Chemical and Cytotoxic Constituents from the Formosan Casearia membranacea Hance
Casearia membranacea Hance (Flacourtiaceae) is a tree found in the northern region of Taiwan. Bioassay-directed fractionation of the MeOH-layer has resulted in the isolation of six new clerodane diterpenes, Caseamembrins A-F (1-6) along with a known compound, rel-(2S,5R,6R,
The structures of compounds 1-6 were determined by the physical methods such as IR¡Bmass¡Boptical rotation, 1D¡B2D NMR spectral analysis, and the published reports about the data of related compounds .
The spectral data of 1-6 are in conformity with the basic skeleton of clerodane diterpenes previously isolated from Casearia membranacea Hance.. The basic structures of 1-6 contain two 6-membred ring linked with six carbon diene side chain at C-9 and two ester carbonyl functional groups at C-2 and C-18 respetirely.
Compound 1 had an ester carbonyl at C-2 position, with an acetoxyl and a hydroxyl group at C-19/6 position, the structure of 1 was assigned as rel-(2S,5R,6R,8S,9S,10R,18S,19R)-18-butanoyloxy-19-acetoxy-18,19
-epoxy-6-hydroxy-2-(2-methylbutanoyloxy)cleroda-3,13(16),14-triene (Caseamembrin A). Compound 2 had a methoxyl group at C-18 position, that 2 has the structure of rel-(2S,5R,6R,8S,9S,10R,18S,19R)-18-methoxy
-19-acetoxy-18,19-epoxy-6-hydroxy-2-(2-methylbutanoyloxy)cleroda-3,13(16),14-triene (Caseambrin B). Compound 3 had an acetoxyl at C-19 position, and two hydroxyl group at C-6/7. Compound 3 was assigned the structure of rel-(2S,5R,6R,7R,8S,9S,10R,18S,19R)-18-butanoyloxy-19-
13(16),14- triene (Caseamembrin C). Compound 4 had two acetoxyl at C-7/19 and hydroxyl group at C-6, the assignment of its structure as rel-(2S,5R,6S,7R,8S,9S,10R,18S,19R)-18-butanoyloxy-19-acetoxy
-18,19-epoxy-6-hydroxy-7-acetoxy-2-(2-methylbutanoyloxy)cleroda-3,13(16),14- triene (Caseamembrin D). Compound 5 had two acetoxyl at C-18/19 position, and a hydroxyl group at C-6 position. 5 was established as rel-(2S,5R,6R,8S,9S,10R,18S,19R)-18,19-diacetoxy-18,19-epoxy-6-
hydroxy-2-(2-methylbutanoyloxy)cleroda-3,13(16),14-triene (Caseamembrin E). Compound 6 had a hydroxyl group at C-6 position and it was deduced that the C-18/19 acetal ring was opened thus forming the two aldehydic units. The structure of 6 was established as rel-(2S,5R,6R,7R,8S,9S,10R,18S,19R)-6-hydroxy-2-(2-methylbutanoyloy)
cleroda-3,13(16),14-triene-18,19-dicarboxyaldehyde (Caseamembrin F).
It is worthy to mention that this is the first report of the isolation of 1-6 from a natural source. In a preliminary pharmacological aporach (cytotoxicity), compounds 1-6 exhibited moderate cytotoxicity against (NUGC-3) and (HONE-1) cancer cells with IC50 0~1¢Mvalues at 20mg/ml.
Advisor:YA-CHING SHEN; CHUN-NAN LIN; YAO-HAUR KUO
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Date of Publication:07/23/2003