Vissers Anne M, Caligiani Augusta, Sforza Stefano, Vincken Jean-Paul, Gruppen Harry
Laboratory of Food Chemistry, Wageningen University and Research, Wageningen, The Netherlands.
Department of Food Science, University of Parma, Parma, Italy.
Phytochem Anal. 2017 Nov;28(6):487-495. doi: 10.1002/pca.2697. Epub 2017 Jun 13.
Phlorotannins are complex mixtures of phloroglucinol oligomers connected via C-C (fucols) or C-O-C (phlorethols) linkages. Their uniformity in subunits and large molecular weight hamper their structural analysis. Despite its commercial relevance for alginate extraction, phlorotannins in Laminaria digitata have not been studied.
To obtain quantitative and structural information on phlorotannins in a methanolic extract from L. digitata.
The combined use of C and H NMR spectroscopy allowed characterisation of linkage types and extract purity. The purity determined was used to calibrate the responses obtained with the colorimetric 2,4-dimethoxybenzaldehyde (DMBA) and Folin-Ciocalteu (FC) assays. Using NP-flash chromatography, phlorotannin fractions separated on oligomer size were obtained and enabled structural and molecular weight characterisation using ESI-MS and MALDI-TOF-MS.
The fucol-to-phlorethol linkage ratio was 1:26 and the extract was 60.1% pure, determined by NMR spectroscopy. For DMBA, the response of the extract was 12 times lower than that of phloroglucinol, whereas there was no difference for FC. By accounting for differences in response, the colorimetric assays were applicable for quantification using phloroglucinol as a standard. The phlorotannin content was around 4.5% DM. Fucol- and phlorethol-linkage types were annotated based on characteristic MS fragmentations. Structural isomers of phlorotannins up to a degree of polymerisation of 18 (DP18) were annotated and identification of several isomers hinted at branched phloroglucinol oligomers. With MALDI-TOF-MS phlorotannins up to DP27 were annotated.
By combining several analytical techniques, phlorotannins in L. digitata were quantified and characterised with respect to fucol-to-phlorethol linkage ratio, molecular weight (distribution), and occurrence of structural isomers. Copyright © 2017 John Wiley & Sons, Ltd.
间苯三酚单宁是通过C-C（岩藻醇）或C-O-C（间苯二酚）键连接的间苯三酚低聚物的复杂混合物。它们亚基的一致性和大分子量阻碍了其结构分析。尽管海带中的间苯三酚单宁在海藻酸盐提取方面具有商业相关性，但尚未对其进行研究。
获取海带甲醇提取物中间苯三酚单宁的定量和结构信息。
结合使用碳谱和氢谱核磁共振光谱法可表征连接类型和提取物纯度。所测定的纯度用于校准通过比色法2,4-二甲氧基苯甲醛（DMBA）和福林-酚（FC）测定获得的响应。使用正相快速色谱法，根据低聚物大小分离间苯三酚单宁级分，并使用电喷雾电离质谱（ESI-MS）和基质辅助激光解吸电离飞行时间质谱（MALDI-TOF-MS）对其进行结构和分子量表征。
通过核磁共振光谱法测定，岩藻醇与间苯二酚的连接比例为1:26，提取物纯度为60.1%。对于DMBA，提取物的响应比间苯三酚低12倍，而对于FC则没有差异。通过考虑响应差异，比色法可使用间苯三酚作为标准进行定量。间苯三酚单宁含量约为4.5%干物质。基于特征性的质谱裂解对岩藻醇和间苯二酚连接类型进行了注释。对聚合度高达18（DP18）的间苯三酚单宁的结构异构体进行了注释，对几种异构体的鉴定暗示了支链间苯三酚低聚物的存在。使用MALDI-TOF-MS对聚合度高达DP27的间苯三酚单宁进行了注释。
通过结合多种分析技术，对海带中的间苯三酚单宁进行了定量，并在岩藻醇与间苯二酚连接比例、分子量（分布）和结构异构体存在方面进行了表征。版权所有©2017约翰威立父子有限公司。
