Serrulatane and Decipiene Terpenoids from Eremophila platycalyx subsp. woolgorong
Jianzhong Zhu, Louise Kjaerulff, Susan J. Semple, Dan StaerkAbstract
The chemical profile of the root bark extract of Eremophila platycalyx subsp. woolgorong was investigated, leading to the identification of 12 previously unreported (2−7, 11, 12a, 13, and 14) and 5 known (1, 8, 9, 10, and 12b) terpenoids. Among them, eremoplawone A (2) stands out with a unique chemical scaffold. The planar structures were established through extensive analysis of HRMS and NMR data. Relative configurations were determined using ROESY spectra, and absolute configurations were established by comparison of experimental and calculated ECD spectra, as well as DFT-GIAO NMR calculations. Two groups of compounds (6a/12a and 11/14) were found to interchange during HPLC separation, and an interconversion mechanism has been proposed. Lastly, the antibacterial activity of the isolated compounds against Staphylococcus aureus and Pseudomonas aeruginosa was investigated, revealing bactericidal activity of 11/14 with a minimum inhibitory concentration of 8.6 ± 0.2 μg/mL against S. aureus.