Kleinhospitine E and Cycloartane Triterpenoids from Kleinhovia hospita
- J Nat Prod. 2018 Jul 27;81(7):1619-1627. doi: 10.1021/acs.jnatprod.8b00211.
- 1. School of Pharmaceutical Sciences, College of Medical, Pharmaceutical and Health Sciences , Kanazawa University , Kanazawa , 920-1192 , Japan.
- 2. Department of Pharmacognosy-Phytochemistry, Faculty of Pharmacy , Hasanuddin University , Makassar , Indonesia.
- 3. Tokyo University of Pharmacy and Life Sciences , Hachioji , Tokyo 192-0392 , Japan.
- 4. Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy , University of North Carolina , Chapel Hill , North Carolina 27599-7568 , United States.
- 5. Duke University Medical Center , Durham , North Carolina 27710 , United States.
- 6. Chinese Medicine Research and Development Center , China Medical University and Hospital , Taichung 401 , Taiwan.
A novel cycloartane triterpenoid alkaloid, kleinhospitine E (1), six new cycloartane triterpenoids (2-7), three known cycloartane triterpenoids (8-10), and taraxerone (11) were isolated from a methanol extract of Kleinhovia hospita. Their structures were elucidated by 1D- and 2D-NMR spectroscopy as well as HRMS analysis. The absolute configurations of all isolated compounds were determined from their ECD spectra by comparison with theoretical values. Kleinhospitine E (1) is the first cycloartane alkaloid possessing an unusual γ-lactam with an oxopropylidene side chain. Compounds 2, 3, and 6 were assigned as cycloartane triterpenoids with a 9α,10α-cyclopropyl ring, which is found rarely among naturally occurring compounds, while 4 and 5 were established as isomers of compound 3 containing a 21,23-diacetal side chain. Biological evaluation revealed that compounds 4 and 9 exhibited more potent antiproliferative activities against a multidrug-resistant tumor cell line compared with its parent chemosensitive cell line. Furthermore, compound 6 exhibited submicromolar anti-HIV activity.