Ophiorrhines F and G, Key Biogenetic Intermediates of Ophiorrhine Alkaloids from <i>Ophiorrhiza japonica</i> and Their Immunosuppressant Activities

Abstract

Continued interest in bioactive alkaloids led to the isolation of two undescribed alkaloids, ophiorrhines F (<b>1</b>) and G (<b>2</b>), from the aerial parts of <i>Ophiorrhiza japonica.</i> Their structures were elucidated based on spectroscopic methods, electronic circular dichroism, and calculated NMR with DP4+ analysis. These two alkaloids represent key biological genetic intermediates in the formation of ring C in the ophiorrhines. Compound <b>1</b> exhibited good inhibition on LPS-induced B cell proliferation with an IC₅₀ value of 0.38 μM and showed significant selective inhibitory activity on a B cell proliferation response with a selective index of 548.42. A preliminary study indicated that <b>1</b> may have a new mechanism of immunosuppression.