Antimicrobial Effects against Oral Pathogens and Cytotoxicity of Glycyrrhiza uralensis Extract

A Screen of Traditional Chinese Medicinal Plant Extracts Reveals 17 Species with Antimicrobial Properties

Background/Objectives: Antimicrobial resistance (AMR) is a growing threat that undermines the effectiveness of global healthcare. The Centers for Disease Control and Prevention and the World Health Organization have identified numerous microbial organisms, particularly members of the ESKAPEE pathogens, as critical threats to global health and economic security. Many clinical isolates of these pathogens have become completely resistant to current antibiotics, making treatment nearly impossible. Herbal remedies, such as those found in Traditional Chinese Medicine (TCM), have been practiced for thousands of years and successfully used to treat a wide range of ailments, including infectious diseases. Surprisingly, despite this extensive knowledge of folk medicine, no plant-derived antibacterial drugs are currently approved for clinical use. As such, the objective of this study is to evaluate the antimicrobial properties of extracts derived from TCM plants. Methods: This study explores a comprehensive library comprising 664 extracts from 132 distinct TCM plant species for antimicrobial properties against gram-negative (Escherichia coli) and gram-positive (Micrococcus luteus) bacteria using liquid and solid in vitro assays. Results: Intriguingly, our results reveal 17 plant species with potent antimicrobial properties effective primarily against gram-positive organisms, including Streptococcus aureus and epidermidis. A literature search revealed that nearly 100 purified compounds from the identified TCM plants were previously isolated and confirmed for their antimicrobial properties, collectively inhibiting 45 different bacterial species. Conclusions: Our results indicate that phytobiotics from the identified plants could serve as potential candidates for novel antimicrobials.

Biological, Antifungal, and Physical Efficacy of a Denture Cleanser Formulated with Cnidium officinale Extracts

BACKGROUND/OBJECTIVES

We aimed to assess the antifungal efficacy and impact of a denture cleanser containing Cnidium officinale extract on the surface characteristics of denture base materials, as well as its physical and biological properties.

METHODS

The experimental denture cleansers were formulated with C. officinale at concentrations of 100 and 150 μg/mL, combined with 1% cocamidopropyl betaine as a natural surfactant. Antifungal efficacy was evaluated using zone-of-inhibition assays against Candida albicans, revealing inhibition zones of 20 ± 1.8 mm for the 100 μg/mL concentration and 23.6 ± 1.6 mm for the 150 μg/mL concentration. Surface property assessments-including hardness, roughness, color stability, and solubility measurements-demonstrated no significant differences compared to the control group. Biological evaluations included the quantification of polyphenol and flavonoid content.

RESULTS

The C. officinale-based cleanser showed significant antifungal activity without affecting the hardness, roughness, color stability, or solubility of denture base materials. Biological tests revealed no cytotoxicity and minimal mucosal irritation. Polyphenol and flavonoid contents were quantitatively measured, revealing higher concentrations in the experimental groups, which were correlated with significant antifungal activity. These compounds are known for their roles in disrupting microbial processes and enhancing antimicrobial effects. These findings suggest that the C. officinale-based denture cleanser effectively inhibits C. albicans while preserving the physical properties of denture base materials.

CONCLUSIONS

This study highlights the potential of C. officinale in denture cleanser formulations, promoting denture hygiene and oral health. Future research should prioritize long-term clinical evaluations and formulation optimization.

A Comprehensive Review of Licorice: The Preparation, Chemical Composition, Bioactivities and Its Applications

Licorice (Glycyrrhiza) is a medicinal and food homologue of perennial plants derived from the dried roots and rhizomes of the genus Glycyrrhiza in the legume family. In recent years, the comprehensive utilization of licorice resources has attracted people's attention. It is widely utilized to treat diseases, health food products, food production, and other industrial applications. Furthermore, numerous bioactive components of licorice are found using advanced extraction processes, which mainly include polyphenols (flavonoids, dihydrostilbenes, benzofurans, and coumarin), triterpenoids, polysaccharides, alkaloids, and volatile oils, all of which have been reported to possess a variety of pharmacological characteristics, including anti-oxidant, anti-inflammatory, antibacterial, antiviral, anticancer, neuroprotective, antidepressive, antidiabetic, antiparasitic, antisex hormone, skin effects, anticariogenic, antitussive, and expectorant activities. Thereby, all of these compounds promote the development of novel and more effective licorice-derived products. This paper reviews the progress of research on extraction techniques, chemical composition, bioactivities, and applications of licorice to provide a reference for further development and application of licorice in different areas.

Poly (Methyl Methacrylate)-Containing Silver-Phosphate Glass Exhibits Potent Antimicrobial Activity without Deteriorating the Mechanical and Biological Properties of Dental Prostheses

Poly (methyl methacrylate) (PMMA) is a commonly used denture material with poor antimicrobial effects. This study investigated the antimicrobial effects of PMMA-containing silver-phosphate glass. We fabricated a novel material comprising PMMA-containing silver-phosphate glass. Then, microhardness, flexural strength, and gloss unit were analyzed. Antimicrobial activity against Streptococcus mutans and Candida albicans was investigated. Colony-forming units were counted, and antimicrobial rates were measured. Biocompatibility tests were performed using a colorimetric MTT assay for evaluating cell metabolic activity. The microhardness, flexural strength, and gloss unit of the experimental groups (with silver-phosphate glass) were not significantly different from those of the control group (no silver-phosphate glass) (P > 0.05), which showed clinically valid values. With increasing proportions of silver-phosphate glass, the antimicrobial activity against the two microorganisms increased (P < 0.05). Furthermore, S. mutans showed more than 50% antimicrobial activity in 4%, 6%, and 8% experimental groups, C. albicans showed more than 50% antimicrobial activity in 6% and 8% groups, and a statistically significant difference in antimicrobial activity was observed compared to the control (P < 0.05). The cell viability of the experimental groups was not significantly different from that of the control group (P > 0.05). Both control and experimental groups showed approximately 100% cell viability. These results suggest that silver-phosphate glass is a promising antimicrobial material in dentistry.

Antimicrobial Synergy between Aminoglycosides and Licorice Extract in Listeria monocytogenes

Listeria monocytogenes is a foodborne pathogen that can develop serious invasive infections. Among foodborne pathogens, L. monocytogenes exhibits the highest case fatality despite antibiotic treatment, suggesting the current therapy should be improved. Although ampicillin and gentamicin are used as a combination therapy to treat listeriosis, our results showed there is no synergy between the two antibiotics. We discovered that aqueous extract of licorice generated significant antimicrobial synergy when combined with aminoglycosides, such as gentamicin, in L. monocytogenes. In the presence of 1 mg/mL licorice extract, for instance, the minimum inhibitory concentration (MIC) of gentamicin was reduced by 32-fold. Moreover, antimicrobial synergy with licorice extract made gentamicin-resistant clinical isolates of L. monocytogenes susceptible to gentamicin. Given the common use of licorice as a food sweetener in Western countries and a herb in Oriental medicine, our findings suggest that licorice extract can be potentially used as an antibiotic adjuvant to improve the efficacy of antimicrobial treatment of listeriosis.

Pharmacological Effects and Underlying Mechanisms of Licorice-Derived Flavonoids

Glycyrrhizae Radix et Rhizoma is the most frequently prescribed natural medicine in China and has been used for more than 2,000 years. The flavonoids of licorice have garnered considerable attention in recent decades due to their structural diversity and myriad pharmacological effects, especially as novel therapeutic agents against inflammation and cancer. Although many articles have been published to summarize different pharmacological activities of licorice in recent years, the systematic summary for flavonoid components is not comprehensive. Therefore, in this review, we summarized the pharmacological and mechanistic data from recent researches on licorice flavonoids and their bioactive components.

A Randomized, Double-Blind, Placebo-Controlled Clinical Trial of a Mouthwash Containing Glycyrrhiza uralensis Extract for Preventing Dental Caries

This study sought to confirm the effect of using a mouthwash containing Glycyrrhiza uralensis extract for oral health management by investigating changes in the pH of dental plaque and bacteria that cause dental caries. A randomized, double-blind, placebo-controlled study was conducted on 60 subjects categorized in either the Glycyrrhiza uralensis extract gargle group (n = 30) or the saline gargle group (n = 30). Scaling was conducted in order to ensure the homogeneity of the oral environment, while gargling was performed once daily before the subjects went to bed for 5 days based on the group. Caries activity was assessed using the Cariview test, while detection of the bacteria that cause dental caries was confirmed using microbiological analysis. All clinical measurements and evaluations were conducted by two trained dental hygienists under the supervision of a dentist. Based on the analysis of dental caries activity and dental caries-causing bacteria, the Glycyrrhiza uralensis extract gargle group showed a clear decrease in bacteria compared to the saline gargle group. Glycyrrhiza uralensis extract demonstrated no risk of tooth demineralization. It also showed excellent antibacterial activity through inhibition and effective reduction of bacteria that cause dental caries. Therefore, the mouthwash containing Glycyrrhiza uralensis extract is an effective oral care product suitable for use as an effective dental caries prevention agent.

Surface Characterization, Biocompatibility and Antifungal Efficacy of a Denture-Lining Material Containing Cnidium officinale Extracts

Herein, we investigated the surface characterization and biocompatibility of a denture-lining material containing Cnidium officinale extracts and its antifungal efficacy against Candida albicans. To achieve this, a denture-lining material containing various concentrations of C. officinale extract and a control group without C. officinale extract were prepared. The surface characterization and biocompatibility of the samples were investigated. In addition, the antifungal efficacy of the samples on C. albicans was investigated using spectrophotometric growth and a LIVE/DEAD assay. The results revealed that there was no significant difference between the biocompatibility of the experimental and control groups (p > 0.05). However, there was a significant difference between the antifungal efficiency of the denture material on C. albicans and that of the control group (p < 0.05), which was confirmed by the LIVE/DEAD assay. These results indicate the promising potential of the C. officinale extract-containing denture-lining material as an antifungal dental material.

Surface Characterization, Antimicrobial Activity, and Biocompatibility of Autopolymerizing Acrylic Resins Coated with Reynoutria elliptica Extract

We conducted surface characterization to assess the biocompatibility and investigate the antimicrobial activity against oral pathogens in autopolymerizing acrylic resins, coated with light-curable coating resin, containing various concentrations of Reynoutria elliptica extract (0, 200, 400, and 600 µg/mL). The R. elliptica extract powder was prepared using a freeze-drying technique. Further, a goniometer and microhardness tester were used to determine the water contact angle, and Vickers hardness, respectively; color measurements were performed on the uncoated and coated acrylic resin disks. The polyphenol content of the extracts from the coated acrylic resin disk was analyzed using UV-VIS spectroscopy. The antimicrobial activity of the coated acrylic resin disk against Streptococcus mutans and Candida albicans was observed for 24 and 48 h by measuring the optical density using spectrophotometry. In addition, biocompatibility was confirmed by testing the cell viability according to ISO 10993-5. The water contact angle, Vickers hardness, and color change values of the coated acrylic resin disks were not significantly different from the control. Polyphenol was detected in all experimental groups, with no significant differences between the experimental groups. The experimental groups exhibited significant antimicrobial activity against S. mutans and C. albicans compared to the control group, after 48 h of incubation. The cell viability between the control and experimental groups was not significantly different. The proposed coating resin containing R. elliptica extract is applicable on dental acrylic resins, due to their antimicrobial properties and excellent biocompatibility, with no deterioration of surface characteristics.