Laccase-Catalyzed Synthesis of Added-Value Polymers from Cork and Grape Extracts.

The development of products from natural plant sources, including agriculture and food wastes, contributes significantly to the circular economy and global sustainability. Cork and grape wastes were employed as the primary sources in this study to obtain compounds of interest under mild extraction conditions. Laccase was applied to oxidize the cork and grape extracts, with the aim of producing value-added molecules with improved properties. Ultraviolet-visible (UV-vis) spectroscopy was assessed to monitor the oxidation process, and characterization of the end products was performed by matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) spectroscopy. The antioxidant and antiaging properties were evaluated by means of ABTS, DPPH, FRAP, and SPF testing. Overall, as compared to their monomeric counterparts, the polymeric compounds displayed remarkable antioxidant and antiaging characteristics after laccase oxidation, showing tremendous potential for applications in the food, pharmaceutical, cosmetic, and textile industries.

Deep Eutectic Solvents as Suitable Solvents for Lipase-Catalyzed Transesterification Reactions.

In this work, three deep eutectic mixtures (DES 1: choline chloride/urea; DES 2: choline chloride/glycerol; and DES 3: tetrabutylammonium bromide/imidazole) were investigated as mediums for the synthesis of glucose laurate and glucose acetate. Aiming to achieve a greener and more sustainable approach, the synthesis reactions were catalyzed by lipases from Aspergillus oryzae (LAO), Candida rugosa (LCR), and porcine pancreas (LPP). The hydrolytic activity of lipases against p-nitrophenyl hexanoate revealed no evidence of enzyme inactivation when DES were used as medium. Regarding the transesterification reactions, combining LAO or LCR with DES 3 resulted in the efficient production of glucose laurate (from glucose and vinyl laurate) (conversion >60 %). The best result for LPP was observed in DES 2, with 98 % of product production after 24 hours of reaction. When replacing vinyl laurate by a smaller hydrophilic substrate, vinyl acetate, a distinct behavior was observed. LCR and LPP performed better in DES 1, yielding more than 80 % of glucose acetate after 48 hours of reaction. The catalytic activity of LAO was less pronounced, reaching only nearly 40 % of product in DES 3. The results highlight the potential of combining biocatalysis with greener and environmentally-safer solvents, for the synthesis of differentiated chain-length sugar fatty acid esters (SFAE).

Lipase-Catalysed Polymerization of Eutectic Mixtures.

Aiming to reduce the toxicity and operational costs often associated to chemical processes, the enzymatic synthesis is applied herein as a sustainable route for producing polyesters. The use of NADES' (Natural Deep Eutectic Solvents) components as a source of monomers for the synthesis of polymers through lipase-catalyzed esterification in an anhydrous medium is detailed for the first time. Three NADES composed by glycerol and an organic base, or acid, were used to produce polyesters, through polymerization reactions catalyzed by Aspergillus oryzae lipase. High polyester conversion rates (above 70 %), containing at least 20 monomeric units (glycerol:organic acid/base (1 : 1)), were observed by matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) analysis. The NADES monomers' capacity for polymerization, along with their non-toxicity, cheap cost, and simplicity of production, sets up these solvents as a greener and cleaner approach for the synthesis of high value-added products.

Chitosan Nano/Microformulations for Antimicrobial Protection of Leather with a Potential Impact in Tanning Industry.

Tanned leather can be attacked by microorganisms. To ensure resistance to bacteria on leather surfaces, protection solutions need to be developed, addressing both environmental issues and economic viability. In this work, chitosan nano/microparticles (CNP) and chitosan/silver nano/microstructures (CSNP), containing silver nanoparticles around 17 nm size, were incorporated into leather, obtained from the industrial process. Low loads of chitosan-based nano/microformulations, 0.1% mass ratio, resulted in total bacteria reduction (100%) after 2 h towards Gram-positive Staphylococcus aureus, both with CNP and CSNP coatings. Otherwise, comparable tests with the Gram-negative bacteria, Klebsiella pneumoniae, Escherichia coli, showed no significant improvement under the coating acidic conditions. The antimicrobial activity was evaluated by standard test methods: (1) inhibition halo and (2) dynamic contact conditions. The developed protection of leather either with CNP or CSNP is much higher than the one obtained with a simple chitosan solution.

(3S,4R)-3,4-Dihydroxy-N-alkyl-l-homoprolines: synthesis and computational mechanistic studies.

This is the first synthetic report of (3S,4R)-dihydroxy-N-alkyl-l-homoprolines described so far. 2,4-O-Benzylidene-d-erythrose was obtained from d-glucose with an improved yield, and then transformed into the title (3S,4R)-dihydroxy-N-alkyl-l-homoprolines, in a two-step strategy, with excellent overall yields. Hydrogenolysis of the benzyl group led to the NH congener. The synthesis of final products from 1,4-lactone intermediates was studied by computational means either under acidic or basic conditions. The theoretical mechanism studies fully explain the experimental results: (a) an equilibrium between l-homoprolines and their bicyclic counterparts is established in acids; (b) the equilibrium suffers a complete displacement towards the l-homoproline side in a basic medium.

Total Stereoselective Michael Addition of N- and S- Nucleophiles to a d-Erythrosyl 1,5-Lactone Derivative. Experimental and Theoretical Studies Devoted to the Synthesis of 2,6-Dideoxy-4-functionalized-d- ribono-hexono-1,4-lactone.

The synthesis of a 1,5-lactone 2,4- O-alkylidene-d-erythrose derivative was found to be a highly stereoselective template in Michael addition trough the reaction of a d-erythrosyl 1,5-lactone derivative with nitrogen and sulfur nucleophiles. The sulfur adducts formed are 1 (d-erythrose derivative):1 (nucleophile), and the nitrogen adducts are 1:2. Both were then treated under HCl to give 2,6-dideoxy-4-functionalized-d- ribono-hexono-1,4-lactone by a reaction cascade in high overall yield. Reaction's scale up even improves the yield. The theoretical and computational results clearly explain the origin of the stereoselectivity, and the energetic course of reactions starting with nitrogen and sulfide nucleophiles. Considering that the 1,4-lactones obtained in this work offer a new molecular scaffold for organic synthesis, these new results provide a solid theoretical platform that can be used to speed up synthesis of other derivatives in a stereo- and regioselective way.