Antimicrobial Activity of Drimanic Sesquiterpene Compounds from Drimys winteri against Multiresistant Microorganisms.

In this work, a group of ten sesquiterpene drimanes, including polygodial (1), isopolygodial (2), and drimenol (3) obtained from the bark of Drimys winteri F. and seven synthetic derivatives, were tested in vitro against a unique panel of bacteria, fungi, and oomycetes with standardized procedures against bacterial strains K. pneumoniae, S. tiphy, E. avium, and E. coli. The minimum inhibitory concentrations and bactericidal activities were evaluated using standardized protocols. Polygodial (1) was the most active compound, with MBC 8 µg/mL and MIC 16 µg/mL in E. avium; MBC 16 µg/mL and MIC 32 µg/mL in K. pneumoniae; MBC 64 µg/mL and MIC 64 µg/mL in S. typhi; and MBC 8 µg/mL and MIC 16 µg/mL and MBC 32 µg/mL and MIC 64 µg/mL in E. coli, respectively. The observed high potency could be attributed to the presence of an aldehyde group at the C8-C9 position. The antifungal activity of 1 from different microbial isolates has been evaluated. The results show that polygodial affects the growth of normal isolates and against filamentous fungi and oomycetes with MFC values ranging from 8 to 64 µg/mL. Sesquiterpene drimanes isolated from this plant have shown interesting antimicrobial properties.

Rootstock increases the physiological defence of tomato plants against Pseudomonas syringae pv. tomato infection.

Climate change has intensified the infection of tomato plants by pathogens such as Pseudomonas syringae pv. tomato (Pst). Rootstocks may increase plant tolerance to leaf phytopathogens. The aim of this study was to evaluate the effects of the tolerant Poncho Negro (R) tomato rootstock on physiological defence and the role of hydrogen sulfide (H2S) in susceptible Limachino (L) tomato plant responses to Pst attack. Ungrafted (L), self-grafted (L/L), and grafted (L/R) plants were infected with Pst. Rootstock increased the concentration of antioxidant compounds including ascorbate in the scion. Tolerant rootstock induced an increase of H2S in the scion, which correlated with enhanced expression of the SlAPX2 gene. A high accumulation of salicylic acid was observed in Pst-inoculated grafted L/L and L/R plants, but this was higher in L/R plants. The increase of H2S during Pst infection was associated with a reduction of ethylene in L/R plants. Our study indicates that the Poncho Negro rootstock reduced the symptoms of bacterial speck disease in the Limachino tomato plants, conferring tolerance to Pst infection. This study provides new knowledge about the impact of rootstock in the defence of tomato plants against leaf pathogens that could be used in sustainable management of tomato cultivation.

Antitumoral Activity of Leptocarpha rivularis Flower Extracts against Gastric Cancer Cells.

Leptocarpha rivularis is a native South American plant used ancestrally by Mapuche people to treat gastrointestinal ailments. L. rivularis flower extracts are rich in molecules with therapeutic potential, including the sesquiterpene lactone leptocarpin, which displays cytotoxic effects against various cancer types in vitro. However, the combination of active molecules in these extracts could offer a hitherto unexplored potential for targeting cancer. In this study, we investigated the effect of L. rivularis flower extracts on the proliferation, survival, and spread parameters of gastric cancer cells in vitro. Gastric cancer (AGS and MKN-45) and normal immortalized (GES-1) cell lines were treated with different concentrations of L. rivularis flower extracts (DCM, Hex, EtOAc, and EtOH) and we determined the changes in proliferation (MTS assay, cell cycle analysis), cell viability/cytotoxicity (trypan blue exclusion assay, DEVDase activity, mitochondrial membrane potential MMP, and clonogenic ability), senescence (ß-galactosidase activity) and spread potential (invasion and migration assays using the Boyden chamber approach) in all these cells. The results showed that the DCM, EtOAc, and Hex extracts display a selective antitumoral effect in gastric cancer cells by affecting all the cancer parameters tested. These findings reveal an attractive antitumoral potential of L. rivularis flower extracts by targeting several acquired capabilities of cancer cells.

Cytotoxic Activity, Topoisomerase I Inhibition and In Silico Studies of New Sesquiterpene-aryl Ester Derivatives of (-) Drimenol.

In this study, we aimed to evaluate two sets of sesquiterpene-aryl derivatives linked by an ester bond, their cytotoxic activities, and their capacity to activate caspases 3/7 and inhibit human topoisomerase I (TOP1). A total of 13 compounds were synthesized from the natural sesquiterpene (-)-drimenol and their cytotoxic activity was evaluated in vitro against three cancer cell lines: PC-3 (prostate cancer), HT-29 (colon cancer), MCF-7 (breast cancer), and an immortalized non-tumoral cell line (MCF-10). From the results, it was observed that 6a was the most promising compound due to its cytotoxic effect on three cancer cell lines and its selectivity, 6a was 100-fold more selective than 5-FU in MCF-7 and 20-fold in PC-3. It was observed that 6a also induced apoptosis by caspases 3/7 activity using a Capsase-Glo-3/7 assay kit and inhibited TOP1. A possible binding mode of 6a in a complex with TOP1-DNA was proposed by docking and molecular dynamics studies. In addition, 6a was predicted to have a good pharmacokinetic profile for oral administration. Therefore, through this study, it was demonstrated that the drimane scaffold should be considered in the search of new antitumoral agents.

Chemical Analysis and In Vitro Bioactivity of Essential Oil of Laurelia sempervirens and Safrole Derivatives against Oomycete Fish Pathogens.

In this study, the essential oil (EO) from Laurelia sempervirens was analyzed by GC/MS and safrole (1) was identified as the major metabolite 1, was subjected to direct reactions on the oxygenated groups in the aromatic ring and in the side chain, and eight compounds (4 to 12) were obtained by the process. EO and compounds 4-12 were subjected to biological assays on 24 strains of the genus Saprolegnia, specifically of the species 12 S. parasitica and 12 S. australis. EO showed a significant effect against Saprolegnia strains. Compound 6 presents the highest activity against two resistant strains, with minimum inhibitory concentration (MIC) and minimum oomyceticidal concentration (MOC) values of 25 to 100 and 75 to 125 µg/mL, respectively. The results show that compound 6 exhibited superior activities compared to the commercial controls bronopol and azoxystrobin used to combat these pathogens.

Antioxidant and Anti-Proliferative Activity of Essential Oil and Main Components from Leaves of Aloysia polystachya Harvested in Central Chile.

The aim of this study was to determine, first, the chemical composition of Aloysia polystachya (Griseb) Moldenke essential oil, from leaves harvested in central Chile; and second, its antioxidant and cytotoxic activity. Eight compounds were identified via gas chromatography-mass spectrometry (GC-MS) analyses, with the most representative being R-carvone (91.03%), R-limonene (4.10%), and dihydrocarvone (1.07%). For Aloysia polystachya essential oil, antioxidant assays (2,2-diphenyl-1-picrylhydrazyl (DPPH), H2O2, ferric reducing antioxidant power (FRAP), and total reactive antioxidant potential (TRAP)) showed good antioxidant activity compared to commercial antioxidant controls; and anti-proliferative assays against three human cancer cell lines (colon, HT-29; prostate, PC-3; and breast, MCF-7) determined an IC50 of 5.85, 6.74, and 9.53 µg/mL, and selectivity indices of 4.75, 4.12, and 2.92 for HT-29, PC-3, and MCF-7, respectively. We also report on assays with CCD 841 CoN (colon epithelial). Overall, results from this study may represent, in the near future, developments for natural-based cancer treatments.

Chemical Composition, Antioxidant and Anticancer Activities of Leptocarpha rivularis DC Flower Extracts.

An evaluation of antioxidant and anticancer activity was screened in Leptocarpha rivularis DC flower extracts using four solvents (n-hexane (Hex), dichloromethane (DCM), ethyl acetate (AcOEt), and ethanol (EtOH)). Extracts were compared for total extract flavonoids and phenol contents, antioxidant activity (2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH), ferric reducing antioxidant potential (FRAP), total reactive antioxidant properties (TRAP) and oxygen radical absorbance capacity (ORAC)) across a determined value of reduced/oxidized glutathione (GSH/GSSG), and cell viability (the sulforhodamine B (SRB) assay). The most active extracts were analyzed by chromatographic analysis (GC/MS) and tested for apoptotic pathways. Extracts from Hex, DCM and AcOEt reduced cell viability, caused changes in cell morphology, affected mitochondrial membrane permeability, and induced caspase activation in tumor cell lines HT-29, PC-3, and MCF-7. These effects were generally less pronounced in the HEK-293 cell line (nontumor cells), indicating clear selectivity towards tumor cell lines. We attribute likely extract activity to the presence of sesquiterpene lactones, in combination with other components like steroids and flavonoids.

In vitro antioxidant and antiproliferative effect of the extracts of Ephedra chilensis K Presl aerial parts.

BACKGROUND: Ephedra chilensis K Presl, known locally as pingo-pingo, is a Chilean endemic plant used in traditional medicine as an anti-inflammatory and used in other treatments. However, unlike for the other Ephedra species, there have been no reports on the antioxidant and cytotoxic effects of this plant. The present study aims to explore the potential applications of E. chilensis extract as a cytotoxic agent against in vitro cancer cell lines and to explore the relationship between this extract and antioxidant activity. METHODS: Total anthraquinone, flavonoid, and phenolic contents, as well as antioxidant activity (DPPH, FRAP, and TRAP assays) and cytotoxic effect on several cancer cell lines (MCF-7, PC-3, DU-145, and HT-29) were measured for the hexane, dichloromethane and ethanol extracts of E. chilensis. In addition, several correlations among the phytochemical content, antioxidant activity, and cytotoxic effect were evaluated. Finally, GC-MS analyses of the most active extracts were carried out to identify their major components and to relate these components to the cytotoxic effect. RESULTS: Antioxidant activity was found in the EtOH extracts of Ephedra, and the results were correlated with the phenolic content. For the cytotoxic activity, the non-polar extracts of E. chilensis had the highest antiproliferative effect for the MCF-7 and PC-3 cancer lines; the extract was shown to be up to three times more selective than doxorubicin. However, the cytotoxic effect was not correlated with the antioxidant activity. Lastly, the GC-MS analysis showed a high concentration of saturated fatty acids (mainly n-hexadecanoic acid) and terpenoids (mainly 4-(hydroxy-ethyl)-γ-butanolactone). CONCLUSION: The cytotoxic activity and selectivity of the non-polar extracts of E. chilensis for the MCF-7 and PC-3 cell lines could be related to the terpenic compounds and fatty acids of the extracts or to the synergistic effect of all of the compounds in the extracts. These non-polar extracts can be used for the development of new drugs against breast and prostate cancer.

Isocordoin analogues promote apoptosis in human melanoma cells via Hsp70.

Isocordin 1 and a series of 4-oxyalkyl-isocordoin analogues 2-8 were evaluated for their cytotoxicity effect against human melanoma cells (A2058). Analogues 4, 5, and 6 showed a higher inhibitory activity with IC50 values of 12.91 ± 0.031, 24.88 ± 0.013, and 11.62 ± 0.017, respectively. These analogues, 4, 5, and 6, also induced an apoptotic response at 12.5- and 25-µM concentrations. They inhibited the expression of antiapoptotic proteins Bcl-2 and Hsp70, a critical factor that promotes tumour cell survival. In contrast, Bax and caspase-9 expression, and caspase-3 enzyme resulted activated. These results were correlated to a DNA fragmentation typical of apoptosis and an increase of intracellular reactive oxygen species (ROS) levels. Alternatively, at higher concentration (50 µM), when the capacity of the cells to sustain Hsp70 synthesis is reduced, our results seem to indicate that necrosis was induced by a further increase in ROS production. Therefore, the central finding in the present study is that these molecules downregulates Hsp70 expression. Altogether, these results suggest that 4-oxyalkyl-isocordoin analogues 4, 5, and 6 deserve to be deeply investigated for a possible application as Hsp70 inhibitor in the management of melanoma.

Structure-Activity Relationship of Dialkoxychalcones to Combat Fish Pathogen Saprolegnia australis.

To investigate the anti-Saprolegnia activities of chalconic compounds, nine dialkoxychalcones 2⁻10, along with their key building block 2',4'-dihydroxychalcone 1, were evaluated for their potential oomycide activities against Saprolegnia australis strains. The synthesis afforded a series of O-alkylated derivatives with typical chalcone skeletons. Compounds 4⁻10 were reported for the first time. Interestingly, analogue 8 with the new scaffold demonstrated remarkable in vitro growth-inhibitory activities against Saprolegnia strains, displaying greater anti-oomycete potency than the standard drugs used in the assay, namely fluconazole and bronopol. In contrast, a dramatic loss of activity was observed for O-alkylated derivatives 2, 3, 6, and 7. These findings have highlighted the therapeutic potential of the natural compound 1 scaffold to be exploitable as a drug lead with specific activity against various Saprolegnia strains.

Synthesis and Antiproliferative Activity of New Cyclodiprenyl Phenols against Select Cancer Cell Lines.

Six new cyclodiprenyl phenols were synthesized by direct coupling of perillyl alcohol and the appropriate phenol. Their structures were established by IR, HRMS and mainly NMR. Three human cancer cell lines-breast (MCF-7), prostate (PC-3) and colon (HT-29)-were used in antiproliferative assays, with daunorubicin and dunnione as positive controls. Results described in the article suggest that dihydroxylated compounds 2⁻4 and monohydroxylated compound 5 display selectivity against cancer cell lines, cytotoxicity, apoptosis induction, and mitochondrial membrane impairment capacity. Compound 2 was identified as the most effective of the series by displaying against all cancer cell lines a cytotoxicity close to dunnione antineoplastic agent, suggesting that the cyclodiprenyl phenols from perillyl alcohol deserve more extensive investigation of their potential medicinal applications.

Biopesticide Activity from Drimanic Compounds to Control Tomato Pathogens.

Tomato crops can be affected by several infectious diseases produced by bacteria, fungi, and oomycetes. Four phytopathogens are of special concern because of the major economic losses they generate worldwide in tomato production; Clavibacter michiganensis subsp. michiganensis and Pseudomonas syringae pv. tomato, causative agents behind two highly destructive diseases, bacterial canker and bacterial speck, respectively; fungus Fusarium oxysporum f. sp. lycopersici that causes Fusarium Wilt, which strongly affects tomato crops; and finally, Phytophthora spp., which affect both potato and tomato crops. Polygodial (1), drimenol (2), isonordrimenone (3), and nordrimenone (4) were studied against these four phytopathogenic microorganisms. Among them, compound 1, obtained from Drimys winteri Forst, and synthetic compound 4 are shown here to have potent activity. Most promisingly, the results showed that compounds 1 and 4 affect Clavibacter michiganensis growth at minimal inhibitory concentrations (MIC) values of 16 and 32 µg/mL, respectively, and high antimycotic activity against Fusarium oxysporum and Phytophthora spp. with MIC of 64 µg/mL. The results of the present study suggest novel treatment alternatives with drimane compounds against bacterial and fungal plant pathogens.

Hemi-Synthesis and Anti-Oomycete Activity of Analogues of Isocordoin.

An efficient synthesis of a series of 4'-oxyalkyl-isocordoin analogues (2-8) is reported for the first time. Their structures were confirmed by ¹H-NMR, 13C-NMR, and HRMS. Their anti-oomycete activity was evaluated by mycelium and spores inhibition assay against two selected pathogenic oomycetes strains: Saprolegnia parasitica and Saprolegnia australis. The entire series of isocordoin derivatives (except compound 7) showed high inhibitory activity against these oomycete strains. Among them, compound 2 exhibited strong activity, with minimum inhibitory concentration (MIC) and minimum oomyceticidal concentration (MOC) values of 50 µg/mL and 75 µg/mL, respectively. The results showed that 4'-oxyalkylated analogues of isocordoin could be potential anti-oomycete agents.

Synthesis and Evaluation of Novel Oxyalkylated Derivatives of 2',4'-Dihydroxychalcone as Anti-Oomycete Agents against Bronopol Resistant Strains of Saprolegnia sp.

A series of novel oxyalkylchalcones substituted with alkyl groups were designed and synthesized, and the antioomycete activity of the series was evaluated in vitro against Saprolegnia strains. All tested O-alkylchalcones were synthesized by means of nucleophilic substitution from the natural compound 2',4'-dihydroxychalcone (1) and the respective alkyl bromide. The natural chalcone (1) and 10 synthetic oxyalkylchalcones (2-11) were tested against Saprolegnia parasitica and Saprolegnia australis. Among synthetic analogs, 2-hydroxy,4-farnesyloxychalcone (11) showed the most potent activity against Saprolegnia sp., with MIC and MOC values of 125 µg/mL (similar to bronopol at 150 µg/mL) and 175 µg/mL, respectively; however, 2',4'-dihydroxychalcone (1) was the strongest and most active molecule, with MIC and MOC values of 6.25 µg/mL and 12.5 µg/mL.

In Vitro Antimicrobial Activity of Embothrium coccineum Used as Traditional Medicine in Patagonia against Multiresistant Bacteria.

Embothrium coccineum J.R. Forst. & G. Forst is an evergreen tree that has been used as a folk remedy for the treatment of neuralgia, tooth pains, wound healing, and glandular conditions, as well as an antiseptic agent against bacterial infection. The antibacterial activities of sequential extracts (hexane, dichloromethane, ethyl acetate, and ethanol) from the leaves of E. coccineum were evaluated by means of the micro-dilution assay against six (Escherichia coli; Klebsiella pneumoniae; Proteus mirabilis; Pseudomonas aeruginosa; Staphylococcus aureus and Streptococcus pyogenes) multiresistant bacteria strains. Ethyl acetate extract showed the best spectra of antibacterial activity against all tested bacteria, and was analyzed by gas chromatography-mass spectrometry (GC-MS) for its composition. The results of the present work provide useful baseline information for the potential development and use of nanoparticles and/or nanofibers doped with extracts of E. coccineum in the fight against multiresistant bacteria, which would allow the validation of the traditional use of E. coccineum by native peoples of Patagonia as an antimicrobial agent in the biomedical Field.

Psoralea glandulosa as a potential source of anticancer agents for melanoma treatment.

With the aim of identifying novel agents with antigrowth and pro-apoptotic activity on melanoma cancer, the present study was undertaken to investigate the biological activity of the resinous exudate of aerial parts from Psoralea glandulosa, and its active components (bakuchiol (1), 3-hydroxy-bakuchiol (2) and 12-hydroxy-iso-bakuchiol (3)) against melanoma cells (A2058). In addition, the effect in cancer cells of bakuchiol acetate (4), a semi-synthetic derivative of bakuchiol, was examined. The results obtained show that the resinous exudate inhibited the growth of cancer cells with IC50 value of 10.5 µg/mL after 48 h of treatment, while, for pure compounds, the most active was the semi-synthetic compound 4. Our data also demonstrate that resin is able to induce apoptotic cell death, which could be related to an overall action of the meroterpenes present. In addition, our data seem to indicate that the apoptosis correlated to the tested products appears, at least in part, to be associated with an increase of reactive oxygen species (ROS) production. In summary, our study provides the first evidence that P. glandulosa may be considered a source of useful molecules in the development of analogues with more potent efficacy against melanoma cells.

Chemical Characterization and Anti-Oomycete Activity of Laureliopsis philippianna Essential Oils against Saprolegnia parasitica and S. australis.

Laureliopsis philippiana (Looser) R. Schodde (Monimiaceae) is a native tree widespread in the forest areas in the south of Chile and Argentina, known for its medicinal properties and excellent wood. The aim of this study was to evaluate the chemical composition of L. philippiana leaf and bark essential oils (EOs) using gas chromatography-mass spectrometry (GC-MS), and to quantify its anti-oomycete activity, specifically against Saprolegnia parasitica and S. australis. Only six components were identified in leaf EO, 96.92% of which are phenylpropanoids and 3.08% are terpenes. As for bark EO, 29 components were identified, representing 67.61% for phenylpropanoids and 32.39% for terpenes. Leaf EO was characterized mainly by safrole (96.92%) and ß-phellandrene (1.80%). Bark EO was characterized mainly by isosafrole (30.07%), safrole (24.41%), eucalyptol (13.89%), methyleugenol (7.12%), and eugenol (6.01%). Bark EO has the most promising anti-Saprolegnia activity, with a minimum inhibition concentration (MIC) value of 30.0 µg/mL against mycelia growth and a minimum fungicidal concentration (MFC) value of 50.0 µg/mL against spores; for leaf EO, the MIC and MFC values are 100 and 125 µg/mL, respectively. These findings demonstrate that bark EO has potential to be developed as a remedy for the control of Saprolegnia spp. in aquaculture.

Study on the cytotoxic activity of drimane sesquiterpenes and nordrimane compounds against cancer cell lines.

Twelve drimanes, including polygodial (1), isopolygodial (2), drimenol (3), confertifolin (4), and isodrimenin (5), were obtained from natural sources. Semi-synthetic derivatives 6-12 were obtained from 1 and 2, and cytotoxic activity was evaluated in vitro against cancer cell lines (HT-29, MDA-MB231, DHF, MCF-7, PC-3, DU-145, and CoN). IC50 values were determined at concentrations of 12.5-100 µM of each compound for 72 h. In addition, it was found that polygodial (1), 8, and 12 induced changes in mitochondrial membrane permeability in CoN, MCF-7, and PC-3 cells.

Control of Peach Brown Rot Disease Produced by Monilinia fructicola and Monilinia laxa Using Benzylidene-Cycloalkanones.

Fruit rots caused by filamentous fungi such as Monilinia fructicola and Monilinia laxa have a strong impact on crop yield and fruit commercialization, especially as they affect a wide variety of stone fruits. The antifungal efficacy of benzylidene-cycloalkanones has been previously described in in vitro assays against M. fructicola; so, this study aims to evaluate the in vivo inhibitory potential of these hybrids on fruits that have been inoculated with M. fructicola, and use molecular docking to visualize the main interactions of these molecules in the active site of the enzyme succinate dehydrogenase (SDH). The results indicate that compound C achieves the highest inhibition of both Monilinia species (15.7-31.4 µg/mL), spore germination in vitro (<10 µg/mL), and has promising results in vivo, without causing phytotoxicity in fruits. The results from molecular docking suggest that hydroxyl groups play a crucial role in enhancing the binding of compound C to SDH and contribute to the formation of hydrogen bonds with amino acid residues on the enzyme active site.

Structure-Activity Relationship of Natural Dihydrochalcones and Chalcones, and Their Respective Oxyalkylated Derivatives as Anti-Saprolegnia Agents.

Saprolegnia sp. is a pathogenic oomycete responsible for severe economic losses in aquaculture. To date, there is no treatment for its control that is effective and does not pose a threat to the environment and human health. In this research, two dihydrochalcones 1 and 2, and three chalcones 3-5, isolated from the resinous plant Adesmia balsamica, as well as their synthesized oxyalkylated derivatives 6-29 already reported and a new synthesized series of oxyalkylchalcones 30-35, were evaluated for their anti-saprolegnia activity and structure-activity relationship as potential control and treatment agents for strains of Saprolegnia parasitica and S. australis. Among the molecules tested, natural 2',4'-dihydroxychalcone (3) and new oxyalkylchalcone 34 were the most potent antisaprolegnia agents against both strains, even with better results than the commercial control bronopol. On the other hand, the structure-activity relationship study indicates that the contributions of steric and electrostatic fields are important to enhance the activity of the compounds, thus the presence of bulky substituents favors the activity.