Denilson Ferreira Oliveira

Antibacterial activity of plant extracts from Brazil against fish pathogenic bacteria

The aim of this work was to evaluate the antibacterial activity of Brazilian plants extracts against fish pathogenic bacteria. Forty six methanolic extracts were screened to identify their antibacterial properties against Streptococcus agalactiae, Flavobacterium columnare and Aeromonas hydrophila. Thirty one extracts showed antibacterial activity.

Plant extracts to control "Alternaria alternata" in Murcott tangor fruits

BACKGROUND Alternaria alternata causes the Alternaria brown spot disease (ABS) in many tangerines and their hybrids worldwide. Plant extracts offer an alternative method for controlling this disease, which control is based on chemical fungicides. AIMS To identify plant species with antifungal properties against A. alternata, the causal agent of the ABS. METHODS Plant extracts prepared from leaves, barks, flowers, and stalks collected from 105 plant species in the State of Minas Gerais, Brazil, were tested for activity against the fungus A. alternata in vitro and in vivo. RESULTS The most promising extract was obtained from Anadenanthera colubrina, which reduced the disease on Murcott tangor fruits to levels obtained with commercial fungicides. Artemisia annua, Cariniana estrelensis, Ficus carica, and Ruta graveolens presented moderate in vitro antifungal activity, but no effects were observed on the disease when the extracts were applied to fruits inoculated with the fungus. Besides, A. colubrina was the most active extract against A. alternata in the in vitro assay. CONCLUSIONS The results obtained in the in vitro and in vivo assays suggested that the fungal growth test, which uses 96-well polypropylene plates, seems to be appropriate for selecting potential plant species for testing new methods to control ABS.

Evaluation of the antifungal activity by plant extracts against Colletotrichum gloeosporioides Penz

Com vistas a contribuir para o desenvolvimento de metodos mais eficientes e menos agressivos ao ambiente que aqueles disponiveis para o controle de Colletotrichum gloeosporioides Penz, causador da mancha manteigosa em cafeeiros, buscou-se identificar especies vegetais produtoras de substâncias ativas contra o referido patogeno. Para tanto, prepararam-se extratos de 48 especies vegetais, coletadas na regiao do Alto Rio Grande, em Minas Gerais, para serem submetidos a testes in vitro com o mencionado fungo. Constatou-se que os melhores resultados foram obtidos com os extratos oriundos de Digitalis lanata Ehrh, Origanum manjorona L., Plantago lanceolata Hook. e Stevia rebaudiana (Bertoni) Bertoni que inibiram a germinacao dos esporos de C. gloeosporioides. Alguns dos extratos ativos tambem foram submetidos a diluicoes em solucao aquosa de Tween 80 a 1%, o que permitiu observar que, na proporcao de 1:2 ou 1:3 (extrato: solucao aquosa), os extratos perdiam a atividade antifungica. Verificou-se tambem que alguns dos extratos ativos nao alteraram suas atividades quando submetidos ao processo de liofilizacao. Desse modo, identificaram-se varias plantas promissoras na pesquisa por novas substâncias bioativas para o controle de C. gloeosporioides, com destaque para O. manjorona L., que inibiu 96% da germinacao dos esporos do referido fungo.

Identification of the antimicrobial substances produced by Solanum palinacanthum (Solanaceae)

To find out natural antimicrobial agents as alternative in therapeutics and to preserve food, the methanol extract of Solanum palinacanthum aerial parts was submitted to purification steps guided by antibacterial and antifungal assays. As a consequence, the flavonoid rutin and 3,5-dicaffeoylquinic acid were isolated by column chromatography and high performance liquid chromatography, and identified by mass and nuclear magnetic resonance spectrometry. Minimal inhibitory concentrations (MIC) of the quinic acid derivative against Aeromonas hydrophila, Bacillus subtilis, Staphylococcus aureus and the fungus Aspergillus ochraceus were 250, 1000, 1000 and > 568 microg/mL, respectively. Against the same microorganisms, MIC for rutin were 1000, > 1000, > 1000 and 35 microg/mL, respectively. Rutin was very promising for A. ochraceus control, since its MIC against such fungus was close to the one observed for benzalkonium chloride, which is used as a fungicide in Brazil.

In vitro studies of the anthelmintic activity of Picrolemma sprucei Hook. f. (Simaroubaceae)

1300 ppm (1.3 g / L), water and ethanol extracts prepared from stems or roots of Picrolemma sprucei Hook. f. were lethal (85-90 % mortality) in vitro to Haemonchus contortus (Barber Pole Worm) larvae, a gastrointestinal nematode parasite found in domestic and wild ruminants. Neosergeolide and isobrucein B were isolated in 0.0083 and 0.0070 % yield from dry, ground P. sprucei stems (0.89 kg). Neosergeolide, isobrucein B and the anthelmintic drug standard levamisole all caused comparable mortality rates (68-77 %) in vitro to H. contortus at similar concentrations (81-86 ppm). The anthelmintic activity of P. sprucei infusions (teas), alcohol extracts, and neosergeolide and isobrucein B, has therefore been demonstrated for the first time.

Purification of two substances from bulbs of onion ( Allium cepa L.) with nematicidal activity against Meloidogyne exigua Goeldi

To contribute to the development of a new method for Meloidogyne exigua Goeldi control, a nematode widely disseminated through Brazilian coffee fields, this work aimed to purify the nematicidal substances produced by onion (Allium cepa L.). Thus, the methanolic extract of onion bulbs was concentrated under reduced pressure and submitted to a purification process guided by in vitro assays with second-stage juveniles (J2) of M. exigua. After several steps, two nematicidal substances that seemed to be interconverting when in solution were isolated. When exposed to 500 ppm aqueous solutions of substances 1 and 2, 55 and 38% of the J2, respectively, were dead after 24 h. Very preliminary nuclear magnetic resonance spectroscopy studies suggested that these substances correspond to a pair of carbohydrates.

Toxicidade de filtrados fúngicos a meloidogyne incognita

In the search for new nematicidal molecules, 18 fungal species filtrates and seven fungus mycelium extracts were studied in vitro to see their influence on hatching, mobility and mortality of second stage juveniles (J2) of Meloidogyne incognita. Fungal filtrates were obtained from fifteen day Czapek cultures. Methanol was used as solvent to obtain fungus mycelium extracts. Paecilomyces lilacinus, Fusarium moniliforme and Fusarium oxysporum filtrates reduced J2 motility and hatching, and increased J2 mortality (P < 0,05) similarly to Aldicarb. Some fungus filtrates reduced J2 mobility without leading to death. Aspergillus flavus, Cylindrocarpon magnusianum, Fusarium solani and Mortierella sp. filtrates reduced (P < 0,05) only J2 hatching. Production of toxic fungus metabolites was not dependent on the amount of mycelium produced. P. lilacinus produced toxic filtrates after one day culturing. Since then, toxicity increased steadily, reaching 100% J2 mortality on the thirteenth day.

Toxicity of copaiba extracts to armyworm (Spodoptera frugiperda)

The objective of this study was to evaluate the effects of methanolic extracts from leaves, peels, seeds and pulps from fruits of Copaifera langsdorffii on Spodoptera frugiperda. Extracts derived from leaves and fruit peels were more toxic to S. frugiperda than the others. Hence, they were added to the artificial diet and used in further experiments with the second instar larvae of the insect, which presented larval growth reduction, prolonged period of development, increased mortality, and lower fertility and fecundity of adults. Lower egg viability was also observed when the insect was treated with extracts of leaves and fruit peels in the larvae stage. Moreover, when subjected to ultrastructural analysis under a scanning electron microscope, such eggs showed abnormalities in the aeropylar and micropylar regions. Both extracts also increased the excretion of protein in the insect feces and inhibited trypsin activity in the in vitro test. Consequently, C. langsdorffii presents potential to be used in the development of new products to control the fall armyworm.

Efeito de extratos orgânicos, associados ao surfactante Tween 80, na germinação e crescimento de plântulas de alface

This work aimed at identifying, through bioassay, the effect of organic extracts of pigweed (Amaranthus retroflexus L.), signal grass (Brachiaria plantaginea (Link.) Hitchc.), ageratum (Ageratum conyzoides L.) and three corn cultivars (AG1051, C333 and C435) on lettuce (Lactuca sativa L. cv. Marisa AG216) germination and seedling. Thus, the methanolic extracts of their straws were concentrated under vacuum and dissolved in 1% (v/v) aqueous surfactant Tween 80. Then, the resulting solutions were applied to filter papers contained in Petri dishes, where lettuce was sowed. Distilled water and 1% Tween 80 were used as controls treatment. The corn cultivar extracts AG1051, pigweed and ageratum promoted reduction of the germination index in relation to the control with distilled water. The germination percentage was affected by ageratum extract (82.5% less than the control). All extracts and the surfactant Tween 80 promoted inhibition lettuce seedling growth with reduction of root length between 9.53 and 14.83 mm and hypocotyls between 21.64 to 30.95 mm.

Rhizobacteria able to produce phytotoxic metabolites

To contribute for the development of environmental friendly methods for weed control, a selection of rhizobacteria able to produce phytotoxic substances was carried out. Initially, 35 strains previously isolated from plants in the south of Minas Gerais State (Brazil) were grown in tryptic soy broth. After removal of bacterial cells, the resulting liquids were freeze-dried and extracted with methanol/ethyl acetate (1:1). The extracts were concentrated under vacuum and dissolved in water to be submitted to a lettuce (Lactuca sativa L.) seed assay. Metabolites produced by five strains reduced the number of normal seedlings to values statistically bellow the one observed for the negative control, being the most expressive results obtained with Bacillus cereus Frankland and Frankland, isolated from Ricinus communis L., which was able to cause rotted rootlets to 82.4% of seedlings. The bacterium metabolites also avoided germination of 52% Brachiaria decumbens Stapf seeds and the remaining 48% resulted in abnormal seedlings. Metabolites from B. cereus were submitted to a purification process guided by the lettuce seed assay. As a consequence, one substance causing rotted rootlets to all lettuce seedlings during the seed assay at 0.057 g/L was isolated and will be identified in future studies.