RESUMO
The essential oils extracted from leaves of the Southern Brazilian native species Drimys angustifolia Miers (DA) and Drimys brasiliensis Miers (DB) by Clevenger distillation were analyzed by gas chromatography/mass spectrometry (GC/MS). The oils of DA and DB consisted predominantly of monoterpenoids and sesquiterpenoids. The largest components of DA oil were bicyclogermacrene (19.6%), sabinene (9.7%)and myrcene (5.2%), while DB oil was characterized by cyclocolorenone (18.2%), followed by terpinen-4-ol (8.7%) and alpha-gurjunene (6.9%). Laboratory tests were carried out to determine the repellency of the essential oils to the drywood termite Cryptotermes brevis (Isoptera: Kalotermitidae). It was observed that the oil showed repellency at the concentrations 25, 12.5, and 6.25 μg/mL. The oils of both species exhibited a negative repellency index, which represents repellent activity, except for DA oil at the highest concentration, which was attractive. Five deaths (11% of the termitesample) were observed at 25 μg/mL DA, in the fourhour repellency test, while four deaths occurred at 12.5 μg/mL (approximately 9%). The essential oil of DB did not cause any termite deaths...
Os óleos essenciais obtidos das folhas das árvores nativas do sul do Brasil Drimys angustifolia Miers (DA)e Drimys brasiliensis Miers (DB) foram analisados por cromatografia gasosa acoplada a espectrometria de massas (CG/EM). O óleo de DA foi caracterizado pela presença de monoterpenóides e sesquiterpenóides, biciclogermacreno (19,6%), seguido por sabineno (9,7%) e mirceno (5,2%). O óleo de DB foi caracterizado por sesquiterpenóides e monoterpenóides, ciclocolorenona (18,2%), seguido por terpinen-4-ol (8,7%) e alfagurjuneno(6,9%). Os testes foram realizados a fim de se determinar o potencial repelente dos óleos essenciais contra o cupim de madeira seca Cryptotermes brevis (Isoptera: Kalotermitidae) nas doses de 25, 12,5, e 6,25 μg/mL. Ambas as espécies mostraram índice de repelência negativo, o que representa a ocorrência da atividade repelente, exceto na maior concentração de DA, na qual o óleo mostrou-se atraente. Cinco mortes foram observadas na concentração de 25 μg/mL de DA, correspondendo a 11% do total em quatro horas de análise, sendo que 9% ocorreram na concentração de 12,5 μg/mL. No caso do óleo essencial de DB não foram observadas mortes de cupins...
Assuntos
Drimys , Repelentes de Insetos , Isópteros , Óleos VoláteisRESUMO
Canatoxin, a urease isoform from Canavalia ensiformis seeds, shows insecticidal activity against different insect species. Its toxicity relies on an internal 10 kDa peptide (pepcanatox), released by hydrolysis of Canatoxin by cathepsins in the digestive system of susceptible insects. In the present work, based on the N-terminal sequence of pepcanatox, we have designed primers to amplify by PCR a 270-bp fragment corresponding to pepcanatox using JBURE-II cDNA (one of the urease isoforms cloned from C. ensiformis, with high identity to JBURE-I, the classical urease) as a template. This amplicon named jaburetox-2 was cloned into pET 101 vector to obtain heterologous expression in Escherichia coli of the recombinant protein in C-terminal fusion with V-5 epitope and 6-His tag. Jaburetox-2Ec was purified on Nickel-NTA resin and bioassayed in insect models. Dysdercus peruvianus larvae were fed on cotton seed meal diets containing 0.01% (w/w) Jaburetox-2Ec and, after 11 days, all individuals were dead. Jaburetox-2Ec was also tested against Spodoptera frugiperda larvae and caused 100% mortality. In contrast, high doses of Jaburetox-2Ec were innocuous when injected or ingested by mice and neonate rats. Modeling of Jaburetox-2Ec, in comparison with other peptide structures, revealed a prominent beta-hairpin motif consistent with an insecticidal activity based on either neurotoxicity or cell permeation.