Antibacterial activity of flavonoids and their structure-activity relationship: An update review

Chemical composition, antibacterial potential, and toxicity of the extracts from the stem bark of Hancornia speciosa Gomes (Apocynaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Hancornia speciosa is a medicinal plant popularly used to treat different medical issues, including infectious diseases. Exploring the therapeutic potentialities of the extracts from medicinal plants combined with conventional antibiotic drugs is a promising horizon, especially considering the rising microbial resistance.

AIM OF THE STUDY

This study aimed to characterize the chemical composition of the ethereal (EEHS) and methanolic (MEHS) extracts of the stem bark of H. speciosa, and also evaluate their antibacterial and drug-modifying activity, and toxicity.

MATERIALS AND METHODS

The extracts were characterized by gas chromatography coupled to mass spectrometry (GC-MS). Additionally, total phenol and flavonoid contents were determined. The antibacterial and antibiotic-modifying activity was evaluated against strains of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa using the serial microdilution method, obtaining the minimum inhibitory concentration (MIC). The toxicity assay was carried out using the Drosophila melanogaster model.

RESULTS

Thirty compounds were identified in the extracts of the stem bark of H. speciosa, with triterpenoids being predominant in both extracts. Additionally, fatty alcohols, carbohydrates, fatty acids, phenolic acids, and phytosterols were identified in both extracts. EEHS and MEHS extracts had considerable phenol contents (346.4 and 340.0 mg GAE/g, respectively). Flavonoids were detected in a lower proportion (7.6 and 6.9 mg QE/g, respectively). H. speciosa extracts did not display intrinsic antibacterial activity against the bacterial strains evaluated, however, they were capable of modifying the activity of gentamicin, erythromycin, and norfloxacin. EEHS increased the efficacy of norfloxacin against E. coli and S. aureus, reducing MIC values by 50%. MEHS potentiated the action of gentamicin against all bacterial strains, especially against E. coli. The extracts did not display toxicity at clinically relevant concentrations against D. melanogaster.

CONCLUSION

The stem bark of H. speciosa was considered a rich source of bioactive compounds. Our findings evidenced the therapeutic potential of H. speciosa extracts for the development of new pharmaceutical therapeutics against bacteria. Although the extracts did not exhibit intrinsic antibacterial activity, they enhanced the efficacy of commercial antibiotic drugs and were non-toxic at clinically relevant concentrations. Future studies are needed to elucidate the mechanisms of action of these extracts, ensuring their safety and efficacy.

Synergistic effect of phenylpropanoids and flavonoids with antibiotics against Gram-positive and Gram-negative bacterial strains

CONTEXT

The increase in bacterial resistance to currently available medications, which increases mortality rates, treatment costs is a global problem, and highlights the need for novel classes of antibacterial agents or new molecules that interact synergistically with antimicrobials.

OBJECTIVE

The current work explores the potential synergistic effects of certain natural phenylpropanoids and flavonoids on ciprofloxacin (CIP), ampicillin (AMP), gentamicin (GEN), and tetracycline (TET).

MATERIALS AND METHODS

The adjuvant role of cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid, ferulic acid methyl ester, sinapic acid, apigenin, and luteolin was evaluated by determining the MIC (minimal inhibitory concentration) values of antibiotics in the presence of subinhibitory concentrations (200, 100, and/or 50 µM) of the compounds in Gram-positive and Gram-negative bacterial strains using a 2-fold broth microdilution method. The 96-well plates were incubated at 37 °C for 18 h, and dimethyl sulfoxide was used as a solvent control.

RESULTS

The combination of luteolin with CIP, reduced the MIC values of the antibiotic from 0.625 to 0.3125 µM and to 0.078 µM in 100 and 200 µM concentration, respectively, in sensitive Staphylococcus aureus. Sinapic acid decreased the MIC value of CIP from 0.625 to 0.3125 µM in S. aureus, from 1.56 to 0.78 µM in Klebsiella pneumoniae, and the MIC of GEN from 0.39 to 0.095 µM in Pseudomonas aeruginosa strains.

DISCUSSION AND CONCLUSIONS

These findings are useful in delaying the development of resistance, as the required antibacterial effect can be achieved with the use of lower concentrations of antibiotics.

Antimicrobial activities of natural flavonoids against foodborne pathogens and their application in food industry

The application of natural alternatives as food preservatives has gained much attention due to the escalating negative perception of synthetic preservatives among consumers and the spread of drug-resistance foodborne pathogens. Natural flavonoids have the potential to be employed for food safety due to their antimicrobial properties against a wide range of foodborne pathogenic microorganisms. In this perspective, we reviewed the antimicrobial activities of natural flavonoids, the mechanism of action, as well as their application for food safety and quality. Various strategies for the incorporation of flavonoids into food products were highlighted, including direct addition to food formulations, encapsulation as micro or nanocarriers, and incorporation into edible or active films and coatings. Furthermore, we discussed the current challenges of industrial application of flavonoids, and proposed future trends to enhance their potential as natural preservatives. This review provides a theoretical foundation for the further development and application of flavonoids for food safety.

Multifunctional pH-responsive hydrogel dressings based on carboxymethyl chitosan: Synthesis, characterization fostering the wound healing

Antibiotic abuse is increasing the present rate of drug-resistant bacterial wound infections, producing a significant healthcare burden globally. Herein, we prepared a pH-responsive CMCS/PVP/TA (CPT) multifunctional hydrogel dressing by embedding the natural plant extract TA as a nonantibiotic and cross-linking agent in carboxymethyl chitosan (CMCS) and polyvinylpyrrolidone (PVP) to prompt wound healing. The CPT hydrogel demonstrated excellent self-healing, self-adaptive, and adhesion properties to match different wound requirements. Importantly, this hydrogel showed pH sensitivity and exhibited good activity against resistant bacteria and antioxidant activity by releasing TA in case of bacterial infection (alkaline). Furthermore, the CPT hydrogel exhibited coagulant ability and could rapidly stop bleeding within 30 s. The biocompatible hydrogel effectively accelerated wound healing in a full-thickness skin defect model by thickening granulation tissue, increasing collagen deposition, vascular proliferation, and M2-type macrophage polarization. In conclusion, this study demonstrates that multifunctional CPT hydrogel offers a candidate material with potential applications for infected skin wound healing.

Flavonoidal alkaloids: Emerging targets for drug discovery from Nature's bounty

This paper explores the potential of flavonoid alkaloids, a unique class of compounds that contain both flavonoid and alkaloid structures, as emerging targets for drug discovery. These compounds exhibit diverse biological activities, such as anti-inflammatory, anti-cancer, and anti-diabetic effects, which are attributed to the combination of different flavonoid scaffolds and alkaloid groups. Flavonoid alkaloids have attracted researchers' attention due to their diverse structures and important bio-activities. Therefore, this review summarizes recent advances in the extraction, purification, structural characterization, synthesis pathways and biological activities of flavonoid alkaloids from natural sources. Finally, the potential prospects and challenges associated with this class of compounds in pharmacological research are discussed along with details of a mechanistic investigation and future clinical applications in this research field.

Total flavonoids of litchi Seed alleviates schistosomiasis liver fibrosis in mice by suppressing hepatic stellate cells activation and modulating the gut microbiomes

Infection with Schistosoma japonicum (S. japonicum) is an important zoonotic parasitic disease that causes liver fibrosis in both human and domestic animals. The activation of hepatic stellate cells (HSCs) is a crucial phase in the development of liver fibrosis, and inhibiting their activation can alleviate this progression. Total flavonoids of litchi seed (TFL) is a naturally extracted drug, and modern pharmacological studies have shown its anti-fibrotic and liver-protective effects. However, the role of TFL in schistosomiasis liver fibrosis is still unclear. This study investigated the therapeutic effects of TFL on liver fibrosis in S. japonicum infected mice and explored its potential mechanisms. Animal study results showed that TFL significantly reduced the levels of Interleukin-1β (IL-1β), Tumor Necrosis Factor-α (TNF-α), Interleukin-4 (IL-4), and Interleukin-6 (IL-6) in the serum of S. japonicum infected mice. TFL reduced the spleen index of mice and markedly improved the pathological changes in liver tissues induced by S. japonicum infection, decreasing the expression of alpha-smooth muscle actin (α-SMA), Collagen I and Collagen III protein in liver tissues. In vitro studies indicated that TFL also inhibited the activation of HCSs induced by Transforming Growth Factor-β1 (TGF-β1) and reduced the levels of α-SMA. Gut microbes metagenomics study revealed that the composition, abundance, and functions of the mice gut microbiomes changed significantly after S. japonicum infection, and TLF treatment reversed these changes. Therefore, our study indicated that TFL alleviated granulomatous lesions and improved S. japonicum induced liver fibrosis in mice by inhibiting the activation of HSCs and by improving the gut microbiomes.

Enhancing the antioxidant potential of ESIPT-based naringenin flavonoids based on excited state hydrogen bond dynamics: A theoretical study

Exploring antioxidant potential of flavonoid derivatives after ESIPT process provides a theoretical basis for discovering compounds with higher antioxidant capacity. In this work, employing the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods, the antioxidant potential of two citrus-derived naringenin flavonoids after ESIPT process is explored. Based on studies of ESIPT process including IMHB intensity variations, potential energy curves, and transition state, these molecules exist only in enol and keto⁎ forms due to ultra-fast ESIPT. The HOMOs are utilized to explore electron-donating capacity, demonstrating that the molecules in keto⁎ form is stronger than that in enol form. Furthermore, the atomic dipole moment corrected Hirshfeld population (ADCH) and Fukui functions indicate that the sites attacked by the electrophilic free radical of the two molecules in the keto⁎ form are O3 and O5' respectively, and both are more active than in the enol form. Overall, a comprehensive consideration of the ESIPT process and antioxidant potential of flavonoid derivatives will facilitate the exploration and design of substances with higher antioxidant capacity.

Plant-Derived Antimicrobials and Their Crucial Role in Combating Antimicrobial Resistance

Antibiotic resistance emerged shortly after the discovery of the first antibiotic and has remained a critical public health issue ever since. Managing antibiotic resistance in clinical settings continues to be challenging, particularly with the rise of superbugs, or bacteria resistant to multiple antibiotics, known as multidrug-resistant (MDR) bacteria. This rapid development of resistance has compelled researchers to continuously seek new antimicrobial agents to curb resistance, despite a shrinking pipeline of new drugs. Recently, the focus of antimicrobial discovery has shifted to plants, fungi, lichens, endophytes, and various marine sources, such as seaweeds, corals, and other microorganisms, due to their promising properties. For this review, an extensive search was conducted across multiple scientific databases, including PubMed, Elsevier, ResearchGate, Scopus, and Google Scholar, encompassing publications from 1929 to 2024. This review provides a concise overview of the mechanisms employed by bacteria to develop antibiotic resistance, followed by an in-depth exploration of plant secondary metabolites as a potential solution to MDR pathogens. In recent years, the interest in plant-based medicines has surged, driven by their advantageous properties. However, additional research is essential to fully understand the mechanisms of action and verify the safety of antimicrobial phytochemicals. Future prospects for enhancing the use of plant secondary metabolites in combating antibiotic-resistant pathogens will also be discussed.

Molecular docking studies, DFT, and ADMET calculations of some flavonoids and their characteristic structural features involved in inhibition of pro-inflammatory enzymes

Inflammation is an immune system response triggered by pathogens, damaged cells, or stimuli. Some regulatory enzymes, such as phosphodiesterase, hyaluronidase, collagenase, and lipoxygenase, play an essential role in the inflammatory process. Polyphenolic compounds, such as flavonoids, are active suppressors of inflammatory cytokines, modulators of transcription factors, and inflammation-related pathways. A set of flavonoid structures was screened and docked against inflammation pathway enzymes. Amentoflavone has been shown to cause interactions with phosphodiesterase enzymes, while Bilobetin and Silibinin demonstrated an increase in binding energy with collagenase enzymes. The retrieved compounds from the docking study were subjected to DFT theory. The results showed that the LUMO orbital is located on the flavonoid part. The thermochemical parameters indicated that Silibinin is more stable than other compounds. The ADMET profile predicted that Silibinin can be used orally among the compounds. Silibinin can be introduced as a promising anti-inflammatory agent demonstrating phosphodiesterase and collagenase inhibitory properties.

Bioactivity-Guided Isolation of Secondary Metabolites with Antioxidant and Antimicrobial Activities from Camellia fascicularis

Camellia fascicularis has important ornamental, medicinal, and food values, which also have tremendous potential for exploiting bioactivities. We performed the bioactivity-guided (antioxidant and antimicrobial) screening of eight fractions obtained from the ethyl acetate phase of C. fascicularis. The antioxidant activity was measured by DPPH, ABTS, and FRAP, and the antibacterial activity was measured by the minimum inhibitory concentration (MIC) of Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. The results of bioactivity-guided isolation indicated that the major antioxidant compounds in the ethanolic extracts of C. fascicularis may be present in fractions (Fr.) (A-G, obtained after silica gel column chromatography). Fr. (D-I, obtained after silica gel column chromatography) is a fraction of C. fascicularis with antimicrobial activity. The structures of compounds were determined by spectral analysis and nuclear magnetic resonance (NMR) combined with the available literature on secondary metabolites of C. fascicularis leaves. In this study, 17 compounds were identified, including four phenolics (1, 3-4, and 14), a phenylpropane (2), five terpenoids (5-7, 12, and 15), four flavonoids and flavonoid glycosides (8-10 and 16), and two lignins (13 and 17). Compounds 4-7, 13-15, and 17 were isolated from the genus Camellia for first time. The remaining compounds were also isolated from C. fascicularis for first time. The evaluation of antioxidant and antimicrobial activities revealed that compounds 1, 3, 9, 11, and 17 exhibited higher antioxidant activity than the positive control drug (ascorbic acid), and compounds 4, 8, 10, and 13 showed similar activity to ascorbic acid. The other compounds had weaker or no significant antioxidant activities. The MIC of antibacterial activity for compounds 4, 7, and 11-13 against P. aeruginosa was comparable to that of the positive control drug tetracycline at 125 µg/mL, and other secondary metabolites inhibited E. coli and S. aureus at 250-500 µg/mL. This is also the first report of antioxidant and antimicrobial activities of compounds 5-7, 13-15, and 17. The results of the study enriched the variety of secondary metabolites of C. fascicularis and laid the foundation for further research on the pharmacological efficacy and biological activity of this plant.

Coumarin derivatives ameliorate the intestinal inflammation and pathogenic gut microbiome changes in the model of infectious colitis through antibacterial activity

Coumarin, a phenolic compound, is a secondary metabolite produced by plants such as Tanga and Lime. Coumarin derivatives were prepared via Pechmann condensation. In this study, we performed in vitro and in vivo experiments to determine the antimicrobial and gut immune-regulatory functions of coumarin derivatives. For the in vitro antimicrobial activity assay, coumarin derivatives C1 and C2 were selected based on their pathogen-killing activity against various pathogenic microbes. We further demonstrated that the selected coumarin derivatives disrupted bacterial cell membranes. Next, we examined the regulatory function of the coumarin derivatives in gut inflammation using an infectious colitis model. In an in vivo infectious colitis model, administration of selected C1 coumarin derivatives reduced pathogen loads, the number of inflammatory immune cells (Th1 cells and Th17 cells), and inflammatory cytokine levels (IL-6 and IL-1b) in the intestinal tissue after pathogen infection. In addition, we found that the administration of C1 coumarin derivatives minimized abnormal gut microbiome shift-driven pathogen infection. Potential pathogenic gut microbes, such as Enterobacteriaceae and Staphylococcaceae, were increased by pathogen infection. However, this pathogenic microbial expansion was minimized and beneficial bacteria, such as Ligilactobacillus and Limosilactobacillus, increased with C1 coumarin derivative treatment. Functional gene enrichment assessment revealed that the relative abundance of genes associated with lipid and nucleotide metabolism was reduced by pathogen infection; however, this phenomenon was not observed in C1 coumarin derivative-treated animals. Collectively, our data suggest that C1 coumarin derivative is effective antibacterial agents that minimize pathogen-induced gut inflammation and abnormal gut microbiome modulation through their antibacterial activity.

Adsorption of Flavonoids in a Transcriptional Regulator TtgR: Relative Binding Free Energies and Intermolecular Interactions

Antimicrobial resistance in bacteria often arises from their ability to actively identify and expel toxic compounds. The bacterium strain Pseudomonas putida DOT-T1E utilizes its TtgABC efflux pump to confer robust resistance against antibiotics, flavonoids, and organic solvents. This resistance mechanism is intricately regulated at the transcriptional level by the TtgR protein. Through molecular dynamics and alchemical free energy simulations, we systematically examine the binding of seven flavonoids and their derivatives with the TtgR transcriptional regulator. Our simulations reveal distinct binding geometries and free energies for the flavonoids in the active site of the protein, which are driven by a range of noncovalent forces encompassing van der Waals, electrostatic, and hydrogen bonding interactions. The interplay of molecular structures, substituent patterns, and intermolecular interactions effectively stabilizes the bound flavonoids, confining their movements within the TtgR binding pocket. These findings yield valuable insights into the molecular determinants that govern ligand recognition in TtgR and shed light on the mechanism of antimicrobial resistance in P. putida DOT-T1E.

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.

Five Underutilized Ecuadorian Fruits and Their Bioactive Potential as Functional Foods and in Metabolic Syndrome: A Review

The Ecuadorian Amazon harbors numerous wild and cultivated species used as food, many of which are underutilized. This review explores the bioactive potential of five such fruits-Borojó (Alibertia patinoi); Chonta (Bactris gasipaes); Arazá (Eugenia stipitata); Amazon grape (Pourouma cecropiifolia), a wild edible plant; and Cocona (Solanum sessiliflorum)-and their applications against metabolic syndrome. This study highlights their health-promoting ingredients and validates traditional medicinal properties, emphasizing their significance in improving health and mitigating the effects of the Western diet. These fruits, integral to Ecuadorian cuisine, are consumed fresh and processed. Chonta is widely cultivated but less prominent than in pre-Hispanic times, Borojó is known for its aphrodisiac properties, Cocona is traditional in northern provinces, Arazá is economically significant in food products, and Amazon grape is the least utilized and researched. The fruits are rich in phenolics (A. patinoi, E. stipitata) and carotenoids (B. gasipaes, E. stipitata), which are beneficial in controlling metabolic syndrome. This study advocates for more research and product development, especially for lesser-known species with high phenolic and anthocyanin content. This research underscores the economic, cultural, and nutritional value of these fruits, promoting their integration into modern diets and contributing to sustainable agriculture, cultural preservation, and public health through functional foods and nutraceuticals.

The Development of a Method for Obtaining Tripleurospermum inodorum (L.) Sch. Bip. Herb Extract Enriched with Flavonoids and an Evaluation of Its Biological Activity

The development of new drugs derived from plant sources is of significant interest in modern pharmacy. One of the promising plant sources for introduction into pharmaceuticals is Tripleurospermum inodorum (L.) Sch. Bip., also known as Tripleurospermum perforatum (Merat.) M. This plant has been shown to possess various biological activities, including anti-inflammatory, antimicrobial, and antimycotic activities, among others. However, a review of the current literature reveals a paucity of studies investigating the chemical composition of the herb Tripleurospermum inodorum (L.) Sch. Bip. This study presents the development of a method for obtaining an extract of the herb Tripleurospermum inodorum (L.) Sch. Bip. enriched with flavonoids, harvested before flowering and butonization. This study focused on determining the optimal conditions for extraction, including the concentration of the extractant (ethanol), extraction time, raw material/extractant ratio, extraction frequency, complexation reaction time, amount of aluminum chloride solution, and amount of diluted acetic acid. The results indicate that herbs harvested during this specific period exhibited a higher flavonoid content compared to those collected during butonization and flowering. Moreover, this study demonstrated that the flavonoid content could exceed 7% mg REq/100 g D.W. through a one-hour extraction process. Furthermore, the flavonoid content was found to be 7.65 ± 0.03 mg REq/100 g D.W. following a three-minute ultrasound-assisted extraction process, followed by thermal extraction. A qualitative analysis identified a variety of phenolic compounds in the extract, such as chlorogenic acid, 5-O-p-coumaroylquinic acid, 1-O-p-coumaroylquinic acid, luteolin-7-glucoside, quercetin-3-glucoside, luteolin-7-rutinoside, 3,5-O-dicaffeoylquinic acid, quercetin-3-O-malonylglucoside, apigenin-7-glucoside, luteolin-3-malonylglucoside, cynarin, rhamnetin-3-(O-dimethyl rhamnosyl glucosylglucoside), and luteolin. Moreover, this study demonstrated the antimicrobial, anti-inflammatory, anticoagulant, anti-aggregation, and antioxidant activities of the aqueous alcoholic extract from T. inodorum herb (ETIH) against pathogens such as Staphylococcus aureus, Escherichia coli, and Candida albicans. Additionally, the extract exhibited comparable anti-inflammatory effects on diclofenac sodium. These findings contribute to the understanding of the potential pharmacological applications of the developed herb extract.

Natural product nanozymes of herbal extract galangin in managing hepatocellular carcinoma

Numerous local herbal extract species have been investigated as potential medicinal ingredients due to their promising anti-cancer properties. However, the primary constraint of the class of plant flavonoids lies in their low solubility and limited membrane permeability, leading to chemical instability and restricted bioavailability that impede biomedical applications. In this study, we have developed an ideal nanozyme-Galazyme, comprising galangin-loaded copper Nanozyme coated by DSPE-PEG, which amplifies oxidative stress to induce apoptosis via the regulation of reactive oxygen species (ROS) generation and mitogen-activated protein kinase (MAPK) activation. Galazyme exhibited significant peroxidase mimetic activity, demonstrating its potential to generate ROS and elevate oxidative stress. Upon uptake by HepG-2 cells, Galazyme efficiently converts excess hydrogen peroxide (H2O2) into highly reactive •OH radicals and upregulates MAPK expression, leading to the activation of Bax and Caspase 3, thereby promoting irreversible tumor cell apoptosis. Both in vitro and in vivo results demonstrate that Galazyme inhibits tumor cell growth and induces apoptosis by generating ample ROS and activating the MAPK pathway. Our study offers novel evidence supporting the enhancement of Galazyme-induced apoptosis through the upregulation of Bax and Caspase 3, along with the elucidation of the interaction between MAPK and apoptosis.

Natural Products with Potential Effects on Hemorrhoids: A Review

Hemorrhoid disease is a common anorectal disorder affecting populations worldwide, with high prevalence, treatment difficulties, and considerable treatment costs. Compared to other treatment options, medical therapy for hemorrhoids offers minimal harm, more dignity to patients, and is more economical. Unfortunately, there are few chemical hemorrhoid medications available clinically, which makes the search for efficacious, cost-effective, and environmentally friendly new medication classes a focal point of research. In this context, searching for available natural products to improve hemorrhoids exhibits tremendous potential. These products are derived from nature, predominantly from plants, with a minor portion coming from animals, fungi, and algae. They have excellent coagulation pathway regulation, anti-inflammatory, antibacterial, and tissue regeneration activities. Therefore, we take the view that they are a class of potential hemorrhoid drugs, prevention products, and medication add-on ingredients. This article first reviews the factors contributing to the development of hemorrhoids, types, primary symptoms, and the mechanisms of natural products for hemorrhoids. Building on this foundation, we screened natural products with potential hemorrhoid improvement activity, including polyphenols and flavonoids, terpenes, polysaccharides, and other types.

Plant Flavonoids with Antimicrobial Activity against Methicillin-Resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) has become a serious threat to human public health and global economic development, and there is an urgent need to develop new antimicrobial agents. Flavonoids are the largest group of plant secondary metabolites, and the anti-S. aureus and anti-MRSA activities of flavonoids have now been widely reported. The aim of this Review is to describe plant-derived flavonoid active ingredients and their effects and mechanisms of inhibitory activity against MRSA in order to provide insights for screening novel antimicrobial agents. Here, 85 plant-derived flavonoids (14 flavones, 21 flavonols, 26 flavanones, 9 isoflavones, 12 chalcones, and 3 other classes) with anti-MRSA activity are reviewed. Among these flavonoids, flavones and isoflavones generally showed the most significant anti-MRSA activity (MICs: 1-8 μg/mL). The results of the present Review display that most of the flavonoids with excellent anti-MRSA activity were derived from Morus alba L. and Paulownia tomentosa (Thunb.) Steud. The antibacterial mechanism of flavonoids against MRSA is mainly achieved by disruption of membrane structures, inhibition of efflux pumps, and inhibition of β-lactamases and bacterial virulence factors. We hope this Review can provide insights into the development of novel antimicrobials based on natural products for treating MRSA infections.

Applications of magnetic solid-phase extraction in the sample preparation of natural product analysis (2020-2023)

Sample preparation, including extraction, separation, and purification, is a vital process for natural product analysis. As an attractive sample pretreatment method, magnetic solid-phase extraction (MSPE) has gained plenty of attention, mainly due to its simpler operation, less consumption of organic solvents, and shorter processing time than traditional SPE. This updated review is devoted to summarizing the applications of MSPE based on different magnetic nanomaterials in the analysis of various natural products in complex matrixes, such as biological samples, plants, and Chinese herbal preparations in the past four years (2020-2023). The preparation and fabrication of different materials are briefly introduced. Furthermore, the extraction mechanism and interaction forces between adsorbent and analytes are elaborated, and the advantages and disadvantages of different adsorbents coupled with various analytical methods for MSPE of different natural products are summarized. Moreover, the future trends and opportunities for MSPE in the natural product analysis are discussed. It is expected that this work can provide updated information for future research on the applications of MSPE in such fields.

Chrysin based pyrimidine-piperazine hybrids: design, synthesis, in vitro antimicrobial and in silico E. coli topoisomerase II DNA gyrase efficacy

Ten chrysin-based pyrimidine-piperazine hybrids have been evaluated in vitro for antimicrobial activity against eleven bacterial and two fungal strains. All compounds 5a-j exhibited moderate to good inhibition, with MIC values ranging from 6.25 to 250 µg/ml. At 6.25 µg/ml and 12.5 µg/ml MIC values, respectively, compounds 5b and 5h demonstrated the most promising potency against E. coli, outperforming ampicillin, chloramphenicol, and ciprofloxacin. None of the substances had the same level of action as norfloxacin. 5a, 5d, 5g, 5h, and 5i have exhibited superior antifungal efficacy than Griseofulvin against C. albicans with 250 µg/ml MIC. All the compounds were also individually docked into the E. coli DNA gyrase ATP binding site (PDB ID: 1KZN) and CYP51 inhibitor (PDB ID: 5V5Z). The most active compound, 5h and 5g displayed a Glide docking score of - 5.97 kcal/mol and - 10.99 kcal/mol against DNA gyrase and 14α-demethylase enzyme CYP51 respectively. Potent compounds 5b, 5h, and 5g may be used to design new, innovative antimicrobial agents, according to in vitro, ADMET, and in silico biological efficacy analyses.

Novel MAXPOWER biological antibacterial liquid for eradicating oral Helicobacter pylori

BACKGROUND

Eradication of oral Helicobacter pylori (H. pylori) not only reduces the infection rate from the transmission route but also improves the success rate of intragastric eradication. MAXPOWER Biological Bacteriostatic Liquid, developed in our previous work, is a composite biological preparation with strong antibacterial ability and unique antibacterial mechanism. The present study evaluated the efficacy of the MAXPOWER biocontrol solution on H. pylori and its success rate in eradicating oral H. pylori in clinical patients.

METHODS

Live-dead cell staining and hemolysis test were used to evaluate the cellular safety of MAXPOWER biocontrol solution; plate spreading, live-dead bacterial staining, and scanning electron microscopy methods were used to evaluate its antimicrobial effect against H. pylori. Transcriptomics was used to analyze the changes in H. pylori genes before and after treatment. After seven days of gavage treatment, H&E staining and mice feces were collected for 16SrDNA sequencing to evaluate the animals' safety. Oral H. pylori-positive patients were randomized to be given a placebo and MAXPOWER Bio-Bacteriostatic Liquid gargle for seven days to evaluate the effect on oral H. pylori eradication.

RESULTS

In vitro tests demonstrated that this product has excellent biocompatibility and hemocompatibility and can effectively eradicate oral H. pylori. In vivo tests further showed that it has good biosafety and virtually no adverse effect on intestinal microflora. Transcriptomics analysis revealed that it kills H. pylori cells mainly by disrupting their cell membranes and metabolism. Additionally, the results of randomized controlled trials on humans disclosed that the oral H. pylori eradication rates achieved by MAXPOWER Biological Antibacterial Liquid were 71.4% and 78.9% according to the intention-to-treat and the per-protocol analysis, respectively.

CONCLUSION

MAXPOWER Biological Antibacterial Liquid is both safe and efficacious in the eradication of oral H. pylori.

TRIAL REGISTRATION

This study was retrospectively registered in the ClinicalTrials.gov Trial Registry on 21/09/2023 (NCT06045832).

A Comprehensive Analytical Review of Polyphenols: Evaluating Neuroprotection in Alzheimer's Disease

Alzheimer's Disease (AD), a prevalent neurodegenerative disorder, is the primary cause of dementia. Despite significant advancements in neuroscience, a definitive cure or treatment for this debilitating disease remains elusive. A notable characteristic of AD is oxidative stress, which has been identified as a potential therapeutic target. Polyphenols, secondary metabolites of plant origin, have attracted attention due to their potent antioxidant properties. Epidemiological studies suggest a correlation between the consumption of polyphenol-rich foods and the prevention of chronic diseases, including neurodegenerative disorders, which underscores the potential of polyphenols as a therapeutic strategy in AD management. Hence, this comprehensive review focuses on the diverse roles of polyphenols in AD, with a particular emphasis on neuroprotective potential. Scopus, ScienceDirect, and Google Scholar were used as leading databases for study selection, from 2018 to late March 2024. Analytical chemistry serves as a crucial tool for characterizing polyphenols, with a nuanced exploration of their extraction methods from various sources, often employing chemometric techniques for a holistic interpretation of the advances in this field. Moreover, this review examines current in vitro and in vivo research, aiming to enhance the understanding of polyphenols' role in AD, and providing valuable insights for forthcoming approaches in this context.

Antimicrobial Properties of Flavonoid Derivatives with Bromine, Chlorine, and Nitro Group Obtained by Chemical Synthesis and Biotransformation Studies

The search for new substances of natural origin, such as flavonoids, is necessary in the fight against the growing number of diseases and bacterial resistance to antibiotics. In our research, we wanted to check the influence of flavonoids with chlorine or bromine atoms and a nitro group on pathogenic and probiotic bacteria. We synthesized flavonoids using Claisen-Schmidt condensation and its modifications, and through biotransformation via entomopathogenic filamentous fungi, we obtained their glycoside derivatives. Biotransformation yielded two new flavonoid glycosides: 8-amino-6-chloroflavone 4'-O-β-D-(4″-O-methyl)-glucopyranoside and 6-bromo-8-nitroflavone 4'-O-β-D-(4″-O-methyl)-glucopyranoside. Subsequently, we checked the antimicrobial properties of the aforementioned aglycon flavonoid compounds against pathogenic and probiotic bacteria and yeast. Our studies revealed that flavones have superior inhibitory effects compared to chalcones and flavanones. Notably, 6-chloro-8-nitroflavone showed potent inhibitory activity against pathogenic bacteria. Conversely, flavanones 6-chloro-8-nitroflavanone and 6-bromo-8-nitroflavanone stimulated the growth of probiotic bacteria (Lactobacillus acidophilus and Pediococcus pentosaceus). Our research has shown that the presence of chlorine, bromine, and nitro groups has a significant effect on their antimicrobial properties.

Integrated Metabolomic and Transcriptomic Analysis Reveals the Underlying Antibacterial Mechanisms of the Phytonutrient Quercetin-Induced Fatty Acids Alteration in Staphylococcus aureus ATCC 27217

The utilization of natural products in food preservation represents a promising strategy for the dual benefits of controlling foodborne pathogens and enhancing the nutritional properties of foods. Among the phytonutrients, flavonoids have been shown to exert antibacterial effects by disrupting bacterial cell membrane functionality; however, the underlying molecular mechanisms remain elusive. In this study, we investigated the effect of quercetin on the cell membrane permeability of Staphylococcus aureus ATCC 27217. A combined metabolomic and transcriptomic approach was adopted to examine the regulatory mechanism of quercetin with respect to the fatty acid composition and associated genes. Kinetic analysis and molecular docking simulations were conducted to assess quercetin's inhibition of β-ketoacyl-acyl carrier protein reductase (FabG), a potential target in the bacterial fatty acid biosynthesis pathway. Metabolomic and transcriptomic results showed that quercetin increased the ratio of unsaturated to saturated fatty acids and the levels of membrane phospholipids. The bacteria reacted to quercetin-induced stress by attempting to enhance fatty acid biosynthesis; however, quercetin directly inhibited FabG activity, thereby disrupting bacterial fatty acid biosynthesis. These findings provide new insights into the mechanism of quercetin's effects on bacterial cell membranes and suggest potential applications for quercetin in bacterial inhibition.

Depiction of new flavonoids from Nyctanthus arbor-tristis, their antimicrobial activity and drug-likeness prediction

Bioactive compounds derived from medicinal plants, such as alkaloids, tannins and flavonoids, possess significant medicinal properties. These compounds have a broad and versatile impact on human nutrition and physiology, contributing to the treatment and management of various diseases. The isolation, structure elucidation and inhibition studies of two novel flavonoids against specific microorganisms, from the leaves of Nyctanthus arbor-tristis are reported in this study. It has been observed for the first time that the presence of an acyl aliphatic moiety, along with the O- glycoside unit at C-7, and the hydroxyl group at C-5, C-4' position in apigenin significantly enhanced antimicrobial activity. Moreover, bioactivity was also investigated through 'Molinspiration' on various parameters followed by the 'rule of five'. This study can be used to highlight the need for the potential development of natural therapeutic products with fewer side effects.

Structure optimizing of flavonoids against both MRSA and VRE

Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE) cause more than 100,000 deaths each year, which need efficient and non-resistant antibacterial agents. SAR analysis of 162 flavonoids from the plant in this paper suggested that lipophilic group at C-3 was crucial, and then 63 novel flavonoid derivatives were designed and total synthesized. Among them, the most promising K15 displayed potent bactericidal activity against clinically isolated MRSA and VRE (MICs = 0.25-1.00 μg/mL) with low toxicity and high membrane selectivity. Moreover, mechanism insights revealed that K15 avoided resistance by disrupting biofilm and targeting the membrane, while vancomycin caused 256 times resistance against MRSA, and ampicillin caused 16 times resistance against VRE by the same 20 generations inducing. K15 eliminated residual bacteria in mice skin MRSA-infected model (>99 %) and abdominal VRE-infected model (>92 %), which was superior to vancomycin and ampicillin.

Polymethoxylated flavones from the leaves of Vitex negundo have fungal-promoting and antibacterial activities during the production of broad bean koji

Broad bean paste is a popular condiment in Asian countries. Leaves of Vitex negundo Linn. were used extensively in China during the koji-making of broad bean paste. Spreading V. negundo leaves on raw broad beans during fermentation was able to facilitate the rapid growth of fungi to form mature koji. We isolated two strains of fungi from mature koji, and four strains of bacteria from the rotten broad beans resulting from a failed attempt. According to microbial activity assays, two polymethoxylated flavones, 5-hydroxy-3,6,7,8,3',4'-hexamethoxy flavone (HJ-1) and 5,4'-dihydroxy-3,6,7,8,3'-pentamethoxy flavone (HJ-2) were isolated from V. negundo leaves, and the fungal growth promotion and inhibition of bacterial growth of these two compounds were found to improve the production of broad bean koji. This study reveals the compounds present in V. negundo leaves with bioactivity against important microbes in koji manufacture, and provides a theoretical basis for the application of V. negundo in broad bean paste production.

Baicalin Weakens the Virulence of Porcine Extraintestinal Pathogenic Escherichia coli by Inhibiting the LuxS/AI-2 Quorum-Sensing System

Porcine extraintestinal pathogenic Escherichia coli (ExPEC) is a pathogenic bacterium that causes huge economic losses to the pig farming industry and considerably threatens human health. The quorum sensing (QS) system plays a crucial role in the survival and pathogenesis of pathogenic bacteria. Hence, it is a viable approach to prevent ExPEC infection by compromising the QS system, particularly the LuxS/AI-2 system. In this study, we investigated the effects of baicalin on the LuxS/AI-2 system of ExPEC. Baicalin at concentrations of 25, 50, and 100 μg/mL significantly diminished the survival ability of ExPEC in hostile environments and could inhibit the biofilm formation and autoagglutination ability in ExPEC. Moreover, baicalin dose-dependently decreased the production of AI-2 and down-regulated the expression level of luxS in PCN033. These results suggest that baicalin can weaken the virulence of PCN033 by inhibiting the LuxS/AI-2 system. After the gene luxS was deleted, AI-2 production in PCN033 was almost completely eliminated, similar to the effect of baicalin on the production of AI-2 in PCN033. This indicates that baicalin reduced the production of AI-2 by inhibiting the expression level of luxS in ExPEC. In addition, the animal experiment further showed the potential of baicalin as a LuxS/AI-2 system inhibitor to prevent ExPEC infection. This study highlights the potential of baicalin as a natural quorum-sensing inhibitor for therapeutic applications in preventing ExPEC infection by targeting the LuxS/AI-2 system.

Using Subcritical Water to Obtain Polyphenol-Rich Extracts with Antimicrobial Properties

The use of green extraction methods that meet the criteria of sustainable and environmentally friendly technologies has been increasing in recent decades due to their many benefits. In this respect, extracts obtained using subcritical water are also gaining increased attention because of their potential antioxidant and antimicrobial properties. Their antimicrobial activity is mainly due to the presence of various polyphenolic compounds. Although the exact mechanism of the antibacterial action of polyphenolic compounds has not yet been fully investigated and described, polyphenols are known to affect the bacterial cell at several cellular levels; among other things, they cause changes and ruptures in the cell membranes of the bacterial cell, affect the inactivation of bacterial enzymes and damage bacterial DNA. The difference in the strength of the antimicrobial activity of the extracts is most likely a result of differences in their lipophilicity and in the number and position of hydroxyl groups and double bonds in the chemical structure of polyphenols. By changing the extraction conditions, especially the temperature, during subcritical water extraction, we affect the solubility of the compounds we want to extract. In general, as the temperature increases, the solubility of polyphenolic compounds also increases, and the reduction of the surface tension of subcritical water at higher temperatures also enables faster dissolution of polyphenolic compounds. Different bacterial strains have different sensitivity to different extracts. However, extracts obtained with subcritical water extraction demonstrate strong antimicrobial activity compared to extracts obtained with conventional methods.

Biomedical applications of stimuli-responsive "smart" interpenetrating polymer network hydrogels

In recent years, owing to the ongoing advancements in polymer materials, hydrogels have found increasing applications in the biomedical domain, notably in the realm of stimuli-responsive "smart" hydrogels. Nonetheless, conventional single-network stimuli-responsive "smart" hydrogels frequently exhibit deficiencies, including low mechanical strength, limited biocompatibility, and extended response times. In response, researchers have addressed these challenges by introducing a second network to create stimuli-responsive "smart" Interpenetrating Polymer Network (IPN) hydrogels. The mechanical strength of the material can be significantly improved due to the topological entanglement and physical interactions within the interpenetrating structure. Simultaneously, combining different network structures enhances the biocompatibility and stimulus responsiveness of the gel, endowing it with unique properties such as cell adhesion, conductivity, hemostasis/antioxidation, and color-changing capabilities. This article primarily aims to elucidate the stimulus-inducing factors in stimuli-responsive "smart" IPN hydrogels, the impact of the gels on cell behaviors and their biomedical application range. Additionally, we also offer an in-depth exposition of their categorization, mechanisms, performance characteristics, and related aspects. This review furnishes a comprehensive assessment and outlook for the advancement of stimuli-responsive "smart" IPN hydrogels within the biomedical arena. We believe that, as the biomedical field increasingly demands novel materials featuring improved mechanical properties, robust biocompatibility, and heightened stimulus responsiveness, stimuli-responsive "smart" IPN hydrogels will hold substantial promise for wide-ranging applications in this domain.

Comparative evaluation of the antibacterial activity of curcumin-coated gutta-percha versus nanocurcumin-coated gutta-percha against Escherichia coli: An in vitro study

Introduction

Due to its biological and antibacterial qualities, many plants, including curcumin, are used as phytomedicines in dentistry. They are primarily used as intracanal medication in endodontics to prevent probable chemical side effects and also to address antimicrobial resistance. Curcumin nanoformulations have improved antibacterial activity and improved dispersion, making them the superior form of curcumin. The purpose of this study was to assess curcumin and nanocurcumin's antibacterial properties. As a gutta-percha coating, they are to be tested against Escherichia coli.

Materials and Methods

The study employs the standard strain of E. coli, ATCC 25922. The antibacterial activity of gutta-percha cones against E. coli is assessed after coating them with suspensions of curcumin and nanocurcumin. Scanning electron microscopy is utilized to evaluate the coatings' continuity.

Results

The gutta-percha cones that are untreated, coated with curcumin, and coated with nanocurcumin exhibit significantly different levels of antibacterial activity. There is statistically significant variation in their antibacterial activity.

Conclusion

(1) Compared to curcumin-coated and untreated gutta-percha cones, those coated with nanocurcumin exhibit a stronger antibacterial activity. (2) Compared to uncoated gutta-percha cones, gutta-percha cones coated with curcumin exhibit more antibacterial action.

Flavonol profiles of mature leaves allow discriminating Toona sinensis Roem from different north-south geographical origins across China with varied antioxidant activities

Toona sinensis (A. Juss.) Roem, a multipurpose economic tree, is widely cultivated across Asia, but its high-yielding mature leaves are largely overlooked. This study systematically analysed the flavonols in the mature leaves of T. sinensis from 44 different geographic locations across China, using HPLC-DAD and HPLC-ESI-MS2 techniques. In total, 18 flavonols were detected, among which 6 (f1, f3, f7, f14, f15, and f17) were firstly identified in this plant. Significant variations in quality among different T. sinensis varieties were observed (p < 0.01). Through OPLS-DA analysis, all samples could be clearly categorised into two distinct geographical groups. The northern varieties (N1-N20) exhibited concise flavonol fingerprints with higher total flavonol content (TFC) (727.55 ± 22.79 mg/100 g fresh weight, FW), predominantly non-acylated flavonols (705.95 ± 21.65 mg/100 g FW), particularly quercetin glycosides (614.60 ± 22.76 mg/100 g FW). In contrast, the southern varieties (S1-S24) presented more intricate flavonol profiles with lower TFC (622.81 ± 21.82 mg/100 g FW) and balanced amounts of quercetin (344.75 ± 16.41 mg/100 g FW) and kaempferol glycosides (278.06 ± 12.29 mg/100 g FW). Notably, the southern samples possessed higher content of acylated flavonols (184.50 ± 12.87 mg/100 g FW), especially galloylated ones, which contributed to their heightened antioxidant activities. Quercetin 3-O-rhamnoside (f11') and kaempferol 3-O-galloyglucoside (f11) were determined to be the crucial biomarkers for quality discrimination. Considering quality control of mature T. sinensis leaves as potential resources for natural flavonol extraction, this study suggested that their northern/southern geographic origins should be distinguished first. Additionally, the flavonol profiles allow for discriminating the origin and assessing the quality of T. sinensis.

Cepharanthine analogs mining and genomes of Stephania accelerate anti-coronavirus drug discovery

Cepharanthine is a secondary metabolite isolated from Stephania. It has been reported that it has anti-conronaviruses activities including severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Here, we assemble three Stephania genomes (S. japonica, S. yunnanensis, and S. cepharantha), propose the cepharanthine biosynthetic pathway, and assess the antiviral potential of compounds involved in the pathway. Among the three genomes, S. japonica has a near telomere-to-telomere assembly with one remaining gap, and S. cepharantha and S. yunnanensis have chromosome-level assemblies. Following by biosynthetic gene mining and metabolomics analysis, we identify seven cepharanthine analogs that have broad-spectrum anti-coronavirus activities, including SARS-CoV-2, Guangxi pangolin-CoV (GX_P2V), swine acute diarrhoea syndrome coronavirus (SADS-CoV), and porcine epidemic diarrhea virus (PEDV). We also show that two other genera, Nelumbo and Thalictrum, can produce cepharanthine analogs, and thus have the potential for antiviral compound discovery. Results generated from this study could accelerate broad-spectrum anti-coronavirus drug discovery.

The Role of Natural and Synthetic Flavonoids in the Prevention of Marine Biofouling

Marine biofouling is a major concern for the maritime industry, environment, and human health. Biocides which are currently used in marine coatings to prevent this phenomenon are toxic to the marine environment, and therefore a search for antifoulants with environmentally safe properties is needed. A large number of scientific papers have been published showing natural and synthetic compounds with potential to prevent the attachment of macro- and microfouling marine organisms on submerged surfaces. Flavonoids are a class of compounds which are highly present in nature, including in marine organisms, and have been found in a wide range of biological activities. Some natural and synthetic flavonoids have been evaluated over the last few years for their potential to prevent the settlement and/or the growth of marine organisms on submerged structures, thereby preventing marine biofouling. This review compiles, for the first-time, natural flavonoids as well as their synthetic analogues with attributed antifouling activity against macrofouling and microfouling marine organisms.

Levofloxacin and Ciprofloxacin Co-Crystals with Flavonoids: Solid-State Investigation for a Multitarget Strategy against Helicobacter pylori

In this paper, we address the problem of antimicrobial resistance in the case of Helicobacter pylori with a crystal engineering approach. Two antibiotics of the fluoroquinolone class, namely, levofloxacin (LEV) and ciprofloxacin (CIP), have been co-crystallized with the flavonoids quercetin (QUE), myricetin (MYR), and hesperetin (HES), resulting in the formation of four co-crystals, namely, LEV∙QUE, LEV∙MYR, LEV2∙HES, and CIP∙QUE. The co-crystals were obtained from solution, slurry, or mechanochemical mixing of the reactants. LEV∙QUE and LEV∙MYR were initially obtained as the ethanol solvates LEV∙QUE∙xEtOH and LEV∙MYR∙xEtOH, respectively, which upon thermal treatment yielded the unsolvated forms. All co-crystals were characterized by powder X-ray diffraction and thermal gravimetric analysis. The antibacterial performance of the four co-crystals LEV∙QUE, LEV∙MYR, LEV2∙HES, and CIP∙QUE in comparison with that of the physical mixtures of the separate components was tested via evaluation of the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). The results obtained indicate that the association with the co-formers, whether co-crystallized or forming a physical mixture with the active pharmaceutical ingredients (API), enhances the antimicrobial activity of the fluoroquinolones, allowing them to significantly reduce the amount of API otherwise required to display the same activity against H. pylori.

Phenolic Compound, Antioxidant, Antibacterial, and In Silico Studies of Extracts from the Aerial Parts of Lactuca saligna L

Medicinal plants are considered a major source for discovering novel effective drugs. To our knowledge, no studies have reported the chemical composition and biological activities of Moroccan Lactuca saligna extracts. In this context, this study aims to characterize the polyphenolic compounds distributed in hydro-methanolic extracts of L. saligna and evaluate their antioxidant and antibacterial activities; in addition, in silico analysis based on molecular docking and ADMET was performed to predict the antibacterial activity of the identified phenolic compounds. Our results showed the identification of 29 among 30 detected phenolic compounds with an abundance of dicaffeoyltartaric acid, luteolin 7-glucoronide, 3,5-di-O-caffeoylquinic acid, and 5-caffeoylquinic acid with 472.77, 224.30, 196.79, and 171.74 mg/kg of dried extract, respectively. Additionally, antioxidant activity assessed by DPPH scavenging activity, ferric reducing antioxidant power (FRAP) assay, and ferrous ion-chelating (FIC) assay showed interesting antioxidant activity. Moreover, the results showed remarkable antibacterial activity against Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, Enterococcus faecalis, Staphylococcus aureus, and Listeria monocytogenes with minimum inhibitory concentrations between 1.30 ± 0.31 and 10.41 ± 0.23 mg/mL. Furthermore, in silico analysis identified three compounds, including Apigenin 7-O-glucuronide, Quercetin-3-O-glucuronide, and 3-p-Coumaroylquinic acid as potent candidates for developing new antibacterial agents with acceptable pharmacokinetic properties. Hence, L. saligna can be considered a source of phytochemical compounds with remarkable activities, while further in vitro and in vivo studies are required to explore the main biological activities of this plant.

Genus Monanthotaxis: a review on distribution, ethnomedicinal uses and phytochemistry

This article reviews the geographical distribution, ethnomedicinal applications, and phytochemistry of the genus Monanthotaxis Baill, tribe Uvariae of the family Annonaceae. The reviewed works of literature were collected from various electronic databases including Google Scholar, PubMed, Science Direct, The International Plant Names Index (IPNI), and Research Gate. During this review, ninety-eight species of the genus Monanthotaxis were found to be widely distributed in tropical Africa. Some of those species are used in folkloric medicine by various communities to manage diseases and disease conditions such as fever, vomiting, headache, stomach-ache, malaria, helminthiasis, and hysteria. In the past 44 years (1979 to 2023), one hundred and nineteen secondary metabolites with different biomedical potentials have been reported from this genus. The reported compounds are categorised into flavonoids, alkaloids, terpenoids, polyoxygenated cyclohexane, and cyclohexene derivatives, benzyl derivatives, cinnamic acid derivatives, and stilbenoids. Most of the reported compounds showed an array of bioactivities corroborating the use of some members of the genus in folkloric medicine.

Potential of Flavonoids as Promising Phytotherapeutic Agents to Combat Multidrug-Resistant Infections

BACKGROUND

Considering the limited number of current effective treatments, Multidrug- Resistant (MDR) illnesses have grown to be a serious concern to public health. It has become necessary to look for new antimicrobial drugs because of the emergence of resistance to numerous kinds of antibiotics. The use of flavonoids is one phytotherapeutic strategy that has been researched as a potential remedy for this issue. Secondary plant compounds called flavonoids have been found to have an antibacterial effect against resistant microorganisms.

OBJECTIVE

This review seeks to give readers a glimpse into contemporary studies on flavonoids' potential to fight MDR infections.

METHODS

A systematic search was conducted on electronic databases (PubMed, Scopus, and Google Scholar) using relevant keywords such as flavonoids, MDR infections, antimicrobial activity, and resistance microbes. Studies that investigated the antimicrobial activity of flavonoids against resistant microbes were included in this review.

RESULTS

Most research found that flavonoids have antibacterial efficacy against resistant microorganisms, and some also showed that they have synergistic benefits with traditional antibiotics. The flavonoids quercetin, kaempferol, apigenin, and luteolin were the most often investigated ones. According to research, flavonoids affect microbial gene expression, inhibit microbial enzymes, and disrupt the integrity of microbial cell membranes. Additionally, a few studies have noted the flavonoids' low toxicity and safety.

CONCLUSION

For the treatment of infections that are resistant to many drugs, flavonoids constitute a promising class of phytotherapeutic agents. To develop flavonoid-based treatment methods for treating MDR illnesses and assess the potential of flavonoids as adjuvants to conventional antimicrobial drugs, more study is required.

Synergistic effects of essential oils and phenolic extracts on antimicrobial activities using blends of Artemisia campestris, Artemisia herba alba, and Citrus aurantium

This study explores the synergistic antibacterial effects of essential oils (EOs) and phenolic extracts from three plants against foodborne pathogenic bacteria. The present work aimed to investigate the synergistic effects of the binary and the ternary combinations of extracts using different blend proportions of the following plant extracts: Artemisia campestris (AC), Artemisia herba alba (AHA), and Citrus aurantium (CA). The antimicrobial activities of EOs and phenolic extracts were determined and evaluated against five strains. For the EOs, the results of the DIZ showed the existence of synergism for different combinations of binary blends, such as AC/AHA or AHA/CA against Escherichia coli, and AC/CA against Enterobacter faecalis. In addition, ternary blends of AC:AHA:CA at a ratio of 1/6:2/3:1/6 exhibited a synergy effect, as measured by the CI, against E. coli. On the other hand, for the phenolic extracts, synergistic effects were noticed for binary blends of AC/CA at different ratios against E. coli, E. faecalis, and Pseudomonas aeruginosa strains. Similarly, ternary blends of phenolic extracts presented synergy against E. coli, E. faecalis, P. aeruginosa strains, and even C. albicans. In this case, the blending ratios were crucial determining factors for maximizing the synergy effect. The study established that the proportion of a single drug could play an essential role in determining the bioefficacy of a drug combination treatment. Therefore, the results showed the importance of studying the modulation of antibacterial activities based on the proportions of extracts in the mixture and finding the range of proportions (as determined by SLMD) that have a synergistic/additive/antagonistic effect with no or low side effects, which can be used in a food preservation system.

Shikonin and Alkannin inhibit ATP synthase and impede the cell growth in Escherichia coli

Naturally occurring naphthoquinones, shikonin and alkannin, are important ingredients of traditional Chinese medicine Zicao. These constituents are reported to have many therapeutic uses, such as wound healing; scar treatment; and anti-inflammation, anti-acne, anti-ulcer, anti-HIV, anticancer, and antibacterial properties. The primary objective of this investigation was to explore the effect of shikonin and alkannin on Escherichia coli ATP synthase and its cell growth. Shikonin caused complete (100 %) inhibition, and alkannin caused partial (79 %) inhibition of wild-type E. coli ATP synthase. Both caused partial (4 %-27 %) inhibition of ATP synthase with genetically modified phytochemical binding site. The growth inhibition of strains expressing normal, deficient, and mutant ATP synthase by shikonin and alkannin, corroborated the inhibition observed in isolated normal wild-type and mutant ATP synthase. Trivial inhibition of mutant enzymes indicated αR283D, αE284R, βV265Q, and γT273A are essential for formation of the phytochemical binding site where shikonin and alkannin bind. Further, shikonin was a potent inhibitor of ATP synthase than alkannin. The antimicrobial properties of shikonin and alkannin were tied to the binding at phytochemical site of microbial ATP synthase. Selective targeting of bacterial ATP synthase by shikonin and alkannin may be an advantageous alternative to address the antibiotic resistance issue.

Research status of indole-modified natural products

Indole is a heterocyclic compound formed by the fusion of a benzene ring and pyrrole ring, which has rich biological activity. Many indole-containing compounds have been sold on the market due to their excellent pharmacological activity. For example, vincristine and reserpine have been widely used in clinical practice. The diverse structures and biological activities of natural products provide abundant resources for the development of new drugs. Therefore, this review classifies natural products by structure, and summarizes the research progress of indole-containing natural product derivatives, their biological activities, structure-activity relationship and research mechanism which has been studied in the past 13 years, so as to provide a basis for the development of new drug development.

Antimicrobial Activity and Mechanisms of Walnut Green Husk Extract

Walnut green husks (WGHs), by-products of walnut production, are believed to possess antimicrobial properties, making them a potential alternative to antibiotics. In this study, the antibacterial activities of three extracts, derived from WGH, against Staphylococcus aureus, Bacillus subtilis, and Escherichia coli were investigated, and the antibacterial mechanisms of an anhydrous ethanol extract of WGH (WGHa) were examined. The results showed that WGHa exhibited inhibitory effects on all tested bacteria. The ultrahigh-performance liquid chromatography-tandem mass spectrometry analysis revealed that the major active compounds present in WGHa were terpenoids, phenols, and flavonoids. Treatment with WGHa resulted in the leakage of intracellular ions and alkaline phosphatase; a reduction in intracellular ATP content, ATPase activity, and nucleic acid content; as well as cellular metabolic viability. The transmission electron microscopy images showed varying degrees of cell deformation and membrane damage following WGHa treatment. The transcriptome sequencing and differentially expressed gene enrichment analyses revealed an up-regulation in pathways associated with RNA degradation, translation, protein export, and oxidative phosphorylation. Conversely, pathways involved in cell movement and localization, as well as cell wall organization and carbohydrate transport, were found to be down-regulated. These findings suggest that WGHa alters cell membrane permeability and causes damage to the cell wall. Additionally, WGHa interferes with cellular energy metabolism, compromises RNA integrity, and induces DNA replication stress, consequently inhibiting the normal growth and proliferation of bacteria. These findings unveiled the antimicrobial mechanisms of WGHa, highlighting its potential application as an antibiotic alternative.

Recent advances in anti-inflammatory active components and action mechanisms of natural medicines

Inflammation is a series of reactions caused by the body's resistance to external biological stimuli. Inflammation affects the occurrence and development of many diseases. Anti-inflammatory drugs have been used widely to treat inflammatory diseases, but long-term use can cause toxic side-effects and affect human functions. As immunomodulators with long-term conditioning effects and no drug residues, natural products are being investigated increasingly for the treatment of inflammatory diseases. In this review, we focus on the inflammatory process and cellular mechanisms in the development of diseases such as inflammatory bowel disease, atherosclerosis, and coronavirus disease-2019. Also, we focus on three signaling pathways (Nuclear factor-kappa B, p38 mitogen-activated protein kinase, Janus kinase/signal transducer and activator of transcription-3) to explain the anti-inflammatory effect of natural products. In addition, we also classified common natural products based on secondary metabolites and explained the association between current bidirectional prediction progress of natural product targets and inflammatory diseases.

Mur ligase F as a new target for the flavonoids quercitrin, myricetin, and (-)-epicatechin

MurC, D, E, and F are ATP-dependent ligases involved in the stepwise assembly of the tetrapeptide stem of forming peptidoglycan. As highly conserved targets found exclusively in bacterial cells, they are of significant interest for antibacterial drug discovery. In this study, we employed a computer-aided molecular design approach to identify potential inhibitors of MurF. A biochemical inhibition assay was conducted, screening twenty-four flavonoids and related compounds against MurC-F, resulting in the identification of quercitrin, myricetin, and (-)-epicatechin as MurF inhibitors with IC50 values of 143 µM, 139 µM, and 92 µM, respectively. Notably, (-)-epicatechin demonstrated mixed type inhibition with ATP and uncompetitive inhibition with D-Ala-D-Ala dipeptide and UM3DAP substrates. Furthermore, in silico analysis using Sitemap and subsequent docking analysis using Glide revealed two plausible binding sites for (-)-epicatechin. The study also investigated the crucial structural features required for activity, with a particular focus on the substitution pattern and hydroxyl group positions, which were found to be important for the activity. The study highlights the significance of computational approaches in targeting essential enzymes involved in bacterial peptidoglycan synthesis.

Litsea glaucescens Kuth possesses bactericidal activity against Listeria monocytogenes

Background

Litsea glaucencens Kuth is an aromatic plant used for food seasoning food and in Mexican traditional medicine. Among, L. glaucencens leaves properties, it has proven antibacterial activity which can be used against opportunistic pathogens like Listeria monocytogenes, a foodborne bacteria that is the causal agent of listeriosis, a disease that can be fatal in susceptible individuals. The aim of this work was to investigate the antibacterial activity of L. glaucescens Kuth leaf extracts against L. monocytogenes and to identify its bioactive components.

Material and Methods

L. glaucences leaves were macerated with four solvents of different polarity (n-hexane, dichloromethane, ethyl acetate, and methanol). To determine the capacity to inhibit bacterial proliferation in vitro, agar diffusion and microdilution methods were used. Next, we determined the minimal bactericidal concentration (MBC). Finally, we determined the ratio of MBC/MIC. Metabolites present in the active methanolic extract from L. glaucescens Kuth (LgMeOH) were purified by normal-phase open column chromatography. The structure of the antibacterial metabolite was determined using nuclear magnetic resonance (1H, 13C, COSY, HSQC) and by comparison with known compounds.

Results

The LgMeOH extract was used to purify the compound responsible for the observed antimicrobial activity. This compound was identified as 5,7-dihydroxyflavanone (pinocembrin) by analysis of its spectroscopic data and comparison with those described. The MIC and MBC values obtained for pinocembrin were 0.68 mg/mL, and the ratio MBC/MIC for both LgMeOH and pinocembrin was one, which indicates bactericidal activity.

Conclusion

L. glaucences Kuth leaves and its metabolite pinocembrin can be used to treat listeriosis due the bactericidal activity against L. monocytogenes.

Terminalia petiolaris A.Cunn ex Benth. Extracts Have Antibacterial Activity and Potentiate Conventional Antibiotics against β-Lactam-Drug-Resistant Bacteria

Terminalia petiolaris A. Cunn. Ex Benth. (genus: Terminalia, family: Combretaceae) is native to Australia. Terminalia spp. have traditionally been used to treat various ailments, including bacterial infections. Solvents of varying polarity were used to extract compounds from leaves of this species, and the extracts were tested against a panel of bacteria, including antibiotic-resistant strains. The methanolic and water extracts showed substantial inhibitory activity against several bacteria, including antibiotic-resistant strains in both disc diffusion and liquid dilution assays. Combining these extracts with selected conventional antibiotics enhanced the inhibition of bacterial growth for some combinations, while others showed no significant interaction. In total, two synergistic, twenty-five additive, twenty-three non-interactive and one antagonistic interaction were observed. The methanolic and ethyl acetate plant extracts were found to be non-toxic in Artemia franciscana nauplii toxicity assays. A liquid chromatography-mass spectrometry metabolomics analysis identified several flavonoid compounds, including miquelianin, trifolin and orientin, which might contribute to the observed activities. The potential modes of these active extracts are further discussed in this study.

Phytochemical Profile, Antioxidant Potential, Antimicrobial Activity, and Cytotoxicity of Dry Extract from Rosa damascena Mill

Dry rose extract (DRE) obtained industrially by aqueous ethanol extraction from R. damascena flowers and its phenolic-enriched fraction, obtained by re-extraction with ethyl acetate (EAE) were the subject of this study. 1H NMR of DRE allowed the identification and quantitation of fructose and glucose, while the combined use of HPLC-DAD-ESIMS and HPLC-HRMS showed the presence of 14 kaempferol glycosides, 12 quercetin glycosides, 4 phenolic acids and their esters, 4 galloyl glycosides, 7 ellagitannins, and quinic acid. In addition, the structures of 13 of the flavonoid glycosides were further confirmed by NMR. EAE was found to be richer in TPC and TFC and showed better antioxidant activity (DPPH, ABTS, and FRAP) compared to DRE. Both extracts displayed significant activity against Propionibacterium acnes, Staphylococcus aureus, and S. epidermidis, but showed no activity against Candida albicans. Toxicity tests on normal human skin fibroblasts revealed low toxicity for both extracts with stronger effects observed at 24 hours of treatment that were compensated for over the following two days. Human hepatocarcinoma (HepG2) cells exhibited an opposite response after treatment with a concentration above 350 µg/mL for EAE and 500 µg/mL for DRE, showing increased toxicity after the third day of treatment. Lower concentrations were non-toxic and did not significantly affect the cell cycle parameters of either of the cell lines.

Expanding the Scope of an Amphoteric Condensed Tannin, Tanfloc, for Antibacterial Coatings

Bacterial infections are a common mode of failure for medical implants. This study aims to develop antibacterial polyelectrolyte multilayer (PEM) coatings that contain a plant-derived condensed tannin polymer (Tanfloc, TAN) with inherent antimicrobial activity. Tanfloc is amphoteric, and herein we show that it can be used as either a polyanion or a polycation in PEMs, thereby expanding the possibility of its use in PEM coatings. PEMs are ordinarily formed using a polycation and a polyanion, in which the functional (ionic) groups of the two polymers are complexed to each other. However, using the amphoteric polymer Tanfloc with weakly basic amine and weakly acidic catechol and pyrogallol groups enables PEM formation using only one or the other of its functional groups, leaving the other functional group available to impart antibacterial activity. This work demonstrates Tanfloc-containing PEMs using multiple counter-polyelectrolytes including three polyanionic glycosaminoglycans of varying charge density, and the polycations N,N,N-trimethyl chitosan and polyethyleneimine. The layer-by-layer (LbL) assembly of PEMs was monitored using in situ Fourier-transform surface plasmon resonance (FT-SPR), confirming a stable LbL assembly. X-ray photoelectron spectroscopy (XPS) was used to evaluate surface chemistry, and atomic force microscopy (AFM) was used to determine the surface roughness. The LDH release levels from cells cultured on the Tanfloc-containing PEMs were not statistically different from those on the negative control (p > 0.05), confirming their non-cytotoxicity, while exhibiting remarkable antiadhesive and bactericidal properties against Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus), respectively. The antibacterial effects were attributed to electrostatic interactions and Tanfloc's polyphenolic nature. This work underscores the potential of Tanfloc as a versatile biomaterial for combating infections on surfaces.

Microbial glycosylation of antitubercular agent chlorflavonin

Flavonoids have shown health-benefiting properties, such as antioxidative and anti-inflammatory activities, and are commonly used as nutraceuticals and pharmaceuticals. Although flavonoids are predominantly identified from plants, several filamentous fungal species have also been reported to produce bioactive flavonoids, including chlorflavonin from Aspergillus candidus, a novel halogenated flavonoid with potent antifungal and antitubercular (anti-TB) activities. Unfortunately, the low water-solubility of this molecule may hinder its bioavailability. Glycosylation is an effective method to enhance the polarity of natural products and alter their physicochemical properties. This work focuses on the development of novel water-soluble chlorflavonin derivatives to combat the threat of drug-resistant tuberculosis. In this study, we first increased the production titer of chlorflavonin in A. candidus NRRL 5214 by optimizing the fermentation and purification processes. Next, chlorflavonin-5-O-β-d-glucuronopyranoside (1) and chlorflavonin-7-O-4″-O-methyl-β-d-glucopyranoside (2) were produced from chlorflavonin using Streptomyces chromofuscus ATCC 49982 and Beauveria bassiana ATCC 7159, respectively. Compared to chlorflavonin (4.38 ± 0.54 mg/L in water), the water solubility of the two new glycosides was determined to be 117.86 ± 4.81 mg/L (1) and 124.34 ± 9.13 mg/L (2), respectively. This study provides a promising method to create water-soluble glycosides of chlorflavonin for the development of novel anti-TB drugs.

Luteolin-loaded biocomposites containing tantalum and polyimide with antibacterial effects for facilitating osteogenic differentiation and bone bonding

Polymer-based composites are considered promising candidates for bone repair as they possess some outstanding advantages over ceramic/metallic/polymeric biomaterials. Tantalum (Ta)/polyimide (PI) biocomposites (PT) containing 20 v% (PT20) and 40 v% (PT40) Ta nanoparticles were fabricated, and luteolin (LU) was loaded on PT40 (LUPT40). Compared with PT20 and PI, PT40 with a high Ta content displayed high surface behaviors (e.g., roughness, surface energy, and hydrophilicity). PT40 remarkably improved cell adhesion and multiplication, and LUPT40 with LU displayed further enhancement in vitro. Moreover, LUPT40 evidently boosted osteoblastic differentiation while suppressing osteoclastic differentiation. Furthermore, LUPT40 exhibited good antibacterial effects because of the slow release of LU. The in vivo results confirmed that PT40 markedly promoted bone formation and LUPT40 further enhanced bone formation/bone bonding. In brief, the incorporation of Ta particles improved the surface behaviors of PT40, which stimulated cell response/bone formation. Moreover, the slow release of LU from LUPT40 not only promoted cell response/bone formation but also enhanced bone bonding. The synergistic effects of Ta and LU release from LUPT40 enhanced bone formation/bone bonding. Therefore, LUPT40 would have great potential for the repair of bear-loading bone.