Substituent effects on the antioxidant activity of mono substituted 3,3'-diindolylmethane: a DFT study

Abstract

3,3'-diindolylmethane (DIM) is an indole compound with proven health benefits and thus potential preventive medicine and therapeutic applications. Here in, the origins of the substituent effects on the antioxidant activity of mono substituted 3,3’-diindolylmethane (DIMs) were studied in silico by calculating their thermo chemical properties using the (RO)B3LYP/6-311++G(2df,2p)//B3LYP/6-31G(d) method. It was found that the compounds 2-NHMe-DIM, 2-OH-DIM and 2-MeO-DIM have the lowest BDE(N1- H) values (78.4-78.9 kcal.mol⁻¹), while that for the C8 H bond is observed in the 2-HO-DIM compound (67.0 kcal.mol⁻¹). The presence of substitutes can decrease the ionization energies of the DIMs, however the effects of substitutes on the proton affinity were not clearly observed. The investigation on the HOO‘ radical scavenging following the hydrogen atom transfer mechanism indicated that the compound 2-NHMe-DIM has the highest rate constant with k = 9.72 x 10⁹ L.mol⁻¹,s⁻¹. Thus, it is suggested that the 2-NHMe-DIM is a powerful antioxidant.