Sweden

Dr Per Sjöberg from the Department of Physical and Analytical Chemistry at Uppsala University in Sweden has demonstrated that electrochemistry (EC) coupled to liquid chromatography (LC) and electrospray ionization tandem mass spectrometry (LC/EC/ESI-MS/MS) can be used to rapidly obtain information about the antioxidant activity (i.e., oxidation potential) and capacity (i.e., amount) of polyphenolic compounds, including catechin, kaempferol, resveratrol, quercetin, and quercetin glucosides, in plant extracts.

“Method development is of interest for us at the Department of Analytical Chemistry with the purpose to demonstrate new possibilities to analyse complex samples. Over the past few years we have been involved in a number of research areas such as hyphenation of electrochemistry with mass spectrometry, utilizing information dependent acquisition (IDA) mass spectrometry (MS) to obtain a great deal of analytical information from a complex sample and the extraction of ‘active’ compounds from plant material. Combining our experience in these areas we explored how to rapidly detect and identify polyphenolic antioxidants in plant extracts and presented our findings in Analytical Chemistry [81 (21) 8968-8977 (2009)],” Dr Sjöberg.

The on-line LC/EC/ESI-MS/MS method described by Sjöberg and his team facilitates the detection and characterization of individual antioxidants based on a combination of the obtained m/z values for the antioxidants, the potential dependences for the ion intensities and correlations between the retention times in the LC, EC and MS chromatograms. “As these results provide patterns that can be used in rapid screening for antioxidants in complex samples, the method should be a valuable complement to chemical assays commonly used to determine the total antioxidant capacity of samples. Furthermore, the antioxidant capacity for a mixture of polyphenolic compounds depends on the redox potential employed in the evaluation and this should consequently be taken into account when comparing results from different total antioxidant capacity assays,” he explained.

Sjöberg and his team are currently utilizing the developed method on a number of samples from different origins. When the EC method is performed on-line with LC complex samples can be analysed. “Utilizing MS detection unknown antioxidants can be identified and activity for individual compounds in complex sample can be evaluated. Once the identity of the compound is known, antioxidant capacity (amount) could be determine. However this will require a more or less pure compound which can possibly be obtained from preparative chromatography,” he said.

For more information, contact the author per.sjoberg@kemi.uu.se