New Aspects of the Antioxidant Activity of Glycyrrhizin Revealed by the CIDNP Technique

Quercetin loaded biogenic squalene nano-lipid carriers for the treatment of dry eye syndrome

In this study, quercetin-incorporated squalene nanostructured lipid carriers (QS-NLCs) were developed to mitigate the pathological conditions of dry eye disease (DED). The melt emulsification method was used to prepare QS-NLCs. The resulting NLCs have 93.74 ± 9.32 nm particle size, 43.8 ± 5.42 % drug loading and showed good stability for 90 days at different storage conditions. The structural characterization of NLCs was carried out through DSC, FTIR, and XRD, and the morphological study was conducted using TEM analysis. The morphological study emphasised no agglomeration was present in the formulation, and further -31.47 ± 2.18 mV zeta potential supported the TEM analysis. Also, the QS-NLCs showed a release pattern in which more than 70 % of the drug was released in the medium in 1 h. After that, a sustained release pattern was observed for 6 h. However, QS-NLCs also showed higher ex-vivo corneal permeation, i.e., ∼2.5-fold, as compared to free quercetin. Also, no significant difference was observed in the moisture retention capacity of NLCs when compared with control glycerin. Further, the QS-NLCs showed good anti-inflammatory and cytotoxicity activities against RAW 264.7 and HCECs cell lines, respectively. Furthermore, 18.22 ± 1.23 mm of Schirmer score in a 5-day tear production study and a 2.79-fold increased half-life (T1/2), 3.02-fold enhanced area under the curve (AUC0-∞), and 2.88-fold higher mean retention time (MRT0-∞) were obtained which signified the higher bioavailability of QS-NLCs with higher ocular tolerance ensured by modified Draize test. Most importantly, the proposed QS-NLCs improved the pharmacological activities of quercetin against DED.

Self-nanomicellizing solid dispersion: A promising platform for oral drug delivery

Amorphous solid dispersion (ASD) has been widely used to enhance the oral bioavailability of water-insoluble drugs for oral delivery because of its advantages of enhancing solubility and dissolution rate. However, the problems related to drug recrystallization after drug dissolution in media or body fluid have constrained its application. Recently, a self-nanomicellizing solid dispersion (SNMSD) has been developed by incorporating self-micellizing polymers as carriers to settle the problems, markedly improving the ability of supersaturation maintenance and enhancing the oral bioavailability of drug. Spontaneous formation and stability of the self-nanomicelle (SNM) have been proved to be the key to supersaturation maintenance of SNMSD system. This offers a novel research direction for maintaining supersaturation and enhancing the bioavailability of ASDs. To delve into the advantages of SNMSDs, we provide a concise review introducing the formation mechanism, characterization methods and stability of SNMs, emphasizing the advantages of SNMSDs for oral drug delivery facilitated by SNM formation, and discussing relevant research prospects.

Glycyrrhetinic acid interaction with solvated and free electrons studied by the CIDNP and dissociative electron attachment techniques

Electron transfer plays a crucial role in living systems, including the generation of reactive oxygen species (ROS). Oxygen acts as the terminal electron acceptor in the respiratory chains of aerobic organisms as well as in some photoinduced processes followed by the formation of ROS. This is why the participation of exogenous antioxidants in electron transfer processes in living systems is of particular interest. In the present study, using chemically induced dynamic nuclear polarization (CIDNP) and dissociative electron attachment (DEA) techniques, we have elucidated the affinity of solvated and free electrons to glycyrrhetinic acid (GA)-the aglicon of glycyrrhizin (the main active component of Licorice root). CIDNP is a powerful instrument to study the mechanisms of electron transfer reactions in solution, but the DEA technique shows its effectiveness in gas phase processes. For CIDNP experiments, the photoionization of the dianion of 5-sulfosalicylic acid (HSSA2-) was used as a model reaction of solvated electron generation. DEA experiments testify that GA molecules are even better electron acceptors than molecular oxygen, at least under gas-phase conditions. In addition, the effect of the solvent on the energetics of the reactants is discussed.

Biocompatible arabinogalactan-chitosan scaffolds for photothermal pharmacology in wound healing and tissue regeneration

Delayed wound healing is often caused by bacterial infections and persistent inflammation. Multifunctional materials with anti-bacterial, anti-inflammatory, and hemostatic properties are crucial for accelerated wound healing. In this study, we report a biomacromolecule-based scaffold (ArCh) by uniquely combining arabinogalactan (Ar) and chitosan (Ch) using a Schiff-based reaction. Further, the optimized ArCh scaffolds were loaded with Glycyrrhizin (GA: anti-inflammatory molecule) conjugated NIR light-absorbing Copper sulfide (CuS) nanoparticles. The resultant GACuS ArCh scaffolds were characterized for different wound healing parameters in in-vitro and in-vivo models. Our results indicated that GACuS ArCh scaffolds showed excellent swelling, biodegradation, and biocompatibility in vitro. Further results obtained indicated that GACuS ArCh scaffolds demonstrated mild hyperthermia and enhanced hemostatic, anti-oxidant, anti-bacterial, and wound-healing effects when exposed to NIR light. The scaffolds, upon further validation, may be beneficial in accelerating wound healing and tissue regeneration response.

Elementary processes triggered in curcumin molecule by gas-phase resonance electron attachment and by photoexcitation in solution

Electron-driven processes in isolated curcumin (CUR) molecules are studied by means of dissociative electron attachment (DEA) spectroscopy under gas-phase conditions. Elementary photostimulated reactions initiated in CUR molecules under UV irradiation are studied using the chemically induced dynamic nuclear polarization method in an acetonitrile solvent. Density functional theory is applied to elucidate the energetics of fragmentation of CUR by low-energy (0-15 eV) resonance electron attachment and to characterize various CUR radical forms. The adiabatic electron affinity of CUR molecule is experimentally estimated to be about 1 eV. An extra electron attachment to the π1* LUMO and π2* molecular orbitals is responsible for the most intense DEA signals observed at thermal electron energy. The most abundant long-lived (hundreds of micro- to milliseconds) molecular negative ions CUR- are detected not only at the thermal energy of incident electrons but also at 0.6 eV, which is due to the formation of the π3* and π4* temporary negative ion states predicted to lie around 1 eV. Proton-assisted electron transfer between CUR molecules is registered under UV irradiation. The formation of both radical-anions and radical-cations of CUR is found to be more favorable in its enol form. The present findings shed some light on the elementary processes triggered in CUR by electrons and photons and, therefore, can be useful to understand the molecular mechanisms responsible for a variety of biological effects produced by CUR.

The Endless World of Carotenoids-Structural, Chemical and Biological Aspects of Some Rare Carotenoids

Carotenoids are a large and diverse group of compounds that have been shown to have a wide range of potential health benefits. While some carotenoids have been extensively studied, many others have not received as much attention. Studying the physicochemical properties of carotenoids using electron paramagnetic resonance (EPR) and density functional theory (DFT) helped us understand their chemical structure and how they interact with other molecules in different environments. Ultimately, this can provide insights into their potential biological activity and how they might be used to promote health. In particular, some rare carotenoids, such as sioxanthin, siphonaxanthin and crocin, that are described here contain more functional groups than the conventional carotenoids, or have similar groups but with some situated outside of the rings, such as sapronaxanthin, myxol, deinoxanthin and sarcinaxanthin. By careful design or self-assembly, these rare carotenoids can form multiple H-bonds and coordination bonds in host molecules. The stability, oxidation potentials and antioxidant activity of the carotenoids can be improved in host molecules, and the photo-oxidation efficiency of the carotenoids can also be controlled. The photostability of the carotenoids can be increased if the carotenoids are embedded in a nonpolar environment when no bonds are formed. In addition, the application of nanosized supramolecular systems for carotenoid delivery can improve the stability and biological activity of rare carotenoids.

Silver Nanoparticles and Glycyrrhiza glabra (Licorice) Root Extract as Modifying Agents of Hydrogels Designed as Innovative Dressings

The interest in the application of plant extracts as modifiers of polymers intended for biomedical purposes is constantly increasing. The therapeutical properties of the licorice root, including its anti-inflammatory and antibacterial activity, make this plant particularly promising. The same applies to silver nanoparticles showing antibacterial properties. Thus the main purpose of the research was to design hydrogel dressings containing both licorice root extract and nanosilver so as to obtain a system promoting wound regeneration processes by preventing infection and inflammation within the wound. The first step included the preparation of the plant extract via the solid-liquid extraction using the Soxhlet extractor and the synthesis of silver nanoparticles by the chemical reduction of silver ions using a sodium borohydride as a reducing agent. Subsequently, hydrogels were synthesized via photopolymerization and subjected to studies aiming at characterizing their sorption properties, surface morphology via scanning electron microscopy, and their impact on simulated physiological liquids supported by defining these liquids' influence on hydrogels' structures by FT-IR spectroscopy. Next, the tensile strength of hydrogels and their percentage elongation were determined. Performed studies also allowed for determining the hydrogels' wettability and free surface energies. Finally, the cytotoxicity of hydrogels towards L929 murine fibroblasts via the MTT reduction assay was also verified. It was demonstrated that developed materials showed stability in simulated physiological liquids. Moreover, hydrogels were characterized by high elasticity (percentage elongation within the range of 24-29%), and their surfaces were hydrophilic (wetting angles below 90°). Hydrogels containing both licorice extract and nanosilver showed smooth and homogeneous surfaces. Importantly, cytotoxic properties towards L929 murine fibroblasts were excluded; thus, developed materials seem to have great potential for application as innovative dressings.