ANTIOXIDANTS IN HERBAL TEAS AS FUNCTIONAL INGREDIENTS: EXTRACTION, CHARACTERIZATION, BIOAVAILABILITY, ACTIVITY AND APPLICATIONS

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Effect of in vitro digestion upon the antioxidant capacity of aqueous extracts of Agrimonia eupatoria, Rubus idaeus, Salvia sp. and Satureja montana

Publication . Gião, Maria S.; Gomes, Susana; Madureira, Ana R.; Faria, Ana; Pestana, Diogo; Calhau, Conceição; Pintado, Manuela E.; Azevedo, Isabel; Malcata, F. Xavier

An in vitro digestion/Caco-2 cell culture model was used to assess the stability and bioavailability of phenolic compounds in aqueous extracts of four herbal infusions, traditionally used as functional drinks in Portugal. Alterations in antioxidant power were monitored by ABTS +, whereas the profile of phenolic compounds was ascertained by HPLC-DAD. The bioavailability of rutin – an important flavonoid present in such extracts, and thus a representative of those compounds, was assessed across Caco-2 cells via LC– MS/MS. Our results indicate that several antioxidant compounds are not affected by the (simulated) digestive process, whereas others undergo decreases in their activity throughout said process; a few have their antioxidant capacity hampered under stomach-like conditions. It was also found that rutin can be transported across the Caco-2 cell barrier.

2012Journal article

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Effects of extracts of selected medicinal plants upon hepatic oxidative stress

Publication . Gião, M.S.; Pestana, D.; Faria, A.; Guimarães, J.T.; Pintado, M.E.; Calhau, C.; Azevedo, I.; Malcata, F.X.

Aqueous extracts of a few medicinal plants traditionally used in Portugal have been assayed for their effects upon hepatic oxidative stress in mice. Previous in vitro studies had allowed characterization of agrimony, sage, savory, and raspberry in terms of overall antioxidant capacity and phenolic content. In the present study, the antioxidant effect and safety of these four plants were evaluated in vivo. For this purpose, mice ingested extracts in aqueous form (or water, used as the control) for 4 weeks; damage to lipids, proteins, and DNA was evaluated by oxidative cell biomarkers by the end of that period. Levels of hepatic glutathione and activities of enzymes involved in metabolism thereof were also determined. Finally, catalase and superoxide dismutase (SOD) activities were quantified, as these enzymes play a crucial role in antioxidant defense. When compared with the control, both raspberry and savory produced significant lipid protection; however, protein damage was significantly lower only in raspberry-treated animals. On the other hand, DNA damage was prevented only by savory. All plants led to a decrease in catalase activity, whereas all but sage also produced a decrease in SOD activity. With regard to glutathione levels and activities of enzymes involved in its metabolism, the aforementioned extracts exhibited different effects. In general, raspberry appeared to be the most promising extract, followed by savory, sage, and agrimony, sorted by decreasing performance in protection; the latter was even slightly toxic. Hence, the plants tested possess compounds with interesting biological activities that may support eventual inclusion in food or feed as functional additives.

2010-03Journal article

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Plant aqueous extracts: antioxidant capacity via haemolysis and bacteriophage P22 protection

Publication . Gião, Maria S.; Leitão, Isabel; Pereira, Ana; Borges, André B.; Guedes, Catarina J.; Fernandes, João C.; Belo, Luís; Santos-Silva, Alice; Hogg, Tim A.; Pintado, Manuela E.; Malcata, F. Xavier

The bacteriophage P22/Salmonella Typhimurium system, as well as human erythrocytes have been used to assay for protection, against forced oxidation caused by hydrogen peroxide, brought about by several aqueous extracts of selected adventitious plants grown in Portugal. This study proved, for the first time, that the aforementioned bacteriophage-based system is a suitable method to assess the antioxidant activity of plant extracts; among the 12 plants tested, raspberry (Rubus idaeus), sage (Salvia sp.), savory (Satureja montana) and yarrow (Achillea millefolium) were found to effectively protect against oxidative damage caused by H2O2. Haemolysis was inhibited via pre-treatment with every plant extract tested, except heath at 0.1% (w/v). The two analytical methods produced different results – and for some plants, there was a dependence (either direct or inverse) of the quantitative protection effect on extract concentration, whereas for others no significant dependence was found at all. Savory yielded the most promising results, using either method. Therefore, the P22/Salmonella system can be used as a suitable in vivo assay, and human erythrocytes as a suitable in vitro assay to confirm (or not) the antioxidant capacity of plant extracts in biological matrices.

2010Journal article

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Antioxidant activity of chitooligosaccharides upon two biological systems: erythrocytes and bacteriophages

Publication . Fernandes, João C.; Eaton, Peter; Nascimento, Henrique; Gião, Maria S.; Ramos, Oscar. L.; Belo, Luís; Santos-Silva, Alice; Pintado, Manuela E.; Malcata, F. Xavier

Most of the reports to date on the antioxidant capacity of chitosans and chitooligosaccharides (COS) are based on strictly chemical methods. When studying antioxidants with potential in vivo applications, the method used to evaluate the antioxidant activity should be representative of the conditions in which the antioxidant might have a protective effect. In this work we evaluate the antioxidant activity of two COS mixtures and a low MW chitosan (LMWC) upon two biological oxidizable substrates – erythrocytes and phages, subjected to accelerated oxidation conditions. Our results suggest that COS/LMWC can be used as antioxidants in biological systems. All the tested compounds reduced either the hemolytic and DNA damage, by inhibiting H2O2- and AAPH-radicals. However, the results obtained for these biological assays did not reveal a dose dependence, contrary to the chemical assay, suggesting that the protective concentrations should be established, in order to prevent enhancement of the oxidative damage – i.e. a prooxidant effect.

2010Journal article

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Effect of technological processing upon the antioxidant capacity of aromatic and medicinal plant infusions: from harvest to packaging

Publication . Gião, Maria S.; Pereira, Cláudia I.; Pintado, Manuela E.; Xavier Malcata, F.

Antioxidants are secondary metabolites in plants, designed to protect them from abiotic stress; however, they may also improve one's general health, following regular ingestion. Since most foods from plant origin are consumed only after processing and formulation, the final activity exhibited by their antioxidants may be rather different from that in the original plant. Ten plants empirically used in Portugal in traditional medicine were accordingly studied - agrimony (Agrimonia eupatoria), eucalyptus (Eucalyptus globulus), walnut-tree (Juglans regia), myrtle (Myrtus communis), raspberry (Rubus idaeus), sage (Salvia sp.), savory (Satureja montana), sweet-amber (Hypericum androsaemum), thyme (Thymus vulgaris) and yarrow (Achillea millefolium), for total antioxidant capacity and total phenolic content. Significant variations were found between fresh and frozen forms: most plants decreased those features by 30-80%. However, weather conditions prevailing during plant growth also had a significant impact, besides postharvest storage conditions especially in the case of antioxidant capacity. Typically, a decrease occurred throughout processing and storage, which was maximum for myrtle and minimum for yarrow. The results of this research are useful in attempts to preserve the antioxidant content of plant-derived foods, or of plant additives in foods, via rational manipulation of processing conditions after harvest and throughout storage.

2013Journal article

Open access