Abietane diterpenoids and iridoids from Caryopteris mongolica

Six new abietane diterpenoids (1−6) and five undescribed iridoids (7−11) have been isolated from the aerial parts of Caryopteris mongolica. The intricate structural characterization of these compounds was meticulously undertaken using an array of advanced spectroscopic techniques. This process was further enhanced by the application of DP4+ probability analyses and electronic circular dichroism (ECD) calculations. Following isolation and structural elucidation, the cytotoxicity of these compounds was evaluated. Among them, compound 3 stood out, displaying significant cytotoxic activity against HeLa cells with an IC₅₀ value of 7.83 ± 1.28 μmol·L⁻¹. Additionally, compounds 1, 2, 4, 9, and 10 manifested moderate cytotoxic effects on specific cell lines, with IC₅₀ values ranging from 11.7 to 20.9 μmol·L⁻¹.