Probing structural properties and antioxidant activity mechanisms for eleocarpanthraquinone

Abstract

In this work, we present a computational investigation on the structure and energetics of eleocarpanthraquinone, a newly isolated polyphenolic anthrone-antraquinone. Properties such as bond lengths, angles, atomic charges, bond dissociation enthalpies (BDEs), and ionization potential (IP) were determined through the use of density functional theory (DFT). The B3LYP and M06-2X exchange-correlation functionals were employed along with the 6-31+G(d,p), 6-31++G(d,p), and 6-311+G(d,p) basis sets for performing computations in the gas-phase, water, methanol, and ethanol. The conformation presenting all the hydroxyl groups undergoing hydrogen-bond interactions with neighboring oxygen atoms (conformation 5) was assigned as the most stable structure while its counterpart presenting no hydrogen-bond interaction was found to be 36.45 kcal/mol less stable than conformation 5 in the potential energy surface probed at the B3LYP/6-311+G(d,p) level of theory in the gas-phase, for instance. More importantly, the lowest O-H bond dissociation enthalpy was determined to be 93.80 kcal/mol at the B3LYP/6-311+G(d,p) level of theory in water against the 146.58 kcal/mol regarding the IP computed at the same approach, suggesting the hydrogen atom transfer mechanism as being preferred over the single electron transfer mechanism in regards to the antioxidant potential for the case of eleocarpanthraquinone; the same conclusion was drawn from the outcomes of all the other approaches used.

Photoinduced degradation of indigo carmine: insights from a computational investigation

“…The CAM-B3LYP/6-311+G(d,p) optimized structure is nearly identical (bond lengths within 0.01Å and angles within 0.1°) to that obtained using the M06-2X/6-311+G(d,p) approach. The agreement between structural parameters for these two functionals was observed previously for several organic and inorganic molecules; see for instance [34][35][36][37][38]. Selected bond lengths and angles are also included in Fig.…”

Ability ofB12N12fullerene like nano‐cage for sensing and improving the antioxidant activity of juglone and its derivative: Density functional theory investigation

“…We obtained BDE values of 90.80 and 85.78 kcal/mol at the B3LYP/6-31+G(d,p) level of theory in a previous research endeavor [27]. The differences observed between the values obtained herein and those formerly published might arise from the fact that the B3LYP functional is known to underestimate the reaction energy of the HAT [59][60][61][62].…”

“…Despite the fact that the substituting O H group of Jug OH and its complex present the lowest BDE and BDFE values, the former attractive interactions are not found in their radicals. Indeed, these radicals are stabilized by the OH…O HB, thus showing the importance of HBs in the AOA of phenolic compounds [62,63].…”

Current Trends in Computational Quantum Chemistry Studies on Antioxidant Radical Scavenging Activity

“… 152 − 154 On the other hand, several researchers who used both B3LYP and one of Truhlar’s global hybrids noted that while B3LYP tends to underestimate energies there are no substantial differences and the reactivity patterns hold when the same basis set is used. 60 , 64 , 95 , 123 , 127 …”

“…This is not the only case, for similar geometry–activity relationships have been pinpointed also in other studies. 60 , 91 , 107 , 134 This emphasizes the role of selecting the appropriate conformer for the study as a critical first step in theoretical elaborations.…”