The similar structures of natural compounds and the absence of NMR data for commercial products raise the risk of misidentification. This work reports a case in which purchased samples labeled as "berbamine" from 14 suppliers are oxyacanthine (1). The NMR data of all purchased samples were consistent. The X-ray crystallography characterization of one sample revealed it to be 1. The NMR data of 1 were fully assigned for the first time. Berbamine (2) was isolated from the roots of Berberis sieboldii Miq. The NMR data of 2 were assigned, and its crystal structure was reported for the first time. The authors intend to raise awareness and support the academic/industrial community through a study of this misidentification case.

Structural Similarity in Natural Products Leading to Sample Misidentification: A Case Study of the Bisbenzylisoquinoline Alkaloids Oxyacanthine and Berbamine