Parasitol Res DOI 10.1007/s00436-012-3101-9
ORIGINAL PAPER
Chemical composition and acaricidal activity of essential oil from Lippia sidoides on larvae of Dermacentor nitens (Acari: Ixodidae) and larvae and engorged females of Rhipicephalus microplus (Acari: Ixodidae) Geovany Amorim Gomes & Caio Márcio de Oliveira Monteiro & Tatiane de Oliveira Souza Senra & Viviane Zeringota & Fernanda Calmon & Renata da Silva Matos & Erik Daemon & Roberto Wagner da Silva Gois & Gilvandete Maria Pinheiro Santiago & Mario Geraldo de Carvalho Received: 12 August 2012 / Accepted: 22 August 2012 # Springer-Verlag 2012
Abstract The aim of this work was to identify the compounds and to investigate the acaricidal activity of the essential oil from the leaves of Lippia sidoides on Rhipicephalus microplus and Dermacentor nitens. The oil was obtained by hydrodistillation and analyzed by gas chromatography (GC/FID) and gas chromatography/mass spectrometry. In total, 15 compounds comprising 99.97 % of the total peak area were identified. The main constituent of the essential oil was thymol (67.60 %). The acaricidal activity T. d. O. S. Senra : V. Zeringota : F. Calmon : R. d. S. Matos : E. Daemon Programa de Pós-graduação em Ciências Biológicas, Comportamento e Biologia Animal da Universidade Federal de Juiz de Fora, 36036-900, Juiz de Fora, MG, Brazil G. A. Gomes : M. G. de Carvalho Departamento de Química, Instituto de Ciências Exatas, Universidade Federal Rural do Rio de Janeiro, 23890-000, Seropédica, RJ, Brazil C. M. d. O. Monteiro (*) Programa de Pós-graduação em Ciências Veterinárias, Universidade Federal Rural do Rio de Janeiro, 23890-000, Seropédica, RJ, Brazil e-mail:
[email protected] R. W. d. S. Gois Programa de Pós-Graduação em Química, Universidade Federal do Ceará, Cx Postal 7 6036, CEP 60451-970, Fortaleza, Ceará, Brazil G. M. P. Santiago Departamento de Farmácia, Universidade Federal do Ceará, Rua Capitão Francisco Pedro 1210, CEP 60430-370, Fortaleza, Ceará, Brazil
was assessed by the modified larval packet test, with oil concentrations of 2.5, 5.0, 10.0, 15.0, and 20.0 μl/ml, and by the female immersion test with concentrations of 10.0, 20.0, 40.0, 60.0, and 80.0 μl/ml. The mortality of the R. microplus and D. nitens larvae was greater than 95 % starting at concentrations of 10.0 and 20.0 μl/ml, respectively. In the test with the engorged females, the L. sidoides essential oil starting at a concentration of 40.0 μl/ml caused a significant reduction (p
0.05). Then, each group was immersed for 5 min in oil solutions at concentrations of 10.0, 20.0, 40.0, 60.0, and 80 μl/ml. The control group was immersed for 5 min in a solution of Tween 80 (2 %). After, each female was and maintained individually in petri dishes (6×6 cm) to monitor oviposition (each tick0experimental unit). The experimental groups were maintained in a climate-controlled chamber (27± 1 °C and RH >80±10 %) and the eggs laid were collected daily until the last female died. The egg masses collected from each female were placed in a syringe with the distal end cut, then sealed with hydrophilic cotton and kept under the same temperature and humidity conditions described previously. The following biological parameters were evaluated: female weight before oviposition, egg mass weight, and hatching percentage larvae. The values obtained were used to calculate the egg production index and control percentage. The egg production index (% EPI) was obtained according to the equation proposed by Bennett (1974): EPI ¼ egg mass weight 100=female weight before oviposition . The percentage of control of the treatments, through offspring inhibition, was obtained according to Drummond et al. (1973). First, the index of estimated reproduction (ER) was calculated: ðegg mass weight=female weight before ovipositionÞ hatching percentage 20; 000 , followed by calculation of the control percentage: ðER of control group ER of treated groupÞ= ER of control group 100:. Statistical analysis The Biostat 5.0 software was used for the statistical analyses. The means of the treatments were compared by ANOVA followed by the Tukey test. In cases of nonnormal distribution, the Kruskal–Wallis test was used, followed by the Student–Newman–Keuls test. In the tests with the larvae, the 50 % lethal concentration (LC50) was calculated using the probit method (Finney 1971), using the POLOPC program (LeOra Software, 1987, Berkeley, CA, USA). The Spearman test was also used to calculate the correlation between the oil concentration and larval mortality in the packet tests and also the control percentage in the female immersion test.
Results The essential oil yield was 1.2 % (w/w). Fifteen compounds, representing 99.97 % of the essential oil were identified. Their retention indices in the Optima-5 column and composition percentages are listed in Table 1. Of these, the following compounds were identified: one unsaturated aliphatic alcohol (0.38 %), two monoterpenes hydrocarbons (2.34 %), eight oxygenated monoterpenes (78.71 %), one sesquiterpene
Parasitol Res Table 1 Chemical composition, calculated retention index (RIC), percentages of identified components and classes of the same (%) in the essential oil of fresh leaves of Lippia sidoides Compounds
RIC
Unsaturated aliphatic alcohol Oct-1-en-3-ol Monoterpene hydrocarbons p-Cymene γ-Terpinene Oxygenated monoterpenes 1,8-Cineole cis-Sabinene hydrate Ipsdienol Terpinen-4-ol α-Terpineol Thymol methyl ether Thymol Carvacrol Sesquiterpene hydrocarbons E-Caryophyllene Oxygenated sesquiterpene Caryophyllene oxide
1,576
Monoglycerides 2-Monopalmitin
–a
1-Monoestearin Total
981 1,027 1,060 1,035 1,072 1,145 1,181 1,196 1,230 1,296 1,300 1,415
% 0.38 0.38 2.34 1.82 0.52 78.71 2.35 0.25 0.55 0.55 0.51 0.60 67.60 6.30 2.36 2.36 1.03 1.03 15.15
–a
Table 2 Mean mortality of Rhipicephalus microplus and Dermacentor nitens larvae treated with different concentrations of essential oil from leaves of Lippia sidoides under laboratory conditions (27±1 °C and RH >80±10 %)
7.15 8.00 99.97
a
Monoglyceride identified only by visual comparison of their mass spectra with that provided by the database (NIST21 and NIST107) of the equipment
hydrocarbon (2.36 %), one oxygenated sesquiterpene (1.03 %), and two monoglycerides (15.15 %) (Table 1). In the packet test with R. microplus larvae, the mortality of the group treated with a concentration of 2.5 μl/ml was 0.5 %, which was statistically similar (p>0.05) to the result for the control group (0.4 %). However, in the other treated groups, the mortality presented significant differences (p< 0.05) in relation to the control, with 100 % mortality at the two highest concentrations (15.0 and 20.0 μl/ml) (Table 2). For the D. nitens larvae, the mortality was 0.0 in the group treated at a concentration of 2.5 μl/ml and in the control (p> 0.05). In the other treatments, the mortality rates were significantly different (p
