Radical scavenging activity of some natural tropolones by density functional theory

A G Al-Sehemi,M Alfaifi,A Irfan,A Al Fahad

doi:10.4314/bcse.v31i1.13

A G Al-Sehemi, M Alfaifi + Show 2 more

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https://doi.org/10.4314/bcse.v31i1.13

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Abstract

The ground state neutral geometries of some natural tropolones, i.e. stipitatonic acid (AF1), stipitalide (AF2), stipitaldehydic acid (AF3) and methyl stipitate (AF4) have been optimized by using Density Functional Theory (DFT) at B3LYP/6-31G*, B3LYP/6-31G**, B3LYP/6-31+G* and B3LYP/6-31+G** levels of theory. The excited state geometries of AF1-AF4 were optimized by adopting the Time Dependent Density Functional Theory (TDDFT) at the same levels of theory. The frequencies and cation species of AF1-AF4 were also computed at all the above mentioned levels of theory. We shed light on the electro-optical and molecular properties, e.g. energy gaps, highest occupied molecular orbitals, lowest unoccupied molecular orbitals, absorption wavelengths, electronegativity (χ), hardness (η), electrophilicity (ω), softness (S), electrophilicity index (ωi) and the radical scavenging activity (RSA). Hydrogen atom transfer (HAT) and one-electron transfer mechanisms have been discussed to shed light on the RSA. The smallest ionization potential and bond dissociation energy of AF4 are revealing that this compound would have more RSA than those of other counterparts. KEY WORDS : Density Functional Theory, Tropolones, Molecular properties, Bond dissociation enthalpy, Adiabatic ionization potential Bull. Chem. Soc. Ethiop. 2017 , 31(1), 149-157. DOI: http://dx.doi.org/10.4314/bcse.v31i1.13

Highlights

Oxidative stress prompted by reactive oxygen and nitrogen species can cause destruction to nucleic acids, cellular proteins and lipid membranes which are the sources of cancer and coronary heart disease [1]
The experimental crystal structural geometrical parameters and calculated ones at B3LYP/631G*, B3LYP/6-31G**, B3LYP/6-31+G* and B3LYP/6-31+G** levels of theory have been tabulated in Tables 1 and S1
No variations in the bond lengths and bond angles were observed (AF1-AF4) by changing the level of theory which revealed that basis set has no substantial effect on the bond lengths

Summary

Introduction

Oxidative stress prompted by reactive oxygen and nitrogen species can cause destruction to nucleic acids, cellular proteins and lipid membranes which are the sources of cancer and coronary heart disease [1]. Diouf et al studied the influence of tropolone on the wood degradation and they found weak antioxidative and radical scavenging properties. They showed tropolone can be used as novel environmentally benign preservative systems [2]. Kadoma and co-workers studied the kinetic radical scavenging activity (RSA) of tropolone by induction period method and found very weak antioxidant properties [3]. Quantum chemical calculations and density functional theory (DFT) were applied to calculate the adiabatic ionization potential (IP), bond dissociation enthalpy (BDE) and other radical scavenging properties of antioxidant systems [5,6,7,8,9,10,11]. No calculation about the antioxidant activity of the fungal tropolones stipitatonic acid

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