Protective effects of Eucommia ulmoides Oliv. bark and leaf on amyloid β-induced cytotoxicity.

The objectives of this study were to investigate the protective effects of Eucommia ulmoides Oliv. (EUO) bark and leaf against cytotoxicity induced by amyloid-β peptide (Aβ) and to explore their active components. The PC-12 cells injury mediated by Aβ(25-35) was employed to assess the neuroprotective effects of EUO bark, EUO leaf and various compounds. Intracellular Ca(2+) determination, MTT reduction assay, lactate dehydrogenase leakage evaluation and HO33258/PI staining were used to quantitatively or qualitatively evaluate cell viability and injury. The organic solvents partition and the macroporous resin separation were also applied to tracing the active constituents of EUO bark. Moreover, the effects of 8 compounds (3 iridoid glucoside, 3 phenylpripanoids and 2 flavonoids) were tested to identify the active compounds of EUO leaf. The results demonstrated that the water extracts of EUO barks and leaves, geniposidic acid and chlorogenic acid could efficiently protect PC-12 cells against the cytotoxicity of Aβ(25-35). This research suggests that EUO may represent a potential treatment strategy for Alzheimer's disease. Meanwhile, geniposidic acid and chlorogenic acid are the major active constituents of EUO barks and leaves, respectively.