Two New Anti-Proliferative C18 -Norditerpenes from the Roots of Podocarpus macrophyllus.

Activity-guided fractionation strategy was used to investigate chemical constituents from the roots of Podocarpus macrophyllus. Successfully, two new norditerpenes, 2β-hydroxymakilactone A (1) and 3β-hydroxymakilactone A (2), along with ten known analogues (3 - 12) were isolated. The structures of 1 and 2 were elucidated by spectroscopic analysis including 1D-, 2D-NMR, and HR-ESI-MS data. The previously reported structure of 2,3-dihydro-2α-hydroxypodolide was revised as 2,3-dihydro-2β-hydroxypodolide (3) by spectroscopic analysis, and was further confirmed by X-ray crystallographic analysis. Cytotoxic activities of all isolated compounds against five human solid tumour cell lines (AGS, HeLa, MDA-MB-231, HepG-2, and PANC-1) were evaluated. All of them exhibited anti-proliferative activities (IC50  = 0.3 - 27 μm), except for 10. Compounds 1, 4, 5, 6, and 8 exhibited potent inhibitory activities with IC50  < 1 μm against HeLa and AGS cells.