A new nortriterpenoid, C29H48O6, with a novel skeleton was isolated from the rhizome of Phlomis umbrosa. The compound is composed of a linear array of four fused six-membered rings and a five-membered ring. The central ring has a slightly distorted half-chair conformation, while the other three sixmembered rings adopt chair conformations. There are one intra- and four intermolecular hydrogen bonds, forming an extensive hydrogen-bonding network within the crystal structure.
