Inhibition of pathogenic microbes in oral infectious diseases by natural products: Sources, mechanisms, and challenges

Streptococcus mutans biofilms in the establishment of dental caries: a review

Dental caries is considered as the most common and multifactorial disease worldwide, caused by a variety of oral microorganisms like Streptococcus spp., Veillonella spp., Actinomyces spp., Bifidobacterium spp., and Lactobacillus fermentum, which colonize food debris in oral cavities. Of them, Streptococcus mutans is the predominant bacterium and can induce progressive tooth destruction, especially during dentition. The superior characteristics of S. mutans, such as the presence of the cell surface protein P1 and exopolysaccharide-synthesizing enzymes, acid tolerance, biofilm-forming ability mediated by brpA gene, and multidrug resistance, render it a highly virulent pathogen in the etiology of dental caries. Given its significant role in dental caries, extensive research has been conducted over the past few decades, focusing on the development of specific antimicrobial treatments, and other innovative therapeutic approaches. To gain deeper insights into the genetic diversity and epidemiological patterns of S. mutans, various genotypic methods have been developed and successfully employed. By combining the insights gained from genetic studies of S. mutans with the suitable control measures against the biofilm, we can develop innovative and effective strategies for preventing and treating dental caries.

Ex vivo oral biofilm model for rapid screening of antimicrobial agents including natural cranberry polyphenols

The search has been ongoing for safe and effective antimicrobial agents for control and prevention of oral biofilm associated with disease. Clinical trials for oral specific anti-bacterials are costly and often provide inconclusive results. The simple approach of ex vivo testing of these agents has not demonstrated utility, likely due to variability of effects observed even with a single donor. We show how shed oral biofilms, easily obtained from donor saliva, and tested under optimized conditions, respond reproducibly to anti-bacterial challenges measured by reductions in rRNA accumulation in susceptible taxa. Responses are in part donor specific, but many bacteria taxa were shown to be reproducibly susceptible over a group of donors. For two antibiotics, vancomycin and penicillin G tested at pharmacologic levels, a subset of Gram-positive bacteria was inhibited. A natural product with antibacterial properties, diluted Vaccinium macrocarpon (cranberry) juice, was shown to inhibit a range of oral taxa, including Alloprevotella sp__HMT_473, Granulicatella adiacens, Lachnoanaerobaculum umeaense, Lepotrichia sp__HMT_215, Peptostreptococcus stomatis, Prevotella nanceiensis, Stomatobaculum sp__HMT_097, Veillonella parvula, and kill some targets. The model discussed in this study has promise as a rapid, precise, and reproducible ex vivo method to test and identify potential clinically useful antimicrobial agents active against the oral biofilm community.

Sulforaphane as a promising anti-caries agents: inhibitory effects on Streptococcus mutans and caries control in a rat model

Dental caries has been one of the most prevalent diseases globally over the last few decades, threatening human oral and general health. The most critical aspect in caries control is to inhibit the dominant cariogenic bacteria Streptococcus mutans (S. mutans). Sulforaphane (SFN), a compound found in a wide range of cruciferous plants, has demonstrated bacteriostatic activities against various pathogenic bacteria. The objective of the present study was to investigate the effects of SFN on S. mutans though both in vitro and in vivo experiment. The minimum inhibitory concentration (MIC) against S. mutans was determined at 256 μg/mL. The growth of S. mutans and the biofilm formation were inhibited by SFN in a dose-dependent manner through suppressing the synthesis of extracellular polysaccharide (EPS) and acid production, as well as decreasing the acid tolerance. Meanwhile, SFN significantly weakened the cariogenic properties of S. mutans at sub-inhibitory concentrations, which were further illustrated by quantitative real-time PCR (qRT-PCR). Moreover, SFN were found to inhibit quorum sensing (QS) by downregulate comCDE system in S. mutans. Further investigation using a rat caries model displayed a prominent caries control in the SFN-treated group with no observed toxicity. The notable results demonstrated in this study highlight the potential of SFN as a natural substitute for current anti-caries agents, while also providing valuable insights into the potential applications of SFN in caries control.

Pathophysiological microenvironments in oral candidiasis

Oral candidiasis (OC), a prevalent opportunistic infection of the oral mucosa, presents a considerable health challenge, particularly in individuals with compromised immune responses, advanced age, and local predisposing conditions. A considerable part of the population carries Candida in the oral cavity, but only few develop OC. Therefore, the pathogenesis of OC may depend on factors other than the attributes of the fungus, such as host factors and other predisposing factors. Mucosal trauma and inflammation compromise epithelial integrity, fostering a conducive environment for fungal invasion. Molecular insights into the immunocompromised state reveal dysregulation in innate and adaptive immunity, creating a permissive environment for Candida proliferation. Detailed examination of Candida species (spp.) and their virulence factors uncovers a nuanced understanding beyond traditional C. albicans focus, which embrace diverse Candida spp. and their strategies, influencing adhesion, invasion, immune evasion, and biofilm formation. Understanding the pathophysiological microenvironments in OC is crucial for the development of targeted therapeutic interventions. This review aims to unravel the diverse pathophysiological microenvironments influencing OC development focusing on microbial, host, and predisposing factors, and considers Candida resistance to antifungal therapy. The comprehensive approach offers a refined perspective on OC, seeking briefly to identify potential therapeutic targets for future effective management.

Nano-phytosome loaded Retama raetam extract/colistin: antibacterial, antioxidant activities and in vivo lipopolysaccharide-induced-neurotoxicity inhibition

Antibiotics are misused nowadays, leading to the prevalence of antibiotic resistant bacterial strains; causing the world to move towards natural medicine. Retama raetam had wide medicinal use. In the present study, R. raetam ethanolic extract proved to be active against Pseudomonas aeruginosa with MIC values ranged from 15.62 to 250 µg/ml. Antioxidant analysis showed that the extract had high scavenging activity reached 92.40%. GC/MS analysis revealed that Sparteine and Tributyl acetylcitrate represent the extract major components. Furthermore, the combination between Retama raetam extract and colistin showed a synergistic effect. Moreover, nano-phytosome was designated and optimized to encapsulate Retama raetam extract/Colistin. Nano-phytosome characterized by particle size, Zeta potential, polydispersity index and Entrapment efficiency percentage of 16.92-32.85 nm, -30.40 mV, 0.26 and 89% respectively. The antibacterial activity of the prepared nano-phytosome formula against P. aeruginosa showed promising MIC, MBC, MIC index, and IZ diameter reaching 7.81, 15.62 µg/ml, 2, and 39 mm, respectively. While TEM examination of P. aeruginosa cells treated with nano-phytosome formula revealed cell wall breakage which led to cell death. Finally, P. aeruginosa LPS was used to induce neurodegenerative disease in rat model. Rats treated with nano-phytosome formula showed normal histoarchitecture organization and the cerebral cortex was partially restored compared to control groups.

Sophoraflavanone G: A review of the phytochemistry and pharmacology

Bioactive compounds derived from natural sources have long been investigated for the prevention and treatment of human diseases. Sophoraflavanone G (SFG), a lavandulyl flavanone naturally occurring in several Sophora plant species, belongs to the group of prenylated flavonoids that have garnered significant interest in contemporary research. The natural molecule exhibits a wide range of pharmacological properties and shows remarkable efficacy. Its ability to effectively suppress a range of malignant tumor cells, such as leukemia, breast cancer, and lung cancer, is attributed to its multi-target, multi-pathway, and multi-faceted mechanisms of action. Simultaneously, it can also alleviate various inflammatory diseases by mediating inflammatory mediators and molecular pathways. Furthermore, it has the capability to combat antibiotic resistance, exhibit synergistic antibacterial properties with diverse antibiotics, and prevent and treat various agricultural pests. Theoretically, it can bring benefits to human health and has potential value as a drug. Nevertheless, the drawbacks of poor water solubility and inadequate targeting cannot be overlooked. To comprehensively assess the current research on SFG, leverage its structural advantages and pharmacological activity, overcome its low bioavailability limitations, expedite its progression into a novel therapeutic drug, and better serve the clinic, this article presents a overall retrospect of the current research status of SFG. The discussion includes an analysis of the structural characteristics, physicochemical properties, bioavailability, pharmacological activities, and structure-activity relationships of SFG, with the goal of offering valuable insights and guidance for future research endeavors in this field.

Ethanol extract from Astilbe chinensis inflorescence suppresses inflammation in macrophages and growth of oral pathogenic bacteria

Chronic oral inflammation and biofilm-mediated infections drive diseases such as dental caries and periodontitis. This study investigated the anti-inflammatory and antibacterial potential of an ethanol extract from Astilbe chinensis inflorescence (GA-13-6) as a prominent candidate for natural complex substances (NCS) with therapeutic potential. In LPS-stimulated RAW 264.7 macrophages, GA-13-6 significantly suppressed proinflammatory mediators, including interleukin-6 (IL-6), tumor necrosis factor (TNF), and nitric oxide (NO), surpassing purified astilbin, a known bioactive compound found in A. chinensis. Furthermore, GA-13-6 downregulated the expression of cyclooxygenase-2 (COX2) and inducible nitric oxide synthase (iNOS), indicating an inhibitory effect on the inflammatory cascade. Remarkably, GA-13-6 exhibited selective antibacterial activity against Streptococcus mutans, Streptococcus sanguinis, and Porphyromonas gingivalis, key players in dental caries and periodontitis, respectively. These findings suggest that complex GA-13-6 holds the potential for the treatment or prevention of periodontal and dental diseases, as well as various other inflammation-related conditions, while averting the induction of antibiotic resistance.

Optimization of Flavonoid Extraction from Abelmoschus manihot Flowers Using Ultrasonic Techniques: Predictive Modeling through Response Surface Methodology and Deep Neural Network and Biological Activity Assessment

Understanding the optimal extraction methods for flavonoids from Abelmoschus manihot flowers (AMF) is crucial for unlocking their potential benefits. This study aimed to optimize the efficiency of flavonoid extraction from AMF. After comparing extraction methods, the ultrasonic cell crusher demonstrated superior performance over conventional techniques. Four key factors-solid-to-liquid ratio (1:10 to 1:50 g·mL-1), ethanol concentration (55% to 95%), ultrasonic time (10 to 50 min), and ultrasonic power (5% to 25% of 900 W)-were investigated and normalized using the entropy weight method. This led to a comprehensive evaluation (CE). Optimization of extraction conditions for the ultrasonic cell crusher was achieved through response surface methodology and a deep neural network model, resulting in optimal parameters: ethanol volume fraction of 66%, solid-to-liquid ratio of 1:21 g/mL, extraction efficiency of 9%, and extraction duration of 35 min, yielding a CE value of 23.14 (RSD < 1%). Additionally, the inhibitory effects of the optimized extracts against Streptococcus mutans (S. mutans) were assessed. The results revealed that AMF extract (AMFE) exhibits inhibitory effects on S. mutans, with concomitant inhibition of sucrase and lactate dehydrogenase (LDH). The MIC of AMFE against planktonic S. mutans is 3 mg/mL, with an MBC of 6 mg/mL. Within the concentration range of 1/8 MIC to 2 MIC of AMFE, the activities of sucrase and LDH decreased by 318.934 U/mg prot and 61.844 U/mg prot, respectively. The antioxidant activity of AMFE was assessed using the potassium ferricyanide reduction and phosphomolybdenum methods. Additionally, the effect of AMFE on DPPH, ABTS, and ·OH free radical scavenging abilities was determined. The concentrations at which AMFE exhibited over 90% scavenging rate for ABTS and DPPH free radicals were found to be 0.125 mg/mL and 2 mg/mL, respectively.