Macrocyclic Compounds with Diverse Skeletons from the Roots of <i>Myrica nana</i> and Their Spasmolytic Activity

Six undescribed macrocyclic compounds, including diarylhexanoids (<b>1</b> and <b>2</b>), a diarylhexanoid glucoside (<b>3</b>), diarylheptanoids (<b>4</b> and <b>5</b>), and an aceroside (<b>6</b>), were isolated from the roots of <i>Myrica nana</i> Cheval., along with 11 known analogues (<b>7</b>-<b>17</b>). The structures were elucidated by spectroscopic analysis, as well as by calculated optical rotatory dispersion and derivatization reactions. Metabolites <b>1</b>-<b>3</b>, with a rare macrocyclic diarylhexane skeleton, differ from the familiar macrocyclic diarylheptanoids. The spasmolytic activity of the isolated compounds was evaluated on acetylcholine-induced contraction of isolated rat ileum. All isolated compounds exhibited significant spasmolytic activities with an EC₅₀ ranging from 1.4 to 5.1 μM. The spasmolytic mechanism of action of compound <b>1</b> could be related to the NO production, blockade of muscarinic receptors, K⁺ efflux, and cytosolic calcium reduction.