Narjatamolide, an Unusual Homoguaiane Sesquiterpene Lactone from Nardostachys jatamansi.

Narjatamolide (1), an unusual homoguaiane sesquiterpene lactone, was isolated from the roots and rhizomes of Nardostachys jatamansi DC. It represents the new carbon skeleton of a homoguaiane sesquiterpenoid possessing an additional acetate unit spiro-fused with C-4 and C-15 to form a cyclopropane ring. The structure of 1 was elucidated by extensive spectroscopic analyses, and the absolute configuration was confirmed by the electronic circular dichroism (ECD) calculations and X-ray single-crystal diffraction analysis. Compound 1 showed antiproliferative effects against BEL-7402 cell lines with an IC50 value of 5.67 ± 1.43 µM, and the mechanism study showed that 1 induces cell cycle of BEL-7402 cell lines arrest at G2/M phase.