In this diploma thesis, the phytochemical composition and antioxidant activity of various commercially available acerola extracts were examined. Qualitative analysis of flavonoids, phenolic acids and tannins was performed by thin layer chromatography (TLC) on a thin layer of silica gel, which formed the stationary phase with a mixture of suitable solvents as the mobile phase. Rutin (flavonoids), caffeic and chlorogenic acid (phenolic acids) and gallic acid (tannins) were detected in the fruits by calculating the Rf-values and comparing the color and intensity of the fluorescence zone of the tested and standard solutions. Spectrophotometric determination of the content of flavonoids and phenolic acids was performed using a UVVis spectrophotometer by measuring the absorbance maximum at appropriate wavelengths. In the fruit extracts, slightly lower values of the mentioned bioactive components were determined than was to be expected before conducting the analysis. The amount of flavonoids in the fruits, expressed as isoquercitroside, varies from 0.003% to 0.046%, while the content of phenolic acids was ranged from 0.053% to 0.806% for rosmarinic acid and 0.048% up to 0.995% for chlorogenic acid. Determination of the content of tannins by spectrophotometric methods was not carried out, since the TLC analysis showed barely noticeable amounts in only three samples, while none were found in the rest. Vitamin C content was analyzed by highperformance liquid chromatography. The antioxidant capacity was tested by spectrophotometric methods of determining the ability to capture the DPPH free radical and determining the ability to capture the nitrogen (II) oxide radical.