Yang Lingguang, Yin Peipei, Ho Chi-Tang, Yu Miao, Sun Liwei, Liu Yujun
National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Biotechnology, Beijing Forestry University, Haidian District, Beijing, People's Republic of China.
Department of Food Science, Rutgers University, New Brunswick, NJ, USA.
R Soc Open Sci. 2018 Jun 27;5(6):180364. doi: 10.1098/rsos.180364. eCollection 2018 Jun.
This study aimed to investigate effects of thermal treatments on major phenolics and their antioxidant contributions in leaves and flowers (ATL and ATF, respectively). With ultra performance liquid chromatography-diode array detector-quadrupole time-of-flight-mass spectrometer/mass spectrometer, phenolic compositions of ATF were first characterized and compared with those of ATL. An optimized high performance liquid chromatography fingerprint was then established, and 10 major phenolics existing in both ATL and ATF were quantified. Gallic acid derivatives and flavonol-3--glycosides were found to be their dominant phenolic constituents, with the former being key constituents which was affected by thermal treatments and further influencing the variations of total phenols. Moreover, the mechanism underlining the changes of phenolics in ATL and ATF by the treatments was characterized as a thermolhydrolysis process. During thermal treatments, polymerized gallotannins were hydrolysed to 1,2,3,4,6-pentakis--galloyl-β-d-glucose, ethyl gallate and gallic acid, resulting in more than fivefold and twofold increase of their contents in ATL and ATF, respectively. By contrast, contents and antioxidant contributions of flavonol-3--glycosides gradually decreased during the process.\absbreak Overall, this is, to our knowledge, the first report on the effects of thermal treatments on phenolics and their antioxidant contributions in ATL and ATF, and the three gallic acid derivatives with potentially higher bioactivity could be efficiently achieved by thermal treatments.
本研究旨在探究热处理对叶片和花朵（分别为ATL和ATF）中主要酚类物质及其抗氧化作用的影响。利用超高效液相色谱-二极管阵列检测器-四极杆飞行时间质谱仪/质谱仪，首次对ATF的酚类成分进行了表征，并与ATL的酚类成分进行了比较。随后建立了优化的高效液相色谱指纹图谱，并对ATL和ATF中均存在的10种主要酚类物质进行了定量分析。发现没食子酸衍生物和黄酮醇-3-O-糖苷是它们的主要酚类成分，前者是受热处理影响的关键成分，并进一步影响总酚的变化。此外，热处理导致ATL和ATF中酚类物质变化的机制被表征为热水解过程。在热处理过程中，聚合的五倍子单宁水解为1,2,3,4,6-五-O-没食子酰基-β-D-葡萄糖、没食子酸乙酯和没食子酸，导致它们在ATL和ATF中的含量分别增加了五倍多和两倍多。相比之下，黄酮醇-3-O-糖苷的含量及其抗氧化作用在此过程中逐渐降低。总体而言，据我们所知，这是关于热处理对ATL和ATF中酚类物质及其抗氧化作用影响的首次报道，并且通过热处理可以有效地获得三种具有潜在更高生物活性的没食子酸衍生物。
