Neuroprotective biflavonoids of Chamaecyparis obtusa leaves against glutamate-induced oxidative stress in HT22 hippocampal cells

Abstract Four biflavonoids ( 1–4 ), five flavonoids glycosides ( 5–9 ), two catechins ( 10 , 11 ), two lignans ( 12 – 13 ), neolignan glycoside ( 14 ) and phenylpropanoid glycoside ( 15 ) were isolated from the leaves of Chamaecyparis obtusa (Cupressaceae). Neuroprotective effects of the isolated compounds were evaluated employing HT22 mouse hippocampal cells, a model system to study glutamate-induced oxidative stress. The glutamate injured HT22 cells were protected significantly by amentoflavone ( 3 ), ginkgetin ( 4 ) and (−)-epitaxifolin 3- O - β -D-xylopyranoside ( 9 ). The reduced activities of antioxidant enzymes, superoxide dismutase (SOD), glutathione reductase (GR) in response to high concentration of glutamate were preserved by pre-treatment of 3 , 4 or 9 , while the activities of glutathione peroxidase (Gpx) and catalase (CAT) were little affected. The reduced content of GSH induced by glutamate was also recovered by 3 , 4 or 9 in accommodation with the decrease in ROS production. In addition, the phosphorylation of ERK1/2 induced by glutamate insult was clearly prevented by 3 , while little changed by 4 . Taken together, amentoflavone ( 3 ), ginkgetin ( 4 ) and (−)-epitaxifolin 3- O - β -D-xylopyranoside ( 9 ) derived from C. obtusa could protect HT22 neuronal cells against glutamate-induced oxidative damage through preserving antioxidant enzymes activities and/or inhibiting ERK1/2 activation.