Identification of the Chemical Constituents in Ginger (Zingiber officinale) Responsible for Thermogenesis

To compare the thermogenic properties of crude drugs derived from ginger, the activities to peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1 alpha) of methanol extracts of "Shokyo" (dried rhizome of Z. officinale var. rubens), "Kankyo" (steamed and dried rhizome of Z. officinale var. rubens), "Red ginger" (Indonesian dried rhizome of Z officinale var. rubrum) and "White ginger" (Indonesian dried rhizome of Z. officinale var. amarum), were examined. The extracts of the four specimens were analyzed by liquid chromatography mass spectrometry (LC-MS). The results showed that "Shokyo" and "White ginger" strongly stimulated PGC-1 alpha and that the amount of [10]-shogaol (6) in these was higher than in "Kankyo" and "Red ginger". Gingerol-related compounds were isolated or prepared in order to identify the compounds responsible for stimulating PGC-1 alpha. As a result, [10]-gingerol (3), [10]shogaol (6), [10]-gingerdiols (11, 12) and [10]-gingerdiols 3,5-diacetate (17, 18) were identified as the active constituents, while the main constituents, [6]gingerol (1) and [6]-shogaol (4), did not show any significant PGC-1 alpha activity. These results suggest that gingerol-related compounds with long alkyl side chains contribute to the thermogenic properties of ginger.