Five New Taraxerene-Type Triterpenes from the Branch Barks of Davidia involucrata

Abstract

Abstract:Five new taraxerene-type triterpenes, 2-nor-D-friedoolean-14-en-28-ol (1), 2-nor-D-friedoolean-14-en-3α,28-diol (2), 6α-hydroxy-2-nor-D-friedoolean-14-en-3,21-dione (3), 6α,11α,29-trihydroxy-D-friedoolean-14-en-3,16,21-trione (4), and 6α,23,29-trihydroxy-Dfriedoolean-14-en-3,16,21-trione (5), were isolated from the MeOH extract of the branch barks of Davidia involucrata, together with five known compounds. Their structures were elucidated by means of various spectroscopic analyses. Five of the identified compounds showed moderate cytotoxicities against the cell proliferation of SGC-7901, MCF-7, and BEL-7404.

Chemically Diverse Secondary Metabolites fromDavidia involucrata(Dove Tree)

“…Compounds 5-13 were subjected to evaluation for cytotoxic activities against SGC-7901 human gastric cancer cells, MCF-7 human breast cancer cells, and BEL-7404 human hepatoma cells (Table 1). Gratifyingly, compounds 6-7, 10, and 12 showed moderate cytotoxic activities against all the three cell lines [19].…”

“…Taraxeranetype triterpenoids containing carbonyl moieties at positions 3, 16, and 21 of the taraxerane-type skeleton are observed, such as davinvolunone B (6) and davinvolunone C (7). Both of these compounds, which were highly oxidized, were isolated from the same sample of Davidia involucrata and unequivocally determined by extensive spectroscopic analysis [19].…”

“…A number of oxygenation patterns around a basic taraxerane skeleton were observed ( Figure 3). The dihydroxylated compound myricadiol (5) was isolated from the methanolic extract of the branch bark of Davidia involucrata [19] and the compound had been reported before [20][21][22]. Taraxeranetype triterpenoids containing carbonyl moieties at positions 3, 16, and 21 of the taraxerane-type skeleton are observed, such as davinvolunone B (6) and davinvolunone C (7).…”

“…Oxidation of the methyl group at C-28 in the ursanetype skeleton is also observed. Methanolic extraction of the branch bark of Davidia involucrata yielded six examples euscaphic acid (8) [23], myrianthic acid (9) [24], 3 -O-trans-p-coumaroyl-2 -hydroxy-urs-12-en-28-oic acid (10) [25][26][27], 3 -O-cis-p-coumaroyl-2 -hydroxy-urs-12-en-28-oic acid (11), 3 -O-trans-p-feruloyl-2 -hydroxy-urs-12en-28-oic acid (12), and 3 -O-cis-p-feruloyl-2 -hydroxyurs-12-en-28-oic acid (13) [27] where C-28 had been oxidized to a carboxylic acid functionality [19,28]. Compounds 8-13, which had been previously documented, were characterized by comparison of various spectra including NMR, IR, mass, and specific rotation.…”

“…Triterpenes may rearrange to form a 2-nor-pentacyclic triterpenoid carbon skeleton with 29 carbons and a five-membered A-ring, which was unprecedented to the best of one's knowledge [19,28]. A plausible biosynthetic pathway was proposed and depicted in Scheme 1.…”