Antioxidant Potential of Santowhite as Synthetic and Ascorbic Acid as Natural Polymer Additives

Abstract

A wide variety of additives are used to improve specific characteristics of the final polymeric product. Antioxidant additives (AAs) can prevent oxidative stress and thus the damage of polymeric materials. In this work, the antioxidant potential and thus the applicability of Santowhite (SW) as synthetic and ascorbic acid (Asc) as natural AAs were explored by using computational tools. Two density functional theory (DFT) methods, M05-2X and M06-2X, have been applied in combination with the 6-311++G(2d,2p) basis set in gas phase. Three antioxidant mechanisms have been considered: hydrogen atom transfer (HAT), single electron transfer-proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET). Bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), and electron transfer enthalpy (ETE) have been computed for each potential hydrogen donor site. The results indicate that the antioxidant potential of Asc is higher than SW. Furthermore, some of the C-H bonds, depending on their position in the structures, are potent radical scavengers, but O-H groups are more prone to donate H-atoms to free radicals. Nonetheless, both additives can be potentially applied to safeguard common polymers and prohibit oxidative stress-induced material deterioration.

Comparative study of the antioxidant capability of EDTA and Irganox

“…The HAT mechanism involves a hydrogen atom transfer from hydrogen donor sites, such as methyl group, hydroxyl group and others, of the antioxidant compound to the free radical. From a thermodynamic point of view, the antioxidant potential can be measured by the bond dissociation enthalpy of the corresponding X–H bond, where the lower the BDE the greater the antioxidant capacity of the compound [ 6 , 12 , 14 , 16 , 29 ]. The BDE values for all unique X–H bonds of EDTA have been calculated and compared ( Tables S1 and S2 ).…”

“…AH +• is radical cation created when an electron transferred from the antioxidant, A‾ is an anion which is formed after a proton loss has been occurred. By using the above equations, parameters such as bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), and electron transfer enthalpy (ETE) can be determined and these can be used in the assessment of antioxidant potential of molecules [ 12 , 14 , 30 , 31 , 32 ]. From these parameters, we can evaluate the antioxidant activity of the molecules.…”

“…The applied methodologies were previously validated in similar studies including thermochemistry, kinetics, and non-covalent interactions, especially those involving free radical reactions. Furthermore, because it has previously been utilized successfully in the study of similar systems and processes, the M06-2X/6–311++G(2d,2p) level of theory was chosen to be employed throughout the discussion in this article [ 12 , 14 , 26 , 36 , 37 , 38 , 39 , 40 , 41 ]. The structures' potential hydrogen donor sites (C–H and O–H) were all taken into account and compared.…”

“…There are many types of fresh fruits and vegetables rich in vitamin C like citrus fruits, kiwifruit, strawberries, papaya, blackcurrant, tomato, broccoli, and carrot [ 14 ] and other natural antioxidant additives. On the other hand, numerous synthetic antioxidants are frequently used as additives including butylated hydroxytoluene (BHT) [ 15 , 16 ], tert -butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA) [ 12 ], santowhite (SW) [ 14 ], propyl gallate (PG), ethylenediaminetetraacetic acid (EDTA) ( Figure 1 ), Irganox 1010, Irganox 1035, and Irganox 1076 ( Figure 1 ).

Figure 1 2 D chemical structure of EDTA and various Irganox types which have the same base unit (highlighted in green frame) studied in the present work.

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Possible Side Effects of Polyphenols and Their Interactions with Medicines

“…Polyphenols, with their numerous functionall groups, double bonds, and aromatic rings, have an ideal structure to act as effective antioxidants [ 1 , 6 , 37 ]. First of all, polyphenols can scavenge already-formed free radicals, such as a hydroxyl radical ( • OH) or the superoxide anion radical (O 2 −• ), as well as quench reactive oxygens species such as hydrogen peroxide (H 2 O 2 ) or singlet oxygen ( 1 O 2 ) by donating a single electron (SET) or by hydrogen atom transfer (HAT) [ 38 , 39 , 40 , 41 , 42 ]. Thus, they might prevent the initiation and interruption of yet-to-be-initiated radical reactions, such as the peroxidation of lipids, the oxidation of proteins and sugars, and oxidative damage to nucleic acids [ 1 , 43 ].…”