Flavonoids are plant secondary compounds that represent a low molecular polyphenols. They have broad spectrum of biological activity, demonstrating immune modulating, anti-inflammatory, anti-asthma, -cancer and other activities. The impact of phenolic compounds is based on their antioxidant features. The aim of the thesis was to evaluate the antioxidative and hepatoprotective effects of ethanolic extacts of P. major, L. nobilis, O. basilicum in terms of the cytotoxic effects of CCl4 with the simultaneous study of histomorphology and key biochemical indicators of hepatocytes toxic damage. The mechanisms of their effects are monitored, as well as examine the possibility of their use in the treatment of hepatitis of various etiologies. The highest amount of flavonoids has been found in O. basilicum (27.2 μg/ml), the lowest in P. major's (10.9 μg/ml) extract, despite among the studied extracts the highest antiradical activity has L.nobilis, the lowest O. basilicum. According to the results all three extracts contain quercetin and morin. It should be noted that the amount of quercetin and morin in extracts are correlated with antiradical and antibacterial activity, respectively. Results of in vivo experiments have shown that when L.nobilis, O. basilicum, P. major extracts administered simultaneously with CCl4 the increase in life duration of experimental rats as compared to control at 480, 96 and 48 hours, respectively. It was showed that in case of abdominal CCl4 injection of the rats in blood plasma the increase of biochemical key indicators of hepatocyte and kidney damage, such as aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase and γ-glyutamiltransferase amount was observed. At simultaneous injection of L.nobilis extract and CCl4 in blood plasma AST, ALT, alkaline phosphatase, γ-glyutamiltransferase decrease in 21%, 30%, 68% and 35%, respectively, compared with animals injected only CCl4. The results show the L.nobilis extract hepatocyte and kidney cells protective activity. Rat liver functional condition has been evaluated by "dark" layers measuring on microphotos, as well as by De–Ritis ratio determination methods (serum ALT and AST activities relation) that also show L.nobilis extract hepatoprotective activity during CCl4 intoxication. The results show that in case of L.nobilis and CCl4 injection, there is a decrease in hemorrhagic and hepatotoxic injury area in 47%. The results show, that L.nobilis extract has expressed antihemorrhagic and hepatoprotective activity, related to CCl4 toxic effects.