Tuberculatm, a new lignan apioside, was isolated from Haplophyllum tuberculatum. Chemical transformations and spectral evidence established its structure as 4-O-(β-D-apiofuranosyl)-6,7-dimethoxy-1-(3',4'-methylenedioxyphenyl)-3-hydroxymethylnaphthalene-2-carboxylic acid lactone. Three other known 1-aryl-2,3-naphthalide lignans, diphyllin, justicidin A and B occurring with tuberculatm were isolated and characterized.