ABSTRACT
The neotropical bracken fern Pteridium arachnoideum (Kaulf.) Maxon. (Dennstaedtiaceae) is described as an aggressive pioneer plant species. It invades abandoned or newly burned areas and represents a management challenge at these invaded sites. Native to the Atlantic Forest and Cerrado (Tropical Savanna) Brazilian biomes, P. arachnoideum has nevertheless become very problematic in these conservation hotspots. Despite some reports suggesting a possible role of allelopathy in this plant's dominance, until now there has been little evidence of isolated and individually identified compounds with phytotoxic activities present in its tissues or in the surrounding environment. Thus, the aim of this study was to investigate the allelopathic potential of P. arachnoideum by isolating and identifying any secondary metabolites with phytotoxic activity in its tissues, litter, and soil. Bioguided phytochemical investigation led to the isolation and identification of the proanthocyanidin selligueain A as the major secondary compound in the green fronds and litter of this fern. It is produced by P. arachnoideum in its green fronds, remains unaltered during the senescence process, and is the major secondary compound present in litter. Selligueain A showed phytotoxic activity against the selected target species sesame (Sesamum indicum) early development. In particular, the compound inhibited root and stem growth, and root metaxylem cell size but did not affect chlorophyll content. This compound can be considered as an allelochemical because it is present in the soil under P. arachnoideum patches as one of the major compounds in the soil solution. This is the first report of the presence of selligueain A in any member of the Dennstaedtiaceae family and the first time an isolated and identified allelochemical produced by members of the Pteridium species complex has been described. This evidence of selligueain A as a putative allelochemical of P. arachnoideum reinforces the role of allelopathy in the dominance processes of this plant in the areas where it occurs.
Subject(s)
Allelopathy , Pteridium/chemistry , Pteridium/physiology , Antibiosis , Brazil , Molecular Structure , Phytochemicals/chemistry , Phytochemicals/toxicity , Plant Extracts/chemistry , Plant Extracts/toxicity , Plant Roots/chemistry , Plant Roots/cytology , Plant Roots/growth & development , Proanthocyanidins , Sesamum/growth & development , Soil/chemistry , Triticum/physiologyABSTRACT
La enfermedad de Hansen, fue traída a América después de su descubrimiento. En Costa Rica los primeros informes de la presencia de la enfermedad datan de 1734. En diciembre de 1984 tenemos en el país una prevalencia de 642 casos, lo que nos da una tasa de 26 por 100.000 hab. La provincia con mayor prevalencia es Guanacaste y la de menor prevalencia es Heredia. La edad más afectada es entre los 30 y 60 años y el sexo que predomina es el masculino, a razón de 1.70. Ha habido un incremento en el diagnóstico de las formas cerradas (L.T. y L.I) en los últimos años. La edad de diagnóstico en la incidencia (últimos 12 años), cuyo predominio se establece en pacientes mayores de 15 años, a partir de 1979 empieza su disminución