Naturally Occurring 5-Lipoxygenase Inhibitors. VI. Structures of Ardisiaquinones D, E, and F from Ardisia sieboldii

New 1, 4-benzoquinone derivatives, ardisiaquinones D (2), E (4), and F (5) along with the known ardisiaquinones A (1) and B (3) have been isolated from the leaves of Ardisia sieboldii (Myrsinaceae) and shown to be 5-lipoxygenase inhibitors. Their structures have been elucidated by spectroscopic analysis and chemical degradation. The degree of inhibition of 5-lipoxygenase activity by the ardisiaquinones and some derivatives of ardisiaquinone A is reported.