Excito-repellent and Pesticide-Likeness Properties of Essential Oils on Carpophilus dimidiatus (Fabricius) (Nitidulidae) and Oryzaephilus mercator (L.) (Silvanidae)

Carpophilus dimidiatus (Fabricius) (Nitidulidae) and Oryzaephilus mercator (L.) (Silvanidae) are insect pests that cause severe damage in important walnut growing regions in the northwest of Argentina. The current management approaches for these pests involve the use of unsafe phosphorus pesticides whose overuse have led to farmworker poisoning, pest resistance issues, and environmental contamination. Plant extracts, particularly essential oils, are an alternative source of insect control agents. Excito-repellent essential oils can be used to develop ecofriendly tools for managing the pest population without affecting quality and visual appearance of the stored walnuts. Laboratory studies were conducted to assess the excito-repellent effects of C. dimidiatus and O. mercator of 12 essential oils derived from aromatic plants used as food additives and traditional medicine in Argentina: Aloysia citrodora (AC), Aloysia gratissima (AG), Aloysia gratissima var. Gratissima (AGG), Blepharocalyx salicipholius (BS), Hyptis mutabilis (HM), Lippia junelliana (LJ), Lippia turbinata (LT), Mentha x piperita (MP), Minthostachys mollis (MM), Minthostachys verticillata (MV), Origanum vulgare(OV), and Rosmarinus officinalis (RO). The most bioactive EOs (ERijk ≥ 70%) were Aloysia gratissima var. Gratissima (AGG), Minthostachys verticillata, and Lippia junelliana. Their bioactivity profile and chemical space, characterized from GC-MS measures, Generalized Estimating Equations, and Hierarchical Cluster Analysis, revealed that they are mixtures of very functionalized molecules with physicochemical properties similar to those of insecticides with low residual property that enter the insect body through the respiratory system by inhalation. The AGG, MV, and LJ oils are promising as protective agents of walnut products. In our laboratory, studies of their formulations for use in integrated pest management programs are still ongoing.

Antifungal activity of extracts from Justicia species against Fusarium graminearum

Fusarium graminearum causes destructive ear rot diseases in maize and wheat. New antifungals are essential to combat this pathogen, and aerial parts of Justicia species (Acanthaceae) are a potential source. We investigated the antifungal activity of extracts from stems and leaves of five Justicia species native to Northwest Argentina. The aerial parts were subjected to sequential extractions with dichloromethane, ethyl acetate, and methanol. The resulting extracts were tested by the disc diffusion method against F. graminearum strains. Only the leaf and stem extracts from J. xylosteoides displayed inhibitory effects, with the dichloromethane leaf extract as the most active. The compounds involved were identified as the lignans hinokinin, savinin, and isohibalactone. Both the dichloromethane extract and hinokinin synergised with tebuconazole, and inhibited deoxynivalenol biosynthesis. The identified compounds warrant further research as additives to azole fungicides for F. graminearum control.

Chemical composition and insecticidal activity of essential oils from cultivated and native aromatic plants of Argentina against Carpophilus dimidiatus (Fabricius) (Nitidulidae) and Oryzaephilus mercator (L.) (Silvanidae)

Essential oils from aerial parts of six aromatic plants were analysed by GC-MS. The major compounds identified were γ-terpinene (11.5%), cuminaldehyde (26.6%) and γ-terpinen-7-al (40.6%) in Cuminum cyminum, trans-anethol (95.2%) in Pimpinella anisum, α-pinene (11.6%), limonene (21.0%), β-caryophyllene (22.3%) and α-humulene (16.7%) in Lippia integrifolia, limonene (40.8%) and artemisia ketone (19.3%) in Lippia junelliana, trans-β-ocimene (15.6%), 4-ethyl-4-methyl-1-hexene (24.5%), trans-tagetone (20.5%) and verbenone (27.2%) in Tagetes minuta, 1,8-cineole (17.9%),elixene (10.3%) and spathulenol (13.8%) in Aloysia gratissima. Oils with strong insecticidal activity on Carpophilus dimidiatus and Oryzaephilus mercator were from P. anisum (LC50 = 4 µl/L; LC100 = 10 µl/L) and T. minuta (LC50=10.19-12.57 µl/L; LC100=20 µl/L). Scents of C. cyminum and L. junelliana were strong insecticides on O. mercator (LC50=7.02-7.17 µl/L; LC100=10.00-20.00 µl/L). The insecticidal activity was associated to the whole content of C10 molecules and oxygenated constituents. The P. anisum oil is promising as protective agent of nut products.

Synthesis and Evaluation of New Halogenated GR24 Analogs as Germination Promotors for Orobanche cumana

Orobanche and Striga are parasitic weeds extremely well adapted to the life cycle of their host plants. They cannot be eliminated by conventional weed control methods. Suicidal germination induced by strigolactones (SLs) analogs is an option to control these weeds. Here, we reported two new halogenated (+)-GR24 analogs, named 7-bromo-GR24 (7BrGR24) and 7-fluoro-GR24 (7FGR24), which were synthesized using commercially available materials following simple steps. Both compounds strongly promoted seed germination of Orobanche cumana. Their EC50 values of 2.3±0.28×10-8M (7BrGR24) and 0.97±0.29×10-8M (7FGR24) were 3- and 5-fold lower, respectively, than those of (+)-GR24 and rac-GR24 (EC50=5.1±1.32-5.3±1.44×10-8; p<0.05). The 7FGR24 was the strongest seed germination promoter tested, with a stimulation percentage of 62.0±9.1% at 1.0×10-8M and 90.9±3.8% at 1.0×10-6M. It showed higher binding affinity (IC50=0.189±0.012μM) for the SL receptor ShHTL7 than (+)-GR24 (IC50=0.248±0.032μM), rac-GR24 (IC50=0.319±0.032μM), and 7BrGR24 (IC50=0.521±0.087μM). Molecular docking experiments indicated that the binding affinity of both halogenated analogs to the strigolactone receptor OsD14 was similar to that of (+)-GR24. Our results indicate that 7FGR24 is a promising agent for the control of parasitic weeds.

Antifungal activity of Euphorbia species against moulds responsible of cereal ear rots

AIMS

This work aimed to identify secondary metabolites from aerial parts of Euphorbia species functional for control of toxigenic Fusarium species responsible of cereal grain rots.

METHODS AND RESULTS

Aerial parts of Euphorbia serpens, Euphorbia schickendantzii and Euphorbia collina were sequentially extracted with hexane, ethyl acetate and methanol. The extracts were tested against strains of Fusarium verticillioides and Fusarium graminearum by microdilution tests. The hexane extract of E. collina provided the lowest IC₅₀ s on both fungal species. Further fractionation showed that cycloartenol (CA) and 24-methylenecycloartanol are associated to the moderate inhibitory effect of the hexane extract on fungal growth.Sublethal concentrations of CA and 24MCA blocked deoxynivalenol (DON) and fumonisins production.CA and 24MCA co-applied with potassium sorbate, a food preservative used for Fusarium control, synergized the growth inhibition of fungi. The mixtures reduced mycotoxins accumulation when applied at sublethal concentrations.

CONCLUSIONS

CA and 24MCA inhibited both fungal growth and mycotoxins production. This fact is an advantage respect to potassium sorbate which increased the mycotoxins accumulation at sublethal concentrations.

SIGNIFICANCE AND IMPACT OF THE STUDY

CA and 24MCA synergized potassium sorbate and their mixtures offer a lower mycotoxigenic risk than potassium sorbate for control of the Fusarium species.

Antifungal activity and toxicity studies of flavanones isolated from Tessaria dodoneifolia aerial parts

Tessaria dodoneifolia [Asteraceae] is traditionally employed in Northwestern Argentina for fungal infections treatment. We report the antifungal activity guided isolation and identification of substances from aerial parts of this species, both individually and in combination with fluconazole (FLU), against Candida albicans strains. Two antifungal flavanones were identified as naringenin (NAR) and pinocembrin (PIN). These compounds could individually inhibit the growth of C. albicans strains. Combinations of NAR and PIN with FLU were synergistic against the FLU resistant and sensitive C. albicans strains. Genotoxic and cytotoxic evaluations were also performed. NAR, PIN and their combinations with FLU did not have a genotoxic effect on Bacillus subtilis rec strains. Finally, these compounds did not show cytotoxicity at concentrations below 80 μg/mL.

Chemical composition and larvicidal activity of essential oils from Peganum harmala, Nepeta cataria and Phellodendron amurense against Aedes aegypti (Diptera: Culicidae)

Essential oils from aerial parts of the herbs Peganum harmala and Nepeta cataria, and leaves of the tree Phellodendron amurense were analyzed by GC-FID and GC-MS, and their larvicidal activities were assayed on the early fourth instar larvae of Aedes aegypti. The major constituents of the oils were limonene (14.5%) and thymol (11.5%) in P. harmala, thymol (46.5%), 4aα,7α,7aβ-nepetalactone (18.3%) and 4aα,7β,7aα-neptalactone (19.7%) in N. cataria, eugenol (14.5%) andγ-eudesmol (9.5%) in P. amurense.The oil of N. cataria had a strong larvicidal activity (LC50 < 50 µg/mL; LC90 < 86.8 µg/mL) on A. aegypti while the remaining oils showed a moderated killing effect. The larvicidal activity of N. cataria oil was associated to the contents of 1,8-cineol, camphor, 4aα,7α,7aβ-Nepetalactone, 4aα,7β,7aα-Nepetalactone and thymol. Our results indicate that the oil of N. catariadeserves to be used as a source of larvicidal agents against A. aegypti.

Antifungal activity of Bignoniaceae plants on Aspergillus carbonarius and Aspergillus niger

Twenty four extracts from Bignoniaceae plants of northwest Argentina were tested for antifungal activity against Aspergillus species responsible of the grape black rot. Stems and leaves of Amphilophium cynanchoides, Macfadyena cynanchoides, Tecoma stans and Jacaranda mimosifolia were separately extracted with solvents of increasing polarity to obtain the dichloromethane (fCH₂Cl₂), ethyl acetate (fEtOAc) and methanol extracts (fMeOH). The fCH₂Cl₂ from stem of M. cynanchoides had the lowest IC₅₀ (1.0-1.2 mg/mL) and MID values (0.6-1.2 mg) and the highest ID values (5.0-6.8 mm) on A. niger and A. carbonarius. The main contributors of the antifungal activity of fCH₂Cl₂ were identified as lapachol (MIC = 0.25-1.00 mg/ml) and 1-hydroxy-4-methylanthraquinone (MIC = 0.0625-0.125 mg/mL). These compounds synergized the antifungal activity of sodium metabisulfite and showed an additive effect in mixtures with propiconazol. They might be used as additives of commercial antifungals to protect grapes against A. niger and A. carbonarius.

Antifungal activity and cytotoxicity of extracts and triterpenoid saponins obtained from the aerial parts of Anagallis arvensis L

ETHNOPHARMACOLOGICAL RELEVANCE

Anagallis arvensis L. (Primulaceae) is used in argentinean northwestern traditional medicine to treat fungal infections. We are reporting the isolation and identification of compounds with antifungal activity against human pathogenic yeast Candida albicans, and toxicity evaluation.

AIM OF THE STUDY

to study the antifungal activity of extracts and purified compounds obtained form A. arvensis aerial parts, alone and in combinations with fluconazole (FLU), and to study the toxicity of the active compounds.

MATERIALS AND METHODS

Disk diffusion assays were used to perform an activity-guided isolation of antifungal compounds from the aerial parts of A. arvensis. Broth dilution checkerboard and viable cell count assays were employed to determine the effects of samples and combinations of FLU + samples against Candida albicans. The chemical structures of active compounds were elucidated by spectroscopic analysis. Genotoxic and haemolytic effects of the isolated compounds were determined.

RESULTS

Four triterpenoid saponins (1-4) were identified. Anagallisin C (AnC), exerted the highest inhibitory activity among the assayed compounds against C. albicans reference strain (ATCC 10231), with MIC-0 =1µg/mL. The Fractional Inhibitory Concentration Index (FICI=0.129) indicated a synergistic effect between AnC (0.125µg/mL) and FLU (0.031µg/mL) against C. albicans ATCC 10231. AnC inhibited C. albicans 12-99 FLU resistant strain (MIC-0 =1µg/mL), and the FICI=0.188 indicated a synergistic effect between AnC (0.125µg/mL) and fluconazole (16µg/mL). The combination AnC+ FLU exerted fungicidal activity against both C. albicans strains. AnC exerted inhibitory activity against C. albicans ATCC 10231 sessile cells (MIC₅0=0.5µg/mL and MIC₈₀=1µg/mL) and against C. albicans 12-99 sessile cells (MIC₅0=0.75µg/mL and MIC₈₀=1.25µg/mL). AnC exerted haemolytic effect against human red blood cells at 15µg/mL and did not exerted genotoxic effect on Bacillus subtilis rec strains.

CONCLUSIONS

The antifungal activity and lack of genotoxic effects of AnC give support to the traditional use of A. arvensis as antifungal and makes AnC a compound of interest to expand the available antifungal drugs.

Chemical composition and antifungal activity of essential oils from medicinal plants of Kazakhstan

The composition of essential oils from leaves of Kazakhstan medicinal plants was analysed by GC-MS. The major compounds identified were 1,8-cineole (34.2%), myrcene (19.1%) and α-pinene (9.4%) in Ajania fruticulosa; 1,8-cineole (21.0%), β-thujone (11.0%), camphor (8.5%), borneol (7.3%) and α-thujone (6.5%), in Achillea nobilis; camphor (47.3%), 1,8-cineole (23.9%), camphene (9.8%) and β-thujone (6.0%) in Artemisia terrae-albae; 1,8-cineole(55.8%) and β-pinene (6.2%) in Hyssopus ambiguus; α-thuyene(46.3%) and δ-cadinene(6.3%) in Juniperus sibirica; sabinene (64%) in Juniperus sabina; and α-pinene (51.5%), β-phellandrene (11.2%) and δ-cadinene (6.3%) in Pinus sibirica. The essential oils did not show antifungal effect (MIC > 1.20 mg/mL) on Aspergillus carbonarius and Aspergillus niger, while the oils from A. nobilis, A. terrae-albae, H. ambiguus and J. sabina exhibited moderate and moderate to weak antimicrobial activities on Fusarium verticillioides (MIC = 0.60 mg/mL) and Fusarium graminearum (MIC = 0.60-1.20 mg/mL), respectively. A principal component analysis associated the antifungal activity (r² > 0.80, p = 0.05) with the presence of borneol, camphor, camphene, 1,8-cineole,α- and β-thujone, and of the oxygenated monoterpenes.

Chemical composition and antimicrobial activity of essential oils from Acantholippia deserticola, Artemisia proceriformis, Achillea micrantha and Libanotis buchtormensis against phytopathogenic bacteria and fungi

Essential oils from aerial parts of Acantholippia deserticola, Artemisia proceriformis, Achillea micrantha and Libanotis buchtormensis were analysed by GC-MS. The major compounds identified were β-thujone (66.5 ± 0.2%), and trans-sabinyl acetate (12.1 ± 0.2%) in A. deserticola; α-thujone (66.9 ± 0.4%) in A. proceriformis; 1,8-cineole (26.9 ± 0.5%), and camphor (17.7 ± 0.3%) in A. micrantha and cis-β-ocimene (23.3 ± 0.3%), and trans-β-ocimene (18.4 ± 0.2%) in L. buchtormensis. The oils showed a weak antimicrobial effect (MIC100 > 1.5 mg/ml) on most phytopathogens tested. A moderate antimicrobial activity (MIC100 between 0.5 and 1.5 mg/ml) was displayed by the oils of A. deserticola, A. micrantha and L. buchtormensis on Septoria tritici and by the oil of A. deserticola on Septoria glycine. The antimicrobial activity was associated to the contents of β-thujone, trans-sabinyl acetate and trans-sabinol. Our results indicate that the tested essential oils have little inhibitory potency not suitable for use as plant protection products against the phytopathogens assayed.

Antifungal activity of 4-hydroxy-3-(3-methyl-2-butenyl)acetophenone against Candida albicans: evidence for the antifungal mode of action

The main secondary metabolite of Senecio nutans is 4-hydroxy-3-(3-methyl-2-butenyl)acetophenone (4HMBA). The antifungal activity of this compound and three derivatives was assessed using Candida albicans. 4HMBA exhibited the highest antifungal activity among the assayed compounds. The Fractional Inhibitory Concentration (FIC = 0.133) indicated a synergistic fungicidal effect of 4HMBA (5 mg L(-1)) and fluconazole (FLU) (0.5 mg L(-1)) against the C. albicans reference strain (ATCC 10231). Microscopy showed that 4HMBA inhibits filamentation and reduces cell wall thickness. Our findings suggest that 4HMBA is an interesting compound to diminish resistance to commercial fungistatic drugs such as fluconazole.

Isolation, Identification and Usefulness of Antifungal Compounds from Zuccagnia punctata for Control of Toxigenic Ear Rot Pathogens

Infusion, tincture and decoction of leaves of Zuccagnia punctata Cav. were assayed on growth of Fusarium verticillioides, F. graminearum sensu stricto, F. boothii, F. meridionale, F. subglutinans and F. thapsinum. The tincture showed the lowest IC50 on mycelial growth. A diethyl ether fraction of the tincture showed the highest antifungal activity in microdilution assays on F. verticillioides and F. graminearum. The antifungal constituents were separated by silica gel chromatography and identified as 2′,4′-dihydroxychalcone, 2′,4′-dihydroxy-3′-methoxychalcone and 7-hydroxy-3′,4′-dimethoxyflavone. These chalcones had the lowest MIC and MFC values on F. verticillioides and F. graminearum sensu stricto. 2′,4′-Dihydroxychalcone was mildly toxic and the remaining identified compounds were non-toxic in the brine shrimp assay. 2′,4′-Dihydroxychalcone in mixtures with commercial food preservatives showed additive effects on F. graminearum sensu stricto and synergistic ones on F. verticillioides. 2′,4′-Dihydroxy-3′-methoxychalcone showed synergistic effects in mixtures. Our results suggest that addition of chalcones to food preservatives allows reduction in the doses of the preservatives required for control of Fusarium species.

Isolation, identification and usefulness of antifungal compounds from Zuccagnia punctata for control of toxigenic ear rot pathogens

Infusion, tincture and decoction of leaves of Zuccagnia punctata Cav. were assayed on growth of Fusarium verticillioides, F. graminearum sensu stricto, F. boothii, F. meridionale, F. subglutinans and F. thapsinum. The tincture showed the lowest IC50 on mycelial growth. A diethyl ether fraction of the tincture showed the highest antifungal activity in microdilution assays on F. verticillioides and F. graminearum. The antifungal constituents were separated by silica gel chromatography and identified as 2',4'-dihydroxychalcone, 2',4'-dihydroxy-3'-methoxychalcone and 7-hydroxy-3',4'-dimethoxyflavone. These chalcones had the lowest MIC and MFC values on F. verticillioides and F. graminearum sensu stricto. 2',4'-Dihydroxychalcone was mildly toxic and the remaining identified compounds were non-toxic in the brine shrimp assay. 2',4'-Dihydroxychalcone in mixtures with commercial food preservatives showed additive effects on F. graminearum sensu stricto and synergistic ones on F. verticillioides. 2',4'-Dihydroxy-3'-methoxychalcone showed synergistic effects in mixtures. Our results suggest that addition of chalcones to food preservatives allows reduction in the doses of the preservatives required for control of Fusarium species.

Essential oils from Schinus species of northwest Argentina: Composition and antifungal activity

The composition of the essential oils from leaves (Sal) and fruits of S. areira (Saf), and fruits of S. fasciculatus (Sff) and S. gracilipes (Sgf) were analyzed by GC/MS. The major compounds identified were sabinene (26.0 +/- 0.5%), bicyclogermacrene (14.5 +/- 0.4%), and E-citral (6.7+/- 0.2%) in Sal oil, limonene (27.7 +/- 0.7%), sabinene (16.0+/- 0.5%), beta-phellandrene (14.6 +/- 0.8%) and bicyclogermacrene (8.1 +/- 0.2%) in Saf oil, sabinene (22.7 +/- 0.6%), alpha-phellandrene (18.7 +/- 0.3%), beta-phellandrene (15.7 +/- 0.4%), and bicyclogermacrene (8.1 +/- 0.2%) in Sff oil and beta-pinene (25.4 +/- 0.8%), alpha-pinene (24.7 +/- 0.7%), and sabinene (13.6 +/- 0.4%) in Sgf oil.The antifungal activity of the four oils was evaluated on strains of Fusarium verticillioides and F. graminearum, and the results compared with the effect of epoxyconazole, pyraclostrobin and thyme oil. The Sff oil had the highest antifungal activity among the Schinus oils tested, with MIC100 (F. graminearum) = 6 per thousand and MIC100 (F. verticillioides) = 12 per thousand. A principal component analysis suggests that 9 constituents (alpha-thujene, alpha-terpinene, p-cymene, gamma-terpinene, terpinolene, 1-terpineol, alpha-calacorene, alpha-phellandrene, and terpinen-4-ol) explain the higher antifungal effect of Sff. The MIC100s of Schinus oils were on average 30-60 and 8.5-17 fold lower than those obtained for thyme oil on F. verticillioides and F. graminearum, respectively. In the case of commercial fungicides, their MIC100s were three orders of magnitude lower than those of Schinus oils. The last ones showed an additive interaction when assayed in mixtures with the commecial fungicides and thyme oil. The results suggest that the doses of fungicides required for control of the Fusarium species can be reduced when they are assayed in mixtures with the Schinus oils.

Essential Oils from Schinus Species of Northwest Argentina: Composition and Antifungal Activity

The composition of the essential oils from leaves (Sal) and fruits of S areira (Saf), and fruits of S. fasciculatus (Sff) and S. gracilipes (Sgf) were analyzed by GC/MS. The major compounds identified were sabinene (26.0±0.5%), bicyclogermacrene (14.5±0.4%), and E-citral (6.7±0.2%) in Sal oil, limonene (27.7±0.7%), sabinene (16.0±0.5%), β-phellandrene (14.6±0.8%) and bicyclogermacrene (8.1±0.2%) in Saf oil, sabinene (22.7±0.6%), α-phellandrene (18.7±0.3%), β-phellandrene (15.7±0.4%), and bicyclogermacrene (8.1±0.2%) in Sff oil and β-pinene (25.4±0.8%), α-pinene (24.7±0.7%), and sabinene (13.6±0.4%) in Sgf oil. The antifungal activity of the four oils was evaluated on strains of Fusarium verticillioides and F. graminearum, and the results compared with the effect of epoxyconazole, pyraclostrobin and thyme oil. The Sff oil had the highest antifungal activity among the Schinus oils tested, with MIC100 (F. graminearum) = 6 ± and MIC100 (F. verticillioides) = 12 ±. A principal component analysis suggests that 9 constituents (α-thujene, α-terpinene, p-cymene, γ-terpinene, terpinolene, 1-terpineol, α-calacorene, α-phellandrene, and terpinen-4-ol) explain the higher antifungal effect of Sff. The MIC100s of Schinus oils were on average 30–60 and 8.5–17 fold lower than those obtained for thyme oil on F. verticillioides and F. graminearum, respectively. In the case of commercial fungicides, their MIC100s were three orders of magnitude lower than those of Schinus oils. The last ones showed an additive interaction when assayed in mixtures with the commecial fungicides and thyme oil. The results suggest that the doses of fungicides required for control of the Fusarium species can be reduced when they are assayed in mixtures with the Schinus oils.

Antibacterial activities of Ligaria cuneifolia and Jodina rhombifolia leaf extracts against phytopathogenic and clinical bacteria

Six plant extracts prepared from Ligaria cuneifolia and Jodina rhombifolia were screened for their potential antimicrobial activities against phytopathogens and clinically standard reference bacterial strains. Bioautography and broth microdilution methods were used to study samples antibacterial activities against 7 bacterial strains. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of samples were attained. An antibacterial activity guided isolation and identification of active compounds was carried out for L. cuneifolia methanolic extract (LCME). Both methanolic and aqueous extracts from L. cuneifolia showed inhibitory activities against phytopathogenic bacteria, with MICs ranging from 2.5 to 156 μg mL(-1) for LCME and 5 mg mL(-1) for the aqueous extract. None of the three J. rhombifolia extracts showed significant antibacterial activities against phytopathogenic strains (MIC > 5 mg mL(-1)), except for the aqueous extracts against Pseudomonas syringae (MIC = 312 μg mL(-1)). Only LCME showed bactericidal activities against phytopathogenic strains (MBCs = 78 μg mL(-1)). The LCME exhibited significant inhibitory activity against reference clinical strains: Escherichia coli (MIC = 156 μg mL(-1)) and Staphylococcus aureus (MIC = 78 μg mL(-1), MBC = 312 μg mL(-1)). LCME active compounds were identified as flavonol mono and diglycosides, and gallic acid. The antibacterial activity of purified compounds was also evaluated. A synergistic effect against S. aureus was found between gallic acid and a quercetin glycoside. Hence, anti-phytopathogenic bacteria potential compounds isolated from L. cuneifolia could be used as an effective source against bacterial diseases in plants.

Toxigenic potential of Fusarium graminearum isolated from maize of northwest Argentina

Twenty six isolates of Fusarium graminearum from grains of maize hybrids harvested in ±west Argentina were grown on autoclaved rice grain to assess their ability to produce type B trichothecenes. Chemical analysis indicated that 38% of isolates were nivalenol (NIV) producers only, 31% were major NIV producers with high DON(deoxynivalenol)/NIV ratios, 8% were major DON producers with minor NIV production, and 23% were DON producers only. Isolates showed a high variability in their toxigenic potential which was not related to fungal biomass. The distribution of the different chemotypes as well as the high and the low trichothecene-producing Fusarium isolates could not be associated to a geographical origin. Our results confirmed for the first time that isolates of Fusarium graminearum from maize of northwest Argentina are able to produce DON and NIV. A substancial contamination with both NIV and DON is likely in maize from northwest Argentina. Their contents should be quantified in regional surveillances for mycotoxin contamination.

Anti-inflammatory properties of phenolic lactones isolated from Caesalpinia paraguariensis stem bark

ETHNOPHARMACOLOGICAL RELEVANCE

Caesalpinia paraguariensis (D. Parodi) Burkart stem bark infusion (CPBI) is traditionally used in Argentina because their "vulnerary" properties.

AIM OF THE STUDY

CPBI was studied throughout bio-guided purification procedures conducted by in vitro biological assays in order to isolate the main bioactive compounds.

MATERIAL AND METHODS

Anti-inflammatory activity was assessed by enzyme inhibition assays of Hyaluronidase (Hyal) and inducible Nitric Oxide Synthase (iNOS). The antioxidant properties were evaluated by DPPH free radical scavenging assay, lipid peroxidation inhibition assay on erythrocyte membranes, and a cell-based assay that included the fluorescent probe (DCFH-DA) for indicating reactive oxygen species (ROS) generation. Bioactive compounds were purified by chromatographic methods and their structures elucidated using spectroscopic methods (ESI-MS and 1D/2D-(1)H/(13)C-NMR).

RESULTS

Four main bioactive compounds were isolated from CPBI: ellagic acid (1), 3-O-methylellagic acid (2), 3,3'-di-O-methylellagic acid (3) and 3,3'-di-O-methylellagic-4-β-D-xylopyranoside (4). These were bioactive at concentrations in which are present in CPBI, being compounds 2 and 3 the best enzyme inhibitors of Hyal and iNOS, reaching the 90% inhibitory concentration (IC90) values ranging from 2.8 to 16.4 μM, that are better than that of the positive controls, aspirin (IC90: no reached) and aminoguanidine (IC90: 20.2 μM) respectively. Compounds 2 and 3 were also better scavengers for lipoperoxides than butylated hydroxytoluene (BHT), reaching the 90% effective concentration (EC90) at 1.2-4.5 μg/ml, and for DPPH radical (2.5-7.3 μg/ml); moreover compounds were able to exert its scavenging action on intracellular ROS. Structural features relevant to the biological activities are discussed.

CONCLUSIONS

This work provides scientific validity to the popular usage of CPBI.

Trichothecene genotypes and chemotypes in Fusarium graminearum complex strains isolated from maize fields of northwest Argentina

Members of the Fusarium graminearum species complex (Fg complex) cause Gibberella ear rot in maize from northwest Argentina. The potential of these pathogens to contaminate maize grains with type B trichothecenes is a health risk for both humans and animals. We evaluated the reliability of multiplex PCR assays based on TRI3 and TRI12 genes, and single PCR assays based on TRI7 and TRI13 genes to infer trichothecene chemotypes of 112 strains of Fg complex collected from northwest Argentina, checking trichothecene production by chemical analysis. Single and multiplex PCR assays indicated that strains belonging to F. meridionale (87/112) had a NIV genotype. The remainder strains (25/112), which belonged to F. boothii, had a DON genotype (based on single PCR assays) or 15ADON genotype (based on multiplex PCR assays). No strains tested were incorrectly diagnosed with a DON/NIV genotype. Chemical analysis indicated that the F. meridionale strains were NIV producers only (44/87), major NIV producers with unexpected high DON/NIV ratios (36/87), or unexpected major DON producers with minor NIV production (7/87). Strains with atypical DON/NIV production seem to be new phenotypes under a putative NIV genotype, since PCR assays do not provide evidences of a new trichothecene genotype. DON production and absence of its acetylated forms were shown for strains of F. boothii. The inconsistencies between genetic and chemical data highlight the risk of inferring the trichothecenes potentially contaminating food and feedstuffs based only on PCR assays. This study confirms for the first time that strains of Fg complex from maize of northwest Argentina are DON and NIV producers. In addition, dominance of NIV producers in the Fg complex population isolated from maize is unprecedented in Argentina, and of significant concern to food safety and animal production.

Free radical scavenging activities and inhibition of inflammatory enzymes of phenolics isolated from Tripodanthus acutifolius

ETHNOPHARMACOLOGICAL RELEVANCE

Leaf extracts from Tripodanthus acutifolius (Ruiz and Pavón) Van Tieghem have long been used in Argentinean traditional medicine as anti-inflammatory, however, there is no scientific evidence which supports this use in the literature.

AIM OF THE STUDY

The present study was conducted to evaluate the ability of five phenolic compounds purified from infusion prepared from Tripodanthus acutifolius leaves to inhibit key enzymes in inflammatory processes. As anti-inflammatory compounds frequently possess free radical scavenging activities, purified substances were comparatively evaluated to asses their free radical scavenging properties. Genotoxic effects were also evaluated.

MATERIALS AND METHODS

Compounds were evaluated on their ability to inhibit hyaluronidase and cyclooxygenase-2 (COX-2) activities to assess their anti-inflammatory capacities. Free radical scavenging activity was assessed by: 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH), superoxide anion assay and the inhibition on lipid peroxidation. Genotoxicity was evaluated by Bacillus subtilis rec assay.

RESULTS

Fractionation of Tripodanthus acutifolius infusion yielded a novel phenylbutanoid derivative (tripodantoside) and four known flavonoid glycosides (rutin, nicotiflorin, hyperoside and isoquercitrin). Flavonoids produced higher inhibition on hyluronidase activity (IC(50) approximately 1.7 mM) than tripodantoside (IC(50)=27.90 mM). A similar COX-2 inhibition activity was exerted by tripodantoside and monoglycosilated flavonoids (IC(50) approximately 50 microM). Compounds were strong radical scavengers, with effective concentration 50 (EC(50)) values for DPPH in the range of 2.7-6.3 microg/mL, and for superoxide anion in the range of 3.9-8.7 microg/mL. All compounds scavenged peroxyl radicals in the lipid peroxidation assay. The substances showed no genotoxic effects.

CONCLUSIONS

The anti-inflammatory effects, free radical scavenging activities and lack of genotoxicity of purified compounds may support the folk use of infusion from Tripodanthus acutifolius leaves as anti-inflammatory.

A molecular based strategy for rapid diagnosis of toxigenic Fusarium species associated to cereal grains from Argentina

Fusarium species are worldwide causal agents of ear rot in cereals. Their toxigenic potential is a health risk for both humans and animals. In Argentina, most identification of these fungi has been based on morphological and cross-fertility criteria which are time consuming and require considerable expertise in Fusarium taxonomy and physiology. DNA based approaches have been reported as rapid, sensitive and specific alternatives to identify the main fumonisin and trichothecene-producing Fusarium species. In this work, we used PCR assays and the partial sequence of TEF1-alpha gene (Translation Elongation Factor-1 alpha) to identify the fumonisin and trichothecene-producing species in Fusarium isolates from diverse regions of Argentina. The relative efficiency and reliability of those methods to improve mycotoxin risk prediction in this country were also assessed. Species-specific PCR assays were targeted toward multicopy IGS (Intergenic Spacer of rDNA units) and on the toxin biosynthetic genes FUM1 (fumonisins) and TRI13 and TRI7 genes (trichothecenes). PCR assays based on FUM1 gene and IGS sequences allowed detection and discrimination of the fumonisin producers Fusarium proliferatum and Fusarium verticillioides. Molecular identification of nonfumonisin producers from Gibberella fujikuroi species complex was possible after determination of TEF1-alplha gene sequences, which indicated the presence of Fusarium subglutinans, Fusarium andiyazi and Fusarium thapsinum. TEF-1 alpha gene sequences also allowed discrimination of the different species of the Fusarium graminearum complex (F. graminearum sensu lato) as F. graminearum sensu stricto, Fusarium meridionale and Fusarium boothii. The last two species belonged to NIV chemotype and were detected for the first time in the subtropical region of Argentina while F. graminearum sensu stricto was DON producer only, which was also confirmed by specific PCR assays based on TRI137/TRI7 genes. Our results indicated that the PCR assays evaluated in this work are reliable diagnostic tools to detect the main toxigenic Fusarium species associated to cereal grains in Argentina. An extensive epidemiological survey based on the approach presented in this work is currently in progress to know the mycotoxigenic hazard of Fusarium species in cereal grains from the subtropical region of Argentina.

Purification and identification of antibacterial phenolics from Tripodanthus acutifolius leaves

AIMS

To perform an activity-guided purification, identification and quantification of antibacterial compounds from Tripodanthus acutifolius infusion. To validate the antibacterial activity of purified substances.

METHODS AND RESULTS

Bioautographic methods were employed as screening assays for purifying bioactive substances. Purification procedures included sephadex LH-20 column chromatography and reverse phase HPLC. Identification was achieved by spectroscopic methods (UV-Vis, MS, NMR and polarimetry) and chromatographic assays (paper chromatography and HPLC). Antibacterial activity was studied by microdilution, colony count and photometric assays, Sytox green stain and transmission electron microscopy (TEM). Four glycoflavonoids (rutin, nicotiflorin, hyperoside and isoquercitrin) and an unusual phenylbutanoid glycoside (tripodantoside) were purified and identified. Tripodantoside was found at 6.59 +/- 0.82 g per 100 g of dry leaves. The flavonoids showed bactericidal effect at a concentration of 4 mg ml(-1) against Staphylococcus aureus and Pseudomonas aeruginosa strains from American Type Culture Collection, while tripodantoside was almost four times more active than those compounds, with a minimum bactericidal concentration = 1.024 mg ml(-1) against these strains. Tripodantoside aglycone showed bacteriolytic effects on the assayed strains, causing evident damages on cell wall and membrane, while tripodantoside did not exhibit those effects.

CONCLUSIONS

The antibacterial activity of T. acutifolius infusion would be partially attributed to the purified glycoflavonoids and mainly to tripodantoside.

SIGNIFICANCE AND IMPACT

The high extraction yield and the antibacterial activity exhibited by tripodantoside makes this chemical structure of interest to support further studies dealing with chemical modifications to increase the antibacterial activity or to seek another activities.

Antimycotic activity of 5'-prenylisoflavanones of the plant Geoffroea decorticans, against Aspergillus species

The antifungal activity of the ethanolic extract (EE), (3R)-5,7,2',3'-tetrahydroxy-4'-methoxy-5'-prenylisoflavanone (1) and (3R)-7-2'-3'-trihydroxy-4'-methoxy-5'-prenylisoflavanone (2) isolated from Geoffroea decorticans was evaluated against four different species of Aspergillus. Their effect was compared with that displayed by synthetic products. The antifungal activity was assayed by bioautography, hyphal radial growth, hyphal extent and microdilution in liquid medium. The percentage of hyphal radial growth inhibition produced by EE varied between 18.4+/-0.1 and 39.6+/-0.2 for Aspergillus nomius VSC23 and Aspergillus nomius 13137, respectively; and the same value for 1 and 2 were between 31.2+/-0.1-60.8+/-1.5 and 28.9+/-0.7-57.2+/-0.6 for Aspergillus flavus (IEV 018) and Aspergillus nomius 13137, respectively. The values of MIC/MFC determined for EE, 1 and 2 were compared with the actions of ascorbic and sorbic acids, and clotrimazole. The sequence of antifungal potency was clotrimazole>1>2>ascorbic acid>sorbic acid>EE. Consequently, EE as well as the purified substances from Geoffroea decorticans would be used as biopesticides against Aspergillus species. The cytotoxicity was evaluated.

Antibacterial activity of plant extracts from northwestern Argentina

AIMS

To determine the antibacterial and cytotoxic activities of aqueous and ethanolic extracts of northwestern Argentinian plants used in folk medicine. To compare the mentioned activities with those of five commercial antibiotics. To identify the compounds responsible for the antibacterial activity.

METHODS AND RESULTS

Plant extracts were prepared according to traditional uses in northwestern Argentina. Antibacterial activity was assayed by agar dilution in Petri dishes and broth dilution in 96-well plates. Lethal dose 50 (LD(50)) was determined by the Artemia salina assay. Phytochemical analysis was performed by sample adsorption on silica gel, thin-layer chromatography (TLC), bioautography and UV-visible spectra. The results showed that Tripodanthus acutifolius aqueous extracts have lower minimal inhibitory concentrations (MIC) (502 and 506 microg of extracted material (EM) per ml for infusion and decoction, respectively) than cefotaxim MIC (640 microg ml(-1)) against Acinetobacterfreundii (303). These data were lower than their LD(50). Tripodanthus acutifolius tincture showed lower MIC (110 microg of EM per ml) and minimal bactericidal concentration (MBC) (220 microg of EM per ml) than cefotaxim (MIC and MBC of 320 microg ml(-1)) for Pseudomonasaeruginosa. This extract also showed a MIC/MBC of 110/220 microg of EM per ml, lower than oxacillin (MIC/MBC of 160/220 microg ml(-1)) for Staphylococcus aureus (ATCC 25923). The cytotoxicity of all extracts were compared with that of commercial antibiotics. Rutin (3,3',4',5,7-pentahydroxyflavone 3-beta-rhamnosilglucoside), iso-quercitrin (3,3',4',5,7-pentahydroxyflavone 3-beta-glucoside) and a terpene would be partially responsible for the antibacterial activity of T. acutifolius infusion.

CONCLUSIONS

Tripodanthus acutifolius extracts had the ability to inhibit bacterial growth. The antibacterial activity differs with the applied extractive method, and it could be partially attributed to glycoflavonoids. This paper contributes to the knowledge of antibacterial capacity of plants from northwestern Argentina.

SIGNIFICANCE AND IMPACT OF THE STUDY

These antibacterial activities support further studies to discover new chemical structures that can contribute to alleviate or cure some illnesses.

Propolis from the northwest of Argentina as a source of antifungal principles

AIMS

To determine the antimycotic and cytotoxic activities of partially purified propolis extract on yeasts, xylophagous and phytopathogenic fungi. To compare these activities with pinocembrin and galangin isolated from this propolis and with the synthetic drugs ketoconazole and clortrimazole.

METHODS AND RESULTS

Ethanolic propolis extract was partially purified by cooling at -20 degrees C. Two of its components were isolated by HPLC and identified as pinocembrin and galangin. The antifungal activity was assayed by bioautography, hyphal radial growth, hyphal extent and microdilution in liquid medium. Cytotoxicity was studied with the lethality assay of Artemia salina. The obtained results were compared with the actions of ketoconazole and clortrimazole. The results showed that the antifungal potency of ketoconazole and clortrimazole is higher than pinocembrin, galangin and the partially purified propolis extract in this order. Otherwise, the cytotoxicity of the synthetic drugs is also the highest.

CONCLUSIONS

Partially purified propolis extract inhibits fungal growth. The comparison of its relative biocide potency and cytotoxicity with synthetic drugs and two components of this propolis (pinocembrin and galangin) showed that the propolis from 'El Siambón', Tucumán, Argentina, is a suitable source of antifungal products.

SIGNIFICANCE AND IMPACT OF THE STUDY

The partially purified propolis extract and its isolated compounds, pinocembrin and galangin, have the capacity of being used as antifungals without detriment to the equilibrium of agroecosystems. The impact of this study is that the preparation of agrochemicals with reduced economic costs using a partially purified preparation as the active principle is possible.