Investigation of antioxidant properties of some plants was carried out. A group of plants exhibited antimicrobial activity was studied in detail. Efficiency of plants as antioxidants was tested by the influence of their extracts on the yield of photochemiluminescence of Gly-Trp solutions. Antioxidant properties were examined under conditions when their own absorption was minimized. Riboflavin as additional sensitizer was used in this experiment for superoxide generation. The antioxidant effect was evaluated with regard to single dose of plant extracts and their concentration in human organism. The effect decreases in the following consequence: Hypericum perforatum>> Potentilla erectra>> Ledum palustre>> Plantago major>> Salvia officinalis>> Chamomilla recutita>> Arctostaphylos uva.