Structurally diverse diterpenoids and phenanthrene derivatives from the roots of Baliospermumsolanifolium

Ten undescribed diterpenoids (1-10) and three undescribed phenanthrene derivatives (11-13), together with seven known compounds, were isolated from the roots of Baliospermum solanifolium. Their structures were determined by a combination of spectroscopic data analysis, electronic circular dichroism calculations and single-crystal X-ray diffraction studies. Compounds 1-7 (baliosperoids A-G) represent the examples of 20-nor-ent-podocarpane class first discovered in nature. In particular, compound 7 possesses a unique 2,3-seco ring system incorporating γ-butanolide moiety. All isolates were assessed for their cytotoxic activities against HT-29, HCT-116, HCT-15, MCF-7, and A549 cell lines as well as their inhibitory effects on lipopolysaccharide-induced NO production in RAW264.7 cells. Compound 1, a 20-nor-ent-podocarpane-type diterpenoid possessing a Δ^1,2 double bond, not only exhibited considerable proliferation inhibition against five human cancer cell lines, with IC₅₀ values ranging from 4.13 to 23.45 μM, but also displayed the most potent inhibitory activity on NO production with IC₅₀ value at the nanomolar level (0.63 ± 0.21 μM).