RESUMO

The aim of this study was to evaluate the antibacterial activity of nanoemulsions of Baccharis dracunculifolia essential oil. The volatile compounds of the essential oil were identified using gas chromatography-mass spectrometry. The properties of the nanoemulsions (droplet size, polydispersity index, pH, and electrical conductivity) were determined. The antibacterial activities of the essential oil and its nanoemulsions were evaluated using MIC, MBC, and disk diffusion. The microorganisms used were: Gram-positive bacteria (Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 14579, Streptococcus mutans ATCC 25175, and Enterococcus faecalis ATCC 29212) and Gram-negative bacteria (Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC BAA-1706, Salmonella enterica ATCC 14028, and Escherichia coli ATCC 25922). The major volatile compounds of the B. dracunculifolia essential oil were limonene (19.36%), (E)-nerolidol (12.75%), bicyclogermacrene (10.76%), and ß-pinene (9.60%). The nanoemulsions had a mean droplet size between 13.14 and 56.84 nm. The nanoemulsions presented lower and statistically significant MIC values compared to the essential oil, indicating enhancement of the bacteriostatic action. The disk diffusion method showed that both the nanoemulsions and the essential oil presented inhibition zones only for Gram-positive bacteria, while there were no results against Gram-negative bacteria, indicating that B. dracunculifolia essential oil has a better antimicrobial effect on Gram-positive microorganisms.

RESUMO

Essential oils from the leaves of four species of Piper obtained through hydrodistillation were analyzed using GC-MS andmultivariate data analysis. The chemical analysis enabled the identification of qualitative and quantitative differences among the oils. ß-selinene (32.44 ± 1.14%), (E)-nerolidol (44.23 ± 2.23%), ß-caryophyllene (19.11 ± 0.40%) and caryophyllene oxide (16.92 ± 0.21%) were identified as the major constituents of the P. mollipilosum, P. brachypetiolatum, P. glandulosissimum and P. madeiranum oils, respectively. The differences in the chemical profiles of the oils were confirmed by principal component analysis. All four species exhibited antioxidant activity. The oil from P. brachypetiolatum achieved the best results on the DPPH test (EC50 = 64.8 µg/ml) and with the ABTS radical (EC50 = 159.7 µg/ml).

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RESUMO

The composition of chemical weaponry of termite soldiers show interspecific and intraspecific variation. However, spatial effects on the qualitative and quantitative compositions of these substances in Neotropical termites are poorly known. Hexane extracts of heads and the defensive secretion of soldiers of Constrictotermes cyphergaster from four localities in Northeast Brazil were analyzed by gas chromatography and mass spectrometry. Chemical analysis allowed the detection of 54 compounds from the head extract and from the direct extraction of the defensive secretion of soldiers, and the percentage of common substances and the presence of exclusive substances varied depending on the spatial distance between colonies. The profile of the chemical armament of soldiers consists basically of terpenoids: monoterpenes (45.53%-71.97 - for head extract and 57.41% - 78.56 for secretion) and sesquiterpenes (19.69% - 35.78% for head extract and 18.41% - 33.31%for secretion). In general, the main component of the chemical arsenal, regardless of the methodology used for extraction, was α-pinene (27.98-50.44%). Two chemotypes were identified based on chemical differences between populations of ecoregions with distinct spatial-environmental and climate characteristics: (1) α-pinene <33%; (2) α-pinene >33% for both extracts (head and secretion). The results reveal a similar pattern of chemical differentiation for soldiers in both extracts (head and secretion), with increasing differences as a function of distance between the analyzed colonies.

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RESUMO

The aim of this study was to test the effectiveness of essential oils form Piper aduncum, Melaleuca leucadendra and Schinus terebinthifolius and their blends by fumigation and residual contact on Tetranychus urticae and its natural enemy, Neoseiulus californicus. Bioassays were performed in a greenhouse with the best blend of the oils and compared to the individual oils and Vertimec® (positive control). The main constituents identified by GC-MS were dillapiole, (E)-nerolidol and limonene in the oils from P. aduncum (76.5%), M. leucadendra (87.3%) and S. terebinthifolius (unripe/ripe fruits, 42.5/34.1%). The P. aduncum and M. leucadendra oils were the most toxic to the pest. Among the blends, the greatest toxicity to T. urticae occurred by residual contact with the M. leucadendra + S. terebinthifolius ripe fruit blend (50/50). The evaluation of the effects on N. californicus showed the compatibility of the oils and blends with the predator mite for use in the integrated management of T. urticae. ß-Caryophyllene was the most toxic, independent of the method used. Based on toxicities of 11 oil constituents, the structure-activity relationship of these compounds is also discussed. This study showed that the acaricidal effect of the Piper, Melaleuca and Schinus oils can easily be increased by the binary combination of these oils. The binary blend between the oils of the Melaleuca leaves and ripe Schinus fruit in the greenhouse was effective at controlling the mite after 72 h, exhibiting the same level of toxicity as that found for the positive control (Vertimec 18 EC).

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RESUMO

The essential oil from the leaves of Lippia gracilis was investigated for fumigant and residual activity against Tetranychus urticae (Acari: Tetranychidae) and Neoseiulus californicus (Acari: Phytoseiidae). The results were compared to eugenol, Ortus® and Azamax®, as positive controls. Gas chromatography (GC) and GC/mass spectrometry analysis enabled the identification of 28 compounds, accounting for 99.1 ± 0.6% of the essential oil. The major constituents were carvacrol (61%), p-cymene (11%) and thymol (11%). Mites were more susceptible to the oil in fumigant tests than in residual tests. Among the components, thymol and ß-caryophyllene had the greatest fumigant and residual toxicity against T. urticae, respectively. The role of selected constituents (carvacrol, p-cymene, thymol, limonene, ß-pinene, 1,8-cineole, terpinolene and ß-caryophyllene) in the acaricidal properties of the L. gracilis essential oil is also discussed. Fumigant and residual effects of Lippia oil were more selective than eugenol with regard to a natural enemy of T. urticae, Neoseiulus californicus. Experiments under greenhouse conditions demonstrated greater toxicity of the Lippia oil in comparison to the positive control at 24, 48 and 72 h after treatment. The results suggest that Lippia oil is a good candidate for the formulation of a botanical acaricide for the integrated management of T. urticae.

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The compositions of the essential oils from unripe (UFr) and ripe (RFr) fruits of Schinus terebinthifolius were analyzed by GC and GC/MS. The major compound identified in both oils was limonene (UFr = 44.1 +/- 1.3%; RFr = 31.8 +/- 1.2%), followed by alpha-phellandrene (15.7 +/- 0.4%) in the UFr oil and thujene (21.7 +/- 0.9%) in the RFr oil. Repellent and toxicity activities of the two oils were also evaluated, and the results compared with eugenol. The UFr oil was more active in the fumigation tests (LC50 = 1.46 microL/L of air), whereas the RFr oil was more active in the sealed dishes (SD) than open dishes (OD) contact assay (LC50 = 3.04 microL/cm2) and not significantly different from eugenol. Both oils exhibited significant repellent activity comparable with that of eugenol. The results suggest that the repellent activity of these oils in association with its toxicity could be a great advantage for the integrated management of T. urticae.

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The chemical composition of the essential oils from Protium giganteum and P. aracouchine was determined, for the first time, using GC-MS analysis. From the oil of P. giganteum, 32 components were identified, representing 93.9% of the oil, and from P. aracouchine, 29 components, representing 97.8% of the oil. Among the compounds identified in the P. giganteum oil, 93.6% were sesquiterpenes, with beta-caryophyllene (26.0 +/- 0.8%), globulol (9.3 +/- 0.2%), alpha-cadinol (7.0 +/- 0.5%), alpha-humulene (6.4 +/- 0.1%) and germacrene D (6.2 +/- 0.3%) as the major components. Among the 29 compounds identified in the P. aracouchine oil, 95.9% were sesquiterpenes as well, with spathulenol (31.8 +/- 1.6%), alpha-cis-bergamotene (8.8 +/- 0.2%) and viridiflorol (9.7 +/- 0.7%) as the major components.

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The repellency and fumigant toxicities of the peel essential oils of Citrus sinensis var. pêra (LP), C. sinensis var. mimo (LM), and C. aurantium (LL) cultivated in northeast Brazil were evaluated against Tetranychus urticae. Analysis of the oils by GC and GC/MS led to the identification of twenty-eight components, which represented 99.9%, 99.7% and 99.3% of the total constituents of the LP, LM and LL oils, respectively. Limonene was the main component found in all three oils. Other main components were alpha-pinene (1.5% in LP; 1.4% in LM), myrcene (5.7% in LP; 5.9% in LM and 5.6% in LL) and linalool (2.4% in LP; 2.3% in LM and 3.9% in LL). The best repellency action was observed for LM at 2.0%, followed by LL oil and eugenol, both of them at 2.5%. The Citrus oils were less active than eugenol (LC50 = 0.004 microL/L air) and phosphine, which revealed 100% mortality at 2 x 10(-3) g/L (66.7% of the recommended dose). However, the most potent fumigant toxicity was found with LL oil, with an LC50 value of 1.63 microL/L air, followed by the oils from LM and LP with LC50 values of 2.22 microL/L air and 4.63 microL/L air, respectively. The associated fumigant and repellent properties of these Citrus peel oils, particularly those of C. aurantium and C. senensis var. mimo, could be used to advantage for the control of T. urticae.

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