Monoterpene indole glycoalkaloids from the hook-bearing branches of <i>Uncaria rhynchophylla</i>

Twelve monoterpene indole glycoalkaloids, comprising of three new ones, 19-<i>epi</i>-rhynchophylloside A (<b>1</b>), 7-<i>epi</i>-rhynchophylloside A (<b>2</b>), and 7-<i>epi</i>-anthocephalusine A (<b>3</b>), were isolated from the hook-bearing branches of <i>Uncaria rhynchophylla</i>. The structures and absolute configurations of <b>1-3</b> were elucidated by analysis of MS, NMR, ECD, and single-crystal X-ray diffraction or TDDFT-ECD calculations. Glycoalkaloids <b>1</b> and <b>3</b> showed significant immunosuppressive activity against the proliferation of B lymphocyte induced by LPS with broad selective index.