Plants have occupied different aspects of our life, we use them in cosmetics, medicine, as spices and food, as dyes and in oil the industry. Most of these plants are known for one of their plant organs, and these are generally not flowers, petals and tepals. It is industrial practice to use a certain part of the plant while the other parts are mostly ignored and not used. From an ecological and economic point of view, „partial“ exploitation of plants is not sustainable. The aim of this thesis was to compare the qualitative and quantitative composition of bioactive compounds, and the antioxidant potential of ethanolic extracts of tepals/petals of saffron, common mallow, real tobacco, sunflower and medicinal calendula in order to contribute to a better understanding of the biopotential of this plant material. The proportion of different groups of bioactive compounds and the antioxidant capacity of the extracts were determined spectrophotometrically. Saffron tepal extracts contained a significantly higher proportion of total phenolic compounds, hydroxycinnamic acids, flavonols and proanthocyanidins compared to other analyzed samples. The 70% ethanol extract of tobacco contained more total flavonoids compared to other investigated flowering plants. Sunflower petal extracts had the highest proportion of total flavonoids in 40% ethanol. I noted a significantly higher proportion of carotenoids in the extracts of marigold and sunflower petals. In all three used methods of measuring antioxidant capacity, sunflower and common mallow petals had the highest values in extracts with 40% ethanol, while sunflower petals were the most effective in extracts with 70% ethanol. Based on this, I conclude that sunflower and common mallow petals are richer in antioxidants than other samples.