Identification of cytoprotective constituents of the flower buds of Tussilago farfara against glucose oxidase-induced oxidative stress in mouse fibroblast NIH3T3 cells and human keratinocyte HaCaT cells

A new cytoprotective compound, 1-[(4 S )-3,4-dihydro-4-hydroxy-2,2-dimethyl-2 H -1-benzopyran-6-yl]-ethanone ( 1 ) was isolated from the flower buds of Tussilago farfara L. (Compositae), together with eight known compounds, 3,4-dicaffeoyl isoquinic acid ( 2 ), trans -cinnamic acid ( 3 ), 4-hydroxyacetophenone ( 4 ), 4,5-dicaffeoylquinic acid methyl ester ( 5 ), 3,5-dicaffeoylquinic acid methyl ester ( 6 ), 4-hydroxybenzoic acid ( 7 ), isoquercetrin ( 8 ), and ligucyperonol ( 9 ). Compounds 2–4 were found in this plant for the first time. The isolates 1–9 , were tested for their cytoprotective activities against glucose oxidase-induced oxidative stress in mouse fibroblast NIH3T3 cells and human keratinocyte HaCaT cells. Among them, 1 and 3 showed significant cytoprotective activities as determined by MTT assay and lactate dehydrogenase leakage, indicating their possibility as the potent cytoprotective agents. The structure of 1 was determined by spectroscopic data analysis including 1D- and 2D-NMR experiments, and its absolute configuration was elucidated by a circular dichroism.