Neuroprotective Compounds Isolated from the Methanolic Extract of Lonicera japonica

A $CH_3Cl$ extract from the flower of Lonicera japonica (Lauraceae) significantly protected primary cultures of rat cortical cells injured by the excitotoxic amino acid, L-glutamate. Loganin (1), secoxyloganin (2), caffeic acid (3) rutin (4), hyperoside (5), quercetin-3-O-glucoside (6), lonicerin (7), kaempferol-3-O-rutinoside (8), luteolin-7-O-b-D-glucopyranoside (9), quercetin (10) and luteolin (11) were isolated by bioactivity-guided fractionation from the $CH_3Cl$ fraction and further separated using chromatographic techniques. Caffeic acid, lonicerin, kaempferol-3-O-rutinoside, quercetin and luteolin had significant neuroprotective activities against glutamate-induced neurotoxicity in primary cultures of rat cortical cells at concentrations ranging from $0.1{\mu}M$ to $10.0\;{\mu}M$.