No abstract

The Essential Oils (EOs) from the leaves of species Cinnamomum verum J. Presl are used in the pharmaceutical industry for their numerous biological activities. Currently, the main compound of C. verum EO is eugenol which has acaricidal activity; however, a rare chemotype with benzyl benzoate as the main component can be found. Benzyl benzoate is recognized as an acaricide; however, studies of the C. verum EOs benzyl benzoate chemotype on Rhipicephalus microplus were not reported. The aim of this study was to evaluate the acaricide activity of an EO from a rare chemotype of C. verum, as well as purified benzyl benzoate, against larvae and engorged females of R. microplus resistant to amidines and pyrethroids. The EO was extracted from C. verum leaves and the compounds present were identified using a gas phase chromatograph coupled to a mass spectrometer. Efficacy against R. microplus was assessed by the larval packet and the engorged female immersion tests. A rare chemotype of C. verum was found to produce EOs with benzyl benzoate (65.4%) as the main compound. The C. verum essential oil was 3.3 times more efficient on the R. microplus larvae than was benzyl benzoate. However, no differences were found on the R. microplus engorged females. This is the first report regarding the acaricidal activity of C. verum with chemotype benzyl benzoate, and this compound showed acaricidal activity on R. microplus larvae.

Some aromatic plants such as Thymbra capitata, Origanum vulgare, and Calamintha baetica are used in some Portuguese traditional meat dishes, particularly in rabbit meat, tomato salads, fish food, escargot, and olives. In the present work, the antioxidant ability of the essential oils extracted from T. capitata, O. vulgare, C. baetica, and Th. mastichina cultivated in a field of the Regional Direction of Agriculture of Algarve (Portugal) was studied. The oils, extracted by hydrodistillation, were analysed by gas chromatography and gaschromatography coupled to mass spectrometry. The antioxidant activity was determined using a modified thiobarbituric acid-reactive substances (TBARS) method, measuring the scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical method, determining the reducing power method, and monitoring the chelating effect on ferrous ions method. The results showed that the oils from O. vulgare and T. capitata had practically the same capacity of preventing the lipid oxidation of those of BHT and BHA. T. capitata oil was the most effective for the scavenging effect on DPPH as any capacity for this effect was practically absent in the oils of Th. mastichina and C. baetica. These results can be explained by the relative high concentrations of phenol compounds in those plants. The essential oil isolated from C. baetica possessed the best ability of chelating ferrous ions, something practically inexistent in the remaining other plant samples and the BHT and BHA. The reducing power of the essential oils was much lower than those observed for the synthetic antioxidants, nevertheless among the oils, those from O. vulgare and T. capitata were the most effective. The chelating effect of the C. baetica oil can be used as a synergistic antioxidant, that is, this oil can be used together with a phenolic antioxidant in the food product, but at lower levels.

The fall armyworm, Spodoptera frugiperda, causes damage at several stages of the maize crop cycle. Due to its resistance to synthetic insecticides and the high costs of pest control, there is an ever-increasing amount of research on alternative or complementary products that have a minor environmental and financial impact on agriculture. Therefore, the aim of this study was to evaluate the chemical composition and insecticidal potential of Ocimum gratissimum (african basil) leaves essential oil and the effect of its major component, thymol, on S. frugiperda control. Gas Chromatography (GC) and Gas Chromatography-Mass Spectrometry (GC-MS) analysis identified p-cymene, γ-terpinene, and thymol compounds as the main constituents of the oil, which presented a yield of 4.75%. Among the 30 identified compounds, thymol (33.2%) was the major constituent, representing 97.8% of the total oil. The efficacy of both the oil and thymol standard (Sigma-Aldrich) was evaluated against S. frugiperda using topical acute toxicity and contact surface tests at different concentrations. The oil was more active than thymol standard, with topical acute toxicity of LD50 at 0.020 μl/insect and LC50 at 0.171 μl/cm2 for contact surface toxicity. The oil proved to be superior to the thymol standard, offering an effective and promising alternative for the control of S. frugiperda, which is most likely due to the contribution of other oil components that acted synergistically. Consequently, this result provides an opportunity for further study and the development of an effective fall armyworm control system.

No abstract