In vitro studies of the antibacterial activity of Copaifera spp. oleoresins, sodium hypochlorite, and peracetic acid against clinical and environmental isolates recovered from a hemodialysis unit

Synthesis, Antibacterial Effects, and Toxicity of Licochalcone C

Drug-resistant bacteria constitute a big barrier against current pharmacotherapy. Efforts are urgent to discover antibacterial drugs with novel chemical and biological features. Our work aimed at the synthesis, evaluation of antibacterial effects, and toxicity of licochalcone C (LCC), a naturally occurring chalcone. The synthetic route included six steps, affording a 10% overall yield. LCC showed effects against Gram-positive bacteria (MIC = 6.2-50.0 µg/mL), Mycobacterium species (MIC = 36.2-125 µg/mL), and Helicobacter pylori (MIC = 25 µg/mL). LCC inhibited the biofilm formation of MSSA and MRSA, demonstrating MBIC50 values of 6.25 μg/mL for both strains. The investigations by fluorescence microscopy, using PI and SYTO9 as fluorophores, indicated that LCC was able to disrupt the S. aureus membrane, similarly to nisin. Systemic toxicity assays using Galleria mellonella larvae showed that LCC was not lethal at 100 µg/mL after 80 h treatment. These data suggest new uses for LCC as a compound with potential applications in antibacterial drug discovery and medical device coating.

Carbon dots electrochemically prepared from dopamine and epigallocatechin gallate for hypochlorite detection with high selectivity via a dynamic quenching mechanism

Monitoring hypochlorite levels in water is of great importance because of its high toxicity and wide applications as water disinfectants. In this manuscript, carbon dot (CD) was electrochemically prepared by using dopamine and epigallocatechin gallate (molar ratio 1:1) as the carbon source for efficient hypochlorite determination. By electrolyzing the solution at 10 V for 12 min with PBS as an electrolyte, dopamine would react with epigallocatechin at the anode, and through polymerization, dehydration, and carbonization, strong blue-fluorescent CDs were obtained. CDs were characterized by UV-Vis spectroscopy, fluorescence spectroscopy, high-resolution transmission electron microscopy, FT-IR, etc. These CDs have an excitation wavelength at 372 nm and an emission wavelength at 462 nm, owing an average particle size of 5.5 nm. The presence of hypochlorites can quench the fluorescence of CDs, and its reduction in intensity is linear with hypochlorite concentration over the range of 0.5-50 μM, ΔF/F₀ = 0.0056 + 0.0194C_ClO^-, R²=0.997. The detection limit achieved 0.23 μM (S/N = 3). The mechanism for fluorescence quenching is via a dynamic process. Different from many other fluorescence methods based on the strong oxidizing ability of hypochlorites, our method shows strong selectivity toward hypochlorites over other oxidizing agents such as H₂O₂. The assay was validated by the detection of hypochlorites in water samples, with recoveries between 98.2% and 104.3%.

Antibacterial Activity of Isobavachalcone (IBC) Is Associated with Membrane Disruption

Isobavachalcone (IBC) is a natural prenylated chalcone with a broad spectrum of pharmacological properties. In this work, we newly synthesized and investigated the antibacterial activity of IBC against Gram-positive, Gram-negative and mycobacterial species. IBC was active against Gram-positive bacteria, mainly against Methicillin-Susceptible Staphylococcus aureus (MSSA) and Methicillin-Resistant Staphylococcus aureus (MRSA), with minimum inhibitory concentration (MIC) values of 1.56 and 3.12 µg/mL, respectively. On the other hand, IBC was not able to act against Gram-negative species (MIC > 400 µg/mL). IBC displayed activity against mycobacterial species (MIC = 64 µg/mL), including Mycobacterium tuberculosis, Mycobacterium avium and Mycobacterium kansasii. IBC was able to inhibit more than 50% of MSSA and MRSA biofilm formation at 0.78 µg/mL. Its antibiofilm activity was similar to vancomycin, which was active at 0.74 µg/mL. In order to study the mechanism of the action by fluorescence microscopy, the propidium iodide (PI) and SYTO9 fluorophores indicated that IBC disrupted the membrane of Bacillus subtilis. Toxicity assays using human keratinocytes (HaCaT cell line) showed that IBC did not have the capacity to reduce the cell viability. These results suggested that IBC is a promising antibacterial agent with an elucidated mode of action and potential applications as an antibacterial drug and a medical device coating.

Sensitivity of Staphylococcal Biofilm to Selected Compounds of Plant Origin

Staphylococcus epidermidis is a bacterium that belongs to the human microbiota. It is most plentiful on the skin, in the respiratory system, and in the human digestive tract. Moreover, it is the most frequently isolated microorganism belonging to the group of Coagulase Negative Staphylococci (CoNS). In recent years, it has been recognized as an important etiological factor of mainly nosocomial infections and infections related to the cardiovascular system. On the other hand, Staphylococcus aureus, responsible for in-hospital and out-of-hospital infections, is posing an increasing problem for clinicians due to its growing resistance to antibiotics. Biofilm produced by both of these staphylococcal species in the course of infection significantly impedes therapy. The ability to produce biofilm hinders the activity of chemotherapeutic agents-the only currently available antimicrobial therapy. This also causes the observed significant increase in bacterial resistance. For this reason, we are constantly looking for new substances that can neutralize microbial cells. In the present review, 58 substances of plant origin with antimicrobial activity against staphylococcal biofilm were replaced. Variable antimicrobial efficacy of the substances was demonstrated, depending on the age of the biofilm. An increase in the activity of the compounds occurred in proportion to increasing their concentration. Appropriate use of the potential of plant-derived compounds as an alternative to antibiotics may represent an important direction of change in the support of antimicrobial therapy.

Clinical and Antimicrobial Evaluation of Copaifera langsdorffii Desf. Dental Varnish in Children: A Clinical Study

Background

The objective of this study was to evaluate the clinical and microbiological efficacies of (C. langsdorffii) dental varnish in children at high risk of dental caries..

Methods

This is a longitudinal, randomized, controlled clinical trial. Ninety high-risk caries-free children (ICDAS II = 0) were recruited and randomly divided into three groups: C. langsdorffii, chlorhexidine, or fluoride. The varnishes were applied on the second deciduous molars for three times: baseline (D0), after 90 days (D90), and after 180 days (D180). Saliva was collected on D0, D90, D180, and D360 to evaluate S. mutans reduction. Statistics were carried out by ANOVA, Tukey's test, and the paired t-test.

Results

Copaiba varnish demonstrated significant S. mutans reduction: D360 versus D0 (p < 0.0001), D180 versus D0 (p < 0.001), D360 versus D90 (p < 0.001), D180 versus D90 (p < 0.001), and D360 versus D180 (p < 0.05). Chlorhexidine varnish significantly reduced S. mutans at D180 versus D0 (p < 0.05). Fluoride reduced at D180 versus D0 (p < 0.001).

Conclusions

Three annual applications of this varnish showed substantial antimicrobial activity against S. mutans and caries prevention for up to 12 months.

A Systematic Review of Plants With Antibacterial Activities: A Taxonomic and Phylogenetic Perspective

Background: Antimicrobial resistance represents a serious threat to human health across the globe. The cost of bringing a new antibiotic from discovery to market is high and return on investment is low. Furthermore, the development of new antibiotics has slowed dramatically since the 1950s’ golden age of discovery. Plants produce a variety of bioactive secondary metabolites that could be used to fuel the future discovery pipeline. While many studies have focused on specific aspects of plants and plant natural products with antibacterial properties, a comprehensive review of the antibacterial potential of plants has never before been attempted.

Objectives: This systematic review aims to evaluate reports on plants with significant antibacterial activities.

Methods: Following the PRISMA model, we searched three electronic databases: Web of Science, PubMed and SciFinder by using specific keywords: “plant,” “antibacterial,” “inhibitory concentration.”

Results: We identified a total of 6,083 articles published between 1946 and 2019 and then reviewed 66% of these (4,024) focusing on articles published between 2012 and 2019. A rigorous selection process was implemented using clear inclusion and exclusion criteria, yielding data on 958 plant species derived from 483 scientific articles. Antibacterial activity is found in 51 of 79 vascular plant orders throughout the phylogenetic tree. Most are reported within eudicots, with the bulk of species being asterids. Antibacterial activity is not prominent in monocotyledons. Phylogenetic distribution strongly supports the concept of chemical evolution across plant clades, especially in more derived eudicot families. The Lamiaceae, Fabaceae and Asteraceae were the most represented plant families, while Cinnamomum verum, Rosmarinus vulgaris and Thymus vulgaris were the most studied species. South Africa was the most represented site of plant collection. Crude extraction in methanol was the most represented type of extraction and leaves were the main plant tissue investigated. Finally, Staphylococcus aureus was the most targeted pathogenic bacteria in these studies. We closely examine 70 prominent medicinal plant species from the 15 families most studied in the literature.

Conclusion: This review depicts the current state of knowledge regarding antibacterials from plants and provides powerful recommendations for future research directions.

Copaifera spp. oleoresins impair Toxoplasma gondii infection in both human trophoblastic cells and human placental explants

The combination of pyrimethamine and sulfadiazine is the standard care in cases of congenital toxoplasmosis. However, therapy with these drugs is associated with severe and sometimes life-threatening side effects. The investigation of phytotherapeutic alternatives to treat parasitic diseases without acute toxicity is essential for the advancement of current therapeutic practices. The present study investigates the antiparasitic effects of oleoresins from different species of Copaifera genus against T. gondii. Oleoresins from C. reticulata, C. duckei, C. paupera, and C. pubiflora were used to treat human trophoblastic cells (BeWo cells) and human villous explants infected with T. gondii. Our results demonstrated that oleoresins were able to reduce T. gondii intracellular proliferation, adhesion, and invasion. We observed an irreversible concentration-dependent antiparasitic action in infected BeWo cells, as well as parasite cell cycle arrest in the S/M phase. The oleoresins altered the host cell environment by modulation of ROS, IL-6, and MIF production in BeWo cells. Also, Copaifera oleoresins reduced parasite replication and TNF-α release in villous explants. Anti-T. gondii effects triggered by the oleoresins are associated with immunomodulation of the host cells, as well as, direct action on parasites.

Characteristics of Listeria Monocytogenes Strains Persisting in a Meat Processing Facility over a 4-Year Period

Listeria monocytogenes can persist in food production facilities, resulting in serious threats to consumers due to the high mortality associated with listeriosis, especially in the very young, old and pregnant. We subtyped 124 strains of L. monocytogenes isolated from a meat processing facility in Switzerland by serotyping, multi locus sequence typing (MLST) typing and whole genome sequencing. We then analyzed their ability to form biofilms and their resistance to the disinfectants benzalkonium chloride (BC) and peracetic acid (PAA). The genotyping results of the strains showed that several clonal populations of L. monocytogenes belonging to CC9, CC204 and CC121 had persisted in this meat processing facility for at least four years. All of the strains showed biofilm forming capacity comparable to a known high biofilm forming strain. Known efflux pumps for BC were present in CC204, CC9 (brcABC) and CC121 (qacH) strains, while strains from other CC showed very low minimal inhibitory concentrations (MICs) for BC. For PAA, minimal bactericidal concentrations of 1.2–1.6% for 20 min and minimal inhibitory concentrations between 0.1 and 0.2% were observed. These values were close to or above the recommended concentration for use (0.5–1%), suggesting that PAA might be ineffective at controlling L. monocytogenes in this and potentially other meat processing facilities.

Investigation of Safety Profile of Four Copaifera Species and of Kaurenoic Acid by Salmonella/Microsome Test

Trees of the Copaifera genus are native to the tropical regions of Latin America and Western Africa. Copaifera sp is widely used as a popular medicine and it has various ethnopharmacological indications, including gonorrhea, bronchitis, asthma, skin ulcers, ulcers, sore throat, uterine infections, general inflammations, cancer, and leishmanioses. Kaurenoic acid is a naturally occurring diterpene found in Copaifera and has been used as an anti-inflammatory, treatment of ulcer, leishmaniasis, and cancer. Bearing in mind the fact that the Ames test is an excellent tool to assess the safety of extracts, oils, and phytochemicals isolated from medicinal plants, from it, we evaluate the mutagenic potential of four species, between oleoresins (C. oblongifolia; C. langsdorffii) and leaves extracts (C. lucens; C. multijuga), of the Copaifera genus and also of kaurenoic acid, which is one of its major compounds. The results showed that the Copaifera spp. and kaurenoic acid did not induce an increase in the number of revertant colonies, without mutagenic effect in experiments, in the all concentrations evaluated by Ames test. The results obtained in our study support the safe use of the Copaifera genus medicinal plants selected and of kaurenoic acid.

Antibacterial, Preservative, and Mutagenic Potential of Copaifera spp. Oleoresins Against Causative Agents of Foodborne Diseases

Foodborne diseases (FBDs) are a serious public health concern worldwide. In this scenario, preservatives based on natural products, especially plants, have attracted researchers' attention because they offer potential antimicrobial action as well as reduced health impact. The genus Copaifera spp., which is native of tropical South America and West Africa, contains several species for which pharmacological activities, including antibacterial effects, have been described. On the basis of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), antibiofilm activity (inhibition and eradication), preservative capacity, and Ames test, we evaluated the antibacterial, preservative, and mutagenic potential of Copaifera spp. oleoresins against the causative agents of FBDs. The Copaifera duckei, Copaifera reticulata, Copaifera paupera, and Copaifera pubiflora oleoresins displayed promising MIC/MBC values-from 12.5 to 100 μg/mL-against Staphylococcus aureus (American Type Culture Collection [ATCC] 29213), Listeria monocytogenes (ATCC 15313), and Bacillus cereus (ATCC 14579). C. duckei, C. reticulata, C. paupera, and C. pubiflora oleoresin concentrations ranging from 25 to 200 μg/mL and from 100 to 400 μg/mL inhibited biofilm formation and eradicated biofilms, respectively. The oleoresins did not exert mutagenic effects and had superior food preservative action to sodium benzoate (positive control). In conclusion, Copaifera oleoresins exhibit potential antibacterial activity and are not mutagenic, which makes them a promising source to develop novel natural food preservatives to inhibit foodborne pathogens.