Identification and structural modification of ent-rosane diterpenoids from Euphorbia milii inhibiting RANKL-induced osteoclastogenesis.

[Display omitted] • Sixteen undescribed, structurally diverse and novel diterpenoids were characterized from Euphorbia milii. • Thirteen synthetic derivatives were prepared, and a 12-fold increase in inhibitory potency was gained through structural derivation. • Fifteen anti-osteoclastogenesis diterpenoids were identified. Phytochemical study on Euphorbia milii , a common ornamental plant, resulted in the identification of thirteen new ent -rosane diterpenoids (1 – 13), three new ent -atisane diterpenoids (14 – 16), and a known ent -rosane (17). Their structures were delineated using spectroscopic data, quantum chemical calculations, and X-ray diffraction experiments. Euphomilone F (1) represented a rare ent -rosane-type diterpenoid with a 5/7/6 skeleton. Euphoainoid G (8) was a rare rosane diterpenic acid. Compounds 9 and 10 carried infrequent tetrahydrofuran rings, and compounds 11 – 13 was 18- nor - ent -rosane diterpenoids. All isolates were evaluated for their inhibitory effects on RANKL-induced osteoclasts. Notably, compounds with aromatic ester groups (2 – 7) showed promising activities (IC 50 < 10 μM), underscoring the significance of acylated A-ring moieties in the ent -rosane skeleton for anti-osteoclastogenesis. Thirteen synthetic derivatives were obtained through esterification of 17. Of these, compound 27 exhibited remarkable improvement, with an IC 50 of 0.8 μM, more than a 12-fold increase in potency compared to the parent compound 17 (IC 50 > 10 μM). This work presents a series of new ent -rosane diterpenoids with potential antiosteoporosis agents. [ABSTRACT FROM AUTHOR]