Alkaloids and chemical diversity of Stemona tuberosa. 
Phytochemical investigation of the chemical components of Stemona tuberosa led to the isolation of two new alkaloids named tuberostemonine K (1) and tuberospironine (2), together with the known tuberostemonine (3).  The new structures of 1 and 2 were elucidated through extensive spectroscopic analyses, while the molecular structure of 3 was confirmed by X-ray analysis.  A gradient reversed-phase HPLC-ELSD method was established for the investigation of the chemical diversity of S. tuberosa from 13 localities, and four types of chemical variation featured by the major components 3, neotuberostemonine (4), croomine (5), and stemoninine (6), respectively, were observed.