In the present study, we investigated the phenolic composition of the methanol extract from the aboveground of two plants of Turkish flora; Datura innoxia and Dipsacus laciniatus. In addition, the antioxidant (phosphomolybdenum, CUPRAC, FRAP, DPPH, ABTS) and enzyme inhibitory activities (a-amylase and tyrosinase), and total phenolic and flavonoids contents were determined in these plant extracts. The results showed high significant differences among plants (p <= 0.05) for the antioxidant capacities measured with the different methods, the enzyme inhibitory activities, and the all identified phenolic compounds except for hyperoside. From a total of 23 identified phenolic compounds, 19 were found in both plants. The main flavonoids identified were (+)-catechin and (-)-epicatechin and hyperoside. (+)-Catechin and (-)-epicatechin showed very high concentrations in D. innoxia (12937.39 +/- 108.86 and 24147.64 +/- 2512.35 mu g/g of dry plant, respectively) and in D. laciniatus (4947.99 +/- 14.18 and 13171.30 +/- 2410.76 mu g/g of dry plant, respectively). Hyperoside had interesting contents with comparable values (115.11 +/- 16.20 in D. innoxia, and 110.77 +/- 16.32 mu g/g of dry plant in D. laciniatus). The major phenolic acid was chlorogenic acid especially in D. laciniatus (12124.22 +/- 598.13 mu g/g of dry plant). These compounds were correlated to the high antioxidant and enzyme inhibitory activities for both species and confirm their medicinal traditional uses. Hence, further screening of bioactive compounds in different organs such as flowers and roots of these plants is crucial for the discovering of new source of natural antioxidants and enzyme inhibitors.