Separation and identification of phenolic derivatives in plant extracts by novel analytical techniques
The pharmacological properties attributed to cassis, juice of the blackcurrant, (Ribes nigrum spp., Saxifragaceae), and the root bark of the osage orange tree (Maclura pomifera Raf., Moracea) can at least be partially attributed to their high content of plant phenolics. Previous studies on these plants were done before the new methods of analysis were available, and modern techniques have now been used to evaluate their phenolic content. Liquid chromatography atmospheric pressure chemical-ionization mass spectrometry (LC-APCI-MS) was used to analyse the cassis extract. The major anthocyanins and flavonoids present in cassis were identified by their unique APCI mass spectra. A fraction containing only the anthocyanins was also subjected to capillary electrophoresis (CE). Previous published CE methods for the analysis of anthocyamins did not take into account their degradation in non-acidic media. The newly developed method uses buffers at the pH 1.5 with improving stability of the analytes and sensitivity of the method. Two new extraction techniques, namely, superciritcal fluid extraction (SFE) and pressurized fluid extraction (PEE), were evaluated to extract plant material. Both methods proved to be as efficient to extract the root bark of the osage orange tree as the traditional extraction procedures. A new flavanone was extracted by SFE, and a possible chemical structure is proposed. LC-APCI-MS was used to analyse extracts from the root bark and fruit of the osage orange tree. The APCI mass spectra permitted the identification of the prenylated xanthones and flavanones present in ether extracts of the root bark. The methanolic extracts of the root bark were also subjected to LC-APCI-MS, and two rare C-glycosyl xanthones were identified. Their complete chemical structures are not known, but some possible structures were proposed. LC-APCI-MS of extracts of the fruit Osage orange tree led to the identification of three new compounds, but their chemical structures were not investigated. There is currently much interest in the study of plant phenolics, and the new analytical methods here proposed are expected to considerably expedite and improve their analysis in plant extracts.