Nine new alkaloids of the koumine (1−4),
humantenine (5−7), and yohimbane (8, 9) types as well as 12
known analogues were isolated from the leaves and vine stems
of Gelsemium elegans. Compound 1 is the first N-4-demethyl
alkaloid of the koumine type, compound 7 is the first norhumantenine
alkaloid, and compounds 8 and 9 are the first N-
1-oxide and the first seco-E-ring alkaloids, respectively, of the
yohimbane type. Compounds 1 and 7 exhibited moderate
cytotoxicity against five human tumor cell lines with IC50
values in the range 4.6−9.3 μM.