Biol. Pharm. Bull. 30(6) 1164—1166 (2007)

fects, such as methyl brevifolincarboxylate, from the leaves of Phyllanthus niruri, ebricoic acid from the extract of Phellinus givus, and forsythiaside from the fruit of Forsythia suspensa. In our attempts to search for compounds with vasorelaxant effects from various plants, in the present study we isolated three constituents from the heartwood of Acer nikoense (Aceraceae): A. nikoense is a Japanese folk medicine used as a remedy primarily for hepatic disorders. Constituents previously isolated from the bark and leaves are diarylheptanoids, phenolic compounds, and tannin, and their bioactivities such as antiinflammatory effects and protective effects against hepatic injury were also reported. First, we found that the organic extract from the heartwood of A. nikoense showed vasorelaxant effects on rat aorta with or without endothelium. Second, scopoletin (1), cleomiscosin A (2), and aquillochin (3) were isolated as major constituents using SiO2 chromatography. 8) Moreover, the results of our literature search revealed that 1 had vasorelaxant effects by inhibiting intracellular calcium mobilization from norepinephrine (NE)-sensitive stores. Consequently, we focused on the vasorelaxant effects of 2 and 3 isolated from the organic extract of the heartwood of A. nikoense and investigated their effects in comparison with that of 1, which was used as a positive control in the present study.