A new alkaloid, uncanidine A (1) and 14 known alkaloids (2-15) were isolated from the hook-bearing branches of Uncaria rhynchophylla. Their structures were elucidated by spectroscopic analyses, including 1D-, 2D-NMR, HR-ESI-MS, ECD, as well as comparison with the data reported in the literature. Noteworthily, uncanidine A (1) was a novel Uncaria alkaloid which possessed a 6/5/6/6/6/5 hexacyclic ring system. In addition, uncanidine A (1) was found to inhibit the generation of NO from RAW 264.7 cells stimulated by LPS. © 2022 The Japan Institute of Heterocyclic Chemistry