Iridoids from Phlomis umbrosa.

Two epimeric pairs of iridoid aglycones, named shanzhigenin methyl ester and 1-epishanzhigenin methyl ester, and 8-acetylshanzhigenin methyl ester and 8-acetyl-1-epishanzhigenin methyl ester, were isolated from Phlomis umbrosa roots, along with five known iridoid glucosides. The four iridoid aglycones are reported for the first time from a natural source. Their structures were established by spectroscopic methods, mainly 1D- and 2D-NMR spectroscopic experiments, and chemical methods.