In this work the influence of extragent on the antioxidant (AO) effect of individual extracts and their mixtures on kinetics of cumene oxidation were investigated on the example of nine medicinal plants. It was shown that the effective concentration of AO in investigated extracts increases with increasing of polarity of extragent (except for ethanol). For each used extract have been defined their antioxidant activities (AOA), i.e. RO2 + InH → ROOH + In reaction speed constants.At combined action of various plants extracts, and also same plant extracts extracted by different extragents the there were found effects of additivity, synergism and antagonism of inhibition. Maximum effect of synergism was shown by the mixture of strawberry leaves ethanol extract with falcaria leaves acetone extract (23%), and maximum effect of antagonism was shown the mixture of ethanol and benzene extracts of falcaria leaves (39%).The received results can be used in various scopes of extracts (or in various areas of extracts use) as stabilizers of oxidation and as medicines for the medical purposes.