Stable DOPG/Glycyrrhizin Vesicles with a Wide Range of Mixing Ratios: Structure and Stability as Seen by Scattering Experiments and Cryo-TEM

Glycyrrhiza glabra L. Saponins Modulate the Biophysical Properties of Bacterial Model Membranes and Affect Their Interactions with Tobramycin

The global challenge of antibiotic resistance necessitates innovative approaches to improving the efficacy of existing therapeutics while mitigating their environmental impact. This study investigates the role of saponins derived from Glycyrrhiza glabra root extract in modulating interactions of tobramycin, a broad-spectrum aminoglycoside antibiotic, with model bacterial membranes composed of phosphatidylglycerol. Using Langmuir monolayers and vesicle models, we demonstrated that GgC saponins disrupt lipid packing, increasing membrane fluidity and altering biophysical properties. The addition of saponins at concentrations between 1.25 and 10 mg/L reduces the compressibility modulus of the lipid monolayer, with a decrease ranging from 25 to over 50%. ζ potential and dynamic light scattering analyses indicated that GgC-tobramycin interactions modify the surface charge without causing membrane lysis. These membrane changes could potentially facilitate enhanced interactions of antibiotics with bacterial cells. Importantly, these findings suggest the potential of natural surfactants such as saponins to improve antibiotic efficacy, possibly enabling reduced antibiotic dosages. This study provides insights into using saponins alongside antibiotics as a sustainable approach to addressing antibiotic resistance.

Decomposition of mixed DMPC-aescin vesicles to bicelles is linked to the lipid's main phase transition: A direct evidence by using chain-deuterated lipid

This work investigates the conversion of bicelles into larger sheets or closed vesicles upon dilution and temperature increase for a system composed of the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and the saponin aescin. Due to its peculiar amphiphilic character, aescin is able to decompose DMPC bilayers into smaller, rim-stabilized bicelles. Aspects of the transition process are analyzed in an aescin content- and temperature-dependent manner by photon correlation spectroscopy (PCS), turbidimetry and small-angle neutron scattering (SANS). Both the conversion of bicelles into vesicles induced by temperature increase and the decomposition process upon cooling are presumably related to the main phase transition temperature Tm of DMPC. Therefore, not only conventional DMPC, but also chain-deuterated d54-DMPC was used due to its significantly lower Tm-value compared to the conventional DMPC. It will be demonstrated that the reconversion of vesicle structures (present at low aescin content) into bicelles shows a strong hysteresis effect whereas this is not observed for the reconversion at high aescin amounts, at which for high temperature still bicelle structures are present. The results indicate formation of a trapped state, correlated with the lipid's Tm and the decomposition of vesicles into bicelles is only possible if the lipid membrane entirely adopts the rigid phase state.

Small-Angle Neutron Scattering for Studying Lipid Bilayer Membranes

Small-angle neutron scattering (SANS) is a powerful tool for studying biological membranes and model lipid bilayer membranes. The length scales probed by SANS, being from 1 nm to over 100 nm, are well-matched to the relevant length scales of the bilayer, particularly when it is in the form of a vesicle. However, it is the ability of SANS to differentiate between isotopes of hydrogen as well as the availability of deuterium labeled lipids that truly enable SANS to reveal details of membranes that are not accessible with the use of other techniques, such as small-angle X-ray scattering. In this work, an overview of the use of SANS for studying unilamellar lipid bilayer vesicles is presented. The technique is briefly presented, and the power of selective deuteration and contrast variation methods is discussed. Approaches to modeling SANS data from unilamellar lipid bilayer vesicles are presented. Finally, recent examples are discussed. While the emphasis is on studies of unilamellar vesicles, examples of the use of SANS to study intact cells are also presented.

Liposomal Formulations Loaded with a Eugenol Derivative for Application as Insecticides: Encapsulation Studies and In Silico Identification of Protein Targets

A recently synthesized new eugenol derivative, ethyl 4-(2-methoxy-4-(oxiran-2-ylmethyl)phenoxy)butanoate, with a high insecticidal activity against Sf9 (Spodoptera frugiperda) insect cells, was encapsulated in the liposomal formulations of egg-phosphatidylcholine/cholesterol (Egg-PC:Ch) 70:30 and 100% dioleoylphosphatidylglycerol (DOPG), aiming at the future application as insecticides. Compound-loaded DOPG liposomes have sizes of 274 ± 12 nm, while Egg-PC:Ch liposomes exhibit smaller hydrodynamic diameters (69.5 ± 7 nm), high encapsulation efficiency (88.8 ± 2.7%), higher stability, and a more efficient compound release, thus, they were chosen for assays in Sf9 insect cells. The compound elicited a loss of cell viability up to 80% after 72 h of incubation. Relevantly, nanoencapsulation maintained the toxicity of the compound toward insect cells while lowering the toxicity toward human cells, thus showing the selectivity of the system. Structure-based inverted virtual screening was used to predict the most likely targets and molecular dynamics simulations and free energy calculations were used to demonstrate that this molecule can form a stable complex with insect odorant binding proteins and/or acetylcholinesterase. The results are promising for the future application of compound-loaded nanoliposome formulations as crop insecticides.

Recent advances in glycyrrhizin metabolism, health benefits, clinical effects and drug delivery systems for efficacy improvement; a comprehensive review

BACKGROUND

Glycyrrhizin (GL) is a major active constituent of licorice root (Glycyrrhiza glabra) that is considered one of the oldest and most frequently employed botanicals in Chinese medicine and worldwide, with most effects attributed to its rich GL content. Structurally, GL a triterpene saponin that is widely used as a flavoring agent in foodstuffs and cosmetics, and also proposed for various clinical applications with a myriad of health benefits. Pharmacological and biological activities of GL include antiviral, anti-inflammatory, antioxidant, and anticancer activities (in vitro and in vivo). Currently, there is no comprehensive review on GL biological effects and its action mechanisms.

PURPOSE

This review summarizes GL pharmacological actions from a molecular biology perception, presented on its metabolism and side effects based on in vitro, in vitro and clinical studies. Moreover, the potential of GL as a nanomedicine delivery system is also summarized. The progress in drug delivery research using GL presented herein is expected to provide a theoretical basis for developing other novel drugs formulations.

METHODS

A systematic review was carried out in several electronic databases (Science Direct, SpringerLink, CNKI, PubMed, Web of Science, Elsevier, and Scopus), using the following key words: glycyrrhizin "AND" bioactivity "OR" clinic "OR" therapeutic "OR" drug delivery. This search included manuscripts published between 1989 and 2021.

RESULTS

126 researches were selected and summarized in this review. The analysis of these studies indicated that GL has antiviral activity against different viruses. Further, GL efficiently suppressed the respiratory manifestations associated with COVID-19 by reducing the expression of angiotensin converting enzyme 2 (ACE2) that employed by the virus as an entry point. Otherwise, GL was found to induce antioxidant, anti-inflammatory, immune-modulatory, and anticancer activity. Besides, diminution the particle size of GL to nanometer size significantly augments their action and biodistribution.

CONCLUSION

This article summarizes the pharmacological actions of GL. The potential of GL as a nanomedicine delivery system is also presented. Nevertheless, most studies reported provide no deep insight of GL health effects warranting for more future studies to elucidate its action mechanism and potential therapeutic benefits through preclinical and clinical trials.