Antimalarial and neuroprotective ent-abietane diterpenoids from the aerial parts of Phlogacanthus curviflorus

Six new ent-abietane diterpenoids, abientaphlogatones A−F ( 1 − 6 ), along with two undescribed ent-abietane diterpenoid glucosides, abientaphlogasides A−B ( 7 − 8 ) and four known analogs were isolated from the aerial parts of Phlogacanthus curviflorus (P. curviflorus). The structures of these compounds were determined using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), one-dimensional and two-dimensional nuclear magnetic resonance (NMR) spectroscopy, electronic circular dichroism (ECD) spectra, and quantum chemical calculations. Notably, compounds 5 and 6 represented the first reported instances of ent-norabietane diterpenoids from the genus Phlogacanthus. In the β-hematin formation inhibition assay, compounds 2 , 4 , 7 − 10 , and 12 displayed antimalarial activity, with IC₅₀ values of 12.97−65.01 μmol·L⁻¹. Furthermore, compounds 4 , 5 , 8 , and 10 demonstrated neuroprotective activity in PC12 cell injury models induced by H₂O₂ and MPP⁺.