Spectroscopic analysis on structure-affinity relationship in the interactions of different oleanane-type triterpenoids with bovine serum albumin

Mechanistic insights into monomer level prevention of amyloid aggregation of lysozyme by glycyrrhizic acid

As the primary bioactive compound of glycyrrhiza rhizome, the triterpene glycoside conjugate Glycyrrhizic acid (GA) has demonstrated neuroprotective effects in vivo. This study evaluates the effectiveness of GA as an inhibitor of GuHCl-induced amyloid aggregation of hen egg white lysozyme (HEWL). Fibril formation as measured by Thioflavin-T fluorescence, 90⁰ light scattering, and 8-Anilinonaphthalene-1-sulfonic acid (ANS) fluorescence illustrated ∼90 % prevention of fibrils at [GA]/[HEWL] ≥2:1. Images of Transmission electron microscopy evidence for the absence of any fibril or amorphous aggregation products. The spectral characteristics of soluble HEWL were in close resemblance to unfolded monomer. Computational and fluorescence investigations performed to analyse GA-HEWL interactions demonstrated slightly higher affinity of GA to unfolded HEWL and aggregation-prone regions. The likely mechanism of monomer level aggregation prevention by GA as dermined by computational, stability, and ANS experiments illustrated that GA modulated the compactness, solvent-accessible surface, and solvent-exposed hydrophobic surfaces of aggregation-prone state of HEWL. Our findings corroborate GA as an effective inhibitor of HEWL amyloid formation. To our knowledge, GA interaction-induced inhibition of aggregation-prone states has not been previously discussed. GA's modulation of aggregation-prone states of disease-related proteins will successfully develop GA as an amyloid inhibitor for clinical trials of amyloidosis and neurodegenerative illnesses.

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.

A mutispectroscopic study on the structure-affinity relationship of the interactions of bisphenol analogues with bovine serum albumin

Bisphenol A (BPA) is a recognized endocrine-disrupting chemical (EDC), and its analogues also exert negative effects on health. The structure-affinity relationship between the structures of nine bisphenol (BP) analogues and the conformational changes of bovine serum albumin (BSA) was studied by various characterization methods and molecular docking. BPs including BPA and its analogues, bisphenol B (BPB), bisphenol C (BPC), bisphenol AP (BPAP), bisphenol M (BPM), bisphenol P (BPP), bisphenol Z (BPZ), diethylstilbestrol (DES) and dienestrol (DS) interacted with BSA. At the concentration of 3.85 × 10^-5 mol l^-1, DS was found to lead to 64% quenching, while BPAP, BPM and DES quenched 60%, 59% and 55% of BSA fluorescence, respectively. The values of ΔH (-19.31-135.42 kJ mol^-1) and ΔS (12.52-495.63 J mol^-1 K^-1) indicated that hydrophobic interactions and hydrogen bonds played important roles in the binding process. The binding constants of DS (8.87 × 10⁴ l mol^-1), DES (3.05 × 10⁴ l mol^-1), BPAP (1.52 × 10⁴ l mol^-1), BPC (1.16 × 10⁴ l mol^-1) and BPM (1.10 × 10⁴ l mol^-1) to BSA were greater than that of BPA (1.18 × 10³ l mol^-1) to BSA, indicating that they may exert more negative effects than BPA. The molecular structure differences of these BPs partly affected their ability to bind to BSA. The binding constants of BPB/BPP to BSA were smaller due to the steric hindrance of ethyl and benzene ring. BPs with conjugated double bond structures (DS and DES) and benzene ring structures (BPM, BPP, BPAP) had a greater influence on the conformation of BSA.

In silico and experimental studies of bovine serum albumin-encapsulated carbenoxolone nanoparticles with reduced cytotoxicity

Carbenoxolone (CBX) is a semi-synthetic plant derivative with pleiotropic pharmacological properties like anti-microbial and anti-inflammatory activities. Though approved for treatment of gastric ulcers, its use is limited due to adverse effects such as cytotoxicity. Bovine serum albumin (BSA) is a natural, non-toxic protein with high water-solubility and low immunogenicity, and is widely used as a nanocarrier for targeted drug delivery. In the present study, controlled release BSA-CBX nanoparticles (NPs) were synthesized by desolvation method to reduce drug cytotoxicity. These NPs showed desirable physicochemical properties such as particle size (∼240 nm), polydispersity index (0.08), zeta potential (-7.12 mV), drug encapsulation efficiency (72 %), and were stable for at least 3 months at room temperature. The drug was released from the BSA-CBX NPs in a biphasic manner in vitro following non-fickian diffusion. Computational analysis determined that the binding between BSA and CBX occurred through van der Waals forces, hydrophobic interactions, and hydrogen bonds with 93 % steric stability. Further, the cytotoxic assays demonstrated ∼1.8-4.9-fold reduction in cytotoxicity using three human cell lines (A549, MCF-7, and U-87). Subsequently, this novel CBX formulation with BSA as an efficient carrier can potentially be used for diverse biomedical applications.

Screening and analysis of xanthine oxidase inhibitors in jute leaves and their protective effects against hydrogen peroxide-induced oxidative stress in cells

Jute (Corchorus capsularis L.) is an annual herb of the bast fiber plant and has great potentials in food and medicinal usages because of its various bioactivities. In this study, ultrafiltration coupled with high-performance liquid chromatography-mass spectrometry was established for screening xanthine oxidase inhibitors from the jute leaves extract. Under the optimum screening conditions, three inhibitors were successfully screened and identified as chlorogenic acid, echinacoside, and isorhamnetin-rutinoside with UV and MS data. The fluorescent quenching analysis showed that three inhibitors quenched the fluorescence intensities of enzyme with different binding capacities. For further exploring the bioactivity of three inhibitors, the protective effects on hydrogen peroxide-induced oxidative stress was investigated using human normal liver cell (LO2), human gastric mucosal epithelial cell (GES-1), and human umbilical vein endothelial cell (HUVEC). As a result, they exhibited protective effects on three injured cells in dose-dependent manners without cytotoxicity. To evaluate the difference among different jute species obtained in our laboratories, the amounts of three compounds in ten samples were assessed and analyzed. The results showed that it could be divided into three groups. The jute leaves showed nutrient and medical potentials and deserved further research on pharmaceutical and biochemical utilization in future.

A drug library screen identifies Carbenoxolone as novel FOXO inhibitor that overcomes FOXO3-mediated chemoprotection in high-stage neuroblastoma

The transcription factor FOXO3 has been associated in different tumor entities with hallmarks of cancer, including metastasis, tumor angiogenesis, maintenance of tumor-initiating stem cells, and drug resistance. In neuroblastoma (NB), we recently demonstrated that nuclear FOXO3 promotes tumor angiogenesis in vivo and chemoresistance in vitro. Hence, inhibiting the transcriptional activity of FOXO3 is a promising therapeutic strategy. However, as no FOXO3 inhibitor is clinically available to date, we used a medium-throughput fluorescence polarization assay (FPA) screening in a drug-repositioning approach to identify compounds that bind to the FOXO3-DNA-binding-domain (DBD). Carbenoxolone (CBX), a glycyrrhetinic acid derivative, was identified as a potential FOXO3-inhibitory compound that binds to the FOXO3-DBD with a binding affinity of 19 µM. Specific interaction of CBX with the FOXO3-DBD was validated by fluorescence-based electrophoretic mobility shift assay (FAM-EMSA). CBX inhibits the transcriptional activity of FOXO3 target genes, as determined by chromatin immunoprecipitation (ChIP), DEPP-, and BIM promoter reporter assays, and real-time RT-PCR analyses. In high-stage NB cells with functional TP53, FOXO3 triggers the expression of SESN3, which increases chemoprotection and cell survival. Importantly, FOXO3 inhibition by CBX treatment at pharmacologically relevant concentrations efficiently repressed FOXO3-mediated SESN3 expression and clonogenic survival and sensitized high-stage NB cells to chemotherapy in a 2D and 3D culture model. Thus, CBX might be a promising novel candidate for the treatment of therapy-resistant high-stage NB and other "FOXO-resistant" cancers.

Influence of Human Serum Albumin Glycation on the Binding Affinities for Natural Flavonoids

Increasing the degree of glycation in diabetes could affect the ability of plasma proteins in binding to small molecules and active compounds. In this study, the influence of glycation of Human serum albumin (HSA) on the binding affinities for six dietary flavonoids was investigated by fluorescence spectra. Glycated HSA was prepared through incubation with glucose and characterized by several methods to confirm the glycation. It was found that the level of glycation increased with the increasing incubation time. The glycation of HSA increased the binding affinities for flavonoids by 1.40 to 48.42 times, which indicates that modifications caused by the glycation may have different influences on the interactions of flavonoids with HSA at separate binding sites on this protein. These results are valuable for understanding the influence of diabetes on the metabolism of flavonoids and other bioactive small molecules in human body.

Explication of bovine serum albumin binding with naphthyl hydroxamic acids using a multispectroscopic and molecular docking approach along with its antioxidant activity

In the present investigation, the protein-binding properties of naphthyl-based hydroxamic acids (HAs), N-1-naphthyllaurohydroxamic acid (1) and N-1-naphthyl-p-methylbenzohydroxamic acid (2) were studied using bovine serum albumin (BSA) and UV-visible spectroscopy, fluorescence spectroscopy, diffuse reflectance spectroscopy-Fourier transform infrared (DRS-FTIR), circular dichroism (CD), and cyclic voltammetry along with computational approaches, i.e. molecular docking. Alteration in the antioxidant activities of compound 1 and compound 2 during interaction with BSA was also studied. From the fluorescence studies, thermodynamic parameters such as Gibb's free energy (ΔG), entropy change (ΔS) and enthalpy change (ΔH) were calculated at five different temperatures (viz., 298, 303, 308, 313 or 318 K) for the HAs-BSA interaction. The results suggested that the binding process was enthalpy driven with dominating hydrogen bonds and van der Waals' interactions for both compounds. Warfarin (WF) and ibuprofen (IB) were used for competitive site-specific marker binding interaction and revealed that compound 1 and compound 2 were located in subdomain IIA (Sudlow's site I) on the BSA molecule. Conclusions based on above-applied techniques signify that various non-covalent forces were involved during the HAs-BSA interaction. Therefore the resulted HAs-BSA interaction manifested its effect in transportation, distribution and metabolism for the drug in the blood circulation system, therefore establishing HAs as a drug-like molecule.

Role of pannexin-1 in the cellular uptake, release and hydrolysis of anandamide by T84 colon cancer cells

The large pore ion channel pannexin-1 (Panx1) has been reported to play a role in the cellular uptake and release of anandamide (AEA) in the hippocampus. It is not known whether this is a general mechanism or limited to the hippocampus. We have investigated this pharmacologically using T84 colon cancer cells. The cells expressed Panx1 at the mRNA level, and released ATP in a manner that could be reduced by treatment with the Panx1 inhibitors carbenoxolone and mefloquine and the Panx1 substrate SR101. However, no significant effects of these compounds upon the uptake or hydrolysis of exogenously applied AEA was seen. Uptake by T84 cells of the other main endocannabinoid 2-arachidonoylglycerol and the AEA homologue palmitoylethanolamide was similarly not affected by carbenoxolone or mefloquine. Total release of tritium from [³H]AEA-prelabelled T84 cells over 10 min was increased, rather than inhibited by carbenoxolone and mefloquine. Finally, AEA uptake by PC3 prostate cancer and SH-SY5Y neuroblastoma cells, which express functional Panx1 channels, was not inhibited by carbenoxolone. Thus, in contrast to the hippocampus, Panx1 does not appear to play a role in AEA uptake and release from the cells studied under the conditions used.

Molecular Structure-Affinity Relationship of Flavonoids in Lotus Leaf (Nelumbo nucifera Gaertn.) on Binding to Human Serum Albumin and Bovine Serum Albumin by Spectroscopic Method

Lotus leaf has gained growing popularity as an ingredient in herbal formulations due to its various activities. As main functional components of lotus leaf, the difference in structure of flavonoids affected their binding properties and activities. In this paper, the existence of 11 flavonoids in lotus leaf extract was confirmed by High Performance Liquid Chromatography (HPLC) analysis and 11 flavonoids showed various contents in lotus leaf. The interactions between lotus leaf extract and two kinds of serum albumins (human serum albumin (HSA) and bovine serum albumin (BSA)) were investigated by spectroscopic methods. Based on the fluorescence quenching, the interactions between these flavonoids and serum albumins were further checked in detail. The relationship between the molecular properties of flavonoids and their affinities for serum albumins were analyzed and compared. The hydroxylation on 3 and 3’ position increased the affinities for serum albumins. Moreover, both of the methylation on 3’ position of quercetin and the C₂=C₃ double bond of apigenin and quercetin decreased the affinities for HSA and BSA. The glycosylation lowered the affinities for HSA and BSA depending on the type of sugar moiety. It revealed that the hydrogen bond force played an important role in binding flavonoids to HSA and BSA.