Study of the potential of some plant species and natural and synthetic products for the control of leaf-cutter ants

Abstract

Leaf-cutting ants belonging to the genera Atta and Acromyrmex are widely distributed in the Americas and have been considered to be among the most destructive herbivores in the area, causing damages to agriculture, cattle-raising and mainly to reforestation programs. The control of leaf-cutting ants had been made, in the near past, using organochlorides and organophosphorus insecticides. However, due to the restriction to the use of these insecticides, there has been a need for the search of new alternatives for ant control. Based on popular information, especially from farmers, who have been using plants to control leaf-cutting ants; on literature data and on experience accumulated in the past years, the group has been working on some selected plants such as Sesamum indicum, Ricinus communis, Canavalia ensiformis, Ipomoea batatas and Virola sebifera, Picramnia teapensis, Pilocarpus riedelianus, Pilocarpus grandiflorus, Pilocarpus sp, Carapa guianensis, Trichilia casaretti and Raulinoa echinata in order to identify their active compounds against the ants; to understand their interactions with the symbiotic fungus and the plants, as well as to know the micro-biota related to the symbiotic fungus of the ants. These compounds may become a potential specific natural insecticide for leaf-cutting ants and/or a fungicide to their symbiotic fungus. The isolation of the active compounds has been carried out by using laboratory bioassays associated with chromatographic methods. Several active compounds have been isolated and identified by spectroscopic analysis. We have also worked in the structural modification of these compounds to get synthetic analogs with stronger activity. Several active components have already been obtained, such as ricinin, lignans, glycerides, coumarins, monoterpenes, flavonoids, synthetic derivatives based on sesamin and in amides containing the piperonyl group. The interaction between the breeds and the queen and them with the symbiotic fungus have been studied and this study has been leading to important observations on the compounds involved in this interaction, that should be confirmed in new studies. One of these observations is the metabolization of the sugar by the symbiotic fungus. For the next years, our group is intending to continue to this studies, in the sense of to complete the works accomplished partially with the mentioned plants, besides increasing the work with new plants and some items that showed to be very interesting during the course of our researches. The group is proposing to synthesize some derivatives based on sesamin, amides, coumarins, flavonoids, ricinin and its derivative, aiming to determine the active groups, to eliminate the toxicity to man and other mammals and to obtain compounds with stronger biological activities to the ant nest... (AU)