Isolierung neuer Xanthone aus Metaxya rostrata

Stefanie Rindler
2019 unpublished
The aim of this diploma thesis was to isolate new xanthones from Metaxya rostrata (C. Presl). Since this plant is used in Costa Rican ethnomedicine against gastrointestinal complaints, cytotoxic components had been isolated in a phyto-chemical examination, including the two xanthones 2-deprenyl-rheediaxanthone B and 2-deprenyl-7-hydroxy-rheediaxanthone B, which have been tested on colorectal cancer cell lines. During the investigation of fractions from previous work, a yellow fluorescent
more » ... d was detected by TLC, which indicated the presence of an unknown xanthone. After enrichment by column chromatography, mass spectrometric and NMR spectroscopic analyzes confirmed a mixture of two derivatives of 2-deprenyl-7-hydroxy-rheediaxanthone B (SR1), namely 2-deprenyl-6-O-methyl-7-hydroxy-rheediaxanthone B und 2-deprenyl-7-methoxy-rheediaxanthone B. To isolate further xanthones, chloroform and ethyl acetate extracts were prepared. For this purpose, the bark and wood of the dried rhizome were separated to analyze their composition. TLC-examination showed no qualitative differences and thus, all chloroform extracts and all ethylacetate extracts were combined. For purification of the ethylacetate extract, column chromatography was performed. In fraction SF16 and SF17 the tannins procyanidin A2, cinnamtannin B1 and aesculitannin B were identified. The chloroform extract was separated in two steps by flash chromatography. By TLC a yellow fluorescent substance was detected in fraction FSF6, which was identified as the mixture SR1. Further column chromatography of this fraction did not result in complete purification of compound SR1.
doi:10.25365/thesis.57340 fatcat:vsaz7jivujdmfdyv4qrukebog4