Molecular profiling of ginsenoside metabolites to identify estrogen receptor alpha activity.

20(S)-Protopanaxadiol (PPD) and 20(S)-Protopanaxatriol (PPT) are major metabolites of ginseng in humans and are considered to have estrogenic activity in cellular bioassays. In this study, we conducted in silico analyses to determine whether PPD and PPT interact with estrogen receptor alpha (ERα) and compared them with ERα agonists, partial agonists, and antagonists to identify their ERα activity. The transcriptome profile of 17β-estradiol (E2), PPD, and PPT in MCF-7 cells expressing ERα was further compared to understand the ERα activity of ginsenoside metabolites. The results showed that PPD and PPT interacted with the 1ERE, 1GWR, and 3UUD ERα proteins in the E2 interaction model, the 3ERD protein in the diethylstilbestrol (DES) interaction model, and the 1X7R protein in the genistein (GEN) interaction model. Conversely, neither the 4PP6 protein of the interaction model with the antagonist resveratrol (RES) nor the 1ERR protein of the interaction model with the antagonist raloxifene (RAL) showed the conformation of amino acid residues. When E2, PPD, and PPT were exposed to MCF-7 cells, cell proliferation and gene expression were observed. The transcriptomic profiles of E2, PPD, and PPT were compared using a knowledge-based pathway. PPD-induced transcription profiling was similar to that of E2, and the neural transmission pathway was detected in both compounds. In contrast, PPT-induced transcription profiling displayed characteristics of gene expression associated with systemic lupus erythematosus. These results suggest that ginsenoside metabolites have ERα agonist activity and exhibit neuroprotective effects and anti-inflammatory actions. However, a meta-analysis using public microarray data showed that the mother compounds GRb1 and GRg1 of PPD and PPT showed metabolic functions in insulin signaling pathways, condensed DNA repair and cell cycle pathways, and immune response and synaptogenesis. These results suggest that the ginsenoside metabolites have potent ERα agonist activity; however, their gene expression profiles may differ from those of E2.