BACKGROUND In a screen of extracts from plants and fungi to detect antileishmanial activity, we found that the ethyl acetate extract of the fungus Nectria pseudotrichia, isolated from the tree Caesalpinia echinata (Brazilwood), is a promising source of bioactive compounds. OBJECTIVES The aims of this study were to isolate and determine the chemical structures of the compounds responsible for the antileishmanial activity of the organic extract from N. pseudotrichia. METHODS Compounds were isolated by chromatographic fractionation using semi-preparative high-performance liquid chromatography, and their chemical structures were determined by analytical and spectral data and by comparison with published data. The antileishmanial activity of the isolated compounds was evaluated in intracellular amastigote forms of Leishmania (Viannia) braziliensis expressing firefly luciferase as reporter gene, and cytotoxicity was determined in Vero and THP-1 mammalian cell lines by MTT assay. FINDINGS Fractionation of the extract yielded seven compounds: 10-acetyl trichoderonic acid A (1), 6′-acetoxy-piliformic acid (2), 5′,6′-dehydropiliformic acid (3), piliformic acid (4), hydroheptelidic acid (5), xylaric acid D (6), and cytochalasin D (7). Compounds 1, 2 and 3 are reported here for the first time. Compounds 1, 2, and 5 were more active, with IC50 values of 21.4, 28.3, and 24.8 µM, respectively, and showed low toxicity to Vero and THP-1 cells. MAIN CONCLUSIONS N. pseudotrichia produces secondary metabolites that are more toxic to intracellular amastigote forms of L. (V.) braziliensis than to mammalian cells.

O emprego de sistemas agrossilvipastoris tem sido importante estratégia de uso de solos, principalmente arenosos pertencentes ao bioma Pampa. Objetivou-se, neste estudo, avaliar a agregação, o teor de C orgânico total (COT) e de N total (NT), o teor de C nas frações físicas e o grau de humificação da MO em um Argissolo Vermelho eutrófico arênico submetido a diferentes sistemas de uso no município de Alegrete, RS. As avaliações foram desenvolvidas em uma floresta homogênea de eucalipto (FH), na entrelinha do sistema agrossilvipastoril sob pastagem (SA) e em campo nativo (CN), nas camadas de 0,000-0,025 m; 0,025-0,075 m; 0,075-0,125 m; e de 0,125-0,225 m. Foram coletadas amostras deformadas de solo para a avaliação de agregados estáveis em água (AEA, %) e dos teores de COT e de NT. Foi realizado o fracionamento físico granulométrico e densimétrico da MO, sendo as frações leve livre (FLL) e fração leve oclusa (FLO) da camada superficial submetidas às análises de Infravermelho com Transformada de Fourier (FTIR) e Ressonância Paramagnética Eletrônica (EPR). Os AEA em todas as camadas e o diâmetro médio ponderado na camada de 0,025-0,075 m indicaram maior degradação estrutural do solo na entrelinha do SA. Teores mais elevados de COT, NT, C da fração grosseira (CFG), C associado aos minerais (CAM), FLL e FLO na camada superficial foram observados na FH. Entre os usos do solo, os espectros de FTIR foram semelhantes, contudo a FLL apresentou bandas mais intensas na região de 1.072 cm-1, sugerindo maiores quantidades de polissacarídeos em relação à FLO. As densidades de spins obtidas por EPR na FLO foram maiores em relação à FLL, indicando maior humificação desta fração.

Pasture-agroforestry systems have become an important strategy for the use of sandy soils in the Pampa Biome. The purpose of this study was to evaluate the aggregation, total organic C (TOC) and total nitrogen (TN), carbon of the physical fractions and humification degree of organic matter (OM). Evaluations were conducted in an Alfisol under homogenous eucalyptus forest (HF), between the rows of a pasture-agroforestry system (PA) and in native pasture (NP) in the layers 0.000-0.025, 0.025-0.075, 0.075-0.125, and 0.125-0.225 m. Disturbed samples were collected to evaluate water-stable aggregates (WSA %), TOC and TN. The physical (granulometrical and densimetrical) fractionation of OM was carried out, and the free light fraction (FLF) and occluded light fraction (OLF) of OM in the surface layer subjected to Fourier Transform Infrared (FTIR) and Electron Paramagnetic Resonance (EPR) analyses. The WSA and mean weight diameter in the layer 0.025-0.075 m indicated a greater degradation of the PA soil. Higher levels of TOC, TN, coarse fraction carbon (CFC), carbon associated with minerals (CAM), FLF and OLF in the surface layer were observed in HF. Between land uses, the FTIR spectra were similar. However, the FLF had more intense bands in the region of 1072 cm-1, suggesting higher amounts of polysaccharides than in the OLF. The spin densities obtained by EPR at OLF were higher than of FLF, indicating a higher humus fraction.

A alfafa é uma das culturas conhecidas que apresentam um tipo específico de alelopatia denominado autotoxicidade. Dessa forma, o objetivo deste trabalho foi avaliar os efeitos da concentração de extratos aquosos de partes (folhas e raízes) da planta de alfafa (material Crioulo) na germinação e no crescimento inicial de plântulas de dois materiais de alfafa (Crioulo e P5454). Placas de Petri contendo 50 sementes de cada variedade foram umedecidas com 10ml dos extratos em duas concentrações: 50% e 100% (extrato puro). Água deionizada foi usada como controle. O delineamento experimental foi inteiramente casualizado, com cinco repetições para cada variedade. Após seis dias da germinação, procedeu-se à contagem do número de sementes germinadas, bem como à medição do comprimento do hipocótilo e da radícula de cada plântula. Os extratos aquosos das folhas inibiram a germinação e o comprimento da radícula e do hipocótilo das duas variedades. No entanto, para o material Crioulo, a inibição na germinação e no desenvolvimento inicial só ocorreu com o uso do extrato puro das folhas, enquanto que na P5454 o extrato diluído a 50% já reduziu tanto a germinação quanto o comprimento das plântulas. Os extratos aquosos das raízes não causaram inibição na germinação nem no comprimento das plântulas. Os resultados sugerem variações intra-específicas na tolerância aos compostos aleloquímicos e uma produção preferencial dos mesmos na parte aérea da planta de alfafa, material Crioulo.

Alfalfa is one of the known crops that present a specific type of allelopathy called autotoxicity. Hence, this research was aimed at evaluating the concentration effects of aqueous extracts of plant parts (leaves and roots) of alfalfa (var. Crioula) on germination and early development of seedlings of two alfalfa (Crioula and P5454) varieties. Fifty seed of each variety were placed in Petri dishes with moistened filter paper. Aliquots (ten ml) from each part extracts at two concentrations, 50 or 100% (pure extract), were added to petri dishes, and distilled water was used as a control. Treatments placed in Petri dishes were randomly arranged in a completely randomized design with five replicates. Measurements included: germination, and radicle and hypocotyl lengths taken six days after germination. The aqueous extracts of leaves inhibited germination and radicle and hypocotyl length of the two alfalfa varieties. However, on the var. Crioula germination and early development was inhibited only when it was used pure extracts of leaves, while in var. P5454 leaves extracts diluted to 50% already had some reduction on germination and seedlings length. The aqueous extracts of the alfalfa roots did not cause inhibition on germination and seedlings lengths. The results suggest intra-specific variations on tolerance to the allelochemicals and a preferential production of them in the aerial part of the alfalfa plant, var. Crioula.