Noreen Hafiza, Semmar Nabil, Farman Muhammad, McCullagh James S O
Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan.
Institut Supérieur des Sciences Biologiques Appliquées de Tunis, Tunisia.
Asian Pac J Trop Med. 2017 Aug;10(8):792-801. doi: 10.1016/j.apjtm.2017.07.024. Epub 2017 Aug 19.
To evaluate the total phenolic content and compare the antioxidant activity of various solvent extracts and fractions from the aerial parts of Coronopus didymus through various assays.
Total phenolic content was determined using the Folin-Ciocalteu assay and the in vitro antioxidant activity of a number of different extracts was investigated in a dose-dependent manner with three different methods: the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and ferric reducing antioxidant power (FRAP) assays. A flavone was isolated from the most active ethanolic extract with high antioxidant activity using size exclusion chromatography. IC values were calculated for the DPPH and ABTS methods. The FRAP activity was assessed in terms of μM Fe (II) equivalent.
The phenolic content was found to be highest in the ethanol extract (CDA Et; 47.8 mM GAE) and the lowest in the dichloromethane extract (CDA DCM; 3.13 mM GAE). The ethanol extract showed high radical scavenging activity towards DPPH and ABTS radicals with IC values of (7.80 × 10) and (4.32 × 10) μg/mL, respectively. The most active ethanol extract had a FRAP value of 1921.7 μM Fe (II) equivalent. The isolated flavone F10C (5,7,4'-trihydroxy-3'-methoxy flavone) was far more effective for scavenging free radicals in the DPPH and ABTS assays with IC of 43.8 and 0.08 μg/mL, than the standard trolox, with IC values of 97.5 and 21.1 μg/mL, respectively. In addition, the flavone F10C and the standard ascorbic acid had FRAP values of 1621.7 and 16 038.0 μM Fe (II) equivalents, respectively.
The total phenolic content of extracts in decreasing order is ethanol extract (CDA Et) > acetone extract (CDA ACE) > phenolic extract (CDA MW) > n-hexane extract (CDA nHX)> chloroform extract (CDA CHL) > dichloromethane extract (CDA DCM). The ordering of extracts in terms of antioxidant activity from highest to lowest is CDA Et > CDA MW > CDA DCM > CDA CHL > CDA ACE > CDA nHX in DPPH, ABTS and FRAP assays. A significant relationship is found between antioxidant potential and total phenolic content, suggesting that phenolic compounds are the major contributors to the antioxidant activity of C. didymus.
通过多种测定方法评估双二歧繁缕地上部分不同溶剂提取物及其馏分的总酚含量，并比较其抗氧化活性。
采用福林-酚试剂法测定总酚含量，并通过三种不同方法以剂量依赖方式研究多种不同提取物的体外抗氧化活性：2,2-二苯基-1-苦基肼（DPPH）法、2,2'-联氮-双-（3-乙基苯并噻唑啉-6-磺酸）二铵盐（ABTS）法和铁还原抗氧化能力（FRAP）法。使用尺寸排阻色谱从具有高抗氧化活性的最活跃乙醇提取物中分离出一种黄酮。计算DPPH法和ABTS法的半数抑制浓度（IC）值。FRAP活性以μM Fe（II）当量评估。
发现乙醇提取物（CDA Et；47.8 mM没食子酸当量）中的酚含量最高，二氯甲烷提取物（CDA DCM；3.13 mM没食子酸当量）中的酚含量最低。乙醇提取物对DPPH和ABTS自由基表现出高自由基清除活性，IC值分别为（7.80×10）和（4.32×10）μg/mL。最活跃的乙醇提取物的FRAP值为1921.7 μM Fe（II）当量。分离出的黄酮F10C（5,7,4'-三羟基-3'-甲氧基黄酮）在DPPH和ABTS测定中清除自由基的效果比标准曲克芦丁更有效，其IC值分别为43.8和0.08 μg/mL，而标准曲克芦丁的IC值分别为97.5和21.1 μg/mL。此外，黄酮F10C和标准抗坏血酸的FRAP值分别为1621.7和16038.0 μM Fe（II）当量。
提取物的总酚含量从高到低依次为乙醇提取物（CDA Et）＞丙酮提取物（CDA ACE）＞酚提取物（CDA MW）＞正己烷提取物（CDA nHX）＞氯仿提取物（CDA CHL）＞二氯甲烷提取物（CDA DCM）。在DPPH、ABTS和FRAP测定中，提取物抗氧化活性从高到低的顺序为CDA Et＞CDA MW＞CDA DCM＞CDA CHL＞CDA ACE＞CDA nHX。发现抗氧化潜力与总酚含量之间存在显著关系，表明酚类化合物是双二歧繁缕抗氧化活性的主要贡献者。
