Minor alkaloids from an aqueous extract of the hook-bearing stem of Uncaria rhynchophylla

Abstract

Seven new monoterpene alkaloids (1−7), along with 18 known analogues, were isolated from an aqueous decoction of the hook-bearing stems of Uncaria rhynchophylla (Gou-teng). Their structures were determined by spectroscopic data analysis and electronic circular dichroism (ECD) calculations. Compound 1 is the first monoterpene 22-norindoloquinolizidine alkaloid with a ketene unit, while 2 and 3 are unusual indoloquinolizidine alkaloids having an oxazinane ring.

Graphical Abstract

Keywords:

• Indoloquinolizidine alkaloid
• monoterpene alkaloid
• Rubiaceae
• Uncaria rhynchophylla
• uncarrhynchophylline
• uncarrhynchoside

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Financial support from the National Natural Sciences Foundation of China (grant nos. 81630094), CAMS Innovation Fund for Medical Science (2017-I2M-3-010), and The Drug Innovation Major Project (2018ZX09711001) is acknowledged.