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Abstract No.: TuP-023
Session: Clinical Chemistry Applications
Presentation date: Tue, Aug 29, 2006
Presentation time: 09:50 – 11:20

Antioxidant Activity Evaluation and Characterization of Medicinal Plant Extracts

M. Helena Florencio1,2, Sonia Amaral1,2, M. Lurdes Mira1,2, J. M. F. Nogueira1,3

1 Faculdade Ciencias Universidade Lisboa, Lisboa, Portugal
2 Centro Quimica e Bioquimica, Lisboa, Portugal
3 Centro Ciencias Moleculares e Materiais, Lisboa, Portugal

Correspondence address: M. Helena Florencio, Faculty of Sciences of Lisbon University, Chemistry and Biochemistry, Campo Grande, Lisboa, 1749-016 Portugal.

Web site: http://www.dqb.fc.ul.pt/docentes/hflorencio

Keywords: Electrospray Ionization (ESI); Mass Spectrometry, Gas Chromatography; MS/MS, Liquid Chromatography; Natural Products.

Novel aspect: The determination of the composition of medicinal plant extracts in compounds with potential antioxidant activity, is relevant in terms of their therapeutical properties and also as a useful means for the extracts characterization.

 

Oxygen and nitrogen free radicals are produced under physiological conditions and can be converted to other non-radical species, which are collectively known as oxygen (ORS) and nitrogen (NRS) reactive species. Although free radicals may have useful physiological functions, they are responsible for serious damage in biomolecules, when generated in large amounts. It should therefore be important to prevent, reduce or even eliminate these effects. The human organism has its own antioxidant defences, but their effectiveness decreases along the years. They could however be strengthen by means of antioxidants through the diet. Croton lechleri Muell Arg., Geranium robertianum, Hamamelis virginiana and Uncaria tomentosa extracts have been successfully used for the treatment of cardiac and circulatory diseases. The therapeutical properties of these extracts have been related to the presence of antioxidants, such as flavonoids, in their composition. In order to compare the extracts under study, their total phenolic and flavonolic content were investigated. The antioxidant activity against radicalar species was measured using the ABTS/HRP and the DPPH assays.

Solid phase microextraction followed by capillary gas chromatography coupled to mass spectrometry (HS/SPME/GC-MS) proved to be a powerful tool for identification of the volatile components of these extracts. High performance liquid chromatography and mass spectrometry techniques have successfully been used for identification of the non volatile fraction components. The data obtained showed that Croton lechleri is the richest in terms of phenolic and flavonolic content, whereas Geranium robertianum presents higher antioxidant activity against free radicals. The volatile compounds identified in each extract by means of HS/SPME/GC-MS are mainly phenols and terpenes. These include 1,8-cineole, borneol, 4-terpineol, methylsalycilate and eugenol for Croton lechleri, limonene, linalool, ethyl octanoate, β-ionone and ethyl linoleate for Geranium robertianum, ethyl heptanoate, β-cyclocitral, vitispirane and trans-anethole for Hamamelis virginiana, and α-pinene, myrcene, terpinolene and α-copaene for Uncaria tomentosa. The non-volatile fraction, studied by means of ESI and tandem mass spectrometry, besides flavonoids, of which kaempferol-3-o-rutinoside for Croton lechleri, kaempferol for Geranium robertianum, and myricetin for Uncaria tomentosa, are good examples, is composed by other type of compounds, with potential antioxidant activity, such as alkaloids and tannins. Examples of the latter compounds are taspine for Croton lechleri, and hamamelitannin for Hamamelis virginiana.

One of the authors, Sonia Amaral, gratefully acknowledges a scholarship (SFRH/BD/10201/2002) granted by the Portuguese Foundation for Science and Technology (FCT).