π-π Conjugation Enhances Oligostilbene’s Antioxidant Capacity: Evidence from α-Viniferin and Caraphenol A
Abstractα-Viniferin and caraphenol A, the two oligostilbenes, have the sole difference of the presence or absence of an exocyclic double bond at the π-π conjugative site. In this study, the antioxidant capacity and relevant mechanisms for α-viniferin and caraphenol A were comparatively explored using spectrophotometry, UV-visible spectral analysis, and electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC–ESI–Q–TOF–MS/MS) analysis. The spectrophotometric results suggested that caraphenol A always gave lower IC50 values than α-viniferin in cupric ion-reducing antioxidant capacity assay, ferric-reducing antioxidant power assay, 1,1-diphenyl-2-picryl-hydrazl radical (DPPH•)-scavenging, and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical-scavenging assays. In UV-visible spectra analysis, caraphenol A was observed to show enhanced peaks at 250–350 nm when mixed with Fe2+, but α-viniferin exhibited no similar effects. UPLC–ESI–Q–TOF–MS/MS analysis revealed that α-viniferin mixed with DPPH• produced radical adduct formation (RAF) peak (m/z = 1070–1072). We conclude that the antioxidant action of α-viniferin and caraphenol A may involve both redox-mediated mechanisms (especially electron transfer and H+-transfer) and non-redox-mediated mechanisms (including Fe2+-chelating or RAF). The π-π conjugation of the exocyclic double bond in caraphenol A can greatly enhance the redox-mediated antioxidant mechanisms and partially promote the Fe2+-chelating mechanism. This makes caraphenol A far superior to α-viniferin in total antioxidant levels. View Full-Text
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Li, X.; Xie, Y.; Xie, H.; Yang, J.; Chen, D. π-π Conjugation Enhances Oligostilbene’s Antioxidant Capacity: Evidence from α-Viniferin and Caraphenol A. Molecules 2018, 23, 694.
Li X, Xie Y, Xie H, Yang J, Chen D. π-π Conjugation Enhances Oligostilbene’s Antioxidant Capacity: Evidence from α-Viniferin and Caraphenol A. Molecules. 2018; 23(3):694.Chicago/Turabian Style
Li, Xican; Xie, Yulu; Xie, Hong; Yang, Jian; Chen, Dongfeng. 2018. "π-π Conjugation Enhances Oligostilbene’s Antioxidant Capacity: Evidence from α-Viniferin and Caraphenol A." Molecules 23, no. 3: 694.
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