Antimicrobial natural products: an update on future antibiotic drug candidates

Eugenol-Functionalized Magnetite Nanoparticles Modulate Virulence and Persistence in Pseudomonas aeruginosa Clinical Strains

Efficient antibiotics to cure Pseudomonas aeruginosa persistent infections are currently insufficient and alternative options are needed. A promising lead is to design therapeutics able to modulate key phenotypes in microbial virulence and thus control the progression of the infectious process without selecting resistant mutants. In this study, we developed a nanostructured system based on Fe₃O₄ nanoparticles (NPs) and eugenol, a natural plant-compound which has been previously shown to interfere with microbial virulence when utilized in subinhibitory concentrations. The obtained functional NPs are crystalline, with a spherical shape and 10-15 nm in size. The subinhibitory concentrations (MIC 1/2) of the eugenol embedded magnetite NPs (Fe₃O₄@EUG) modulate key virulence phenotypes, such as attachment, biofilm formation, persister selection by ciprofloxacin, and the production of soluble enzymes. To our knowledge, this is the first report on the ability of functional magnetite NPs to modulate P. aeruginosa virulence and phenotypic resistance; our data highlights the potential of these bioactive nanostructures to be used as anti-pathogenic agents.

Oxygenated pentacyclic triterpenoids from the stems and branches of Enkianthus chinensis

Thirty new pentacyclic triterpenoids, including five oleanane-type (1-5), twenty-three ursane-type (9-23, 26-33) and two taraxerane-type (24 and 25), along with fourteen known triterpenoids, were isolated from the stems and branches of Enkianthus chinensis. Their structures were elucidated by extensive spectroscopic analyses, X-ray crystallographic data and electronic circular dichroism (ECD) techniques. Sixteen compounds (1-5, 9-13, 20, 22, 32, 34-36) bearing a gem-hydroxymethyl group at C-4 represent rare examples of pentacyclic triterpenoids. In the in vitro biological activity evaluation, compounds 8, 9, 12-14, 17, 24, and 44 exhibited potent hepatoprotective effects at 10 μM. Moreover, compound 25 showed latent activity against HSV-1 with an IC₅₀ value of 6.4 μM.

Antimicrobial potential of resin matrices loaded with coffee compounds

This study evaluated the biological behavior of the coffee compounds Trigonelline (T), chlorogenic acid (C), and nicotinic acid (N), correlating with their release from a resin matrix. Minimum inhibitory concentration (MIC) was evaluated against Streptococcus mutans UA159, and cytotoxicity was assessed by methyl tetrazolium salt on OD-21 cells. Resin matrices (bisphenol A-glycidyl-dimethacrylate/triethylene glycol-dimethacrylate 70/30 wt%, camphorquinone/ethyl 4-dimethyl aminobenzoate 0.5/1 wt%) were doped with coffee compounds in different concentrations (10/20/30/40/50 wt%), performing 15 groups (T10-T50, C10-C50, N10-N50), and a control group with no coffee compound. Degree of conversion (DC%) was analyzed by Fourier transform infrared spectroscopy. Antimicrobial properties were evaluated by bioluminescence (Luciferase assay). The release from loaded matrices was analyzed over time (24 hr, 6, 14, 21 and 28 days), using high-performance liquid chromatography (HPLC). Data were submitted to ANOVA/Tukey's test (α = 0.05). MIC for T and C was 6 mg/ml, and 4 mg/ml for N. None of them were cytotoxic. Only T50 and C50 showed lower DC% than control (α < 0.05). Some groups (T30/T40/T50/C40/C50/N50) were strongly antimicrobial, reducing bacterial activity approximately five times compared to control (α < 0.05). For T30, T40, T50, C40, and C50, the HPLC showed a release above or closer to MIC values mainly in 24 hr, but for N50, up to 28 days. In conclusion, the coffee compounds presented antimicrobial activity, depending on their concentration when added in resin matrices, being found a correlation with their release.

Monoterpenes and Sesquiterpenes of Essential Oils from Psidium Species and Their Biological Properties

Psidium (Myrtaceae) comprises approximately 266 species, distributed in tropical and subtropical regions of the world. Psidium taxa have great ecological, economic, and medicinal relevance due to their essential oils' chemical diversity and biological potential. This review reports 18 Psidium species growing around the world and the chemical and biological properties of their essential oils. Chemically, 110 oil records are reported with significant variability of volatile constituents, according to their seasonality and collection sites. Monoterpenes and sesquiterpenes with acyclic (C₁₀ and C₁₅), p-menthane, pinane, bisabolane, germacrane, caryophyllane, cadinane, and aromadendrane skeleton-types, were the primary constituents. The essential oils showed various biological activities, including antioxidant, antifungal, antibacterial, phytotoxic, larvicidal, anti-inflammatory, and cytotoxic properties. This review contributes to the Psidium species rational and economic exploration as natural sources to produce new drugs.

In vitro antiplatelet activity of extract and its fractions of Paulownia Clone in Vitro 112 leaves

BACKGROUND

Paulownia Clone in Vitro 112, also known as Oxytree is a hybrid of Paulownia elongata and Paulownia fortunei, developed under laboratory conditions. Its seeds are sterile, making it a noninvasive variety that can only be propagated in the laboratory. In China, species from the Paulownia genus (Paulowniaceae) are widely used in traditional medicine for the treatment of infectious diseases, such as gonorrhea and erysipelas. It has a broad spectrum of bioactivity, including neuroprotective, antioxidant, antibacterial, antiphlogistic, antiviral, and cytotoxic actions. However, the antiplatelet potential of Paulownia Clone in Vitro 112 has not yet been described.

STUDY DESIGN

The aim of our study was thus to examine the effect of an extract and four fractions from leaves of Paulownia Clone in Vitro 112 on various parameters of platelet activation in an in vitro model.

METHODS

Composition of the investigated extract and fractions was determined by UHPLC-UV-MS. The following parameters of platelet activation were investigated: nonenzymatic lipid peroxidation in resting platelets; enzymatic lipid peroxidation (AA metabolism) in platelets activated by thrombin; superoxide anion (O₂^-.) generation in the resting and activated platelets; platelet adhesion to collagen type I and fibrinogen; platelet aggregation stimulated by various physiological agonists, such as ADP, collagen, and thrombin. The effect of the extract and fractions on extracellular LDH activity, a marker of cell damage, was also determined.

RESULTS

Verbascoside a phenylethnanoid glycoside, was the main secondary metabolite of the extract from leaves of oxytree (constituting approximately 45 % of all compounds). There were also iridoids, such as catalpol, aucubin, and 7-hydroxytomentoside, as well as flavonoids, such as luteolin and apigenin glycosides. Moreover, the extract had stronger antiplatelet properties than the fractions. For example, the extract at 10 μg/mL inhibited five parameters of platelet activation.

CONCLUSIONS

Our results show that Paulownia Clone in Vitro 112 leaves are a new valuable source of compounds with antiplatelet potential.

Local delivery natural products to treat periodontitis: a systematic review and meta-analysis

OBJECTIVES

This study aimed to answer the PICO question: in adults with periodontitis, does subgingival delivery of natural products (NP) after scaling and root planing (SRP) results in a better reduction of probing pocket depth (PPD) when compared with SRP alone or SRP plus placebo?

MATERIAL AND METHODS

A search for trials was carried out in eight databases. Two independent investigators performed all steps of this review. PPD reduction, clinical attachment level (CAL) gain, gingival inflammation, and biofilm accumulation reduction were investigated. We conducted meta-analyses where data could be pooled.

RESULTS

Searches yielded 4771 records, in which 27 trials fulfilled the eligibility. There was a large heterogeneity among trials (I² > 0.69, χ² < 0.000). Only four studies were at low risk of bias. The evidence quality was very low. The effectiveness of NP was demonstrated in a follow-up of 3-6 months considering PPD reduction (8 trials: 0.72 mm [95%CI: 0.23, 1.22]) and CAL gain (5 trials: 1.07 mm [95%CI: 0.36, 1.78]). A significant reduction in periodontal inflammation favors the use of NP. The biofilm accumulation reduction effect of NP was very weak or non-significant.

CONCLUSION

Although the high risk of bias and large heterogeneity of trials impose some restrictions on the validity of effect estimate, this review indicates that adjunctive NP better reduced the PPD when compared to SRP alone or SRP plus placebo in a follow-up of 3-6 months.

CLINICAL RELEVANCE

The evidence of non-responsive patients to conventional periodontal therapy highlights the need for therapeutic alternatives to treat periodontitis.

Naringin inhibits the biofilms of metallo-β-lactamases (MβLs) producing Pseudomonas species isolated from camel meat

Food producing animals harbouring bacteria carrying drug resistance genes especially the metallo-beta-lactamase (MBL) pose high risk for the human population. In addition, formation of biofilm by these drug resistant pathogens represents major threat to food safety and public health. In this study, metallo-β-lactamases (MβLs) producing Pseudomonas spp. from camel meat were isolated and assessed for their biofilm formation. Further, in vitro and in silico studies were performed to study the effect of flavone naringin on biofilm formation against isolated Pseudomonas spp. A total of 55% isolates were found to produce metallo-β-lactamase enzyme. Naringin mitigated biofilm formation of Pseudomonas isolates up to 57%. Disturbed biofilm architecture and reduced the colonization of bacteria on glass was observed under scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM). The biofilm related traits such as exopolysaccharides (EPS) and alginate production was also reduced remarkably in the presence of naringin. Eradication of preformed biofilms (32–60%) was also observed at the respective 0.50 × MICs. Molecular docking revealed that naringin showed strong affinity towards docked proteins with binding energy ranging from −8.6 to −8.8 kcal mol⁻¹. Presence of metallo-β-lactamase producers indicates that camel meat could be possible reservoir of drug-resistant Pseudomonas species of clinical importance. Naringin was successful in inhibiting biofilm formation as well as eradicating the preformed biofilms and demonstrated strong binding affinity towards biofilm associated protein. Thus, it is envisaged that naringin could be exploited as food preservative especially against the biofilm forming food-borne Pseudomonas species and is a promising prospect for the treatment of biofilm based infections.

Efficiency of a Tetracycline-Adjuvant Combination Against Multidrug Resistant Pseudomonas aeruginosa Tunisian Clinical Isolates

The growing number of multidrug resistant strains in Tunisia has become a serious health concern contributing to high rate of mortality and morbidity. Since current antibiotics are rapidly becoming ineffective, novel strategies to combat resistance are needed. Recently, we demonstrated that combination of a tetracycline antibiotic with various polyaminoisoprenyl adjuvants can sustain the life span and enhance the activity of these drugs against Pseudomonas aeruginosa reference strain (PA01). In the context of our continuing studies, the effective approach of antibiotic-adjuvant was investigated against a large panel of P. aeruginosa Tunisian clinical strains collected from the Military Hospital of Tunis. In this paper, we demonstrated that the combination of a farnesyl spermine compound 3 used at concentrations ranging from 2.5 to 10 µM, in the presence of doxycycline or minocycline leads to a significant decrease of P. aeruginosa antibiotic resistance.

Semisynthetic Vitamin E Derivatives as Potent Antibacterial Agents against Resistant Gram-Positive Pathogens

New 5-substituted vitamin E derivatives were semisynthesized, and their antibacterial activity against human Gram-positive and Gram-negative pathogens was evaluated. Several vitamin E analogues were active against methicillin-resistant Staphylococcus aureus (MRSA) and/or methicillin-resistant Staphylococcus epidermidis (MRSE); structure-activity relationships (SARs) are discussed. As a result, it is shown that the presence of a carboxylic acid function at the C-5 position and/or at the end of the side chain is crucial for the antibacterial activity. The bactericidal or bacteriostatic action of three compounds against MRSA and MRSE was confirmed in a time-kill kinetics study, and the cytotoxicity on human cells was evaluated. The preliminary mechanism study by confocal microscopy indicated that those vitamin E analogues led to bacterial cell death through membrane disruption.

Antimicrobial investigation of ethnobotanically selected guinean plant species

ETHNOPHARMACOLOGICAL RELEVANCE

In Guinea, medicinal plants play an important role in the management of infectious diseases including urinary disorders, skin diseases and oral diseases. This study was carried out to collect medicinal plant species employed for the treatment of these diseases and to investigate their antimicrobial potential.

MATERIALS AND METHODS

Based on an ethnobotanical investigation carried out in three Guinean regions, 74 traditional healers and 28 herbalists were interviewed and medicinal plants were collected. The most quoted plant species were evaluated for their antimicrobial activities against Staphylococcus aureus, Escherichia coli, Candida albicans, and in addition against Plasmodium falciparum.

RESULTS

A total of 112 plant species belonging to 102 genera distributed over 42 botanical families were inventoried. Among the selected plant species, promising activities against C. albicans were obtained for the methanolic extracts of the stem bark of Terminalia albida (IC₅₀ 1.2 μg/ml), the leaves of Tetracera alnifolia (IC₅₀ 1.6 μg/ml) and the root bark of Swartzia madagascariensis (IC₅₀ 7.8 μg/ml). The highest activity against S. aureus was obtained for the dichloromethane extracts of the leaves of Pavetta crassipes (IC₅₀ 8.5 μg/ml) and the root of Swartzia madagascariensis (IC₅₀ 12.8 μg/ml). Twenty one extracts, obtained from twelve plant species, were strongly active against Plasmodium falciparum, including the dichloromethane extracts of the root and stem bark of Terminalia albida root (IC₅₀ 0.6 and 0.8 μg/ml), the leaves of Landolphia heudelotii (IC₅₀ 0.5 μg/ml), the stem bark of Combretum paniculatum (IC₅₀ 0.4 μg/ml) and the leaves of Gardenia ternifolia (IC₅₀ 1.3 μg/ml).

CONCLUSION

The present study provides a comprehensive overview of medicinal plants employed by Guinean traditional healers for the treatment of various microbial diseases, including urinary disorders, skin diseases and oral diseases. Some of the studied plant species showed promising antimicrobial activity and could be considered as a potential source for the development of new antifungal and/or antimalarial agents.

Structural Similarities between Some Common Fluorophores Used in Biology, Marketed Drugs, Endogenous Metabolites, and Natural Products

It is known that at least some fluorophores can act as 'surrogate' substrates for solute carriers (SLCs) involved in pharmaceutical drug uptake, and this promiscuity is taken to reflect at least a certain structural similarity. As part of a comprehensive study seeking the 'natural' substrates of 'orphan' transporters that also serve to take up pharmaceutical drugs into cells, we have noted that many drugs bear structural similarities to natural products. A cursory inspection of common fluorophores indicates that they too are surprisingly 'drug-like', and they also enter at least some cells. Some are also known to be substrates of efflux transporters. Consequently, we sought to assess the structural similarity of common fluorophores to marketed drugs, endogenous mammalian metabolites, and natural products. We used a set of some 150 fluorophores along with standard fingerprinting methods and the Tanimoto similarity metric. Results: The great majority of fluorophores tested exhibited significant similarity (Tanimoto similarity > 0.75) to at least one drug, as judged via descriptor properties (especially their aromaticity, for identifiable reasons that we explain), by molecular fingerprints, by visual inspection, and via the "quantitative estimate of drug likeness" technique. It is concluded that this set of fluorophores does overlap with a significant part of both the drug space and natural products space. Consequently, fluorophores do indeed offer a much wider opportunity than had possibly been realised to be used as surrogate uptake molecules in the competitive or trans-stimulation assay of membrane transporter activities.

Recent progresses in marine microbial-derived antiviral natural products

Viruses have always been a class of pathogenic microorganisms that threaten the health and safety of human life worldwide. However, for a long time, the treatment of viral infections has been slow to develop, and only a few antiviral drugs have been using clinically. Compared with these from terrestrial environments, marine-derived microorganisms can produce active substances with more novel structures and unique functions. From 2015 to 2019, 89 antiviral compounds of 8 structural classes have been isolated from marine microorganisms, of which 35 exhibit anti-H1N1 activity. This review surveys systematically marine microbial-derived natural products with antiviral activity and illustrates the impact of these compounds on antiviral drug discovery research.

The potential use of Azolla pinnata as an alternative bio-insecticide

Four different tests showed the effectiveness of Azolla pinnata plant extracts against Aedes aegypti and Aedes albopictus mosquitoes. In the adulticidal test, there was a significant increase in mortality as test concentration increases and A. pinnata extracts showed LC₅₀ and LC₉₅ values of 2572.45 and 6100.74 ppm, respectively, against Ae. aegypti and LC₅₀ and LC₉₅ values of 2329.34 and 5315.86 ppm, respectively, against Ae. albopictus. The ovicidal test showed 100% eggs mortality for both species tested for all the concentrations tested at 1500 ppm, 1000 ppm, 500 ppm, 250 ppm and 125 ppm. Both tested samples of Ae. aegypti and Ae. albopictus did not lay any eggs in the plastic cups filled with the A. pinnata extract but instead opted to lay eggs in the plastic cups filled with water during the oviposition deterrence test. Similarly, the non-choice test of Ae. aegypti mosquitoes laid eggs on the sucrose solution meant for the nutrient source of the mosquitoes instead of in the plastic cup that was designed to facilitate oviposition filled with the extract. This clearly indicates the presence of bioactive compounds which are responsible in adulticidal and ovicidal activity in Aedes mosquitoes and at the same time inducing repellence towards the mosquitoes. The LC–MS results showed mainly three important chemical compounds from A. pinnata extracts such as 1-(O-alpha-D-glucopyranosyl)-(1,3R,25R)-hexacosanetriol, Pyridate and Nicotinamide N-oxide. All these chemicals have been used for various applications such as both emulsion and non-emulsion type of cosmetics, against mosquito vector such as Culex pipens and Anopheles spp. Finally, the overall view of these chemical components from A. pinnata extracts has shown the potential for developing natural product against dengue vectors.

Kaempferol separated from Camellia oleifera meal by high-speed countercurrent chromatography for antibacterial application

Natural biologically active substances have received continuous attention for the potentially beneficial health properties against chronic diseases. In this study, bacteriostatic active substance from Camellia oleifera meal, which is a major by-product of the Camellia oil processing industry, were extracted with continuous phase change extraction (CPCE) method and separated by HSCCC. Compared with traditional extraction methods, CPCE possessed higher extraction efficiency. Two main substances were separated and purified (above 90.0%). The structure of them were further identified by UV, LC-ESI-MS-MS, 1H-NMR, and 13C-NMR as flavonoids F2 kaempferol 3-O-[β-d-glucopyranosyl-(1 → 2)-α-l-rhamnopyranosyl-(1 → 6)]-β-d-glucopyranoside and J2 kaempferol 3-O-[β-d-xylopyranosyl-(1 → 2)-α-l-rhamnopyranosyl-(1 → 6)]-β-d-glucopyranoside for the first time in C. Oleifera meal. The results of antibacterial activity measurement showed that both compounds have excellent antibacterial activity. And the antibacterial stability of F2 were finally confirmed: F2 showed broad spectrum antibacterial activity against Escherichia coli, Staphylococcus aureus, Salmonella enteriditis, Bacillus thuringiensis, Aspergillus niger and Rhizopus nigricans. Besides, F2 exhibited relatively high stable property even at high temperature, acid and metal ion solutions. The findings of this work suggest the possibility of employing C. oleifera meal as an attractive source of health-promoting compounds, and at the same time facilitate its high-value reuse and reduction of environmental burden.

Essentials Oils from Brazilian Eugenia and Syzygium Species and Their Biological Activities

The Eugenia and Syzygium genera include approximately 1000 and 1800 species, respectively, and both belong to the Myrtaceae. Their species present economic and medicinal importance and pharmacological properties. Due to their chemical diversity and biological activity, we are reporting the essential oils of 48 species of these two genera, which grow in South America and found mainly in Brazil. Chemically, a total of 127 oil samples have been described and displayed a higher intraspecific and interspecific diversity for both Eugenia spp. and Syzygium spp., according to the site of collection or seasonality. The main volatile compounds were sesquiterpene hydrocarbons and oxygenated sesquiterpenes, mainly with caryophyllane and germacrane skeletons and monoterpenes of mostly the pinane type. The oils presented many biological activities, especially antimicrobial (antifungal and antibacterial), anticholinesterase, anticancer (breast, gastric, melanoma, prostate), antiprotozoal (Leishmania spp.), antioxidant, acaricidal, antinociceptive and anti-inflammatory. These studies can contribute to the rational and economic exploration of Eugenia and Syzygium species once they have been identified as potent natural and alternative sources to the production of new herbal medicines.

Sinapic Acid Attenuates Cardiovascular Disorders in Rats by Modulating Reactive Oxygen Species and Angiotensin Receptor Expression

The main avoidable risk factor for cardiovascular conditions is high blood pressure (hypertension). At global level, hypertension is believed to be responsible for a 54% stroke-related mortality rate and a 47% mortality rate associated with coronary heart disease. It is postulated that sinapic acid (SA) could help in hypertension management because it displays robust antioxidant, antihyperglycemic, and peroxynitrite scavenging effects. To explore this hypothesis, this work examined the effect of SA on oxidative stress and cardiovascular disease in rats with hypertension by comparison against captopril. For this purpose, 50 male rats were used and equally allocated to five groups, namely, normal control, positive control (L-NAME), L-NAME with concomitant captopril administration, L-NAME with concomitant SA administration, and L-NAME with concomitant administration of both SA and captopril. Results showed that, by contrast to control, L-NAME exhibited marked elevation in serum CK-MB, total cholesterol, triglycerides, VLDL-C, LDL-C, Ang II, AT2R, ET-1, and angiopoietin-2; on the other hand, L-NAME exhibited marked reduction in serum HDL-C, superoxide dismutase (SOD) activity, nitric oxide synthase 3 (NOS3), and glutathione (GSH). Furthermore, joint administration of SA and captopril ameliorated hypertension, enhanced cardiovascular function, hindered hyperlipidemia, and decreased oxidative stress and myocardial hypertrophy displayed by rats with hypertension. Based on such findings, better chemopreventive or therapeutic approaches can be devised to manage hypertension and cardiovascular conditions.

Acacia senegal Extract Rejuvenates the Activity of Phenicols on Selected Enterobacteriaceae Multi Drug Resistant Strains

This study reported the phytochemical composition of two hydroethanolic extracts of Acacia senegal and Acacia seyal trees from Burkina Faso and their activities, alone or in combination with selected antibiotics, against multidrug resistant bacteria. High performance thin layer chromatography (HPTLC) method was used for phytochemical screening. Total phenolic and total flavonoid ant tannins in leaves extracts contents were assessed by spectrophotometric method. The minimal inhibitory concentrations (MICs) of plant extracts and antibiotics were determined using the microdilution method and p-iodonitrotetrazolium chloride. Combinations of extracts and antibiotics were studied using checkerboard assays. Screening revealed the presence of phenolic compounds, flavonoids, and tannins in the hydroethanolic extract (HE) of the leaves. The HE of A. seyal showed the highest total phenolic (571.30 ± 6.97 mg GAE/g), total flavonoids (140.41 ± 4.01 mg RTE/g), and tannins (24.72 ± 0.14%, condensed; 35.77 ± 0.19%, hydrolysable tannins). However, the HE of A. senegal showed the lowest total phenolic (69.84 ± 3.54 mg GAE/g), total flavonoids (27.32 ± 0.57 mg RTE/g), and tannins (14.60 ± 0.01%, condensed; 3.09 ± 0.02%, hydrolysable). The MICs for HE and antibiotics were in the range of 2–512 and 0.008–1024 mg/L, respectively. All tested HE presented an MIC greater than 512 mg/L except HE of A. senegal. The lowest MIC value (128 mg/L) was obtained with HE of A. senegal against Klebsiella aerogenes EA298 and Escherichia coli AG100A. Interesting restoring effects on chloramphenicol and florphenicol activity were detected with alcoholic extracts of A. senegal against resistant E. coli and K. aerogenes strains that overproduce AcrAB or FloR pumps. The adjuvant effect of HE of A. senegal suggests that the crude extract of leaves could be a potential source of molecules for improving the susceptibility of bacteria to phenicols antibiotics.

Durable Antibacterial Cotton Fabrics Based on Natural Borneol-Derived Anti-MRSA Agents

Borneol, a natural extract with unique bicyclic monoterpene structure, has attracted increasing attention due to its broad-spectrum antibacterial properties via membrane disruption mechanism. However, the negligible water solubility of borneol limits its antibacterial efficiency. Herein, borneol-based water-soluble antibacterial agents are designed and synthesized to combat multi-drug resistant bacteria. The integration of borneol with hydrophilic poly(N,N-dimethylethyl methacrylate) (PDMAEMA) polymer chains boosts the antibacterial capability of borneol against Gram-negative, Gram-positive, and even multi-drug resistant bacteria. Methicillin-resistant Staphylococcus aureus (MRSA) are completely killed upon treatment with 50 µg mL^-1 of borneol-based polymers and Escherichia coli are annihilated at 39 µg mL^-1 . It is further demonstrated that the borneol-based antibacterial agents can be grafted onto cotton fabrics as a nonleaching antibacterial agent, which have higher sustained antibacterial activity than cotton fabrics coated with the commercial quaternary ammonium finishing agents (AEM 5700). The functionalized fabrics with excellent bactericidal activity, especially against MRSA, may have great potential applications in managing hospital-acquired infections.

Investigation of Copaifera genus as a new source of antimycobaterial agents

AIM

This paper reports on the antimycobacterial activity of the oleoresins and extracts obtained from Copaifera spp.

MATERIALS & METHODS

The minimum inhibitory concentration (MIC) and fractional inhibitory concentration index techniques helped to evaluate the effect of these oleoresins and extracts against six strains of mycobacteria that cause tuberculosis.

RESULTS & CONCLUSION

Among the assayed oleoresins and plant extracts, the Copaifera langsdorffii, Copaifera duckei, Copaifera reticulata and Copaifera trapezifolia oleoresins provided the lowest MIC values against some of the tested strains. The combination of Copaifera spp. samples with isoniazid did not evidence any synergistic action. Some Copaifera spp. oleoresins may represent a future source for the discovery of new antimycobacterial drugs due to their low MIC values.

Recent progress of antibacterial natural products: Future antibiotics candidates

The discovery of novel antibacterial molecules plays a key role in solving the current antibiotic crisis issue. Natural products have long been an important source of drug discovery. Herein, we reviewed 256 natural products from 11 structural classes in the period of 2016-01/2020, which were selected by SciFinder with new compounds or new structures and MICs lower than 10 μg/mL or 10 μM as criterions. This review will provide some effective antibacterial lead compounds for medicinal chemists, which will promote the antibiotics research based on natural products to the next level.

Therapeutic advances in wound healing

Wound healing is a complex physiological process that occurs in the human body involving the sequential activation of multiple cell types and signaling pathways in a coordinated manner. Chronic wounds and burns clearly decrease quality of life of the patients since they are associated with an increase in physical pain and socio-economical complications. Furthermore, incidence and prevalence of chronic wounds (unlike burns) have been increasing mainly due to population aging resulting in increased costs for national health systems. Thus, the development of new and more cost-effective technologies/therapies is not only of huge interest but also necessary to improve the long-term sustainability of national health systems. This review covers the current knowledge on recent technologies/therapies for skin regeneration, such as: wound dressings; skin substitutes; exogenous growth factor based therapy and systemic therapy; external tissue expanders; negative pressure; oxygen; shock wave, and photobiomodulation wound therapies. Associated benefits and risks as well as the clinical use and availability are all addressed for each therapy. Moreover, future trends in wound care including novel formulations using metallic nanoparticles and topical insulin are herein presented. These novel formulations have shown to be promising therapeutic options in the near future that may change the wound care paradigm.

Transcriptome profiles of Quercus rubra responding to increased O3 stress

BACKGROUND

Climate plays an essential role in forest health, and climate change may increase forest productivity losses due to abiotic and biotic stress. Increased temperature leads to the increased formation of ozone (O3). Ozone is formed by the interaction of sunlight, molecular oxygen and by the reactions of chemicals commonly found in industrial and automobile emissions such as nitrogen oxides and volatile organic compounds. Although it is well known that productivity of Northern red oak (Quercus rubra) (NRO), an ecologically and economically important species in the forests of eastern North America, is reduced by exposure to O3, limited information is available on its responses to exogenous stimuli at the level of gene expression.

RESULTS

RNA sequencing yielded more than 323 million high-quality raw sequence reads. De novo assembly generated 52,662 unigenes, of which more than 42,000 sequences could be annotated through homology-based searches. A total of 4140 differential expressed genes (DEGs) were detected in response to O3 stress, as compared to their respective controls. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of the O3-response DEGs revealed perturbation of several biological pathways including energy, lipid, amino acid, carbohydrate and terpenoid metabolism as well as plant-pathogen interaction.

CONCLUSION

This study provides the first reference transcriptome for NRO and initial insights into the genomic responses of NRO to O3. Gene expression profiling reveals altered primary and secondary metabolism of NRO seedlings, including known defense responses such as terpenoid biosynthesis.

Insight into the screening of potential beta-lactamase inhibitors as anti-bacterial chemical agents through pharmacoinformatics study

Drug resistance is an unsolved and major concern in the bacterial infection. Continuous development of drug-resistance to the antibiotics exponentially rises the danger of bacterial infections. Chemical components from the plants are becoming a major resource of potentially effective therapeutic chemical agents for the wide range of diseases including bacterial infections. In the current study, pharmacoinformatics methodologies were implemented on more than two hundred known phytochemicals to find promising beta-lactamase inhibitors for therapeutically effective anti-bacterial agents. Initially, the molecular docking-based score was used to reduce the chemical space of the selected dataset. Fourteen molecules were found to have more affinity towards the beta-lactamase in compared to the well-known anti-bacterial agent, Avibactam. Binding interactions analysis revealed the strong binding interactions between phytochemicals and catalytic amino residues. For further analysis, molecular dynamics (MD) simulations, density functional theory (DFT) and in silico pharmacokinetics studies were performed. Parameters from MD simulations studies suggested that selected molecules are strong enough to retain in the active site in different orientations of the beta-lactamase. The orbital energies obtained from the DFT study was undoubtedly explained the potentiality of the selected compounds for being effective beta-lactamase inhibitors. The drug-likeness and acceptable pharmacokinetics parameters were observed using in silico ADME analysis. Therefore, observations from the multiple pharmacoinformatics approach explained without any doubt that selected molecules are potential enough being promising anti-bacterial compounds. [Formula: see text] Communicated by Ramaswamy H. Sarma.

Naringin sensitizes the antibiofilm effect of ciprofloxacin and tetracycline against Pseudomonas aeruginosa biofilm

The study aims to explore the combinatorial effect of naringin with antibiotics, ciprofloxacin and tetracycline on Pseudomonas aeruginosa biofilms. The antibiofilm efficacy of selected treatment regimes against P. aeruginosa biofilm were quantified by crystal violet assay, MTT assay, Congo red binding assay, and were visualized by confocal laser scanning microscopy and scanning electron microscopy. All the assays reflected antibiofilm activities, however, combinatorial performances of naringin with antibiotics were found to be more significant. A significant reduction in swimming and swarming motilities along with pellicle formation and altered colony morphology were observed as a result of combinatorial effect. The cytotoxicity of naringin and its antibiotic combinations was assayed on murine macrophage cell line. The applicability of such combinations was tested for their relative eradication against pre-formed biofilm on urinary catheter surface. This finding indicated that naringin potentiates the efficacy of both ciprofloxacin and tetracycline on P. aeruginosa biofilm in comparison to their solo treatment. The finding would help to open hitherto unexplored possibilities of establishing naringin as a potential antibiofilm agent and suggest on the possibility of its use in drug-herb combinations for managing biofilm-associated bacterial infections.

Synthesis and Antimicrobial Evaluation of Side-Chain Derivatives based on Eurotiumide A

Side-chain derivatives of eurotiumide A, a dihydroisochroman-type natural product, have been synthesized and their antimicrobial activities described. Sixteen derivatives were synthesized from a key intermediate of the total synthesis of eurotiumide A, and their antimicrobial activities against two Gram-positive bacteria, methicillin-susceptible and methicillin-resistant Staphylococcus aureus (MSSA and MRSA), and a Gram-negative bacterium, Porphyromonas gingivalis, were evaluated. The results showed that derivatives having an iodine atom on their aromatic ring instead of the prenyl moiety displayed better antimicrobial activity than eurotiumide A against MSSA and P. gingivalis. Moreover, we discovered that a derivative with an isopentyl side chain, which is a hydrogenated product of eurotiumide A, is the strongest antimicrobial agent against all three strains, including MRSA.

Hybrid Plasmonic Photoreactors as Visible Light-Mediated Bactericides

Photocatalytic compounds and complexes, such as tris(bipyridine)ruthenium(II), [Ru(bpy)₃]²⁺, have recently attracted attention as light-mediated bactericides that can help to address the need for new antibacterial strategies. We demonstrate in this work that the bactericidal efficacy of [Ru(bpy)₃]²⁺ and the control of its antibacterial function can be significantly enhanced through combination with a plasmonic nanoantenna. We report strong, visible light-controlled bacterial inactivation with a nanocomposite design that incorporates [Ru(bpy)₃]²⁺ as a photocatalyst and a Ag nanoparticle (NP) core as a light-concentrating nanoantenna into a plasmonic hybrid photoreactor. The hybrid photoreactor platform is facilitated by a self-assembled lipid membrane that encapsulates the Ag NP and binds the photocatalyst. The lipid membrane renders the nanocomposite biocompatible in the absence of resonant illumination. Upon illumination, the plasmon-enhanced photoexcitation of the metal-to-ligand charge-transfer band of [Ru(bpy)₃]²⁺ prepares the reactive excited state of the complex that oxidizes the nanocomposite membrane and increases its permeability. The photooxidation induces the release of [Ru(bpy)₃]²⁺, Ag⁺, and peroxidized lipids into the ambient medium, where they interact synergistically to inactivate bacteria. We measured a 7 order of magnitude decrease in Gram-positive Arthrobacter sp. and a 4 order of magnitude decrease in Gram-negative Escherichia coli colony forming units with the photoreactor bactericides after visible light illumination for 1 h. In both cases, the photoreactor exceeds the bactericidal standard of a log reduction value of 3 and surpasses the antibacterial effect of free Ag NPs or [Ru(bpy)₃]²⁺ by >4 orders of magnitude. We also implement the inactivation of a bacterial thin film in a proof-of-concept study.

Antimicrobial activity and chemical composition of white birch (Betula papyrifera Marshall) bark extracts

Extracts from white birch have been reported to possess antimicrobial properties, but no study has linked the chemical composition of bark extract with antimicrobial activity. This study aimed to identify white birch (Betula papyrifera Marshall) bark extracts with antimicrobial activity and elucidate its composition. In order to obtain the highest extraction yield, bark residues >3 mm were retained for extraction. A total of 10 extraction solvents were used to determine the extraction yield of each of them. Methanol and ethanol solvents extracted a greater proportion of molecules. When tested on eight microorganism species, the water extract proved to have the best antimicrobial potential followed by the methanol extract. The water extract inhibited all microorganisms at low concentration with minimal inhibitory concentration between 0.83 and 1.67 mg/ml. Using ultraperformance liquid chromatography coupled to a time-of-flight quadrupole mass spectrometer, several molecules that have already been studied for their antimicrobial properties were identified in water and methanol extracts. Catechol was identified as one of the dominant components in white birch bark water extract, and its antimicrobial activity has already been demonstrated, suggesting that catechol could be one of the main components contributing to the antimicrobial activity of this extract. Thus, extractives from forestry wastes have potential for new applications to valorize these residues.

Low-Temperature Reverse Water-Gas Shift Process and Transformation of Renewable Carbon Resources to Value-Added Chemicals

The use of CO₂ instead of toxic CO in the production of important chemicals has attracted widespread interest, and the reverse water-gas shift reaction (RWGSR) is the key step for this kind of processes. Although the thermodynamic limitations are overcome by the reaction of CO with other compounds, the temperature of most reactions involving RWGSR is usually very high owing to the inertness of CO₂ . Herein, it was found that Ru₃ (CO)₁₂ could catalyze the RWGSR in the ionic liquid HMimBF₄ without ligand or promoter, and CO could be produced at 80 °C, which was much lower than the temperatures reported to date. Detailed studies showed that the BF₄ ^- in the ionic liquid played a crucial role in the low-temperature RWGSR. Based on the low-temperature RWGSR, three important routes to transform CO₂ into valuable chemicals were developed, including synthesis of xanthone from CO₂ and diaryl ethers, synthesis of phenol and acetic acid from CO₂ and anisole, and production of acetic acid from CO₂ and lignin. The reactions could occur at temperature as low as 80 °C, and low-temperature RWGSR was essential for the reactions under mild conditions. The strategy opens the way to produce value-added chemicals by using CO₂ and H₂ as feedstocks under low temperature.

The antimicrobial activity of coenzyme Q0 against planktonic and biofilm forms of Cronobacter sakazakii

Coenzyme Q₀ (CoQ₀) has demonstrated antitumor, anti-inflammatory, and anti-angiogenic activities. Cronobacter sakazakii is an opportunistic foodborne pathogen associated with high mortality in neonates. In this study, the antimicrobial activity and possible antimicrobial mechanism of CoQ₀ against C. sakazakii were investigated. Moreover, the inactivation effect of CoQ₀ on C. sakazakii in biofilms was also evaluated. The minimum inhibitory concentration (MIC) of CoQ₀ against C. sakazakii strains ranged from 0.1 to 0.2 mg/mL. Treatment caused cell membrane dysfunction, as evidenced by cell membrane hyperpolarization, decreased intracellular ATP concentration and cell membrane integrity, and changes in cellular morphology. CoQ₀ combined with mild heat treatment (45, 50, or 55 °C) decreased the number of viable non-desiccated and desiccated C. sakazakii cells in a time- and dose-dependent manner in reconstituted infant milk. Furthermore, CoQ₀ showed effective inactivation activity against C. sakazakii in biofilms on stainless steel, reducing the number of viable cells and damaging the structure of the biofilm. These findings suggest that CoQ₀ has a strong inactivate effect on C. sakazakii and could be used in food production environments to effectively control C. sakazakii and reduce the number of illnesses associated with it.

Leishmanicidal and antimicrobial activity of primin and primin-containing extracts from Miconia willdenowii

As a part of an ongoing bioprospective project, searching for potential medicinal plants from the Brazilian Atlantic Forest, Miconia willdenowii was selected for its potential leishmanicidal and antimicrobial activities. The crude ethanolic extract of M. willdenowii showed an inhibition of 99.7% of the promastigote forms of Leishmania amazonensis at the concentration of 80 μg/mL. Further investigation of its antimicrobial activity against pathogenic fungi and Gram positive and negative bacteria, revealed a significant antimicrobial activity. A bioguided study with its liquid-liquid partition fractions revealed the hexane fraction (Hex) as the most active against Leishmania, inhibiting 99.2% and 46.9% of the protozoan at concentrations of 40 and 20 μg/mL, respectively. Hex also showed significant antimicrobial activity against Staphylococcus aureus and Candida krusei with IC₅₀ of 15.6 and 62.5 μg/mL, respectively. Purification of Hex led to the isolation of 2-methoxy-6-pentyl-benzoquinone (1, also known as primin) as the active metabolite, probably responsible for the observed antimicrobial and anti-leishmania effects. Primin (1) disclosed leishmanicidal activity (IC₅₀ = 1.25 μM), showing higher potency than the standard drug amphotericin B (IC₅₀ = 5.08 μM), with additional antifungal effects against all tested fungi species. Compound 1 also showed significant activity against S. aureus (IC₅₀ = 8.94 μM), showing a comparable potency with the reference drug chloramphenicol (IC₅₀ = 6.19 μM), but with a potential cytotoxicity towards peripheral human blood mononuclear cells (CC₅₀ = 255.15 μM). Here in, the antimicrobial and anti-L. amazonensis effects of M. willdenowii are reported for the first time, as well as Primin (1) as its probable bioactive metabolite.

Spirocyclic Tetramates by Sequential Knoevenagel and [1,5]-Prototropic Shift

Highly functionalized spirocyclic tetramates were prepared via a sequential Knoevenagel reaction and [1,5]-prototropic shift (T-reaction) of bicyclic tetramates. While these compounds isomerize in solution, stable analogues can be prepared via an appropriate choice of substituents. Further modification of these compounds allows for the introduction of aromatic groups, making them suitable as skeletons for application in medicinal chemistry.

Antibacterial activity of Discaria americana Gillies ex Hook (Rhamnaceae)

ETHNOPHARMACOLOGY RELEVANCE

Discaria americana Gillies ex Hook (sin. Discaria febrifuga and Discaria longispina) (Rhamnaceae) is a plant native from Rio Grande do Sul (Southern Brazil), Uruguay and Argentine, and has been used in Brazilian traditional medicine as antipyretic agent, and for stomach disorders. In Rio Grande do Sul, Uruguay and Argentine, the roots, in decoction, are used as tonic and febrifuge. Although it is a plant widely used by the population, there are no studies proving this popular use.

MATERIAL AND METHODS

The crude neutral methanol extract, and pure isolated alkaloids, were investigated in vitro for antimicrobial activities against four Gram-positive bacteria: Staphylococcus aureus, Bacillus subtillis, Bacillus cereus, Enterococcus faecium; and five Gram-negative bacteria: Escherichia coli, Enterobacter cloacae, Enterobacter aerogenes, Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa.

RESULTS

The crude neutral methanol (CME) extract of the root bark of Discaria americana showed antibacterial activity, ranging from 62.5 to 250 μg mL^-1 (MIC), against the tested bacteria. From the fractions obtained from the crude extract, the basic ethereal fraction (BEF) showed to be more effective, with MICs between 31.5 and 125 μg mL^-1 against the tested bacteria. The bioassay-guided fractionation of the ethyl ether basic fraction yielded eight cyclopeptide alkaloids: frangufoline (1), frangulanine (2), adouetine Y' (3), discarine A (4) discarine B (5), discarine C (6), discarene C (7) and discarine D (8). When evaluated against the Gram-positive bacteria Enterococcus faecium, discarine B (5) proved to be the most active alkaloid with a MIC/MLC = 0.77/1.55 μg mL^-1, near the most active antibacterial agent levofloxacin (MIC/MLC = 0.77/0.77 μg mL^-1). Moreover, discarine C (6) was the more active alkaloid against Salmonella enterica serovar Typhimurium, with a MIC/MLC = 3.1/6.2 μg mL^-1, the same observed for the antibacterial agent azithromycin. Kinetic measurements of the bacteriolytic activities of discarine B (5) against Enterococcus faecium (Gram-positive), and of discarine C (6) against Salmonella enterica serovar Typhimurium (Gram-negative) were determined by optical density based on real time assay, suggesting that both mode of action are partially bacteriolytic.

CONCLUSION

In conclusion, five 14-membered cyclopeptide alkaloids isolated from Discaria americana Gillies ex Hook (Rhamnaceae) showed promising antibacterial activity, making this metabolites a class of scientific interest. The good activity presented by the extract and the alkaloids against the Gram-positive bacteria Enterococcus faecium and against the Gram-negative bacteria Salmonella enterica serovar Typhimurium, Enterobacter. aerogenes and Escherichia coli, corroborate with the popular use of this plant for stomach disorders and as antifebrile.

Chitosan-based (Nano)materials for Novel Biomedical Applications

Chitosan-based nanomaterials have attracted significant attention in the biomedical field because of their unique biodegradable, biocompatible, non-toxic, and antimicrobial nature. Multiple perspectives of the proposed antibacterial effect and mode of action of chitosan-based nanomaterials are reviewed. Chitosan is presented as an ideal biomaterial for antimicrobial wound dressings that can either be fabricated alone in its native form or upgraded and incorporated with antibiotics, metallic antimicrobial particles, natural compounds and extracts in order to increase the antimicrobial effect. Since chitosan and its derivatives can enhance drug permeability across the blood-brain barrier, they can be also used as effective brain drug delivery carriers. Some of the recent chitosan formulations for brain uptake of various drugs are presented. The use of chitosan and its derivatives in other biomedical applications is also briefly discussed.

Antibacterial Effects of Phytic Acid against Foodborne Pathogens and Investigation of Its Mode of Action

This study investigated the antimicrobial mechanism of phytic acid (PA) and its antibacterial effects in combination with ethanol. The MIC of PA on Escherichia coli ATCC 11229, Staphylococcus aureus ATCC 6538P, Bacillus subtilis ATCC 6633, and Salmonella Typhimurium CICC 27483 were 0.24, 0.20, 0.26, and 0.28% (w/w), respectively. E. coli ATCC 11229 and S. aureus ATCC 6538P were selected to investigate the mechanism of PA by analyzing its effects at 1/2MIC and at MIC on the cell morphology, intracellular ATP, and cell membrane integrity. Environmental scanning electron microscope images revealed that PA was able to change the cell morphology and disrupt the intercellular adhesion. PA retarded bacterial growth and caused cell membrane dysfunction, which was accompanied by decreased intracellular ATP concentrations. Flow cytometry analysis further revealed that almost all the bacterial cells were damaged after treatment with PA at its MIC for 2 h. Moreover, PA has a synergistic antimicrobial ability when used in combination with ethanol. These results suggested that PA is effective in inhibiting growth of foodborne pathogens mainly by the mechanism of cell membrane damage and to provide a theoretical basis for the development of natural antimicrobial agents in the food industry.

Plant antimicrobial polyphenols as potential natural food preservatives

BACKGROUND

The growing demand for natural food preservatives in the last decade has promoted investigations on their application for preserving perishable foods. In this context, the present review is focused on discussing the prospective application of plant extracts containing phenolics or isolated plant phenolics as natural antimicrobials in foods. Plant essential oils are outside the scope of this review since utilization of their antimicrobial activity for food preservation has been extensively reviewed.

RESULTS

Although the exact antimicrobial mechanisms of action of phenolic compounds are not yet fully understood, it is commonly acknowledged that they have diverse sites of action at the cellular level. Antimicrobial phenolics can be added directly to the formulation of perishable food products or incorporated into food-contact materials to release them in the immediate zone of perishable foods. Edible coatings or active food packaging materials can thus be used as carriers of plant bioactive compounds.

CONCLUSION

These materials could be an interesting delivery system to improve the stability of phenolics in foods and to improve the shelf life of perishable foods. This review will thus provide an overview of current knowledge of the antimicrobial activity of phenolic-rich plant extracts and of the promises and limits of their exploitation for the preservation of perishable foods. © 2018 Society of Chemical Industry.

Coated electrospun bioactive wound dressings: Mechanical properties and ability to control lesion microenvironment

Advanced wound dressings capable of interacting with lesions and changing the wound microenvironment to improve healing are promising to increase the therapeutic efficacy of this class of biomaterials. Aiming at the production of bioactive wound dressings with the ability to control the wound microenvironment, biomaterials of three different chemical compositions, but with the same architecture, were produced and compared. Electrospinning was employed to build up a biomimetic extracellular matrix (ECM) layer consisting of poly(caprolactone) (PCL), 50/50 dl-lactide/glycolide copolymer (PDLG) and poly(l-lactide) (PLLA). As a post-treatment to broaden the bioactivity of the dressings, an alginate coating was applied to sheathe and functionalize the surface of the hydrophobic electrospun wound dressings, in combination with the extract of the plant Arrabidaea chica Verlot, known for its anti-inflammatory and healing promotion properties. Wettable bioactive structures capable to interact with media simulating lesion microenvironments, with tensile strength and elongation at break ranging respectively from 155 to 273 MPa and from 0.94 to 1.39% were obtained. In simulated exudative microenvironment, water vapor transmission rate (WVTR) values around 700 g/m²/day were observed, while water vapor permeability rates (WVPR) reached about 300 g/m²/day. In simulated dehydrated microenvironment, values of WVTR around 200 g/m²/day and WVPR around 175 g/m²/day were attained.

Current Challenges and Perspectives for the Use of Aqueous Plant Extracts in the Management of Bacterial Infections: The Case-Study of Salmonella enterica Serovars

Worldwide, foodborne diseases are a growing public health problem. Among the infectious bacteria, non-typhoidal Salmonella enterica serovars (NTS) are the major cause of hospitalization and death, and the emergence and spread of their antibiotic-resistance is becoming a worldwide health issue. This, coupled with the restrictions of antibiotics use in agriculture and animal production, calls for alternative approaches to solve this problem. Plant-derived aqueous extracts compounds could provide novel straightforward approaches to control pathogenic bacteria. This review discusses the antimicrobial activity of aqueous plant extracts against Salmonella serovars, the possible mechanisms of action involved, which components/structures might be responsible for such activity, and the current challenges for the use of these extracts/components in Salmonella infection management and their application perspectives.

Carbon Nanotubes as A High-Performance Platform for Target Delivery of Anticancer Quinones

BACKGROUND

In spite of considerable efforts of researchers the cancer deseases remain to be incurable and a percentage of cancer deseases in the structure of mortality increases every year. At that, high systemic toxicity of antitumor drugs hampers their effective use. Because of this fact, the development of nanosystems for targeted delivery of antitumor drugs is one of the leading problem in nanomedicine and nanopharmacy.

OBJECTIVE

To critically examine the modern strategies for carbon nanotubes (CNTs)-based delivery of anticancer quinones and to summarize the mechanisms which can provide high effectiveness and multifunctionality of the CNT-based quinone delivery platform.

RESULTS

Quinones, including anthracycline antibiotics - doxorubicin and daunorubicin, are among the most prospective group of natural and syntetic compounds which exhibit high antitumor activity against different type of tumors. In this review, we focus on the possibilities of using CNTs for targeted delivery of antitumor compounds with quinoid moiety which is ordinarily characterized by high specific interaction with DNA molecules. Quinones can be non-covalently adsorbed on CNT surface due to their aromatic structure and π-conjugated system of double bonds. The characteristic features of doxorubicine-CNT complex are high loading efficiency, pH-dependent release in acidic tumor microenviroment, enough stability in biological fluid. Different types of CNT functionalization, targeting strategies and designs for multifunctional CNT-based doxorubicine delivery platform are disscussed.

CONCLUSION

Nanosystems based on functionalized CNTs are very promising platform for quinone delivery resulting in significant enhancement of cancer treatment efficiency. Functionalization of CNTs with the polymeric shell, especially DNA-based shells, can provide the greatest affinity and mimicry with biological structures.

Changes in the expression of some genes involved in the biosynthesis of secondary metabolites in Cuminum cyminum L. under UV stress

Biotic and abiotic stresses cause special defense reactions in plant organs, which after a series of reactions, these stresses produce secondary metabolites. The effect of ultraviolet radiation on the expression of key genes involved in the biosynthesis of secondary metabolites (Phenylalanine ammonia lyase (PAL), Hydroxymethylglutaryl-CoA reductase (HMG-CoA reductase), GPP synthases, Deoxyribonino heptulosinate 7-phosphate synthase (DAHP), and Deoxy Xylose Phosphate Synthase (DXS)), and the association of these genes with different amounts of secondary metabolites (phenol, terpene, flavonoids, anthocyanins, alkaloids, lycopene, and beta-carotene) was investigated in this study. The results of this study showed that the application of UV-B stress significantly increased the expression of GPPs, HMG-CoA reductase, DXS, DAHPs, and PAL genes compared to the control plants. The expression of two key genes involved in the biosynthesis of phenylpropanoids, including DAHPs and PAL, increased with UV-B stress, and the highest expression was related to the PAL gene. The results revealed that UV-B stress caused a significant increase in total levels of terpenoids, phenols, flavonoids, anthocyanins, alkaloids, beta-carotene, and lycopene. The highest relative expression of all genes was obtained in treatment A (UV-B radiation for 1 h), while in treatment B (UV-B radiation for 2 h), no significant changes were observed in the expression of the genes.

Dual Mode of the Saponin Aescin in Plant Protection: Antifungal Agent and Plant Defense Elicitor

Being natural plant antimicrobials, saponins have potential for use as biopesticides. Nevertheless, their activity in plant-pathogen interaction is poorly understood. We performed a comparative study of saponins' antifungal activities on important crop pathogens based on their effective dose (EC₅₀) values. Among those saponins tested, aescin showed itself to be the strongest antifungal agent. The antifungal effect of aescin could be reversed by ergosterol, thus suggesting that aescin interferes with fungal sterols. We tested the effect of aescin on plant-pathogen interaction in two different pathosystems: Brassica napus versus (fungus) Leptosphaeria maculans and Arabidopsis thaliana versus (bacterium) Pseudomonas syringae pv tomato DC3000 (Pst DC3000). We analyzed resistance assays, defense gene transcription, phytohormonal production, and reactive oxygen species production. Aescin activated B. napus defense through induction of the salicylic acid pathway and oxidative burst. This defense response led finally to highly efficient plant protection against L. maculans that was comparable to the effect of fungicides. Aescin also inhibited colonization of A. thaliana by Pst DC3000, the effect being based on active elicitation of salicylic acid (SA)-dependent immune mechanisms and without any direct antibacterial effect detected. Therefore, this study brings the first report on the ability of saponins to trigger plant immune responses. Taken together, aescin in addition to its antifungal properties activates plant immunity in two different plant species and provides SA-dependent resistance against both fungal and bacterial pathogens.

Root bark of Discaria americana attenuates pain: A pharmacological evidence of interaction with opioidergic system and TRP/ASIC channels

ETHNOPHARMACOLOGICAL RELEVANCE

Discaria americana (Rhamnaceae) root bark infusion have been used in traditional medicine as antipyretic, tonic, ameliorative of stomach and skin diseases and diabetes. This study was designed to investigate whether the methanolic extract of the root bark of Discaria americana (MEDa) exhibits antinociceptive effects in mice. Furthermore, it was investigated the involvement of the opioidergic system in MEDa mechanism of action as well the interactions with TRP/ASIC channels in its effect.

MATERIALS AND METHODS

The antinociceptive effect of intra-gastric gavage (i.g.) of MEDa (0.3-300 mg/kg) was evaluated in mice subjected to acute chemical (acetic-acid, formalin, glutamate, capsaicin, cinnamaldehyde, and acidified saline) or thermal (hot plate) tests of pain. The involvement of opioid system was evaluated in the formalin test. A nonspecific effect of MEDa was observed by measuring locomotor activity and exploratory behavior in open field test.

RESULTS

MEDa significantly reduced the number of writhing induced by acetic acid and inhibited the nociception in the two phases of formalin. These effects were inhibited by pretreatment with naloxone. The nociception induced by hot plate and intraplantar injection of glutamate, capsaicin, cinnamaldehyde and acidified saline were significantly inhibited by MEDa. Only the dose of 300 mg/kg altered the locomotor activity.

CONCLUSIONS

Our results demonstrated, for the first time, that the methanolic extract of the root bark of Discaria americana presents antinociceptive effect in chemical and thermal stimuli and its analgesic properties can be due activation of the opioidergic system. These results support the use of Discaria americana in traditional medicine and demonstrate that this plant presents a therapeutic potential for the development of phytomedicines with antinociceptive profile.

Zerumbone from Zingiber zerumbet (L.) smith: a potential prophylactic and therapeutic agent against the cariogenic bacterium Streptococcus mutans

BACKGROUND

Essential oil obtained from rhizomes of the Zingiber zerumbet (L.) Smith (popularly known in Brazil as bitter ginger) is mainly constituted by the biomolecule zerumbone, which exhibit untapped antimicrobial potential. The aim of this study was to investigate the antimicrobial activity of the zerumbone from bitter ginger rhizomes against the cariogenic agent Streptococcus mutans.

METHODS

Firstly, the essential oil from rhizomes of Zingiber zerumbet (L.) Smith extracted by hydrodistillation was submitted to purification and recrystallization process to obtain the zerumbone compound. The purity of zerumbone was determined through high-performance liquid chromatography analysis. Different concentrations of zerumbone were tested against the standard strain S. mutans (ATCC 35668) by using microdilution method. The speed of cidal activity was determined through a time kill-curve assay. The biological cytotoxicity activity of zerumbone was assessed using Vero cell line through MTT assay.

RESULTS

The zerumbone showed a minimum inhibitory concentration (MIC) of 250 μg/mL and a minimum bactericidal concentration (MBC) of 500 μg/mL against S. mutans. After six hours of bacteria-zerumbone interaction, all concentrations tested starts to kill the bacteria and all bacteria were killed between 48 and 72 h period at the concentration of 500 μg/mL (99,99% of bacteria were killed in comparison with original inoculum). In addition, zerumbone showed no cytotoxicity activity on mammalian continuous cells line.

CONCLUSIONS

These results draw attention to the potential of zerumbone as antimicrobial agent against S. mutans infection, indicating its possible use in the phyto-pharmaceutical formulations as new approach to prevent and treat tooth decay disease.

Leptodactylus latrans Amphibian Skin Secretions as a Novel Source for the Isolation of Antibacterial Peptides

Amphibians´ skin produces a diverse array of antimicrobial peptides that play a crucial role as the first line of defense against microbial invasion. Despite the immense richness of wild amphibians in Argentina, current knowledge about the presence of peptides with antimicrobial properties is limited to a only few species. Here we used LC-MS-MS to identify antimicrobial peptides with masses ranging from 1000 to 4000 Da from samples of skin secretions of Leptodactylus latrans (Anura: Leptodactylidae). Three novel amino acid sequences were selected for chemical synthesis and further studies. The three synthetic peptides, named P1-Ll-1577, P2-Ll-1298, and P3-Ll-2085, inhibited the growth of two ATCC strains, namely Escherichia coli and Staphylococcus aureus. P3-Ll-2085 was the most active peptide. In the presence of trifluoroethanol (TFE) and anionic liposomes, it adopted an amphipathic α-helical structure. P2-Ll-1298 showed slightly lower activity than P3-Ll-2085. Comparison of the MIC values of these two peptides revealed that the addition of seven amino acid residues (GLLDFLK) on the N-terminal of P2-Ll-1298 significantly improved activity against both strains. P1-Ll-1577, which remarkably is an anionic peptide, showed interesting antimicrobial activity against E. coli and S. aureus strain, showing marked membrane selectivity and non-hemolysis. Due to this, P1-L1-1577 emerges as a potential candidate for the development of new antibacterial drugs.