2. Academic Validation
  3. Antioxidant Mechanisms of Echinatin and Licochalcone A

Antioxidant Mechanisms of Echinatin and Licochalcone A

  • Molecules. 2018 Dec 20;24(1):3. doi: 10.3390/molecules24010003.
Minshi Liang 1 2,  Xican Li 3 4,  Xiaojian Ouyang 5 6,  Hong Xie 7 8,  Dongfeng Chen 9 10
Affiliations

Affiliations

  • 1 School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. lminshi@outlook.com.
  • 2 Innovative Research & Development Laboratory of TCM, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. lminshi@outlook.com.
  • 3 School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. lixc@gzucm.edu.cn.
  • 4 Innovative Research & Development Laboratory of TCM, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. lixc@gzucm.edu.cn.
  • 5 School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. oyxiaojian55@163.com.
  • 6 Innovative Research & Development Laboratory of TCM, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. oyxiaojian55@163.com.
  • 7 School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. xiehongxh1@163.com.
  • 8 Innovative Research & Development Laboratory of TCM, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. xiehongxh1@163.com.
  • 9 School of Basic Medical Science, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. chen888@gzucm.edu.cn.
  • 10 The Research Center of Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. chen888@gzucm.edu.cn.
PMID: 30577443 DOI: 10.3390/molecules24010003
Abstract

Echinatin and its 1,1-dimethyl-2-propenyl derivative licochalcone A are two Chalcones found in the Chinese herbal medicine Gancao. First, their antioxidant mechanisms were investigated using four sets of colorimetric measurements in this study. Three sets were performed in aqueous solution, namely Cu2+-reduction, Fe3+-reduction, and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO•)-scavenging measurements, while 1,1-diphenyl-2-picrylhydrazyl radical (DPPH•)-scavenging colorimetric measurements were conducted in methanol solution. The four sets of measurements showed that the radical-scavenging (or metal-reduction) percentages for both echinatin and licochalcone A increased dose-dependently. However, echinatin always gave higher IC50 values than licochalcone A. Further, each product of the reactions of the Chalcones with DPPH• was determined using electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS/MS). The UPLC-ESI-Q-TOF-MS/MS determination for echinatin yielded several echinatin⁻DPPH adduct peaks (m/z 662, 226, and 196) and dimeric echinatin peaks (m/z 538, 417, and 297). Similarly, that for licochalcone A yielded licochalcone A-DPPH adduct peaks (m/z 730, 226, and 196) and dimeric licochalcone A peaks (m/z 674 and 553). Finally, the above experimental data were analyzed using mass spectrometry data analysis techniques, resonance theory, and ionization constant calculations. It was concluded that, (i) in aqueous solution, both echinatin and licochalcone A may undergo an electron transfer (ET) and a proton transfer (PT) to cause the antioxidant action. In addition, (ii) in alcoholic solution, hydrogen atom transfer (HAT) antioxidant mechanisms may also occur for both. HAT may preferably occur at the 4-OH, rather than the 4'-OH. Accordingly, the oxygen at the 4-position participates in radical adduct formation (Raf). Lastly, (iii) the 1,1-dimethyl-2-propenyl substituent improves the antioxidant action in both aqueous and alcoholic solutions.

Keywords

1,1-dimethyl-2-propenyl; antioxidant; dimer; echinatin; licochalcone A; radical adduct formation; α,α-dimethyl-β-propenyl.

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