Activation of PPARgamma by metabolites from the flowers of purple coneflower (Echinacea purpurea).

Thiazolidinediones are insulin sensitizing drugs that target the peroxisome proliferator-activated receptor (PPAR) gamma. An n-hexane extract of the flowers of Echinacea purpurea was found to activate PPARgamma without stimulating adipocyte differentiation. Bioassay-guided fractionations yielded five alkamides, of which one was new, and three fatty acids that all activated PPARgamma. The new alkamide hexadeca-2E,9Z,12Z,14E-tetraenoic acid isobutylamide (5) was identified by analysis of spectroscopic data and found to activate PPARgamma with no concurrent stimulation of adipocyte differentiation. Compound 5 was further shown to increase insulin-stimulated glucose uptake. The data suggest that flowers of E. purpurea contain compounds with potential to manage insulin resistance and type 2 diabetes.