LAQV/REQUIMTE, Department of Chemistry and Biochemistry, Faculty of Sciences, Universidade do Porto, Rua do Campo Alegre, s/n, 4169-007, Porto, Portugal.
LAQV/REQUIMTE, Department of Conservation and Restoration, Nova School of Science and Technology, 2829-516, Monte da Caparica, Portugal.
Sci Rep. 2021 Apr 23;11(1):8811. doi: 10.1038/s41598-021-87969-3.
Iron-gall ink is one of the most important inks in the history of western civilization. The deep black colour results from Fe complexes with phenolic compounds available in gall extracts. Unfortunately, it induces the degradation of both ink and support over time. Furthermore, our knowledge of these complex molecular structures is limited. This work aims to overcome this gap, revealing essential information about the complex structures of these pigments and dyes that will create a breakthrough in the next generation of conservation treatments. It presents the first in-depth phenolic identification and quantification of extracts and inks, prepared with and without gum arabic (an essential additive in medieval recipes). Five representative Iberian recipes were selected and prepared. Their phenolic profile was analysed by HPLC-DAD and HPLC-ESI-MS, which revealed that the phenolic compounds present in higher concentration, in the gall extracts, are pentagalloylglucose and hexagalloylglucose (0.15 ± 0.01-32 ± 3 mg/mL), except for one recipe, in which gallic acid is the main phenolic. The influence of the ingredients is also discussed by deconstructing the recipes: extracts of additives as pomegranate peel and solvents used in the extraction of the galls (vinegar and white wine) were characterized.
铁胆墨水是西方文明史上最重要的墨水之一。其深黑色是由酚类化合物与铁形成的配合物所致，而这些酚类化合物在胆液提取物中含量丰富。不幸的是，这种墨水随着时间的推移会导致墨水和载体的降解。此外，我们对这些复杂分子结构的了解也很有限。本研究旨在弥补这一空白，揭示这些颜料和染料的复杂结构的基本信息，这将为下一代保护处理技术带来突破。该研究首次对用阿拉伯树胶（中世纪配方中的一种重要添加剂）和不用阿拉伯树胶制备的提取物和墨水进行了深入的酚类鉴定和定量分析。选择了五个具有代表性的伊比利亚食谱进行制备，并通过 HPLC-DAD 和 HPLC-ESI-MS 对其酚类成分进行了分析，结果表明，在胆液提取物中，浓度较高的酚类化合物为五没食子酰葡萄糖和六没食子酰葡萄糖（0.15±0.01-32±3mg/mL），但有一种配方中的主要酚类化合物是没食子酸。通过对配方进行解构，还讨论了成分的影响：对添加剂（如石榴皮）和用于提取胆液的溶剂（醋和白葡萄酒）的提取物进行了表征。
