New neuroprotective dibenzylbutane lignans isolated from Machilus thunbergii

Two new dibenzylbutane lignans, namely rel-methyl (2S)-2-hydroxy-2-2'-((2''R,3''R)-4''-guaiacyl-2'',3''dimethylbutyl)-5'-oxo-2',5'-dihydro-2-furanylethnoate (1) and rel-methyl (2S)-2-hydroxy-2-2'-((2''R,3''S)-4''-guaiacyl-2'',3''dimethylbutyl)-5'-oxo-2',5'-dihydro-2-furanylethnoate (2), were isolated from the bark of Machilus thunbergii. Their structures were elucidated by spectral analysis. These two lignans exerted significant neuroprotective activities against glutamate-induced neurotoxicity in primary cultures of rat cortical cells. Compounds 1 and 2 represent a new type of lignan skeleton that has not been reported so far from nature.