In order to study the structure activity relationship of metabolites of ubiquinone, α-tocopherol and phylloquinone (Ia, b, c, IIa, b, c), 3-carboxy-2-butenyl (IIIa, b, c), 6-hydroxy-3-methyl-2-hexenyl (IVa, b, c), 4-hydroxy-3-methylbutyl (Va, b), 4-hydroxy-3-methyl-2-butenyl (VIb, c), ω-carboxyalkyl (VIIa, b, c), and ω-hydroxyalkyl (VIIIa, b) side chains were introduced into the 6-position of 2, 3-dimethoxy-5-methyl-1, 4-benzoquinone and 2, 3, 5-trimethyl-1, 4-benzoquinone, as well as the 3-position of 2-methyl-1, 4-naphthoquinone. The effects of these quinones on the membrane stability of rat-liver lysosomes and on the activity of bovine heart phosphodiesterase were investigated. A good correlation was observed between these activities of the benzoquinone derivatives (VIIa, b).