Theoretical Study on the Radical Scavenging Activity of Shikonin and its Ester Derivatives

Aim of study is to get a further insight on the contribution of the structural features to the radical scavenging potential of shikonin and its ester derivatives. The radical scavenging activity of shikonin and its ester derivatives have been studied by using density functional theory. The hydrogen bond property of the studied structures has been investigated by using the Atoms in Molecules (AIM) theory. The calculated results reveal that the hydrogen bond is important for good scavenging activity. The hydrogen atom transfer mechanism for shikonin and its ester derivatives are difficult to occur. However, shikonin and its ester derivatives appear to be good candidates for the one-electron-transfer mechanism. The shikonin ester derivatives investigated in this study are expected to be of high radical scavenging activity compared with parent compound shikonin. Taking this system as an example, we present an efficient method for the investigation of radical scavenging activity from theoretical point