Antibacterial Effects of Glycyrrhetinic Acid and Its Derivatives on Staphylococcus aureus

Integrated Metabolomic and Transcriptomic Analysis Reveals the Pharmacological Effects and Differential Mechanisms of Isoflavone Biosynthesis in Four Species of Glycyrrhiza

Licorice (Glycyrrhiza L.) is a globally popular medicinal and edible plant, with nearly 30 species distributed across all continents. The usable part is primarily the root. To understand the metabolic differences among different Glycyrrhiza species, we selected four species and performed comprehensive analyses of their roots. Metabolomic profiling was conducted using UPLC-MS/MS and GC-MS, while transcriptomic analysis was carried out using RNA-sequencing. A total of 2716 metabolites were identified, including flavonoids (527 types) and terpenoids (251 types), among various other components. Subsequently, network pharmacology was employed to explore the medicinal value and potential pharmacological ingredients of these metabolites. Joint analysis of transcriptomic and metabolomic data revealed significant differences in differentially accumulated metabolites (DAMs) and differentially expressed genes (DEGs) in pairwise comparisons among the four species. These differences were primarily enriched in the isoflavone pathway. Further investigation into the regulatory mechanisms of isoflavone biosynthesis in different Glycyrrhiza species identified key genes and metabolites involved in isoflavone biosynthesis. Finally, we made reasonable predictions of the potential suitable habitats for the four Glycyrrhiza species, aiming to provide new insights for the development and utilization of licorice resources. The results of this study can serve as a basis for the development and utilization of licorice and for in-depth research on the regulation of isoflavone biosynthesis in licorice.

Glycyrrhetinic acid reduces lung inflammation caused by pneumococcal infection by reducing the toxicity of pneumolysin

Objective

In this study, to provide new methods for the treatment of Streptococcus pneumoniae infection, we aimed to describe the anti-inflammatory and antibacterial value of glycyrrhetinic acid on the basis of its inhibitory effect on bacterial growth (without killing the bacteria) and its reduction of the toxicity of S. pneumoniae.

Methods

A mouse model was established via intranasal administration of Streptococcus pneumoniae D39, and glycyrrhetinic acid was subcutaneously injected for treatment. The wet‒dry ratio, bacterial flora content and inflammatory factor levels in the mouse lungs were determined. Cell experiments were used to evaluate glycyrrhetinic acid-mediated inhibition of PLY hemolysis and A549 cell death, and WB was used to measure glycyrrhetinic acid-mediated inhibition of PLY oligomerization.

Results

Glycyrrhetinic acid reduced the levels of inflammatory factors, the dry‒wet ratio, the abundance of S. pneumoniae in the lungs of infected mice, pneumolysin-mediated A549 cell death, erythrocyte hemolysis and PLY oligoplasia.

Conclusion

Glycyrrhetinic acid can reduce the virulence of S. pneumoniae by preventing the oligomerization of PLY.

One-Step Organic Synthesis of 18β-Glycyrrhetinic Acid-Anthraquinone Ester Products: Exploration of Antibacterial Activity and Structure-Activity Relationship, Toxicity Evaluation in Zebrafish

To combine the activity characteristics of 18β-glycyrrhetinic acid (18β-GA) and anthraquinone compounds (rhein and emodin), reduce toxicity, and explore the structure-activity relationship (SAR) of anthraquinones, 18β-GA-anthraquinone ester compounds were synthesized by one-step organic synthesis. The products were separated and purified by HPLC and characterized by NMR and EI-MS. It was finally determined as di-18β-GA-3-rhein ester (1, New), GA dimer (2, known), 18β-GA-3-emodin ester (3, known), and di-18β-GA-1-emodin ester (4, new). The MIC of three reactants and four products against Escherichia coli and Staphylococcus aureus were detected in vitro. Its developmental toxicity and cardiotoxicity were assessed using zebrafish embryos. The experimental results showed that rhein had the best antibacterial activity against Staphylococcus aureus with MIC50 of 2.4 mM, and it was speculated that -COOH, -OH, and intramolecular hydrogen bonds in anthraquinone compounds would enhance the antibacterial effect, while the presence of-CH3 might weaken the antibacterial activity. Product 1 increased the hatching rate and survival rate of zebrafish embryos and reduced the malformation rate and cardiomyocyte apoptosis. This experiment lays the foundation for further studying the SAR of anthraquinones and providing new drug candidates.

Dipotassium glycyrrhizate prevents oral dysbiosis caused by Porphyromonas gingivalis in an in vitro saliva-derived polymicrobial biofilm model

OBJECTIVES

Oral microbiome dysbiosis prevention is important to avoid the onset and progression of periodontal disease. Dipotassium glycyrrhizate (GK2) is a licorice root extract with anti-inflammatory effects, and its associated mechanisms have been well-reported. However, their effects on the oral microbiome have not been investigated. This study aimed to elucidate the effects of GK2 on the oral microbiome using an in vitro polymicrobial biofilm model.

METHODS

An in vitro saliva-derived polymicrobial biofilm model was used to evaluate the effects of GK2 on the oral microbiome. One-week anaerobic culture was performed, in which GK2 was added to the medium. Subsequently, microbiome analysis was performed based on the V1-V2 region of the 16 S rRNA gene, and pathogenicity indices were assessed. We investigated the effects of GK2 on various bacterial monocultures by evaluating its inhibitory effects on cell growth, based on culture turbidity.

RESULTS

GK2 treatment altered the microbiome structure and decreased the relative abundance of periodontal pathogenic bacteria, including Porphyromonas. Moreover, GK2 treatment reduced the DPP4 activity -a pathogenicity index of periodontal disease. Specifically, GK2 exhibited selective antibacterial activity against periodontal pathogenic bacteria.

CONCLUSIONS

These findings suggest that GK2 has a selective antibacterial effect against periodontal pathogenic bacteria; thus, preventing oral microbiome dysbiosis. Therefore, GK2 is expected to contribute to periodontal disease prevention by modulating the oral microbiome toward a state with low inflammatory potential, thereby utilizing its anti-inflammatory properties on the host.

Identification of TonB-dependent siderophore receptor inhibitors against Flavobacterium columnare using a structure-based high-throughput virtual screening method

TonB-dependent siderophore receptors play a critical transport role for Flavobacterium columnare virulence formation and growth, and have become valuable targets for the development of novel antimicrobial agents. Traditional Chinese medicine has demonstrated notable efficacy in the treatment of fish diseases and includes potential antibacterial agents. Herein, we performed molecular docking-based virtual screening to discover novel TonB-dependent siderophore receptor inhibitors from traditional Chinese medicine and provide information for developing novel antibacterial agents. Firstly, we efficiently obtained 11 potential inhibitors with desirable drug-like characteristics from thousands of compounds in the TCM library based on virtual screening and property prediction. The antibacterial activity of Enoxolone, along with its interaction characteristics, were determined via an MIC assay and molecular dynamic simulation. Transcriptional profiling, along with validation experiments, subsequently revealed that an insufficient uptake of iron ions by bacteria upon binding to the TonB-dependent siderophore receptors is the antibacterial mechanism of Enoxolone. Finally, Enoxolone's acceptable toxicity was illustrated through immersion experiments. In summary, we have used virtual screening techniques for the first time in the development of antimicrobial agents in aquaculture. Through this process, we have identified Enoxolone as a promising compound targeting the TonB-dependent siderophore receptor of F. columnare. In addition, our findings will provide new ideas for the advancement of innovative antimicrobial medications in aquaculture.

Glycyrrhizic Acid Nanoparticles Subside the Activity of Methicillin-Resistant Staphylococcus aureus by Suppressing PBP2a

Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) are classified as high-risk infections that can lead to death, particularly among older individuals. Nowadays, plant nanoparticles such as glycyrrhizic acid are recognized as efficient bactericides against a wide range of bacterial strains. Recently, scientists have shown interest in plant extract nanoparticles, derived from natural sources, which can be synthesized into nanomaterials. Interestingly, glycyrrhizic acid is rich in antioxidants as well as antibacterial agents, and it exhibits no adverse effects on normal cells. In this study, glycyrrhizic acid nanoparticles (GA-NPs) were synthesized using the hydrothermal method and characterized through physicochemical techniques such as UV-visible spectrometry, DLS, zeta potential, and TEM. The antimicrobial activity of GA-NPs was investigated through various methods, including MIC assays, anti-biofilm activity assays, ATPase activity assays, and kill-time assays. The expression levels of mecA, mecR1, blaR1, and blaZ genes were measured by quantitative RT-qPCR. Additionally, the presence of the penicillin-binding protein 2a (PBP2a) protein of S. aureus and MRSA was evaluated by a Western blot assay. The results emphasized the fabrication of GA nanoparticles in spherical shapes with a diameter in the range of 40-50 nm. The data show that GA nanoparticles exhibit great bactericidal effectiveness against S. aureus and MRSA. The treatment with GA-NPs remarkably reduces the expression levels of the mecA, mecR1, blaR1, and blaZ genes. PBP2a expression in MRSA was significantly reduced after treatment with GA-NPs. Overall, this study demonstrates that glycyrrhizic acid nanoparticles have potent antibacterial activity, particularly against MRSA. This research elucidates the inhibition mechanism of glycyrrhizic acid, which involves the suppressing of PBP2a expression. This work emphasizes the importance of utilizing plant nanoparticles as effective antimicrobial agents against a broad spectrum of bacteria.

A review of typical biological activities of glycyrrhetinic acid and its derivatives

Glycyrrhetinic acid, a triterpenoid compound primarily sourced from licorice root, exhibits noteworthy biological attributes, including anti-inflammatory, anti-tumor, antibacterial, antiviral, and antioxidant effects. Despite these commendable effects, its further advancement and application, especially in clinical use, have been hindered by its limited druggability, including challenges such as low solubility and bioavailability. To enhance its biological activity and pharmaceutical efficacy, numerous research studies focus on the structural modification, associated biological activity data, and underlying mechanisms of glycyrrhetinic acid and its derivatives. This review endeavors to systematically compile and organize glycyrrhetinic acid derivatives that have demonstrated outstanding biological activities over the preceding decade, delineating their molecular structures, biological effects, underlying mechanisms, and future prospects for assisting researchers in finding and designing novel glycyrrhetinic acid derivatives, foster the exploration of structure-activity relationships, and aid in the screening of potential candidate compounds.

In Vitro Synergistic Inhibitory Effects of Plant Extract Combinations on Bacterial Growth of Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common pathogens of healthcare-associated infections. Medicinal plants have long been used in the traditional treatment of diseases or syndromes worldwide. Combined use of plant extracts could improve the effectiveness of pharmacological action by obtaining synergism, acting on multiple targets simultaneously, reducing the doses of individual components, and minimizing side effects. We aimed to investigate the synergistic inhibitory effects of selected medicinal plants (Caesalpinia sappan L. (CS), Glycyrrhiza uralensis Fisch. (GU), Sanguisorba officinalis L. (SO), and Uncaria gambir Roxb. (UG)) on the bacterial growth of MRSA and its clinical isolates. SO and UG extracts generated the best synergistic interaction as adjudged by checkerboard synergy assays. MICs of the individual extracts decreased 4-fold from 250 to 62.5 μg/mL, respectively. The SO + UG combination was further evaluated for its effects on bacterial growth inhibition, minimum bactericidal/inhibitory concentration (MBC/MIC) ratio, and time-kill kinetics. The results indicate that the SO + UG combination synergistically inhibited the bacterial growth of MRSA strains with bactericidal effects. SO + UG combination also exhibited more potent effects against clinical isolates. In multistep resistance selection experiments, both standard and isolates of MRSA showed no resistance to the SO + UG combination even after repeated exposure over fourteen passages. Our data suggest that using plant extract combinations could be a potential strategy to treat MRSA infections.

Degradable carrier-free spray hydrogel based on self-assembly of natural small molecule for prevention of postoperative adhesion

Postoperative peritoneal adhesion (PPA) is frequent and extremely dangerous complication after surgery. Different tactics have been developed to reduce it. However, creating a postoperative adhesion method that is multifunctional, biodegradable, biocompatible, low-toxic but highly effective, and therapeutically applicable is still a challenge. Herein, we have prepared a degradable spray glycyrrhetinic acid hydrogel (GAG) based on natural glycyrrhetinic acid (GA) by straightforward heating and cooling without the use of any additional chemical cross-linking agents to prevent postoperative adhesion. The resultant hydrogel was demonstrated to possess various superior anti-inflammatory activity, and multiple functions, such as excellent degradability and biocompatibility. Specifically, spraying characteristic and excellent antibacterial activities essentially eliminated secondary infections during the administration of drugs in surgical wounds. In the rat models, the carrier-free spray GAG could not only slow-release GA to inhibit inflammatory response, but also serve as physical anti-adhesion barrier to reduce collagen deposition and fibrosis. The sprayed GAG would shed a new light on the prevention of postoperative adhesion and broaden the application of the hydrogels based on natural products in biomedical fields.

Multicomponent Antibiofilm Lipid Nanoparticles as Novel Platform to Ameliorate Resveratrol Properties: Preliminary Outcomes on Fibroblast Proliferation and Migration

The well-being of skin and mucous membranes is fundamental for the homeostasis of the body and thus it is imperative to treat any lesion quickly and correctly. In this view, polyphenols might assist and enhance a successful wound healing process by reducing the inflammatory cascade and the production of free radicals. However, they suffer from disadvantageous physico-chemical properties, leading to restricted clinical use. In this work, a complex mixture of PEGylated lipid, Glyceryl monoester, 18-β-Glycyrrhetinic Acid and Menthol was designed to entrap Resveratrol (RSV) as the active ingredient and further produce lipid nanoparticles (LNPs) by homogenization followed by high-frequency sonication. The nanosystem was properly characterized in terms of particle size (DLS, SEM), zeta potential, drug loading, antioxidant power (DPPH), release behaviour, cytocompatibility, wound healing and antibiofilm properties. The optimized lipid mixture was homogeneous, melted at 57-61 °C and encapsulated amorphous RSV (4.56 ± 0.04% w/w). The RSV-loaded LNPs were almost monodispersed (PDI: 0.267 ± 0.010), with nanometric size (162.86 ± 3.12 nm), scavenger properties and suitable DR% and LE% values (96.82 ± 1.34% and 95.17 ± 0.25%, respectively). The release studies were performed to simulate the wound conditions: 1-octanol to mimic the lipophilic domains of biological tissues (where the First Order kinetic was observed) and citrate buffer pH 5.5 according to the inflammatory wound exudate (where the Korsmeyer-Peppas kinetic was followed). The biological and microbiological evaluations highlighted fibroblast proliferation and migration effects as well as antibiofilm properties at extremely low doses (LNPs: 22 μg/mL, corresponding to RSV 5 µM). Thus, the proposed multicomponent LNPs could represent a valuable RSV delivery platform for wound healing purposes.

30th Annual GP2A Medicinal Chemistry Conference

The Group for the Promotion of Pharmaceutical Chemistry in Academia (GP2A) held their 30th annual conference in August 2022 in Trinity College Dublin, Ireland. There were 9 keynote presentations, 10 early career researcher presentations and 41 poster presentations.

Effects of glycyrrhetinic acid β on growth and virulence of Aeromonas hydrophila

Aeromonas hydrophila is a significant pathogen to freshwater farmed animals, and antibiotics are usually used to control the bacterial septicemia caused by A. hydrophila. Due to the severe situation of development and spread of antibiotic resistance, there are stricter restrictions on antibiotics used in aquaculture. To evaluate the feasibility of glycyrrhetinic acid β (GA) as an alternative therapy against bacterial infection, in this study, an A. hydrophila isolated from diseased fish is used to test the antibacterial, anti-virulence activity and therapeutic effect of GA in vitro and in vivo, respectively. Results showed that GA did not affect the growth of A. hydrophila in vitro, while it could down-regulate (p < 0.05) the mRNA expression of the hemolysis-related genes hly and aerA, and significantly inhibited (p < 0.05) hemolytic activity of A. hydrophila. In addition, in vivo test showed that oral administration of GA was ineffective in controlling acute infections caused by A. hydrophila. In conclusion, these findings suggested that GA was a potential anti-virulence candidate against A. hydrophila, but the application of GA for the prevention and treatment of A. hydrophila-related diseases was still a long way.

Glycyrrhetinic acid protects against Multidrug-resistant Acinetobacter baumannii-induced lung epithelial cells injury by regulating inflammation and oxidative stress

Glycyrrhetinic acid (GA) is a bio-effective component of Licorice. The GA is a monomer and the ingredient is an Oleanane-type pentacyclic triterpenes that has been used as a remedy for years. Due to the abuse of antibiotics, people pay attention to the emergence of Multidrug-resistant Acinetobacter baumannii (MDR-AB). As a conditional pathogen, MDR-AB causes severe infection, endangering human lives. Our previous studies found GA played an important role in Yinhua Pinggan, a Chinese medicine. However, whether GA could protect lung epithelium from MDR-AB-induced cell injury was elusive. Herein, we investigated the effects of GA on MDR-AB-infected A549 cells. The results showed GA had slightly antibacterial activity to MDR-AB in the GA (high concentration) but no impact on drug resistance genes. Notwithstanding, GA could reverse MDR-AB-induced cell apoptosis, hampered adhesion and invasion of MDR-AB to cells, and inhibit pro-inflammatory cytokines expression of IL-1β, IL-6, and TNF. Besides, MDR-AB-induced reactive oxygen species, pro-oxidative protein malonaldehyde, and myeloperoxidase of cells were decreased by GA, while antioxidative proteins were recovered, showing antioxidative capacity of GA might play a critical role. The expressions of toll-like receptor (TLRs) - 1, 2, 4, 5, 6, and 9 were increased by MDR-AB infection, while GA reversed the tendency. Interestingly, GA inhibited MDR-AB induced myeloiddifferentiationfactor88 expression (MYD88), one downstream con-factors of TLRs, but no affection on Interferon regulatory Factor 3 (IRF3), the other one, indicating GA inhibited MDR-AB induced cell injury by impact TLR/MYD88 pathway to attenuate inflammation. Altogether, our results demonstrated that GA protects against MDR-AB-induced cell injury through its antioxidative and anti-inflammatory properties, which deserve further study in the future.

Rosmarinic and Glycyrrhetinic Acid-Modified Layered Double Hydroxides as Functional Additives for Poly(Lactic Acid)/Poly(Butylene Succinate) Blends

Immobilizing natural antioxidant and biologically active molecules in layered double hydroxides (LDHs) is an excellent method to retain and release these substances in a controlled manner, as well as protect them from thermal and photochemical degradation. Herein, we describe the preparation of host-guest systems based on LDHs and rosmarinic and glycyrrhetinic acids, two molecules obtained from the extraction of herbs and licorice root, respectively, with antioxidant, antimicrobial, and anti-inflammatory properties. Intercalation between the lamellae of the mono-deprotonated anions of rosmarinic and glycyrrhetinic acid (RA and GA), alone or in the presence of an alkyl surfactant, allows for readily dispersible systems in biobased polymer matrices such as poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and a 60/40 wt./wt. PLA/PBS blend. The composites based on the PLA/PBS blend showed better interphase compatibility than the neat blend, correlated with increased adhesion at the interface and a decreased dispersed phase size. In addition, we proved that the active species migrate slowly from thin films of the composite materials in a hydroalcoholic solvent, confirming the optimization of the release process. Finally, both host-guest systems and polymeric composites showed antioxidant capacity and, in the case of the PLA composite containing LDH-RA, excellent inhibitory capacity against E. coli and S. aureus.

Chemical basis of pregnane X receptor activators in the herbal supplement Gancao (licorice)

Background and aims

The herbal supplement Gancao, also known as licorice, belongs to the genus Glycyrrhiza and has been used worldwide for its hepatoprotective effect. Recent studies have raised concerns about potential herb-drug interactions associated with Gancao via pregnane X receptor (PXR)-mediated induction of hepatic cytochrome P450 3A4 (CYP3A4). The current work aimed to determine the phytochemicals in Gancao that activate PXR and induce CYP3A4.

Methods

DPX2 cells were used for cell-based PXR reporter assays. The phytochemicals in Gancao extract were identified using a metabolomics approach. The effects of PXR activators identified from in vitro studies were further investigated in PXR- and CYP3A4-humanized mouse models.

Results

Gancao was verified to be a PXR-activating herb. Two major phytochemicals in Gancao, glycyrrhizin (GZ) and glycyrrhetinic acid (GA), did not activate PXR in the cell-based reporter assays. However, glabridin was shown to activate PXR in a dose-dependent manner. In vivo studies confirmed that GZ is not a PXR activator and glabridin is a weak PXR activator. Although GA did not active PXR in vitro, it induced CYP3A4 expression in a PXR-dependent manner in the PXR- and CYP3A4-humanized mice.

Conclusions

GZ is not a PXR activator. GA could not activate PXR in cell-based reporter assays but it could activate PXR in vivo. Glabridin is a weak PXR activator. This work provides novel insights into the underlying mechanisms of Gancao-related herb-drug interactions via PXR.

Glycyrrhetinic acid prevents carbapenem-resistant Klebsiella pneumoniae-induced cell injury by inhibiting mitochondrial dysfunction via Nrf-2 pathway

OBJECTIVES

Due to the abuse of antibiotics, the high reoccurrence of drug-resistance strains, such as carbapenem-resistant Klebsiella pneumoniae (CRKP), deteriorates CRKP-infected pneumonia in the clinic, suggesting it is necessary to find new alternatives. Glycyrrhetinic acid (GA), an active ingredient of Yinhuapinggan granule, has antioxidant & anti-inflammatory capacity. Little, however, is known about the effects of GA on CRKP-induced epithelial injury.

METHODS

In this research, we examined the protective effects of GA against pulmonary epithelium damage caused by CRKP infection and potential molecular mechanisms.

RESULTS

Our results noted GA significantly promoted cell survival and reduced pro-inflammatory cytokines production, during CRKP-induced human pulmonary epithelial cell. Mechanically, GA alleviated mitochondrial-damage-induced apoptosis amid CRKP infection by inhibiting mitochondrial damage. Additionally, we found GA inhibited the expression of pro-apoptotic proteins Cyto-c, the Bax, and Caspase-3 while increasing the expression of anti-apoptotic protein Bcl-2. Further exploration found GA could trigger Nrf-2 expression at both gene and protein levels, activating antioxidative proteins to diminish CRKP-induced oxidative stress.

CONCLUSION

Together, our results demonstrated that GA was a promising candidate to alleviate CRKP-infected lung injury as well as a synergist to treat CRKP infection with antibiotics.

Synthesis, Antiviral, and Antibacterial Activity of the Glycyrrhizic Acid and Glycyrrhetinic Acid Derivatives

Glycyrrhizic acid and its primary metabolite glycyrrhetinic acid, are the main active ingredients in the licorice roots (glycyrrhiza species), which are widely used in several countries of the world, especially in east asian countries (China, Japan). These ingredients and their derivatives play an important role in treating many diseases, especially infectious diseases such as COVID-19 and hepatic infections. This review aims to summarize the different ways of synthesising the amide derivatives of glycyrrhizic acid and the main ways to synthesize the glycyrrhitinic acid derivatives. Also, to determine the main biological and pharmacological activity for these compounds from the previous studies to provide essential data to researchers for future studies.

Supplementary Information

The online version contains supplementary material available at 10.1134/S1068162022050132.

Chitin Nanofibril-Nanolignin Complexes as Carriers of Functional Molecules for Skin Contact Applications

Chitin nanofibrils (CN) and nanolignin (NL) were used to embed active molecules, such as vitamin E, sodium ascorbyl phosphate, lutein, nicotinamide and glycyrrhetinic acid (derived from licorice), in the design of antimicrobial, anti-inflammatory and antioxidant nanostructured chitin nanofibrils–nanolignin (CN-NL) complexes for skin contact products, thus forming CN-NL/M complexes, where M indicates the embedded functional molecule. Nano-silver was also embedded in CN-NL complexes or on chitin nanofibrils to exploit its well-known antimicrobial activity. A powdery product suitable for application was finally obtained by spray-drying the complexes co-formulated with poly(ethylene glycol). The structure and morphology of the complexes was studied using infrared spectroscopy and field emission scanning electron microscopy, while their thermal stability was investigated via thermo-gravimetry. The latter provided criteria for evaluating the suitability of the obtained complexes for subsequent demanding industrial processing, such as, for instance, incorporation into bio-based thermoplastic polymers through conventional melt extrusion. In vitro tests were carried out at different concentrations to assess skin compatibility. The obtained results provided a physical–chemical, morphological and cytocompatibility knowledge platform for the correct selection and further development of such nanomaterials, allowing them to be applied in different products. In particular, chitin nanofibrils and the CN-NL complex containing glycyrrhetinic acid can combine excellent thermal stability and skin compatibility to provide a nanostructured system potentially suitable for industrial applications.

Facial Seborrheic Dermatitis in HIV-Seropositive Patients: Evaluation of the Efficacy and Safety of a Non-Steroidal Cream Containing Piroctone Olamine, Biosaccharide Gum-2 and Stearyl Glycyrrhetinate - A Case Series

Facial seborrheic dermatitis is common in HIV-positive patients, and the presence of facial lesions can affect quality of life. The management and control of lesions can be frustrating for both physicians and patients. In this pilot clinical study, we clinically evaluated the effectiveness of a topical non-steroidal cream in treating mild to moderate facial seborrheic dermatitis in 20 HIV-positive patients. The patients applied a twice-a-day topical cream containing zinc PCA, piroctone olamine, hydroxyphenyl propamidobenzoic acid, biosaccharide gum-2, and stearyl glycyrrhetinate for 12 weeks with no topical or oral antifungal or corticosteroid treatment. Signs and symptoms and tolerance were assessed before, during, and at the end of treatment. All of the patients showed clinical improvement after 4 and 12 weeks of treatment. None of the patients had no response to treatment, and no adverse effects were reported. No rescue therapy with corticosteroids was needed. The patients reported a very noticeable improvement in their skin which contributed to high compliance with the protocol requirement.

Facile Preparation of Organo-Modified ZnO/Attapulgite Nanocomposites Loaded with Monoammonium Glycyrrhizinate via Mechanical Milling and Their Synergistic Antibacterial Effect

In this study, monoammonium glycyrrhizinate (MAG) was introduced into cetyltrimethyl ammonium bromide (CTAB)-modified ZnO/attapulgite (APT) via a mechanical process to form performance-enhanced antibacterial nanocomposites (MAG/C–ZnO/APT). The APT supported ZnO nanocomposite (ZnO/APT) was prepared by a conventional precipitation method, and 20–50 nm of globular ZnO nanoparticles were uniformly decorated on APT nanorods. The FTIR and zeta potential analyses demonstrated that modification by CTAB facilitated the loading of MAG into ZnO/APT by H-bonding and electrostatic interactions. Antibacterial evaluation results indicate that MAG/C–ZnO/APT nanocomposites with CTAB and MAG doses of 2.5% and 0.25%, respectively, exhibited synergistically enhanced inhibitory activities against Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus and extended-spectrum β-lactamases Escherichia coli, with minimum inhibitory concentrations of 1, 0.1, 0.25, 5, 0.1, and 2.5 mg/mL, respectively, which are better than those of ZnO/APT, C–ZnO/APT and MAG. Moreover, the nanocomposites had low cytotoxicity on human normal cell line L-O2. Therefore, this study provided a more effective strategy to extend the antibacterial spectrum and strengthen the inhibitory effects of antibiotic-free materials to address increasingly serious situations of microbial infection.

Nanoinhibitory Impacts of Salicylic Acid, Glycyrrhizic Acid Ammonium Salt, and Boric Acid Nanoparticles against Phytoplasma Associated with Faba Bean

Phytoplasmas are economically important plant pathogenic bacterial diseases, causing severe yield losses worldwide. In this study, we tested nanoformulations such as glycyrrhizic acid ammonium salt (GAS), salicylic acid (SA), and boric acid (BA) as novel antimicrobial agents inducing the resistance against the phytoplasma disease in faba bean. The nanoparticles (NP) were foliar-applied to naturally phytoplasma-infected faba bean with three concentrations from each of SA, GAS, and BA, under field conditions. Nested PCR (using universal primer pairs P1/P7 and R16F2n/R16R2) were reacted positively with all symptomatic samples and gave a product size of approximately 1200 bp, while the healthy plant gave no results. Transmission electron microscopy examinations of phytoplasma-infected faba bean plants treated with different nanoparticles revealed that severe damage occurred in phytoplasma particle's structure, degradation, malformation, lysis in the cell membrane, and the cytoplasmic leakage followed by complete lysis of phytoplasma cells. Exogenous application of GAS-NP (1.68 µM), SA-NP (0.28 µM), and BA-NP (0.124 µM) suppressed the infection percentage of phytoplasma by 75%, 50%, and 20%, and the disease severity by 84%, 64%, and 54%, respectively. Foliar application of nanoparticles improved Fv/Fm (maximum quantum efficiency of PSII Photochemistry), PI (the performance index), SPAD chlorophyll (the relative chlorophyll content), shoots height, and leaves number, thus inducing recovery of the plant biomass and green pods yield. The most effective treatment was GAS-NP at 1.68 µM that mediated substantial increases in the shoots' fresh weight, shoots' dry weight, number of pods per plant, and green pods yield by 230%, 244%, 202% and 178%, respectively, compared to those of infected plants not sprayed with nanoparticles. This study demonstrated the utility of using nanoparticles, particularly GAS-NP at 1.68 µM to suppress the phytoplasma infection.

Traditional Uses, Pharmacological Effects, and Molecular Mechanisms of Licorice in Potential Therapy of COVID-19

The current Coronavirus disease 2019 (COVID-19) pandemic has become a global challenge, and although vaccines have been developed, it is expected that mild to moderate patients will control their symptoms, especially in developing countries. Licorice, not only a food additive, but also a common traditional Chinese herbal medicine, which has several pharmacological effects, such as anti-inflammation, detoxification, antibacterial, antitussive, and immunomodulatory effects, especially in respiratory diseases. Since the outbreak of COVID-19, glycyrrhizin, glycyrrhizin diamine and glycyrrhizin extract have been widely studied and used in COVID-19 clinical trials. Therefore, it is a very interesting topic to explore the material basis, pharmacological characteristics and molecular mechanism of licorice in adjuvant treatment of COVID-19. In this paper, the material basis of licorice for the prevention and treatment of COVID-19 is deeply analyzed, and there are significant differences among different components in different pharmacological mechanisms. Glycyrrhizin and glycyrrhetinic acid inhibit the synthesis of inflammatory factors and inflammatory mediators by blocking the binding of ACE 2 to virus spike protein, and exert antiviral and antibacterial effects. Immune cells are stimulated by multiple targets and pathways to interfere with the pathogenesis of COVID-19. Liquiritin can prevent and cure COVID-19 by simulating type I interferon. It is suggested that licorice can exert its therapeutic advantage through multi-components and multi-targets. To sum up, licorice has the potential to adjuvant prevent and treat COVID-19. It not only plays a significant role in anti-inflammation and anti-ACE-2, but also significantly improves the clinical symptoms of fever, dry cough and shortness of breath, suggesting that licorice is expected to be a candidate drug for adjuvant treatment of patients with early / mild COVID-19.

β-Glycyrrhetinic acid inhibits the bacterial growth and biofilm formation by supragingival plaque commensals

β-Glycyrrhetinic acid (BGA) is a natural antibacterial agent. Previous studies reported that BGA has antibacterial effects against several bacteria. This study evaluated the effects of BGA on the regulation of supragingival plaque bacteria. First, the minimum inhibitory concentrations (MICs) of BGA against oral bacteria were measured. Next, the minimum concentrations for inhibition of biofilm formation were evaluated against Streptococcus mutans and Streptococcus sobrinus, possessing insoluble glucan synthesis abilities. The MICs of biofilm formation by these bacteria ranged from 1/8 to 2× MIC. Furthermore, the inhibition effects of BGA against the coaggregation of Porphyromonas gingivalis and Streptococcus gordonii were evaluated. BGA at 32 or 64 μg/mL inhibited the coaggregation of these bacteria after a 30 min incubation. Lastly, the inhibition effects of BGA against human supragingival plaque bacteria were evaluated. Human supragingival plaque samples were obtained from 12 healthy donors. The inhibition effects of BGA against biofilm formation by these plaque bacteria were evaluated. Of 12 samples, the biofilm formation by 11 was significantly attenuated by 128-256 μg/mL of BGA. The number of colony forming units in these biofilms was also significantly attenuated. In conclusion, it was revealed that BGA inhibits the growth and biofilm formation of bacteria, furthermore, the same effect was confirmed with supragingival plaque bacteria. BGA is a good candidate for a natural agent that prevents the outbreak and progression of periodontal disease because it suppresses not only the growth and biofilm formation of bacteria, but also the coaggregation of P. gingivalis with plaque bacteria.

Calorimetric Evaluation of Glycyrrhetic Acid (GA)- and Stearyl Glycyrrhetinate (SG)-Loaded Solid Lipid Nanoparticle Interactions with a Model Biomembrane

Glycyrrhetic acid (GA) and stearyl glycyrrhetinate (SG) are two interesting compounds from Glycyrrhiza glabra, showing numerous biological properties widely applied in the pharmaceutical and cosmetic fields. Despite these appreciable benefits, their potential therapeutic properties are strongly compromised due to unfavourable physical-chemical features. The strategy exploited in the present work was to develop solid lipid nanoparticles (SLNs) as carrier systems for GA and SG delivery. Both formulations loaded with GA and SG (GA-SLNs and SG-SLNs, respectively) were prepared by the high shear homogenization coupled to ultrasound (HSH-US) method, and we obtained good technological parameters. DSC was used to evaluate their thermotropic behaviour and ability to act as carriers for GA and SG. The study was conducted by means of a biomembrane model (multilamellar vesicles; MLVs) that simulated the interaction of the carriers with the cellular membrane. Unloaded and loaded SLNs were incubated with the biomembranes, and their interactions were evaluated over time through variations in their calorimetric curves. The results of these studies indicated that GA and SG interact differently with MLVs and SLNs; the interactions of SG-SLNs and GA-SLNs with the biomembrane model showed different variations of the MLVs calorimetric curve and suggest the potential use of SLNs as delivery systems for GA.

The potential of glycyrrhizin and licorice extract in combating COVID-19 and associated conditions

BACKGROUND

Several recent studies have stated that glycyrrhizin and licorice extract are present in most traditional Chinese medicine formulas used against SARS-CoV-2 in China. Significant data are showing that glycyrrhizin and licorice extract have multiple beneficial activities in combating most features of SARS-CoV-2.

PURPOSE

The aim of current review was to highlight recent progresses in research that showed the evidence of the potential use of glycyrrhizin and licorice extract against COVID-19.

METHODOLOGY

We have reviewed the information published from 1979 to October 2020. These studies demonstrated the effects , use and safety of glycyrrhizin and icorice extract against viral infections,bacterial infections, inflammatory disorders of lung ( in vitro and in vivo).  These studies were collated through online electronic databases research (Academic libraries as PubMed, Scopus, Web of Science and Egyptian Knowledge Bank).

RESULTS

Pooled effect size of articles provides information about the rationale for using glycyrrhizin and licorice extract to treat COVID-19. Fifty studies demonstrate antiviral activity of glycyrrhizin and licorice extract. The most frequent mechanism of the antiviral activity is due to disrupting viral uptake into the host cells and disrupting the interaction between receptor- binding domain (RBD) of SARS-COV2 and ACE2 in recent articles. Fifty studies indicate that glycyrrhizin and licorice extract have significant antioxidant, anti-inflammatory and immunomodulatory effects. Twenty five studies provide evidence for the protective effect of glycyrrhizin and licorice extract against inflammation-induced acute lung injury and cardiovascular disorders.

CONCLUSION

The current study showed several evidence regarding the beneficial effects of glycyrrhizin and licorice extract in combating COVID-19. More randomized clinical trials are needed to obtain a precise conclusion.

Synthesis, Characterization, In Vitro Anticancer Potentiality, and Antimicrobial Activities of Novel Peptide-Glycyrrhetinic-Acid-Based Derivatives

Glycyrrhetinic acid (GA) is one of many interesting pentacyclic triterpenoids showing significant anticancer activity by triggering apoptosis in tumor cell lines. This study deals with the design and synthesis of new glycyrrhetinic acid (GA)-amino acid peptides and peptide ester derivatives. The structures of the new derivatives were established through various spectral and microanalytical data. The novel compounds were screened for their in vitro cytotoxic activity. The evaluation results showed that the new peptides produced promising cytotoxic activity against the human breast MCF-7 cancer cell line while comparing to doxorubicin. On the other hand, only compounds 3, 5, and 7 produced potent activity against human colon HCT-116 cancer cell line. The human liver cancer (HepG-2) cell line represented a higher sensitivity to peptide 7 (IC50; 3.30 μg/mL), while it appeared insensitive to the rest of the tested peptides. Furthermore, compounds 1, 3, and 5 exhibited a promising safety profile against human normal skin fibroblasts cell line BJ-1. In order to investigate the mode of action, compound 5 was selected as a representative example to study its in vitro effect against the apoptotic parameters and Bax/BCL-2/p53/caspase-7/caspase-3/tubulin, and DNA fragmentation to investigate beta (TUBb). Additionally, all the new analogues were subjected to antimicrobial assay against a panel of Gram-positive and Gram-negative bacteria and the yeast candida Albicans. All the tested GA analogues 1-8 exhibited more antibacterial effect against Micrococcus Luteus than gentamicin, but they exhibited moderate antimicrobial activity against the tested bacterial and yeast strains. Molecular docking studies were also simulated for compound 5 to give better rationalization and put insight to the features of its structure.

Antibacterial, Antibiofilm, and Antioxidant Activity of Polysaccharides Obtained from Fresh Sarcotesta of Ginkgo biloba: Bioactive Polysaccharide that Can Be Exploited as a Novel Biocontrol Agent

Staphylococcus aureus (S. aureus) biofilm plays an important role in the persistence of chronic infection due to its resistance to antibiotics. Because of their functional diversity, active polysaccharide is increasingly being applied as a biocontrol agent to inhibit the formation of biofilm by pathogens. In this study, a new polysaccharide, GBSPII-1, isolated from the fresh sarcotesta of Ginkgo biloba L. (G. biloba) was characterized and its effect on antibiofilm formation of S. aureus was examined in vitro. High-Performance Liquid Chromatography (HPLC) analysis showed that GBSPII-1 is an acidic heteropolysaccharide composed of mannose, rhamnose, glucose, glucuronic acid, and galacturonic acid. GBSPII-1 demonstrated a molecular weight of 34 kDa and may affect the accumulation of polysaccharide intercellular adhesion (PIA) by inhibiting icaA, icaB, icaC, and icaD gene expression at subinhibitory concentrations. Under 10 g/L, GBSPII-1 showed an antioxidant effect on the inhibition rate of H₂O₂-induced erythrocyte hemolysis and the scavenging rate of DPPH radicals was 76.5 ± 0.5% and 89.2 ± 0.26%, respectively. The findings obtained in this study indicate that GBSPII-1 has antibacterial effect, is a possible source of natural antioxidants, and may be a potential biocontrol agent for the design of new therapeutic strategies for biofilm-related S. aureus infections.

Development of sodium carboxymethyl cellulose based polymeric microparticles for in situ hydrogel wound dressing formation

18β-glycyrrhetinic acid (Gly), a natural compound obtained from licorice, is known both for the anti-inflammatory and antioxidant activities and for this reason useful for wound treatment. Due to its poor solubility, Gly is not suitable for formulations used in conventional topical products such as gels, foams and creams. Polymeric bioadhesive microparticles (MP), loaded with Gly, were developed to be introduced in the wound bed and swell, once in contact with the exudate, to form a hydrogel in situ able to close the wound. The MP were prepared by spray drying method from the polymeric solution of polysaccharide sodium carboxymethyl cellulose (CMC) and copolymer Soluplus® (SL). Soluplus® introduction in MP composition, using a 3:1 ratio (CMC/SL wt./wt.), allowed to stabilize Gly in non-crystalline form, favoring the improvement of water solubility, and to obtain a spherical with rugged surface MP morphology. Ex vivo studies showed these MP maintain high swelling capability and are able to form in situ a hydrogel for wound repair. The controlled release of Gly from the hydrogel stimulates keratinocyte growth, potentially supporting the physiological healing processes.

Discovery of Gut Bacteria Specific to Alzheimer's Associated Diseases is a Clue to Understanding Disease Etiology: Meta-Analysis of Population-Based Data on Human Gut Metagenomics and Metabolomics

Alzheimer's disease (AD)-associated sequence (ADAS) of cultured fecal bacteria was discovered in human gut targeted screening. This study provides important information to expand our current understanding of the structure/activity relationship of ADAS and putative inhibitors/activators that are potentially involved in ADAS appearance/disappearance. The NCBI database analysis revealed that ADAS presents at a large proportion in American Indian Oklahoman (C&A) with a high prevalence of obesity/diabetes and in colorectal cancer (CRC) patients from the US and China. An Oklahoman non-native group (NNI) showed no ADAS. Comparison of two large US populations reveals that ADAS is more frequent in individuals aged ≥66 and in females. Prevalence and levels of fecal metabolites are altered in the C&A and CRC groups versus controls. Biogenic amines (histamine, tryptamine, tyramine, phenylethylamine, cadaverine, putrescine, agmatine, spermidine) that present in food and are produced by gut microbiota are significantly higher in C&A (e.g., histamine/histidine 95-fold) versus NNI (histamine/histidine 16-fold). The majority of these bio-amines are cytotoxic at concentrations found in food. Inositol phosphate signaling implicated in AD is altered in C&A and CRC. Tryptamine stimulated accumulation of inositol phosphate. The seizure-eliciting tryptamine induced cytoplasmic vacuolization and vesiculation with cell fragmentation. Present additions of ADAS-carriers at different ages including infants led to an ADAS-comprising human sample size of 2,830 from 27 studies from four continents (North America, Australia, Asia, Europe). Levels of food-derived monoamine oxidase inhibitors and anti-bacterial compounds, the potential modulators of ADAS-bacteria growth and biogenic amine production, were altered in C&A versus NNI. ADAS is attributable to potentially modifiable risk factors of AD associated diseases.

Galactosylation of Monosaccharide Derivatives of Glycyrrhetinic Acid by UDP-Glycosyltransferase GmSGT2 from Glycine max

Glycyrrhetinic acid (GA), a pentacyclic triterpenoid aglycone, is the major functional component in licorice which mainly exists in the form of functional glycosides in licorice. The introduction of a sugar moiety to the C-3 OH of GA to yield glycosylated derivatives has been reported, but the late-stage glycosylation of GA-3-O-sugar to form rare GA glycosides with more complexed glycosyl decoration has been rarely reported. In this study, a unique UDP-galactosyltransferase GmSGT2 from Glycine max was found to transfer a galactose to the C2 position of the sugar moiety of GA-3-O-monoglucuronide (GAMG) and GA-3-O-monoglucose. In addition to UDP-galactose, GmSGT2 also recognizes UDP-glucose, UDP-xylose, and UDP-arabinose with relative activities of 32.1-89.2%. Based on a test of 12 typical natural products, GmSGT2 showed high specificity toward the pentacyclic triterpenoid skeleton as the sugar acceptor. Molecular docking was performed to elucidate the substrate recognition mechanism of GmSGT2 toward GAMG.

Novel targets of pentacyclic triterpenoids in Staphylococcus aureus: A systematic review

BACKGROUND

Staphylococcus aureus is an important pathogen both in community-acquired and healthcare-associated infections, and has successfully evolved numerous strategies for resisting the action to practically all antibiotics. Resistance to methicillin is now widely described in the community setting (CMRSA), thus the development of new drugs or alternative therapies is urgently necessary. Plants and their secondary metabolites have been a major alternative source in providing structurally diverse bioactive compounds as potential therapeutic agents for the treatment of bacterial infections. One of the classes of natural secondary metabolites from plants with the most bioactive compounds are the triterpenoids, which comprises structurally diverse organic compounds. In nature, triterpenoids are often found as tetra- or penta-cyclic structures.

AIM

This review highlights the anti-staphylococcal activities of pentacyclic triterpenoids, particularly α-amyrin (AM), betulinic acid (BA) and betulinaldehyde (BE). These compounds are based on a 30-carbon skeleton comprising five six-membered rings (ursanes and lanostanes) or four six-membered rings and one five-membered ring (lupanes and hopanes).

METHODS

Electronic databases such as ScienceDirect, PubMed and Scopus were used to search scientific contributions until March 2018, using relevant keywords. Literature focusing on the antimicrobial and antibiofilms of effects of pentacyclic triterpenoids on S. aureus were identified and summarized.

RESULTS

Pentacyclic triterpenoids can be divided into three representative classes, namely ursane, lupane and oleananes. This class of compounds have been shown to exhibit analgesic, immunomodulatory, anti-inflammatory, anticancer, antioxidant, antifungal and antibacterial activities. In studies of the antimicrobial activities and targets of AM, BA and BE in sensitive and multidrug-resistant S. aureus, these compounds acted synergistically and have different targets from the conventional antibiotics.

CONCLUSION

The inhibitory mechanisms of S. aureus in novel targets and pathways should stimulate further researches to develop AM, BA and BE as therapeutic agents for infections caused by S. aureus. Continued efforts to identify and exploit synergistic combinations by the three compounds and peptidoglycan inhibitors, are also necessary as alternative treatment options for S. aureus infections.

Antibacterial activity of phellodendron bark against Streptococcus mutans

Streptococcus mutans is a major cause of tooth decay due to its promotion of biofilm formation and acid production. Several plant extracts have been reported to have multiple biological activities such as anti-inflammation and antibacterial effects. This study investigated the antibacterial activity of three plant extracts, phellodendron bark (PB), yucca, and black ginger, and found that PB had a stronger effect than the other extracts. Then, the minimum inhibitory concentration (MIC) of PB against 100 S. mutans strains was investigated. The MIC range of PB was 9.8-312.5 µg/mL. PB suppressed the growth kinetics of S. mutans in a dose-dependent manner, even at sub-MICs of PB. Then, we investigated the effect of PB on S. mutans virulence. The PB suppressed biofilm formation at high concentrations, although PB did not affect the expression of glucosyltransferase genes. Additionally, PB suppressed the decrease in pH from adding an excess of glucose. The expression of genes responsible for acid production was increased by the addition of excess glucose without PB, whereas their expression levels were not increased in the presence of 1× and 2× MIC of PB. Although PB showed a bacteriostatic effect on planktonic S. mutans cells, it was found that more than 2× MIC of PB showed a partial bactericidal effect on biofilm cells. In conclusion, PB not only showed antibacterial activity against S. mutans but also decreased the cariogenic activity in S. mutans.

The effects of licorice containing diphenhydramine solution on recurrent aphthous stomatitis: A double-blind, randomized clinical trial

OBJECTIVES

The aim of this study was to compare the efficacy of the diphenhydramine solution (DS) and diphenhydramine-containing glycyrrhiza glabra (DSG) in the treatment of recurrent aphthous stomatitis (RAS).

DESIGN

It was a double-blind randomized clinical trial that was conducted from July to September 2018 at the Faculty of Dentistry, Birjand University of Medical Sciences, Birjand, Iran.

INTERVENTION

DSG was made by adding 5% hydroethanolic extract of licorice to the diphenhydramine elixir. A total of 70 patients diagnosed with RSA were randomly assigned to the DS and DSG groups, each containing 35 patients. Participants were instructed to swish 3 ml of either solution around their mouth for about three minutes four times a day (at least 20 min before each meal and before bedtime) until the complete healing of the oral lesions.

MAIN OUTCOME MEASURES

The primary outcome of this study was to assess the severity of pain prior to the intervention and on the first, third, and fifth days of it. This was done using the visual analog scale (VAS). The duration of wound healing was also measured through photography. The secondary outcome was to record the adverse effects of the intervention. This trial was registered at the Iranian Registry of Clinical Trials under number¹ IRCT20180407039213N1.

RESULTS

The average pain score before the treatment in the DS and DSG groups was 8. 1 ± 1.17 and 7.97 ± 1.72, respectively, and there was apparently no significant difference between them. However, there was a significant difference between the two groups in terms of the average pain scores on the first (7 ± 1.28 versus 5.31 ± 1.28), third (4.02 ± 1.8 vs. 2.86 ± 1.56) and fifth days (1.71 ± 1.69 vs. 0.54 ± 1.31) of the intervention. Indeed, DSG significantly reduced the average wound healing duration by 1.5 days, as compared to DS (P = 0.0001). No adverse effects were observed with the intervention.

CONCLUSION

According to our results, DSG appeared to be more effective in treating RAS than DS alone.

TRIAL REGISTRATION

The trial was registered at Iranian Registry of Clinical Trials before the enrolment of the first patient on June 29, 2019 (registration no: IRCT20180407039213N1, http://www.irct.ir/trial/31497).

Staphylococcus aureus Virulence Affected by an Alternative Nisin A Resistance Mechanism

Nisin A is a bacteriocin produced by Lactococcus lactis and is widely used as a food preservative. Staphylococcus aureus has the BraRS-VraDE system that provides resistance against low concentrations of nisin A. BraRS is a two-component system that induces the expression of the ABC transporter VraDE. Previously, we isolated a highly nisin A-resistant strain with increased VraDE expression due to a mutation in braRS In this study, we isolated S. aureus MW2 mutants with BraRS-VraDE-independent nisin A resistance. These mutants, designated SAN2 ( S. aureus nisin resistant) and SAN469, had a mutation in pmtR, which encodes a transcriptional regulator responsible for the expression of the pmtABCD operon. As a result, these mutants exhibited increased expression of PmtABCD, a transporter responsible for the export of phenol-soluble modulin (PSM). Characterization of the mutants revealed that they have decreased susceptibility to human β-defensin-3 (hBD3) and LL37, which are innate immune factors. Additionally, these mutants showed higher hemolytic activity than the original MW2 strain. Furthermore, in a mouse bacteremia model, the SAN2 strain exhibited a lower survival rate than the original MW2 strain. These results indicate that the increased expression of pmtABCD due to a pmtR mutation is an alternative nisin A resistance mechanism that also affects virulence in S. aureus IMPORTANCE Recently, the emergence of antibiotic-resistant bacteria has resulted in serious problems for chemotherapy. In addition, many antibacterial agents, such as disinfectants and food additives, are widely used. Therefore, there is a possibility that bacteria are becoming resistant to some antibacterial agents. In this study, we investigated whether Staphylococcus aureus can become resistant to nisin A, one of the bacteriocins applied as a food additive. We isolated a highly nisin A-resistant strain designated SAN2 that displayed increased expression of Pmt proteins, which are involved in the secretion of virulence factors called phenol-soluble modulins (PSMs). This strain also showed decreased susceptibility to human antimicrobial peptides and increased hemolytic activity. In addition, SAN2 showed increased lethal activity in a mouse bacteremia model. Our study provides new insights into the possibility that the acquisition of resistance against food preservatives may modulate virulence in S. aureus, suggesting that we need to pay more attention to the use of food preservatives together with antibiotics.

New Technological Approach for Glycyrrethic Acid Oral and Topical Administration

Background:

18β- glycyrrhetinic acid (Gly) is the major bioactive component of licorice roots and rhizomes of the Glycyrrhiza glabra species. It shows many activities such as antiviral, anti-inflammatory, antioxidant, antimicrobial, and antifungal, however, its use in the health field is very limited due to the low water solubility.

Methods:

This paper deals with the development of a new technological approach for Gly dissolution rate enhancement. It consists of Gly intercalation (guest) in the interlamellar spaces between the inorganic spaces (host) of the anionic clays “hydrotalcites” (HTlc) to obtain hybrids MgAl-HTlc-Gly and ZnAl-HTlc-Gly. Gly can find applications in both systemic and local therapies, thus advantages of the use of the hybrids in these two fields were investigated.

Results:

Gly dissolution rate from hybrids in the intestinal environment, site in which it is preferentially absorbed, resulted enhanced (ZnAl-HTlc-Gly > MgAl-HTlc-Gly) compared to the crystalline form, thereby, making them suitable for oral administration as dry powder in hard capsules.

:

For a local therapy, bioadhesive, vaginal emulgels loaded with the hybrids were developed. These showed suitable mucoadhesive property to the vaginal mucosa, necessary to prolong the residence time in the application site. The emulgel containing ZnAl-HTlc-Gly showed a faster and higher release profile than that containing MgAl- HTlc-Gly.

Conclusions:

The obtained results suggest that Gly intercalation into HTlc, especially in ZnAl-HTlc, allows to enhance Gly dissolution when the hybrids are formulated both as oral or topical products.

Exploring Anti-Fungal, Anti-Microbial and Anti-Inflammatory Properties of a Topical Non-Steroidal Barrier Cream in Face and Chest Seborrheic Dermatitis

INTRODUCTION

The pathogenesis of seborrheic dermatitis (SD) is multifactorial and traditional treatments may not target all aspects of it. The aim of this study was to evaluate short-term anti-fungal, anti-microbial, anti-inflammatory and anti-pruritus properties of a novel non-steroidal cream (NSC) containing piroctone olamine, zinc salt of L-pyrrolidone carboxylate (PCA), hydroxyphenyl propamidobenzoic acid, biosaccharide gum-2 and stearyl glycyrrhetinate in patients with face and chest SD.

METHODS

Twelve male subjects affected by SD, presenting face and chest manifestations, were enrolled. Patients were instructed to apply NSC twice a day, performing regular visits at baseline (W0), after 7 (W1) and 14 (W2) days of treatment. A limitation of the study was that no control group treated with the vehicle without active ingredients was enrolled. To evaluate the efficacy of the NSC, investigator's assessments were represented by scoring index (SI) and investigator's global assessment score (IGA). In order to assess NSC anti-fungal and anti-microbial effects, skin scale scrapings were collected and used for Malassezia furfur (MF) and Staphylococcus epidermidis (SE) cultures. In parallel, in order to assess NSC anti-inflammatory effects, gene expression of IL-1α, IL-1β, IL-6, IL-8, and TNF-α was assessed. In addition, anti-pruritus effects were also evaluated through gene expression of cathepsin S and L-histidine decarboxylase.

RESULTS

SI mean scores significantly decreased at W1 and, to a greater extent, at W2 compared with W0. The IGA score registered an important improvement efficacy both for face and chest, from W1 to W2. MF and SE growth was already inhibited at W1, with a more pronounced decrease at W2. Gene expression of all analyzed mediators was significantly reduced at W1 compared to W0.

CONCLUSION

In conclusion, our assessment is that NSC is an effective and well tolerated treatment option for SD with anti-fungal, anti-microbial and anti-inflammatory properties.

TRIAL REGISTRATION

ISRCTN registry, ISRCTN77871064 (retrospectively registered October 17, 2019). EudraCT number, 2019-003813-32.

FUNDING

ISDIN.

Therapeutic Potential of an Endolysin Derived from Kayvirus S25-3 for Staphylococcal Impetigo

Impetigo is a contagious skin infection predominantly caused by Staphylococcus aureus. Decontamination of S. aureus from the skin is becoming more difficult because of the emergence of antibiotic-resistant strains. Bacteriophage endolysins are less likely to invoke resistance and can eliminate the target bacteria without disturbance of the normal microflora. In this study, we investigated the therapeutic potential of a recombinant endolysin derived from kayvirus S25-3 against staphylococcal impetigo in an experimental setting. First, the recombinant S25-3 endolysin required an incubation period of over 15 minutes to exhibit efficient bactericidal effects against S. aureus. Second, topical application of the recombinant S25-3 endolysin decreased the number of intraepidermal staphylococci and the size of pustules in an experimental mouse model of impetigo. Third, treatment with the recombinant S25-3 endolysin increased the diversity of the skin microbiota in the same mice. Finally, we revealed the genus-specific bacteriolytic effect of recombinant S25-3 endolysin against staphylococci, particularly S. aureus, among human skin commensal bacteria. Therefore, topical treatment with recombinant S25-3 endolysin can be a promising disease management procedure for staphylococcal impetigo by efficient bacteriolysis of S. aureus while improving the cutaneous bacterial microflora.

Topical Non-Pharmacological Treatment for Facial Seborrheic Dermatitis

Facial seborrheic dermatitis (FSD) is a chronic and relapsing inflammatory skin disorder occurring in areas of the face rich in sebaceous glands. It clinically manifests as erythematous scaly macules or plaques, often associated with pruritus. Although the pathogenesis of seborrheic dermatitis is not yet fully understood, Malassezia yeast, hormones, sebum levels, and immune response are known to play important roles. Additional factors including drugs, cold temperatures, and stress may exacerbate the condition. Currently, the available treatments do not cure the disease but relieve symptoms. Various pharmacological treatments are available, including antifungal agents, keratolytics, topical low-potency steroids, and calcineurin inhibitors. All of them provide several benefits, but they also have potential side effects. Seborrheic dermatitis tends to have a chronic, recurrent course. To avoid the long-term use of drugs, topical non-pharmacological products such as cosmetics or medical devices may improve clinical outcomes. Products with antimicrobial and anti-inflammatory ingredients such as zinc, piroctone olamine, dihydroavenanthramide, biosaccharide gum-2, and stearyl glycyrrhetinate may speed FSD recovery and avoid flare-ups. Finally, the use of specific cleansers, moisturizers, and sunscreens formulated as light creams or gel/creams should be strongly recommended to all FSD patients. We provide a brief review of the most used non-pharmacological cleansers, topical gel/creams, and specific sunscreens in the management of FSD.

Antibacterial activity of disodium succinoyl glycyrrhetinate, a derivative of glycyrrhetinic acid against Streptococcus mutans

Streptococcus mutans is a cariogenic bacterium that localizes in the oral cavity. Glycyrrhetinic acid (GRA) is a major component of licorice extract. GRA and several derivatives, including disodium succinoyl glycyrrhetinate (GR-SU), are known to have anti-inflammatory effects in humans. In this study, the antimicrobial effect of GRA and its derivatives against the S. mutans UA159 strain were investigated. Minimum inhibitory concentrations (MICs) of GRA and GR-SU showed antibacterial activity against the S. mutans strain, whereas other tested derivatives did not. Because GR-SU is more soluble than GRA, GR-SU was used for further experiments. The antibacterial activity of GR-SU against 100 S. mutans strains was evaluated and it was found that all strains are susceptible to GR-SU, with MIC values below 256 µg/mL. A cell viability assay showed that GR-SU has a bacteriostatic effect on S. mutans cells. As to growth kinetics, sub-MICs of GR-SU inhibited growth. The effect of GR-SU on S. mutans virulence was then investigated. GR-SU at sub-MICs suppresses biofilm formation. Additionally, GR-SU greatly suppresses the pH drop caused by the addition of glucose and glucose-induced expression of the genes responsible for acid production (ldh and pykF) and tolerance (aguD and atpD). Additionally, expression of enolase, which is responsible for the carbohydrate phosphotransferase system, was not increased in the presence of GR-SU, indicating that GR-SU suppresses incorporation of sugars into S. mutans. In conclusion, GR-SU has antibacterial activity against S. mutans and also decreases S. mutans virulence.

Chitin Nanofibrils and Nanolignin as Functional Agents in Skin Regeneration

Chitin and lignin, by-products of fishery and plant biomass, can be converted to innovative high value bio- and eco-compatible materials. On the nanoscale, high antibacterial, anti-inflammatory, cicatrizing and anti-aging activity is obtained by controlling their crystalline structure and purity. Moreover, electropositive chitin nanofibrlis (CN) can be combined with electronegative nanolignin (NL) leading to microcapsule-like systems suitable for entrapping both hydrophilic and lipophilic molecules. The aim of this study was to provide morphological, physico-chemical, thermogravimetric and biological characterization of CN, NL, and CN-NL complexes, which were also loaded with glycyrrhetinic acid (GA) as a model of a bioactive molecule. CN-NL and CN-NL/GA were thermally stable up to 114 °C and 127 °C, respectively. The compounds were administered to in vitro cultures of human keratinocytes (HaCaT cells) and human mesenchymal stromal cells (hMSCs) for potential use in skin contact applications. Cell viability, cytokine expression and effects on hMSC multipotency were studied. For each component, CN, NL, CN-NL and CN-NL/GA, non-toxic concentrations towards HaCaT cells were identified. In the keratinocyte model, the proinflammatory cytokines IL-1α, IL-1 β, IL-6, IL-8 and TNF-α that resulted were downregulated, whereas the antimicrobial peptide human β defensin-2 was upregulated by CN-LN. The hMSCs were viable, and the use of these complexes did not modify the osteo-differentiation capability of these cells. The obtained findings demonstrate that these biocomponents are cytocompatible, show anti-inflammatory activity and may serve for the delivery of biomolecules for skin care and regeneration.

The influence of glycyrrhetinic acid (enoxolone) toothpaste on periodontal treatment outcomes and salivary levels of IL-8, TNF-α, IL-17, MCP-1 and VEGF in patients with chronic periodontitis

This study evaluates the influence of glycyrrhetinic acid (enoxolone) toothpaste on the results of scaling and root planing as well as salivary levels of IL-8, TNF-α, IL-17, MCP-1 and VEGF in patients with chronic periodontitis. Clinical parameters and biomarkers of periodontitis were assessed longitudinally to determine response to the therapy. A 3-month case-controlled study of adults with chronic periodontitis was performed, with 18 patients receiving scaling and root planing and enoxlone toothpaste (group A) and 18 with scaling and root planing with regular toothpaste (group B). Clinical measurements of periodontal disease were recorded and saliva samples were collected at week 0 and 12. Samples were analyzed for immune markers: Interleukin-8 (IL-8), Tumor Necrosis Factor-α (TNF-α), Interleukin-17 (IL-17), Monocyte Chemoattractant Protein -1 (MCP-1) and Vascular Endothelial Growth Factor (VEGF). All parameters of periodontal health improved significantly in both groups by week 12 (p<0.01) with no significant differences between groups. However, improvements in group A were greater than in group B. IL-8, TNF-α, IL-17, MCP-1 and VEGF levels decreased significantly from baseline (p<0.01) in group A only. Salivary levels of IL-8, TNF-α, IL-17, MCP-1 and VEGF seem to reflect disease severity and response to therapy, suggesting their potential utility for monitoring periodontal disease status. Greater improvements of periodontal parameters and significant reduction of salivary biomarkers’ levels suggest potential benefits of glycyrrhetinic acid toothpaste in periodontal therapy.

The relationship between structure and in vitro antistaphylococcal effect of plant-derived stilbenes

Staphylococcus aureus is a major human pathogen that is responsible for both hospital- and community-acquired infections. Stilbenes are polyphenol compounds of plant origin known to possess a variety of pharmacological properties, such as antibacterial, antiviral, and antifungal effects. This study reports the in vitro growth-inhibitory potential of eight naturally occurring stilbenes against six standard strains and two clinical isolates of S. aureus, using a broth microdilution method, and expressing the results as minimum inhibitory concentrations (MICs). Pterostilbene (MICs = 32-128 μg/ml), piceatannol (MICs = 64-256 μg/ml), and pinostilbene (MICs = 128 μg/ml) are among the active compounds that possess the strongest activity against all microorganisms tested, followed by 3'-hydroxypterostilbene, isorhapontigenin, oxyresveratrol, and rhapontigenin with MICs 128-256 μg/ml. Resveratrol (MIC = 256 μg/ml) exhibited only weak inhibitory effect. Furthermore, structure-activity relationships were studied. Hydroxyl groups at ortho-position (B-3' and -4') played crucial roles for the inhibitory effect of hydroxystilbene piceatannol. Compounds with methoxy groups at ring A (3'-hydroxypterostilbene, pinostilbene, and pterostilbene) produced stronger effect against S. aureus than their analogues (isorhapontigenin and rhapontigenin) with methoxy groups at ring B. These findings provide arguments for further investigation of stilbenes as prospective leading structures for development of novel antistaphylococcal agents for topical treatment of skin infections.

Liquorice (Glycyrrhiza glabra): A phytochemical and pharmacological review

In the last years, consumers are paying much more attention to natural medicines and principles, mainly due to the general sense that natural compounds are safe. On the other hand, there is a growing demand by industry for plants used in traditional medicine that could be incorporated in foods, nutraceuticals, cosmetics, or even pharmaceuticals. Glycyrrhiza glabra Linn. belongs to the Fabaceae family and has been recognized since ancient times for its ethnopharmacological values. This plant contains different phytocompounds, such as glycyrrhizin, 18β-glycyrrhetinic acid, glabrin A and B, and isoflavones, that have demonstrated various pharmacological activities. Pharmacological experiments have demonstrated that different extracts and pure compounds from this species exhibit a broad range of biological properties, including antibacterial, anti-inflammatory, antiviral, antioxidant, and antidiabetic activities. A few toxicological studies have reported some concerns. This review addresses all those issues and focuses on the pharmacological activities reported for G. glabra. Therefore, an updated, critical, and extensive overview on the current knowledge of G. glabra composition and biological activities is provided here in order to explore its therapeutic potential and future challenges to be utilized for the formulation of new products that will contribute to human well-being.

Decrease of growth, biofilm and secreted virulence in opportunistic nosocomial Pseudomonas aeruginosa ATCC 25619 by glycyrrhetinic acid

The present study elucidates the antibiofilm and antivirulent capability of glycyrrhetinic acid (GRA) against Pseudomonas aeruginosa ATCC 25619. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of GRA against P. aeruginosa were found to be 160 μg/mL and 420 μg/mL respectively. In an acclimatization resistance analysis using P. aeruginosa, no resistance towards GRA was observed during the habituation period. Adequate penetration of GRA over the biofilm matrix was proposed with the membrane penetration model assembly constructed with the preformed biofilm exhibited the prospective penetration of GRA above the mature biofilm. Furthermore, GRA resulted in the attenuation of virulence factors such as motility, biofilm formation, pyocyanin secretion, secreted proteases with its sub MIC concentrations. The antibiofilm property of GRA was assessed with the light microscopy and high content screening fluorescent imaging system, which clearly demonstrates, the thickness of P. aeruginosa biofilm was reduced to 11.33 ± 2.08 μm from 39 ± 2.51 μm. Transmission Electron Microscopy (TEM) images depicted the morphological changes in cells such as disaggregation of colonies, cell disruption with loss of intracellular material, cytolytic damage, the process of morphological transformation, bacteriolysis indicating the potential effect of GRA.

Novel unsaturated glycyrrhetic acids derivatives: Design, synthesis and anti-inflammatory activity

To develop novel anti-inflammatory agents, a series of unsaturated glycyrrhetic acids were designed, synthesized and evaluated for anti-inflammatory activity using RAW264.7 cells. The structure-activity relationship (SAR) of NO inhibitory activity was analyzed. α,β-Unsaturated glycyrrhetic acids showed better activity, among them, compounds 6k and 6l with piperazine unit exhibited the most potent nitric oxide (NO) and interleukin-6 (IL-6) inhibitory activity (IC₅₀ = 13.3 and 15.5 μM respectively). Furthermore, compound 6k could also significantly suppress LPS-induced iNOS and COX-2 expression and IL-6 production through MAPKs and NF-kB signaling pathway.