Tzima Katerina, Brunton Nigel P, Rai Dilip K
Department of Food BioSciences, Teagasc Food Research Centre Ashtown, Dublin, Ireland.
UCD Institute of Food and Health, University College Dublin, Dublin, Ireland.
J Food Biochem. 2020 Mar;44(3):e13148. doi: 10.1111/jfbc.13148. Epub 2020 Jan 21.
The impact of dechlorophyllization (n-hexane: water partitioning, activated charcoal bleaching, and ChloroFiltr® decolorization) on major polyphenols of two herbal by-products (rosemary and thyme) was assessed. The aim was to produce decolorized extracts for food preservation and improve the quantification of their main phenolics. Activated charcoal bleaching and ChloroFiltr® decolorization effectively removed the chlorophyll a and b, whereas traces were detected after n-hexane: water partitioning. Dechlorophyllized thyme extracts prepared using activated charcoal and ChloroFiltr® had the lowest relative antioxidant capacity index (RACI) values based on 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), ferric reducing antioxidant power (FRAP), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant assays. Conversely, rosemary extracts had positive RACI values following treatment with activated charcoal, whereas n-hexane led to a significant antioxidant loss. Chromatography-mass spectrometry analyses indicated that phenolic diterpenes (carnosol and carnosic acid), as well as rosmarinic acid were in general not significantly decreased (p ˃ .05) after activated charcoal treatment, while n-hexane maintained the flavonoids and phenolic acids with nonsignificant losses. PRACTICAL APPLICATIONS: Commercial exploitation of polyphenol-rich plant based extracts as natural antioxidant agents is impeded by their high chlorophyll content, which when incorporated in food products can result in products that do not meet the consumer expectations for appearance. This study has shown that the activated charcoal bleaching has potentials to remove chlorophyll and retain antioxidant polyphenols in particular diterpenes in fresh herb by-products. Moreover, the commonly used n-hexane was less effective in removing chlorophyll but retained the major flavonoids and phenolic acids. Thus, the choice of chlorophyll removal methods depend on retaining the class of antioxidant polyphenols abundant in the plant matrix.
评估了脱叶绿素处理（正己烷：水分配、活性炭漂白和ChloroFiltr®脱色）对两种草药副产品（迷迭香和百里香）中主要多酚的影响。目的是制备用于食品保鲜的脱色提取物，并改进其主要酚类物质的定量分析。活性炭漂白和ChloroFiltr®脱色有效地去除了叶绿素a和叶绿素b，而正己烷：水分配后仅检测到痕量。基于2,2-联氮-双-3-乙基苯并噻唑啉-6-磺酸（ABTS）、铁离子还原抗氧化能力（FRAP）和2,2-二苯基-1-苦基肼（DPPH）抗氧化试验，用活性炭和ChloroFiltr®制备的脱叶绿素百里香提取物的相对抗氧化能力指数（RACI）值最低。相反，迷迭香提取物经活性炭处理后RACI值为正，而正己烷处理导致抗氧化能力显著损失。色谱-质谱分析表明，酚类二萜（鼠尾草酸和鼠尾草酚酸）以及迷迭香酸在活性炭处理后总体上没有显著减少（p＞0.05），而正己烷处理使黄酮类化合物和酚酸损失不显著。实际应用：富含多酚的植物提取物作为天然抗氧化剂的商业开发受到其高叶绿素含量的阻碍，当将其添加到食品中时，可能导致产品外观不符合消费者期望。本研究表明，活性炭漂白有潜力去除叶绿素，并保留新鲜草药副产品中的抗氧化多酚，特别是二萜类化合物。此外，常用的正己烷在去除叶绿素方面效果较差，但保留了主要的黄酮类化合物和酚酸。因此，叶绿素去除方法的选择取决于保留植物基质中丰富的抗氧化多酚类别。
