Antioxidative Caffeoylquinic Acids and Flavonoids from Hemerocallis fulva Flowers

Tumor necrosis factor-α (TNF-α)-induced reactive oxygen species (ROS) production in HepG2 was used to screen hepatocyte protective compounds from the flowers of Hemerocallis fulva. Three new polyphenols, n-butyl 4-trans-O-caffeoylquinate (1), kaempferol 3-O-{α-L-rhamnopyranosyl(1→6)[α-L-rhamnopyranosyl(1→2)]}-β-D-galactopyranoside (2), and chrysoeriol 7-O-[β-D-glucuronopyranosyl(1→2)(2-O-trans-feruloyl)-β-D-glucuronopyranoside (3), together with four caffeoylquinic acid derivatives (4-7), eight known flavones (8-15), one naphthalene glycoside, stelladerol (16), one tryptophan derivative (17), adenosine (18), and guanosine (19) were isolated from the bioactive fractions of the aqueous ethanol extract of H. fulva flowers. The structures of isolated compounds were characterized by means of spectroscopic data. Compounds 1-3 were described as first isolated natural products. Among the above-mentioned compounds, the caffeoylquinic acid derivatives are the major components with potent free radical scavenging activity in HepG2 cells and are for the first time isolated from H. fulva flowers. A convenient ultraperformance liquid chromatography (UPLC) method was also developed to simultaneously separate and identify caffeoylquinic acids and flavonoids promptly.