Free radical induced degradation and computational studies of hydroxychloroquine in aqueous solution

Hydroxychloroquine (HCQ) is a potential drug molecule for treating malaria. Recently it has also been tried as adjustment in Covid 19 therapy. Interaction of HCQ with free radicals is very important, which controls its stability in the environment where free radicals are generated unintentionally. In this report, we present detailed investigation on the reactions of hydrated electrons (e_aq ^-) and hydroxyl radical (^•OH) with HCQ in aqueous solution through electron pulse radiolysis technique and computational studies. The degradation of HCQ was found to be faster in the case of reaction with ^•OH radicals. However, the degradation could be substantially slowed down in the presence of antioxidants like ascorbic acid and gallic acid. This revealed that the stability of HCQ could be enhanced in an oxidative environment in the presence of these two compounds, which are easily available through food supplements. Various global and local reactivity parameters are also determined to understand the reactivity trend using Hard-Soft Acid-Base (HSAB) principle in the realm of the DFT methods. Computational studies were performed to elucidate the site-specific reactivity trend towards the electrophilic and nucleophilic attack by calculating the condensed Fukui index for various species of HCQ.