π-π Conjugation Enhances Oligostilbene's Antioxidant Capacity: Evidence from α-Viniferin and Caraphenol A.
π-π Conjugation Enhances Oligostilbene's Antioxidant Capacity: Evidence from α-Viniferin and Caraphenol A.
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DOI：
10.3390/molecules23030694
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发表时间：
2018-03-19
期刊：
影响因子：
--
通讯作者：
Chen D
中科院分区：
文献类型：
--
作者：
Li X;Xie Y;Xie H;Yang J;Chen D
α-乙烯素和caraphenol A是两种低聚苯乙烯，唯一的区别是在π-π共轭位点上是否存在外环双键。本研究采用分光光度法、紫外可见光谱法和电喷雾电离四极杆飞行时间串联质谱法（UPLC-ESI-Q-TOF-MS /MS）对α-长春花素和caraphenol A的抗氧化能力及相关机制进行了比较研究。结果表明，在铜离子还原抗氧化能力测定、铁还原抗氧化能力测定、1,1-二苯基-2-苦味基-肼基自由基（DPPH•）清除和2-苯基-4,4,5,5-四甲基咪唑啉-1-氧基- 3-氧化物自由基清除试验中，carap酚A的IC50值均低于α- vinifin。紫外可见光谱分析发现，与Fe2+混合后，carap酚A在250 ~ 350 nm处出现了增强峰，而α- vinifin则没有类似的增强峰。UPLC-ESI-Q-TOF-MS /MS分析表明，α-乙烯醛与DPPH•混合后产生了自由基加合物形成（RAF）峰（m/z = 1070-1072）。我们得出的结论是，α- vinifin和caraphenol A的抗氧化作用可能涉及氧化还原介导的机制（特别是电子转移和H+转移）和非氧化还原介导的机制（包括Fe2+螯合或RAF）。carap酚A中外环双键的π-π共轭可以大大增强氧化还原介导的抗氧化机制，并部分促进Fe2+螯合机制。这使得carapheno A在总抗氧化水平上远优于α- vinifin。
α-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.
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