that the stereochemistry of the parent plant lignan in flaxseed is not a major determinant of EL formation in human subjects. Comparison of EL concentrations obtained with the validated chromatographic methods (HPLC-MS/MS, HPLC-CEAD, and GC-MS) and the time-resolved fluoroimmunoassay (TR-FIA) revealed that the immunoassay method underestimates human serum EL concentrations after the flaxseed ingestion. (Authors abstract)