The antioxidant activity, in terms of radical scavenging capacity, of altogether 15 different lignans was measured by monitoring the scavenging of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). The effect of differences in skeletal arrangement or the degree of oxidation of the lignans was investigated in a structure-activity relationship study. A large variety in the radical scavenging capacities of the different lignans was observed and related to some structural features. Lignans with catechol (3,4-dihydroxyphenyl) moieties exhibited the highest radical scavenging capacity, while the corresponding guaiacyl (3-methoxy-4-hydroxyphenyl) lignans showed a slightly weaker scavenging capacity. In addition, the butanediol structure was found to enhance the activity, whereas a higher degree of oxidation at the benzylic positions decreased the activity. Additionally, the readily available lignans (-)-secoisolariciresinol, a mixture of hydroxymatairesinol epimers and (-)-matairesinol were studied in more detail, including kinetic measurements and identification of oxidation products in the reactions with DPPH and ABAP (2,2-azobis(2-methylpropionamidine) dihydrochloride. The identification of reaction products, by GC-MS, HPLC-MS and NMR spectroscopy, showed that dimerisation of the two aromatic moieties was the major radical termination reaction. Also, the formation of adducts was a predominant reaction in the experiments with ABAP. The kinetic data obtained from the reactions between the lignans and DPPH indicated a complex reaction mechanism.

Owing to their superior mechanical strength and structure similarity to the extracellular matrix, nanocelluloses as a class of emerging biomaterials have attracted great attention in three-dimensional (3D) bioprinting to fabricate various tissue mimics. Yet, when printing complex geometries, the desired ink performance in terms of shape fidelity and object resolution demands a wide catalogue of tunability on the material property. This paper describes surface engineered biomimetic inks based on cellulose nanofibrils (CNFs) and cross-linkable hemicellulose derivatives for UV-aided extrusion printing, being inspired by the biomimetic aspect of intrinsic affinity of heteropolysaccharides to cellulose in providing the ultrastrong but flexible plant cell wall structure. A facile aqueous-based approach was established for the synthesis of a series of UV cross-linkable galactoglucomannan methacrylates (GGMMAs) with tunable substitution degrees. The rapid gelation window of the formulated inks facilitates the utilization of these wood-based biopolymers as the feeding ink for extrusion-based 3D printing. Most importantly, a wide and tunable spectrum ranging from 2.5 to 22.5 kPa of different hydrogels with different mechanical properties could be achieved by varying the substitution degree in GGMMA and the compositional ratio between GGMMA and CNFs. Used as the seeding matrices in the cultures of human dermal fibroblasts and pancreatic tumor cells, the scaffolds printed with the CNF/GGMMA inks showed great cytocompatibility as well as supported the matrix adhesion and proliferative behaviors of the studied cell lines. As a new family of 3D printing feedstock materials, the CNF/GGMMA ink will broaden the map of bioinks, which potentially meets the requirements for a variety of in vitro cell–matrix and cell–cell interaction studies in the context of tissue engineering, cancer cell research, and high-throughput drug screening.

Heterogeneously catalyzed one‐pot reactions combining individual reaction steps into sequences enhance the efficiencies of overall chemical processes by reducing costs, time, and labor efforts. This minireview focuses on the production of chiral compounds by using dynamic kinetic resolution (DKR) and related sequential reactions, utilizing heterogeneous and immobilized metal catalysts and enzymes. Enzymes, especially lipases, often possess high chemical, stereo‐, and regiospecificities under mild reaction conditions. Supported transition‐metal catalysts are effective and widely used for various chemical transformations including racemization and hydrogenation reactions. This minireview discusses both the early and important applications, as well as modern state‐of‐the‐art processes, in which different catalyst combinations are utilized. Also catalyst compatibility issues, including catalyst inhibition and applicability are addressed with specific focus on the racemization catalysts applied in DKRs. Finally, some examples on the utilization of heterogeneous catalysts in flow reactors are presented.

Kinetic resolution and dynamic kinetic resolution, in particular, provide practical tools for synthesis of enantiomerically pure compounds. In the present work, the resolution of rac‐2‐hydroxy‐1‐indanone and racemization of (S)‐2‐hydroxy‐1‐indanone were investigated. Immobilized lipase AK (Pseudomonas fluorescens) was found as the best enzyme catalyst for kinetic resolution and ruthenium supported on Al2O3 as a potential heterogeneous catalyst for racemization of the starting material. By combining the two reactions, a simple dynamic kinetic resolution of rac‐2‐hydroxy‐1‐indanone producing (R)‐1‐oxo‐indan‐2‐yl butanoate was developed. Under optimal conditions, the product was obtained in 92 % ee at approximately 90 % conversion.

Polysaccharides are biorenewable and biodegradable starting materials for the development of functional materials. The synthesis of a monofunctional macroinitiator for single electron transfer-living radical polymerization was successfully developed from a wood polysaccharide-O-acetyl galactoglucomannan (GGM) using a beforehand synthesized amino-functional a-bromoisobutyryl derivative applying reductive amination. The GGM macroinitiator was employed to initiate a controlled radical polymerization of [2-(methacryloyloxy) ethyl]trimethylammonium chloride (MeDMA), methyl methacrylate (MMA), and N-isopropylacrylamide (NIPAM) using Cu 0 / Me 6 -Tren as a catalyst. The either charged or amphiphilic GGM-b-copolymers with different chain lengths of the synthetic block were successfully synthesized without prior hydro-V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 5100-5110