Arbutus unedo L. or strawberry tree is a plant that grows in the Mediterranean area and its leaves of the plant are used as urinary antiseptic, antidiarrheal, astringent, purgative, antioxidant, antihypertensive, antithrombotic and antiinflammatory substance. The plant is rich in various compounds, such as phenolic acids, tannins, fatty acids, vitamins E and C, 􀁛-carotene, triterpene, iridoids, essential oils, sugars, organic acids and flavonoids. The latter group of compounds is responsible for the positive effects in the human body. Flavonoids are polyphenolic compounds that are otherwise present in many other plants and plant products. Although they have shown numerous positive effects in the human body, they can also interact with certain enzymes responsible for drug metabolism and thus interfere with the pharmacological effect of the drug. This primarily refers to cytochrome P450 enzymes, responsible for oxidative biotransformation of 96% of drugs. The aim of this study was to determine the influence of methanolic extracts of strawberry tree on CYP2C8 enzymatic activity. For this purpose, 12 samples of the plant collected over 12 months during 2018 were used. CYP2C8 activity was monitored by the use of paclitaxel as a marker substrate, which is converted to 6-hydroxypaclitaxel by the enzyme. The resulting metabolite was determined using high performance reverse phase liquid chromatography coupled with a UV detection. The result is expressed as the percentage of metabolite produced relative to the control without inhibitors. All samples tested inhibited the formation of 6-hydroxypaclitaxel and the residual enzyme activity ranged from 27% to 54%. The results indicate that strawberry tree extracts can influence the enzymatic activity of CYP2C8, and on the basis of comparison with the chemical composition of the extracts, the effect can be partially related to the polyphenolic constituents of strawberry tree extract.