New alkenyl-1, 4-benzoquinones, ardisianones A (1) and B (2), and the known maesanin (3) an 5-lipoxygenase inhibitors have been isolated from the rhizome of Ardisia japonica. Their structures have been elucidated as 2-methoxy-6-[(Z)-10'-pentadecenyl]-1, 4-benzoquinone and 5-hydroxy-2-methoxy-6-[(Z)-8'-tridecenyl]-1, 4-benzoquinone, respectively, on the basis of spectroscopic data and chemical degradation. Ardisianone A (1), maesanin (3) and belamcandol A (7) have been synthesized starting from belamcandol B (6), readily prepared by Wittig reaction between 9-(2-tetrahydropyanylox)nonanal and 3, 5-dimethoxybenzyltriphenylphsophonium bromide followed by selective demethylation with sodium thioethoxide.