Liriogerphines E–U, further unique sesquiterpene-alkaloid hybrids from the rare Chinese tulip tree

• Published in: Phytochemistry (Oxford) 2024-02, Vol.218, p.113956-113956, Article 113956
• Main Authors: He, Yu-Hang, Xiang, Hong, Li, Qi-Xiu, Wu, Yu-Fei, Jin, Ze-Xin, Hu, Jin-Feng, Mao, Yi-Cheng, Xiong, Juan
• Format: Article
• Language: English
• Subjects: Alkaloids - chemistry; Anti-leukemic effect; Antineoplastic Agents; Liriodendron - chemistry; Liriodendron chinense; Liriogerphines; Magnoliaceae; Molecular Structure; Plant Leaves - chemistry; Sesquiterpene-alkaloid hybrids; Sesquiterpenes - chemistry
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2023.113956

Seventeen undescribed sesquiterpene-alkaloid hybrids (liriogerphines E–U, 1–17) were isolated and identified during a further phytochemical investigation on the branches and leaves of Chinese tulip tree (Liriodendron chinense), a rare medicinal and ornamental plant endemic to China. These unique heterodimers are conjugates of germacranolide-type sesquiterpenoids with structurally diverse alkaloids [i.e., aporphine- (1–15), proaporphine- (16), and benzyltetrahydroisoquinoline-type (17)] via the formation of a C–N bond. The previously undescribed structures were elucidated by comprehensive spectroscopic data analyses and electronic circular dichroism calculations. Such a class of sesquiterpene-alkaloid hybrids presumably biosynthesized via an aza-Michael addition is quite rare from terrestrial plants. In particular, the sesquiterpene-benzyltetrahydroisoquinoline hybrid skeleton has never been reported until the present study. All the isolates were evaluated for their cytotoxic effects against a small panel of leukemia cell lines (Raji, Jeko-1, Daudi, Jurkat, MV-4-11 and HL-60), and some of them exhibited considerable activities. Seventeen previously undescribed hybrids (liriogerphines E–U, 1–17), conjugating by germacranolide-type sesquiterpenoids and structurally diverse alkaloids, were isolated and identified during a further phytochemical investigation on the brunches and leaves of Chinese tulip tree (Liriodendron chinense). These sesquiterpene-alkaloid hybrids were quite rare in terrestrial plants and some of them exhibited significant anti-leukemia activities. [Display omitted] •17 undescribed sesquiterpene-alkaloid hybrids were isolated from Chinese tulip tree.•The structures were established by spectroscopic analysis and chemical calculations.•The hybrids presumably formed by aza-Michael addition were quite rare in nature.•Liriogerphine U is the first example of sesquiterpene-benzylisoquinoline hybrid.•Some isolates exhibited considerable cytotoxicities against six leukemia cell lines.