Zanthoxylum caribaeum (Rutaceae) essential oil: chemical investigation and biological effects on Rhodnius prolixus nymph

A chemical investigation and bioassays against fifth-instar nymphae of the hematophagous insect Rhodnius prolixus, vector of Chagas disease, were conducted with the essential oil from Zanthoxylum caribaeum. The main results may be summarized as follows: (i) 54 components were identified, corresponding to 90.4 % of the relative composition; sesquiterpenes (47.3 %) and monoterpenes (41.2 %) are the major constituents; (ii) muurola-4,5-trans-diene and isodaucene are described for the first time as chemical constituents of the essential oil from leaves of this species; (iii) topical treatment with the crude essential oil induced high levels of paralysis (from 18.88 to 33.33 %) and mortality (from 80 to 98.9 %) depending on the dose applied (0.5 to 5.0 mu l per insect); (iv) feeding treatment with the crude essential oil also induced high levels of mortality (from 48.8 to 100 %) but low levels of paralysis (from 2.22 to 7.77 %) depending on the dose applied (0.5 to 5.0 mu l/ml of blood); (v) in the continuous treatment, only the dose of 5.0 mu l/cm(2) was able to promote statistical significant levels of mortality (63.3 %) but no paralysis were detected. However in this group, occasionally, only few insects displayed malformations of legs and wings after treatment; and (vi) any treatment was able to disrupt the metamorphosis process since the low adult stage emergence observed to all groups was due the high insect mortality. These observations suggest the interference of Z. caribaeum compounds on the triatomine neuroendocrine system. The significance of these results in relation to the relevant biological events in R. prolixus as well as the possible use of insect growth regulators present in Z. caribaeum oil in integrated vector control programs against hematophagous triatomine species is herein discussed.