Iridoids from Phlomis umbrosa

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