Octahydro-Protoberberine and Protoemetine-Type Alkaloids from the Stems of Alangium salviifolium and Their Cytotoxicity

Abstract

Two octahydro-protoberberine alkaloids, alangiifoliumines A (1) and B (2), and two new protoemetine derivatives, alangiifoliumines C (3) and D (4), together with 11 known compounds, have been isolated from the stems of Alangium salviifolium. While the structures of these compounds were elucidated by spectroscopic methods, the absolute configurations of the new alkaloids were determined by conformational analysis and time-dependent density functional theory–electronic circular dichroism spectra calculations on selected stereoisomers. Compounds 1 and 2 represent the first 5,8,8a,9,12,12a,13,13a-octahydro-protoberberine derivatives, in which the aromatic ring D was reduced to cyclohexene. All the compounds isolated were evaluated for their cytotoxic activity against three human cancer cell lines: A-549, HeLa, and SKOV-3. Alkaloids 1, 3, and 6–14 exhibited inhibitory effects against all three human cancer cell lines, with half-maximal inhibitory concentration (IC50) values in the range of 3 nM to 9.4 μM.

Cytotoxic Yohimbine‐Type Alkaloids from the Leaves of Rauvolfia vomitoria

“…To further verified the absolute configurations of 1, the ECD calculations of 1a, 1b, and their enantiomers were performed using TD-DFT at B3LYP/6-311G(2d,2p) level. [17] The experimental ECD of 1 agreed well with the calculated ECD of (3R,4S,15R,16R,17R,18S)-1a, instead of those of (3R,4R,15R,16R,17R,18S)-1b and their enantiomers (Figure 4). Thus, the absolute structure of 1 can be defined as (3R,4S,15R,16R,17R,18S), and named rauvine A.…”

“…Therefore, the structure of 1 should be determined as 1a , instead of 1b . To further verified the absolute configurations of 1 , the ECD calculations of 1a , 1b , and their enantiomers were performed using TD‐DFT at B3LYP/6‐311G(2d,2p) level [17] . The experimental ECD of 1 agreed well with the calculated ECD of (3 R ,4 S ,15 R ,16 R ,17 R ,18 S )‐ 1a , instead of those of (3 R ,4 R ,15 R ,16 R ,17 R ,18 S )‐ 1b and their enantiomers ( Figure 4).…”

A New Fusicoccane‐Type Norditerpene and a New Indone from the Marine‐Derived Fungus Aspergillus aculeatinus WHUF0198

“…For determination of the absolute configuration of 1 , a stereoisomer 1a (2 R ,3 S ,10 S ,11 R ,14 S ) was used as the model compound. The calculated weighted ECD spectrum of 1a was obtained with time‐dependent density functional theory (TDDFT) calculations [20–22] . A systematic conformational analysis was performed for 1a using the Merck Molecular Force Field (MMFF) molecular mechanics force field.…”

“…The calculated weighted ECD spectrum of 1a was obtained with time-dependent density functional theory (TDDFT) calculations. [20][21][22] A systematic conformational analysis was performed for 1a using the Merck Molecular Force Field (MMFF) molecular mechanics force field. The selected stereoisomer was reoptimized using TDDFT at the B3LYP/6-311G (2d, p) level to find the lowest energy conformer.…”

Spiroalanfurantones A–D, Four Eudesmanolide–Furan Sesquiterpene Adducts with a Pentacyclic 6/6/5/5/5 Skeleton from Inula helenium

“…As part of our ongoing program to search for architecturally intriguing bioactive secondary metabolites from medicinal plants in China, four eudesmanolide–furan adducts, spiroalanfurantones A–D ( 1 – 4 ) with an unprecedented pentacyclic 6/6/5/5/5 skeleton (Figure ), were identified from the roots of Inula helenium . Herein are reported the isolation, structure elucidation, and plausible biosynthesis of the four new sesquiterpene lactone adducts.…”