Ginger (Zingiber officinale) and Zingerone Antioxidant Properties Studied Using Hydrodynamic Voltammetry, Zingerone Crystal Structure and Density Functional Theory (DFT)—Results Support Zingerone Experimental Catalytic Behavior Similar to Superoxide

Ginger is a common spice found in many cuisines all over the world that is from the rhizome of <i>Zingiber officinale</i>. Additionally, it has been used in traditional medicinal practices as an aid in many ailments ranging from nausea to muscle pain. The non-volatile compounds of ginger, including zingerone, are responsible for pungency and they have widespread biomedical activities. The crystal structure of zingerone, a 6-gingerol degradation product and phenolic compound, reveals that the C4 hydroxyl group is the fulcrum for strong intermolecular interactions such as (O1-H2…O3) 2.737(2) Å. Our electrochemical results using rotating ring-disk electrode (RRDE) hydrodynamic voltammetry demonstrate that zingerone is an effective scavenger of superoxide radical anions and that zingerone, unlike powdered ginger, is a strong antioxidant with a collection efficiency slope of -6.5 × 10⁴ M^-1. The addition of vitamin C enhances scavenging activity for both zingerone and ginger powder, although the effect is more noticeable with zingerone. Correspondingly, the zingerone/vitamin C efficiency slope value is -5.40 × 10⁵ M^-1. Density Functional Theory (DFT) calculations permit the development of a plausible antioxidant mechanism for zingerone, and zingerone synergistic action with vitamin C, in which zingerone is capable of being regenerated with the assistance of protons that may be provided by ascorbic acid. This mechanism demonstrates that zingerone acts as a strong antioxidant agent by virtue of its C4 hydroxyl group and aromatic system. The scavenging chemical reaction is the same as that obtained through the dismutation of superoxide by superoxide dismutase (SOD) enzymes into hydrogen peroxide and molecular oxygen. Thus, zingerone behaves as a SOD mimic.