tIn this study, the total phenolic content, the antioxidant activity and toxicity of selected Greek medicinalaromatic namely Melissa officinalis L., Origanum vulgare L., Origanum dictamnus L., Salvia officinalis L. andHyssopus officinalis L., were investigated under three different extraction processes. Among the plantsstudied, Melissa officinalis L. showed the highest values in total phenolic content (0.985 ± 0.001 mg caffeicacid/mL) and antioxidant activity (6.61 ± 0.04 mol Trolox/mL) independently of the extraction process.Toxicity evaluation of the infusions prepared in concentrations contained in commercial portions showedthat inhibition values of Origanum vulgare L. and Origanum dictamnus L. were greater than 20% thusfurther research is necessary. Although toxicity of plant extracts examined is not correlated to their totalphenolic content and antioxidant activity, it was linked to the interaction of water soluble and volatileorganic compounds. Interaction of water soluble and volatile organic compounds was evaluated throughthe estimation of synergism ratios (SR), where Origanum vulgare L., presented the maximum synergism(SR = 4.2) in toxicity.