EFFECT OF VARIOUS PH CONDITIONS SIMULATED IN VIVO ON THE ACTIVITY OF LIPOPHILIC ANTIOXIDANTS ISOLATED FROM SELECTED SPICES
 
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Pol. J. Food Nutr. Sci. 2007;57(Special issue 3A):19–22
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ABSTRACT
Extracts of rosemary (Rosemarinus officinalis), thyme (Thymus vulgaris) and marjoram (Origanum majorana) before and after simulated digestion were investigated for their antiradical activity, iron chelation, iron reduction and inhibition of lipid peroxidation. The changes of total phenolic compounds, phenolic acids, quercetin, kaempferol and luteolin contents were measured as well. Digestion in vitro caused a significant increase in the content of total phenolics in all samples. The rosemary extract showed the highest ability to scavenge free DPPH radicals (91.97%). The activities of marjoram and thyme samples were much lower (32.55 and 24%, respectively). Digestion in vitro caused a decrease of activity in all samples. The highest decrease (88.47%) occurred after rosemary extract digestion. The activity of thyme and marjoram extracts decreased about 71.05% and 29.24% respectively. The extracts obtained from marjoram and thyme showed significant chelating power (>76%), whereas the rosemary extract was less active (19.26%). No interchangeable effect of hydrolysis under variable pH conditions on the chelating power was noticed in the study. In vitro digestion had no significant effect on the ability of the rosemary extract to inhibit linoleic acid autooxidation, the activity of this sample was high (about 87%). In the case of the other samples a significant decrease in their activity was observed after the in vitro digestion. The highest losses of activity were observed in the case of the marjoram extract. Reducing power of thyme and marjoram extracts was lower than the activity of rosemary extract but the differences were not truly significant. After digestion the activity of all samples decreased dramatically. In the case of rosemary and marjoram extracts digestion caused about 83% decrease of their activity. The thyme extract after hydrolysis retained 12.26% of its reducing power.
ISSN:1230-0322