Departments of Chemistry, Chemical Engineering, and Materials Science and Engineering and the Laboratory for Synthetic-Biologic Interactions , Texas A&M University , College Station , Texas 77842-3012 , United States.
School of Chemistry , The University of Birmingham , Edgbaston , Birmingham , United Kingdom , B15 2TT.
Biomacromolecules. 2019 Jan 14;20(1):109-117. doi: 10.1021/acs.biomac.8b00771. Epub 2018 Sep 4.
Magnolol, a neolignan natural product with antioxidant properties, contains inherent, orthogonal, phenolic, and alkenyl reactive groups that were used in both direct thermoset synthesis, as well as the stepwise synthesis of a small library of monomers, followed by transformation into thermoset materials. Each monomer from the small library was prepared via a single step functionalization reaction of the phenolic groups of magnolol. Thermoset materials were realized through solvent-free, thiol-ene reactions, and the resulting cross-linked materials were each comprised of thioether and ester linkages, with one retaining the hydrophilic phenols from magnolol, another having the phenols protected as an acetonide, and two others incorporating the phenols into additional cross-linking sites via hydrolytically labile carbonates or stable ether linkages. With this diversity of chemical compositions and structures, the thermosets displayed a range of thermomechanical properties including glass transition temperatures, T, 29-52 °C, onset of thermal degradation, T, from about 290-360 °C, and ultimate strength up to 50 MPa. These tunable materials were studied in their degradation and biological properties with the aim of exploiting the antioxidant properties of the natural product. Hydrolytic degradation occurred under basic conditions (pH = 11) in all thermosets, but with kinetics that were dependent upon their chemical structures and mechanical properties: 20% mass loss was observed at 5, 7, 27, and 40 weeks for the thermosets produced from magnolol directly, acetonide-protected magnolol, bis(allyl carbonate)-functionalized magnolol, and bis(allyl ether)-functionalized magnolol, respectively. Isolated degradation products and model compounds displayed antioxidant properties similar to magnolol, as determined by both UV-vis and in vitro reactive oxygen species (ROS) assays. As these magnolol-based thermosets were found to also allow for extended cell culture, these materials may serve as promising degradable biomaterials.
厚朴酚是一种具有抗氧化性能的新木脂素天然产物，它含有内在的、正交的、酚类和烯丙基反应基团，可用于直接热固性合成，以及小单体库的逐步合成，然后转化为热固性材料。从小库中制备的每个单体都是通过厚朴酚酚基的单步功能化反应来制备的。热固性材料是通过无溶剂的硫醇-烯反应实现的，所得交联材料均由硫醚和酯键组成，其中一种保留了厚朴酚中的亲水性酚，另一种将酚保护为缩酮，还有两种通过水解不稳定的碳酸酯或稳定的醚键将酚引入额外的交联位点。由于这种化学组成和结构的多样性，热固性塑料表现出一系列热机械性能，包括玻璃化转变温度 Tg，29-52°C，热降解起始温度 Td，约 290-360°C，以及高达 50 MPa 的最终强度。这些可调节的材料在其降解和生物性能方面进行了研究，目的是利用天然产物的抗氧化性能。在所有热固性塑料中，在碱性条件（pH = 11）下都会发生水解降解，但降解动力学取决于它们的化学结构和机械性能：直接由厚朴酚、乙酰氧基保护的厚朴酚、双（烯丙基碳酸酯）-功能化的厚朴酚和双（烯丙基醚）-功能化的厚朴酚制成的热固性塑料分别在 5、7、27 和 40 周时观察到 20%的质量损失。分离的降解产物和模型化合物表现出与厚朴酚相似的抗氧化性能，这是通过 UV-vis 和体外活性氧（ROS）测定来确定的。由于这些基于厚朴酚的热固性塑料也允许进行延长的细胞培养，因此这些材料可能成为有前途的可降解生物材料。
