Chemical composition of essential oils of Drimys angustifolia Miers and Drimys brasiliensis Miers and their repellency to drywood termite Cryptotermes brevis (Isoptera: Kalotermitidae)

Abstract

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 termite sample) were observed at 25 μg/mL DA, in the four-hour 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 monoterpenoides e sesquiterpenoides, 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.