Flavonoids have shown a wide range of biological activities including antioxidant and free radiacl scavenging effects, the aim of this study is to determine the relationship between the structural characters and the free radical scavenging potent of these flavonoids.
Two flavonoids isolated from the leaves of launeae nudicaulis (Asteraceae ) which is an endemic medicinal Saharan plant growth up in the south west of Algeria were examined for their DPPH radical scavenging ability and the structure – activity relationship show that the presence of hydroxyl groups in flavonoids skeleton is widely responsible of their important antiradical activity also the presence of an unsaturation at the C2 -C3 bond in conjugation with 4 oxo function increased the radical scavenging activity of flavonoids.