New Polyene Pregnane Steroids From the Stems of Nerium oleander: Structural Characterization and In Vitro Anti-Inflammatory Evaluation.

Phytochemical investigation on the stems of Nerium oleander led to the isolation of four previously undescribed polyene pregnane steroids, namely neristerone A-D (1-4), together with six known analogues (5-10). Their structures were fully elucidated by extensive spectroscopic analysis (UV, IR, HR-ESI-MS, and NMR) and electronic circular dichroism (ECD) calculations. All isolates were evaluated for the inhibitory effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW264.7 macrophages. Notably, compounds 1, 4, and 10 exhibited significant inhibitory activity with IC50 values ranging from 11.27 ± 0.81 to 18.13 ± 1.25 µmol/L, which were lower than that of the positive control dexamethasone (21.48 ± 0.83 µmol/L). A preliminary structure-activity relationship analysis was also discussed. This study expands the chemical diversity of polyene pregnane steroids from N. oleander and provides new insights into their anti‑inflammatory potency.