Lignans and phenolic constituents from Eucommia ulmoides Oliver

Two new lignans, noreucol A (1) and (+)-epicycloolivil (2), along with seven known compounds (3–9) were isolated from the aqueous extract of Eucommia ulmoides Oliver. Compound 1 was a new norlignan and 2 was an epimer at C-7 of (+)-cycloolivil (3). Their structures were elucidated by spectroscopic methods, and the absolute configurations of new compounds were determined by conformational analysis and DFT theoretic electronic circular dichroism spectra calculations. In addition, the neuroprotective activity of compounds 1–3 against glutamate-induced HT-22 cells injury were evaluated, and only compound 1 exhibited moderate effect at the concentrations ranging from 10 ∼ 50 μM.