Probing the Antioxidant Activity of Embelin Related Compounds using DPPH and RRDE
Emmanuel Garcia-Villar ’20, Navar Mercer White ’19, and Professor Sarjit Kaur
Natural antioxidants have received considerable interest in the past decade because various studies have shown their potential to combat the deleterious effects of oxidative radicals in the body. One possible candidate is embelin, a naturally occurring antioxidant from embelia ribes, that has been reported to have anti-tumor, anti-inflammatory and anti-diabetic medicinal effects. In this study, the structure-property relationship of embelin and related compounds was studied to probe the role the enol proton, alkyl group and number of hydroxy groups on antioxidant activity. The antioxidant activities of these compounds were studied by Rotating Ring-Disk Voltammetry (RRDE) and 2,2-diphenyl-1-picrylhydrazyl (DDPH) assays. The reproducibility of DPPH can be a factor, and butylated hydroxytoluene (BHT) was included as a reference. BHT is a well-studied and common synthetic antioxidant that is used to prevent oxidations in foods (oils, for example). DPPH studies showed the following increasing trend in antioxidant activity: 2-methoxy-1,4-napthoquinone < 2-hydroxy-1,4-napthoquinone < BHT < embelin < chloroanilic acid. Preliminary evaluation of RRDE and DPPH studies suggests that the enol proton plays an integral role in antioxidant activity. The varying degree of interaction of embelin-related compounds with superoxide generated electrochemically (RRDE in oxygen saturated DMSO) will be presented for the following compounds: BHT, 4-chlorophenol, 2-hydroxy-1,4-napthoquinone, 2-methoxy-1,4-napthoquinone, embelin, chloroanilic acid, 2,5-dihydroxy-1,4-benzoquinone, and 2,5-dimethoxy-1,4-benzoquinone.