Laboratory evaluation of Clusia fluminensis extracts and their isolated compounds against Dysdercus peruvianus and Oncopeltus fasciatus

ABSTRACT The effects of the hexanic extracts of the fruits and flowers of Clusia fluminensis Planch. & Triana, Clusiaceae, as well as their main constituents, the triterpene lanosterol and the benzophenone clusianone, were evaluated on hemipterans Dysdercus peruvianus and Oncopeltus fasciatus. The topical treatments of insects with the hexanic extracts significantly affected the survival of O. fasciatus, but not that of D. peruvianus. Concomitantly, extracts delayed the development of both hemipterans. Moreover, isolated lanosterol significantly reduced both the survival and development of O. fasciatus and D. peruvianus, while clusianone only reduce the survival of D. peruvianus and marginally inhibited the development of both insects. The results show the specific activity of lanosterol and clusianone against the two evaluated insect species and indicate the potential of compounds derived from C. fluminensis for the development of specific biopesticides for the control of agricultural pests. Subsequent work will examine the mode of action of lanosterol and clusianone isolates from C. fluminensis.

Biocontrol evaluation of extracts and a major component, clusianone, from Clusia fluminensisPlanch. & Triana againstAedes aegypti

Studies evaluated the effects of hexanic extracts from the fruits and flowers ofClusia fluminensis and the main component of the flower extract, a purified benzophenone (clusianone), against Aedes aegypti. The treatment of larvae with the crude fruit or flower extracts from C. fluminensis did not affect the survival ofAe. aegypti (50 mg/L), however, the flower extracts significantly delayed development of Ae. aegypti. In contrast, the clusianone (50 mg/L) isolate from the flower extract, representing 54.85% of this sample composition, showed a highly significant inhibition of survival, killing 93.3% of the larvae and completely blocking development of Ae. aegypti. The results showed, for the first time, high activity of clusianone against Ae. aegypti that both killed and inhibited mosquito development. Therefore, clusianone has potential for development as a biopesticide for controlling insect vectors of tropical diseases. Future work will elucidate the mode of action of clusianone isolated from C. fluminensis.

Towards an understanding of the interactions of Trypanosoma cruzi and Trypanosoma rangeli within the reduviid insect host Rhodnius prolixus

Esta revisão destaca aspectos dos estágios do desenvolvimento de Trypanosoma cruzi e Trypanosoma rangeli em seu hospedeiro invertebrado, Rhodnius prolixus Atenção especial é dada às interações desses parasitas com moléculas presentes no tubo digestivo e na hemolinfa e efeitos da organização das células epiteliais sobre o desenvolvimento do parasita. A susceptibilidade do inseto vetor ao T. cruzi, o qual desenvolve no tubo digestivo, dependem do estado nutricional do hospedeiro, da cepa do parasita e de interações moleculares com compostos tripanolíticos, lectinas e bactérias residentes no tubo digestivo. O T. rangeli invade a hemocele e pode ser reconhecido e ativar o sistema de defesa do inseto vetor, ou seja, o sistema profenoloxidase, fagocitose, microagregação hemocitária,atividade de superóxido e óxido nítrico e a via de biossíntese dos eicosanóides. Estes fatos fornecem uma compreensão melhor das interações parasita-inseto vetor, e também oferecem novas idéias sobre os processos básicos envolvidos na transmissão parasitária.

The distribution of agglutinins and lytic activity against Trypanosoma rangeli and erythrocytes in Rhodnius prolixus and Triatoma infestans tissue extracts and haemolymph

Haemolymph, heads, salivary glands, crops, midguts, hindguts, and Malpighian tubules from Rhodnius prolixus and Triatoma infestans were extracted in phosphate or Tris buffer saline with calcium, and tested for agglutination and lytic activities by microtitration against both vertebrateerythrocytes and cultured epimatigote forms of Trypanosoma rangeli. Haemagglutination activity against rabbit erythrocytes was found in the crop, midgut and hindgut extracts of T. infestans but only in the haemolymph of R. prolixus. Higher titres of parasite agglutinins were found in R. prolixus haemolymph than T. infestans, whilst the converse occurred for the tissue extracts. In addition, the extracts of T. infestans salivary glands, but not those of R. prolixus, showed a trypanolytic activity that was heat-inactivated and was not abolished by pre-incubation with any of the sugars or glycoproteins tested. T. infestans, which is refractory to infection by T. rangeli, thus appears to contain a much wider distribution of agglutinating and trypanolytic factors in its tissues than the more susceptible species, R. prolixus

Aspects of classification of Hemiptera hemocytes from six triatomine species

The objective of this work was to characterize, and compare different morphological types of hemocytes of Rhodnius prolixus, Rhodnius, Rhodnius neglectus, Triatoma infestans, Panstrongylus megistus, and Dipetalogaster maximus. This information provides the basis for studying the cellular immune systems of these insects. Seven morphological hemocyte types wereidentified by phase-contrast microscopy: prohemocytes, plasmatocytes, granular cells, cytocytes, oenocytoids, adipohemocytes and giant cells. All seven types of hemocytes are not present in every species. For example, adipohemocytes and oenocytoids were not observed in P. megistus and P. infestans, and giant cells were rarely found in any of the species studied. The hemocytes of rhodnius and Dipetalogaster are more similar to each other than those from Triatoma and Panstrongylus which in turn closely resemble each other. Emphasis is placed on methodological problems arising in this work wicah are discussed in detail