ABSTRACT Six new dimeric monoterpenoid indole alkaloids, geleganidines D–I ( 1–6 ), together with six known analogues ( 7–12 ), were isolated from the roots of Gelsemium elegans . Compounds 1 and 2 represent the first dimeric Gelsemium alkaloids composed of a humantenine‐type unit and a gelsedine‐type unit, connected through a carbonyl‐derived urea bridge. Compounds 3–6 were new dimeric monoterpenoid indole alkaloids featuring distinct dimerization patterns, including a carbonyl‐derived urea bridge ( 3 ), azo linkages ( 4 and 5 ), and a symmetric C–C‐linked dimer ( 6 ). Their structures and absolute configurations were elucidated by comprehensive spectroscopic analyses, including NMR, single‐crystal X‐ray diffraction, and quantum‐chemical ECD calculations. Among the isolates, compounds 4 , 5 , and 8 exhibited significant in vitro anti‐herpes simplex virus type 1 (HSV‐1) activity, with IC 50 values of 5.01 ± 0.78, 12.55 ± 1.47, and 6.35 ± 0.36 µ M, respectively. A preliminary structure–activity relationship analysis of compounds 1–12 was also discussed.
Zhang et al. (Fri,) studied this question.