Phenylethanoid glycoside from Forsythia koreana (Oleaceae) flowers shows a neuroprotective effect

A repeated column chromatography for Forsythia koreana Nakai. flowers afforded a phenylethane glycoside, which was identified as 8′-(3,4-dihydroxyphenyl)ethyl-O-α-l-rhamnopyranosyl-(1 → 4)-2-O-(E)-caffeoyl-α-l-arabinopyranoside based on spectroscopic analyses of 1D NMR (1H-NMR, 13C-NMR, DEPT), 2D NMR (gCOSY, gHSQC, gHMBC), FAB/MS, specific rotation, and IR spectrometry. This compound was isolated from F. koreana flower for the first time in this study. The compound showed scavenge activities in ORAC and DPPH radicals with the values of 0.83 ± 0.01 and 84.66 ± 0.75% (at the concentration of 500 ppm), respectively. It also inhibited production of NO for RAW 264.7 stimulated by LPS and protected oxidative stress induced by glutamate in HT22-immortalized hippocampal. The IC50 on inhibition of NO production and EC50 value on protective efficacy of oxidative stress were 78.72 ± 1.43 μM and 176.25 ± 7.23 μM, respectively. These results demonstrate that the phenylethanoid glycoside might be useful as a neuroprotective agent because of their antioxidant, anti-inflammatory, and neuroprotective effects.