FOOD SCIENCE ›› 2018, Vol. 39 ›› Issue (16): 90-97.doi: 10.7506/spkx1002-6630-201816014

• Food Chemistry • Previous Articles     Next Articles

Characterization, Antioxidant Activity and Thermostabiltiy of Hydroxytyrosol Polymerization Products Catalyzed by Laccase

XIE Pujun1,2, HUANG Lixin1,2,*, ZHANG Caihong1,2, DING Shasha1, DENG Yejun1, WANG Xiaojie1   

  1. (1. Institute of Chemical Industry of Forest Products, National Engineering Laboratory for Biomass Chemical Utilization, Key and Open Laboratory on Forest Chemical Engineering, National Forestry Administration, Jiangsu Key Laboratory of Biomass Energy and Material, Chinese Academy of Forestry, Nanjing 210042, China; 2. Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing Forestry University, Nanjing 210037, China)
  • Online:2018-08-25 Published:2018-08-17

Abstract: The oxidative polymerization of hydroxytyrosol was catalyzed by laccase. The resultant products were characterized by UV-Vis spectroscopy, FTIR spectroscopy, gel permeation chromatography (GPC) and high performance liquid chromatography-mass spectrometry (HPLC-MS). The results showed that the products were polydisperse (D = 2.1), and mainly consisted of trimer, tetramer and hexamer. Meanwhile, the antioxidant activity and thermal stability of the polymers were assessed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay and thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) with VC and dibutyl hydroxy toluene (BHT) as positive control. The results indicated that the antioxidant activity of hydroxytyrosol polymers was 2.28 and 5.7 times as strong as HT and BHT, respectively and was similar to VC (72% as strong). On the basis of DTG peak temperature (315.1 ℃) and residual percentage (66.09%), the polymers had better thermal stability than VC (228.1 ℃), BHT (236.2 ℃) and HT (314.9 ℃). 3D-FTIR spectra indicated that HT polymers together with the other tested compounds began with O–H bond breaking, forming a quinoid structure by dehydrogenation or carbon-carbon double bond by dehydration. All these findings will provide a good theoretical and practical foundation for deep hydroxytyrosol utilization.

Key words: hydroxytyrosol, laccase, polymer, gel permeation chromatography (GPC), radical scavenging, thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR)

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