The objective of the research was to determine the effect of varying pH conditions (analogous to those within the human digestive tract) on the content of phenolic compounds and on the antioxidant activity of extracts from some selected spices. The research material consisted of the following dried spices: cinnamon (Cinnamomum verum), tarragon (Artemisia dranunculus), and basil (Ocimum basilicum). From those species, methanol extracts were made and hydrolyzed under the varying pH conditions, which simulated the conditions within the human digestive tract. In the samples taken prior to and after the digestion process, the following was determined: antiradical activity, iron chelation, iron reduction strength, and capability to inhibit auto oxidation of the linolic acid. Furthermore, qualitative and quantitative analyses of the phenolic compounds were performed using an HPLC technique. The extract of cinnamon showed the highest antiradical activity (92,48%), the extracts from the remaining species were characterized by an essentially lower capability to neutralize free DPPH^• radicals (from 13.53% to 29%). The varying pH conditions caused the increase in the chelating capability of all the samples analyzed. The digestion process in a simulated in vivo system also contributed to the increase in the capability to inhibit auto-oxidation of the linolic acid. While determining the reducing capability of spices studied, an opposite tendency was found, namely, the in vitro digestion process caused the decrease in the reducing capability of all the spices studied.