Labdane-Type Diterpenes from the Aerial Parts of Their Absolute Configurations and Protective Effects on LPS-Induced Inflammation in Keratinocytes.

Phytochemical investigations of an extract of the aerial parts of led to the isolation of 14 labdane-type diterpenoids, of which compounds -, , and - turned out to be new natural products, while the remaining compounds were isolated for the first time from the genus . Their structures were elucidated using 1D- and 2D-NMR and mass spectrometry, and their absolute configurations were determined by quantum chemical calculation methods. Furthermore, DP4+ NMR chemical shift probability calculations were performed for compounds -, in order to elucidate the orientation of the ambiguous chiral center at C-15, prior to absolute configuration determination.