Neuroprotective lignans from the bark of Machilus thunbergii

The CH2Cl2 fraction of the bark of Machilus thunbergii Sieb. et Zucc. (Lauraceae) significantly protected primary cultures of rat cortical cells exposed to the excitotoxic amino acid, L-glutamate. (-)-Isoguaiacin, meso-dihydroguaiaretic acid, machilin A, (+)-galbelgin, licarin A, (-)-sesamin, and (+)-guaiacin were isolated by bioactivity-guided fractionation from the CH2Cl2 fraction and further separated using chromatographic techniques. Isoguaiacin, meso-dihydroguaiaretic acid, licarin A and (+)-guaiacin had significant neuroprotective activities against glutamate-induced neurotoxicity in primary cultures of rat cortical cells at concentrations ranging from 0.1 muM to 10.0 muM.