Tetracyclic indole alkaloids with antinematode activity from Uncaria rhynchophylla

A new tetracyclic indole alkaloid, 17-O-methyl-3,4,5,6-tetradehydrogeissoschizine, together with seven known ones, were isolated from the aerial part of Uncaria rhynchophylla. Their structures were unambiguously elucidated by spectroscopic methods and comparing with the literature data. Among them, compounds 1, 3, 4 and 6–8 showed potent to moderate antinematode activities against Panagrellus redivevus at a concentration of 250 μg/mL.