LC-ESI-MS with monolithic stationary phase and ESI-MS/MS characterization of proanthocyanidins from selected antinflammatory plants

Proanthocyanidins (condensed tannins, PAs) consisting of oligomers and polymers of flavan-3-ol units are the most widely distributed type of tannins in the plant kingdom. Dietary PAs are hypothesized to be beneficial, possibly due to their antioxidant properties and their ability to complex with macromolecules and metal ions, and they are supposed to play a role in anti-inflammatory activity of several plants [1]. Three central american anti-inflammatory plants were selected for investigating their proanthocyanidin content (B. crassifolia , G. ulmifolia and B. simaruba). Antinflammatory activity probably is related to PA's antioxidant and scavenging activities [2] and to their inhibition of arachidonic acid metabolism via both cyclooxygenase and lypoxygenase pathways [3]. Previous studies reported the presence of PAs in B. crassifolia and G. ulmifolia [4,5], never in B. simaruba. Due to the complexity of PAs structures we have proposed to rationalise the presence of these compounds in the selected plants on the basis of their ESI MS and ESI MS/MS profiles. Direct flow injection/electrospray ionization/ion trap tandem mass spectrometry was used to investigate polyphenolics in extracts of B. crassifolia, B. simaruba, G. ulmifolia. The characteristic fingerprint of the extracts was performed in negative ion mode. Depronated molecules, [M – H]^-, were observed and using IT MS/MS, the fragmentation pattern obtained evidenced the presence of a homologous series of PAs belonging to series of polymers of catechin and epicatechin, among witch galloil derivatives series from B. crassifolia, glycosilated derivatives series from B. simaruba and a number of PAs from G. ulmifolia. In a second stage analytical HPLC-ESI-MS and HPLC-ESI-MS/MS was developed. PAs are very complex to separate with classical C18 stationary phases. In our study we applied the use of a monolithic C18 column, a stationary phase described to produce better resolution in different analytical fields (6). Monoliths are rod-shaped continuous bed silica or polymeric materials, which offer an alternative to conventional particle-packed columns for analytical and preparative liquid chromatography. In the analysis of PAs interesting resolution results were obtained.

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