Solvent role in the lipase-catalysed esterification of cinnamic acid and derivatives. Optimisation of the biotransformation conditions

Cross-Linked Hyaluronan Derivatives in the Delivery of Phycocyanin

An easy and viable crosslinking technology, based on the "click-chemistry" reaction copper(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (click-crosslinking), was applied to graft copolymers of medium molecular weight (i.e., 270 kDa) hyaluronic acid (HA) grafted with ferulic acid (FA) residues bearing clickable propargyl groups, as well as caffeic acid derivatives bearing azido-terminated oligo(ethylene glycol) side chains. The obtained crosslinked materials were characterized from the point of view of their structure and aggregation liability to form hydrogels in a water environment. The most promising materials showed interesting loading capability regarding the antioxidant agent phycocyanin (PC). Two novel materials complexes (namely HA(270)-FA-TEGEC-CL-20/PC and HA(270)-FA-HEGEC-CL-20/PC) were obtained with a drug-to-material ratio of 1:2 (w/w). Zeta potential measurements of the new complexes (-1.23 mV for HA(270)-FA-TEGEC-CL-20/PC and -1.73 mV for HA(270)-FA-HEGEC-CL-20/PC) showed alterations compared to the zeta potential values of the materials on their own, suggesting the achievement of drug-material interactions. According to the in vitro dissolution studies carried out in different conditions, novel drug delivery systems (DDSs) were obtained with a variety of characteristics depending on the desired route of administration and, consequently, on the pH of the surrounding environment, thanks to the complexation of phycocyanin with these two new crosslinked materials. Both complexes showed excellent potential for providing a controlled/prolonged release of the active pharmaceutical ingredient (API). They also increased the amount of drug that reach the target location, enabling pH-dependent release. Importantly, as demonstrated by the DPPH free radical scavenging assay, the complexation process, involving freezing and freeze-drying, showed no adverse effects on the antioxidant activity of phycocyanin. This activity was preserved in the two novel materials and followed a concentration-dependent pattern similar to pure PC.

Do they make a good match? Molecular dynamics studies on CALB-catalyzed esterification of 3-phenylpropionic and cinnamic acids

Lipases are versatile catalysts widely used in industrial biotransformations and laboratory-scale developed reactions with industrial potential. Despite the fact that lipase B from Candida antarctica (CALB) is one of the most widely used lipolytic enzymes, its substrate specificity is still poorly understood. One observed trend is that reactions carried out with carboxylic acids containing a double bond are less efficient on average. Here, we have utilized a combination of in vitro and in silico techniques, to better understand the negative impact of a double bond on CALB-mediated esterification. Then through extensive molecular dynamics (MD) simulations, we were able to map the entry pathway of cinnamic acid and its derivative into the CALB active site, and their interactions with catalytic residues. We observed a 2 step binding mechanism of studied compounds, where they first penetrate the enzyme pocket in a conformation where their carboxylic groups are extended towards the solvent. This is followed by further penetration of the acid into the enzymatic active pocket, and a full rotation within the active site, which orients the acid in a conformation that allows further steps of the esterification reaction. As acids containing a double bond are more rigid, their mobility and thus ability to rotate in the narrow CALB active site is hampered, which provides a structural explanation for the decreased efficiency of such acids. Our data provide insight into the substrate specificity of CALB-mediated esterification, providing important structural guidelines to better understand and potentially improve the efficiency of such reactions.

Chemical Constituents of Thesium chinense Turcz and Their In Vitro Antioxidant, Anti-Inflammatory and Cytotoxic Activities

Three novel compounds (1–3) along with twenty-six known compounds, two known steroids (4–5) and twenty-four known phenylpropanoids (6–29) were isolated from the whole plant of Thesium chinense Turcz. The structures of the three new compounds were elucidated on the basis of ESI-MS, HR-ESIMS, 1D and 2D NMR, IR, UV spectroscopic data. The absolute stereochemistry of compound 1 was determined by the Gauge-Including Atomic Orbitals (GIAO) method. The in vitro antioxidant, anti-inflammatory and cytotoxic activities of the isolated compounds were evaluated by DPPH radical-scavenging assay, LPS-activated RAW 264.7 cells model and CCK-8 kit, respectively. Compound 11 showed high antioxidant activity with an SC50 value of 16.2 ± 1.6 μM. Compound 21 showed considerable anti-inflammatory activity with an IC50 value of 28.6 ± 3.0 μM. Compounds 4 and 5 displayed potent cytotoxic activity against human NCI-H292, SiHa, A549, and MKN45 cell lines, with the compound 4 having IC50 values of 17.4 ± 2.4, 22.2 ± 1.1, 9.7 ± 0.9, 9.5 ±0.7 μM, and the compound 5 having all IC50 values less than 0.1 μM in vitro.

Immobilization of Pseudomonas stutzeri lipase through Cross-linking Aggregates (CLEA) for reactions in Deep Eutectic Solvents

The use of deep eutectic solvents (DES) with buffer as cosolvent (up to 10 % v/v) leads to low-viscous media in which lipases can perform synthetic reactions, instead of hydrolysis. This paper explores the immobilization of Pseudomonas stutzeri lipase (TL) in cross-linking aggregates (CLEA) to deliver robust derivatives that are active in media like choline chloride - glycerol DES with buffer as cosolvent. While the free TL enzyme was markedly inactive in these media, TL-CLEA derivatives perform esterifications and can be reused several times. Overall, results are consistent with previous experiments reported for other lipases in these DES-water media and confirm that CLEA immobilization turns out a very useful and straightforward alternative for generating active (bio)catalysts for DES-aqueous media systems. Immobilized systems open the possibility of performing continuous processes in low-viscous DES-buffer media.