This article presents the synthesis and antioxidant activities of a series of new C-acylated hydroxycoumarins. The compounds were synthesized and characterized using various spectral methods, including Infrared Spectroscopy, Nuclear Magnetic Resonance, and Mass Spectrometry. The biological activities were determined using the DPPH method by assessing the percentage inhibition of the different synthesized compounds. Four new molecules were successfully synthesized: 3-(4-methylbenzoyl)-4-hydroxycoumarin (a), 3-(4-chlorobenzoyl)-4-hydroxycoumarin (b), 3-(4-nitrobenzoyl)-4-hydroxycoumarin (c), and 3-(3,5-dinitrobenzoyl)-4-hydroxycoumarin (d). The percentage of inhibition of the synthesized compounds varies from 52.13% ± 1.04 to 78.13% ± 0.60. Compound (d) is the most active with an inhibition percentage of 78.13% ± 0.60, followed by compound (c) with an inhibition percentage of 72.68% ± 0.37, then compound (b) with an inhibition percentage of 67.38% ± 0.30, and finally compound (a) with an inhibition percentage of 52.13% ± 1.04. These compounds may exhibit interesting biological activities due to their percentage of inhibition. Therefore, these coumarin-derived
compounds could be good antioxidant candidates.

4-hydroxycoumarin, C-acylated derivatives, Nuclear Magnetic Resonance, antioxidant activity