ent-Kaurane Diterpenoids with Neuroprotective Properties from Corn Silk (Zea mays)

Thirteen new ent-kaurane diterpenoids, stigmaydenes A–M (1-13), together with two known compounds (14, 15), were isolated from the crude extract of corn silk (Zea mays). The structures of the compounds were confirmed by comprehensive spectroscopic analyses. The absolute configuration of compound 1 was defined by single-crystal X-ray diffraction. The absolute configurations of the compounds were also confirmed by comparison of experimental and calculated specific rotations. The compounds were evaluated for their neuroprotective effects against H2O2-induced SH-SY5Y cell injury, and compound 8 was active at 100 μM, as determined by flow cytometry (annexin V-FITC/PI staining) and Hoechst 33258 staining. The results suggested that compound 8 could protect neuronal cells from H2O2-induced injury by inhibiting apoptosis in SH-SY5Y cells.