Essential Oil Exposure Research Articles

Odorant Binding Protein C17 Contributes to the Response to Artemisia vulgaris Oil in Tribolium castaneum.

The red flour beetle, Tribolium castaneum (T. castaneum), generates great financial losses to the grain storage and food processing industries. Previous studies have shown that essential oil (EO) from Artemisia vulgaris (A. vulgaris) has strong contact toxicity to larvae of the beetle, and odorant-binding proteins (OBPs) contribute to the defense of larvae against A. vulgaris. However, the functions of OBPs in insects defending against plant oil is still not clear. Here, expression of one OBP gene, TcOBPC17, was significantly induced 12–72 h after EO exposure. Furthermore, compared to the control group, RNA interference (RNAi) against TcOBPC17 resulted in a higher mortality rate after EO treatment, which suggests that TcOBPC17 involves in the defense against EO and induces a declining sensitivity to EO. In addition, the tissue expression profile analysis revealed that the expression of TcOBPC17 was more abundant in the metabolic detoxification organs of the head, fat body, epidermis, and hemolymph than in other larval tissue. The expression profile of developmental stages showed that TcOBPC17 had a higher level in early and late adult stages than in other developmental stages. Taken together, these results suggest that TcOBPC17 could participate in the sequestration process of exogenous toxicants in T. castaneum larvae.

Transcriptome Profiling of the Potato Exposed to French Marigold Essential Oil with a Special Emphasis on Leaf Starch Metabolism and Defense against Colorado Potato Beetle.

Flower strips of French Marigold are commonly used pest repellents in potato fields. However, the effect of French Marigold volatiles on potato metabolism, physiology and induced defense is unknown. Thus, a microarray transcriptome analysis was performed to study the effects of French Marigold essential oil (EO) on laboratory-grown potato. After 8 h of exposure to EO, with gas chromatography/mass spectrometry (GC/MS)-detected terpinolene and limonene as dominant compounds, 2796 transcripts were differentially expressed with fold change >2 compared to expression in controls. A slightly higher number of transcripts had suppressed expression (1493 down- vs. 1303 up-regulated). Since transcripts, annotated to different photosynthesis-related processes, were mostly down-regulated, we selected a set of 10 genes involved in the leaf starch metabolism pathway, and validated microarray patterns using quantitative reverse transcription polymerase chain reaction (RT-qPCR). Except for decreased synthesis and induced decomposition of starch granule in leaves, 8 h long EO exposure slightly elevated the accumulation of sucrose compared to glucose and fructose in subjected potato plants. An in vitro feeding bioassay with Colorado potato beetle showed that EO-induced alternations on transcriptional level and in the sugars’ metabolism caused the enhancement of feeding behavior and overall development of the tested larvae. Results of comprehensive analysis of transcriptional responses in potato exposed to French Marigold EO provide a basis for further elucidation of molecular mechanisms underlying eco-physiological interactions in companion planting cropping systems.

Carlina acaulis and Trachyspermum ammi essential oils formulated in protein baits are highly toxic and reduce aggressiveness in the medfly, Ceratitis capitata

Essential oil (EO)-based botanical insecticides are considered a promising option for Integrated Pest Management (IPM). However, the sublethal effects of EO-based insecticides are understudied. No information is available on the potential effects of EO exposure on insect aggressive traits. In this study, the toxicity of two EOs with documented efficacy on insect vectors and agricultural pests, and which were obtained from the roots of silver thistle (Carlina acaulis L., Asteraceae) and seeds (i.e. schizocarps) of ajwain (Trachyspermum ammi (L.) Sprague, Apiaceae), was evaluated against adults of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (medfly), a cosmopolitan frugivorous pest. Both EOs were formulated in a mucilaginous solution containing sucrose and hydrolyzed proteins, suitable for "attract and kill" tests. After testing the EO ingestion toxicity on medflies, lethal concentrations LC10, and LC30 were calculated. Behavioral tests were carried out to assess the effect of EO feeding on the medfly aggressive traits. Both EOs formulated in protein baits showed promising insecticidal activity on medflies. Lethal concentrations 50 (LC50) of C. acaulis and T. ammi EOs were 1094 ppm and 3963 ppm, respectively. Medflies fed on protein baits treated with EO LC10 and LC30 showed a significant reduction in the overall abundance of aggressive interactions at the population level, as well as shorter aggression duration over control flies. Concerning aggression scores, no differences were found between treated and control flies. This study underlines the promising potential of C. acaulis and T. ammi EOs for the development of eco-friendly formulations to be used in medfly “attract and kill” approaches. It also outlined how exploiting food sources contaminated by low EO concentrations can strongly impact medfly aggressiveness, which is of key importance for the successful reproduction of this important fruit pest.

Chemical characterization, phytotoxic, and cytotoxic activities of essential oil of Mentha longifolia.

The present study assessed the phytotoxic and cytotoxic potential of the essential oil (EO) extracted from aboveground parts of Mentha longifolia (L.) Huds. Gas chromatography-mass spectrometry revealed 39 compounds constituting 99.67% of the EO. The EO was rich in monoterpenoids (mostly oxygenated monoterpenes), which accounted for 89.28% of the oil. The major components in EO were monoterpene ketones such as piperitone oxide (53.83%) and piperitenone oxide (11.52%), followed by thymol (5.80%), and (E)-caryophyllene (4.88%). The phytotoxic activities of EO were estimated against Cyperus rotundus, Echinochloa crus-galli, and Oryza sativa (rice) through pre- and post-emergence assays at concentrations ranging from 10 to 250μg/ml and 0.5-5%, respectively. In pre-emergence assay, the phytotoxic effect of EO was most pronounced on C. rotundus, thereby significantly affecting percent germination, plantlet growth, and chlorophyll content. On the contrary, the impact was comparatively lesser on rice, with ~ 40% germination in response to 250μg/ml of EO treatment. In the post-emergence assay, the spray treatment of EO caused a loss of chlorophyll and wilting in test plants, and subsequently affected the growth of plants, even leading to death in some cases. The cytotoxic activity of EO (at 2.5-50μg/ml) was studied in meristem cells in onion (Allium cepa L.) root tips. EO exposure to the onion roots induced various chromosomal aberrations such as chromosomal bridges, c-mitosis, stickiness, vagrant chromosomes, etc., and negatively affected the mitotic index. At 50μg/ml, EO treatment triggered the complete death of roots. The study concludes that M. longifolia EO has phytotoxic activities due to the mito-depressive effect, along with other physiological effects on target plants. Therefore, EO of M. longifolia could be developed into a novel bioherbicide for sustainable management of weeds in agricultural systems.

Chemical profiling, cytotoxicity and phytotoxicity of foliar volatiles of Hyptis suaveolens

In the present study, the essential oil (EO) of Hyptis suaveolens has been explored for the first time for its phytotoxic and cytotoxic activities. The phytotoxic activity was assessed against rice (Oryza sativa) and its major troublesome weed, Echinochloa crus-galli, under laboratory and screenhouse conditions. GC-MS analysis revealed EO to be monoterpenoid (~ 79% monoterpenes) in nature with α-phellandrene (22.8%), α-pinene (10.1%) and limonene (8.5%) as the major chemical constituents. The laboratory bioassay showed a complete growth inhibitory effect of EO (≥ 2 mg mL−1) towards the germination and seedling growth of E. crus-galli. However, the inhibitory effect on rice was much less (~40% inhibition). EO caused visible injury, reduction in chlorophyll content, cell viability and ultimately led to complete wilting of E. crus-galli plants. In addition, EO altered the cell division in the meristematic cells of Allium cepa as depicted by ~63% decrease in mitotic index. EO exposure induced several aberrations at chromosomal (c-mitosis, anaphase bridges, chromosomal breakage, vagrant chromosomes, and sticky chromosomes) and cytological level (cytoplasm destruction, peripheral nuclei, and bi-nucleate cells). The present study concludes that H. suaveolens EO possesses phytotoxic activity due to its mito-depressive activity, and could serve as a natural herbicide under sustainable agricultural practices.

Penicillium expansum Inhibition on Bread by Lemongrass Essential Oil in Vapor Phase

The antimicrobial activity of lemongrass (Cymbopogon citratus) essential oil (EO) in the vapor phase on the growth of Penicillium expansum inoculated on bread was evaluated, followed by a sensory evaluation of the bread's attributes after EO exposure. The lemongrass EO was extracted from dry leaves of lemongrass by microwave-assisted steam distillation. The chemical composition of the lemongrass EO was determined using a gas chromatograph coupled to a mass spectrometer. The refractive index and specific gravity of the EO were also determined. Bread was prepared and baked to reach two water activity levels, 0.86 or 0.94, and then 10 μL of P. expansum spore (106 spores per mL) suspension was inoculated on the bread surface. Concentrations of lemongrass EO were tested from 125 to 4,000 μL/Lair, whereas mold radial growth was measured for 21 days. For sensory evaluation, breads were treated with lemongrass EO vapor at 0, 500, or 1,000 μL/Lair for 48 h and tested by 25 untrained panelists. The EO yield was 1.8%, with similar physical properties to those reported previously. Thirteen compounds were the main components in the EO, with citral being the major compound. P. expansum was inhibited for 21 days at 20°C with 750 μL of EO/Lair, and its inhibition increased with increasing concentrations of EO. Sensory acceptance of bread exposed to vapor concentrations of 500 or 1,000 μL of EO/Lair or without EO was favorable; similar and no significant differences (P > 0.05) were observed among them.

Chemical composition of Piper gaudichaudianum essential oil and its bioactivity against Lucilia cuprina (Diptera: Calliphoridae)

Piper gaudichaudianum grows abundantly throughout the Brazilian Atlantic Forest. Essential oil extracted from this species has been reported to have larvicidal properties. The aim of the study was to characterize the essential oil (EO) of P. gaudichaudianum and its insecticide activity on the third instar larvae (L3) of Lucilia cuprina under laboratory conditions. Groups of 20 L3 were placed on filter paper impregnated with increasing concentrations of 2.5–30% (v/v), equivalent to 0.39–4.77 μL/cm2, solubilized in ethanol or acetone. The toxicity was determined by L3 mortality after 6, 24 and 48 h after contact. P. gaudichaudianum EO was also characterized using CG/MS. Lethal concentrations of 50% (LC50) 24 and 48 h after EO exposure were found to be 3.69 and 2.19 when solubilized in ethanol and 9.14 and 6.05 μL/cm2 when solubilized in acetone, respectively. The major compounds were germacrene B, δ-cadinene, γ-elemene, (Z)-cariophyllene, α-copaene, (E)-cariophyllene, α-calacorene, α-humulene and (E)-nerolidol. The study demonstrated the significant biological activities of P. gaudichaudianum EO (PGEO) compounds against L. cuprina.

Anesthesia of Epinephelus marginatus with essential oil of Aloysia polystachya: an approach on blood parameters.

This study investigated the anesthetic potential of the essential oil (EO) of Aloysia polystachya in juveniles of dusky grouper (Epinephelus marginatus). Fish were exposed to different concentrations of EO of A. polystachya to evaluate time of induction and recovery from anesthesia. In the second experiment, fish were divided into four groups: control, ethanol and 50 or 300 µL L-1 EO of A. polystachya, and each group was submitted to induction for 3.5 min and recovery for 5 or 10 min. The blood gases and glucose levels showed alterations as a function of the recovery times, but Na+ and K+ levels did not show any alteration. In conclusion, the EO from leaves of A. polystachya is an effective anesthetic for dusky grouper, because anesthesia was reached within the recommended time at EO concentrations of 300 and 400 µL L-1. However, most evaluated blood parameters showed compensatory responses due to EO exposure.

Effects of long-term exposure of lemon essential oil odor on behavioral, hormonal and neuronal parameters in male and female rats

Behavioral, hormonal and neuronal responses to prolonged exposure to the volatile components of essential oil (EO) extracted from citrus lemon were investigated in male and female rats. Animals were exposed to the lemon essence for 2 weeks while in their cage. Anxiety was then determined with the elevated plus-maze apparatus while nociception was evaluated with a phasic thermal pain stimulus (plantar test) and with a chemical pain stimulus (formalin test). At the end of the experimental sessions, brain areas were dissected to measure β-endorphin (β-EP) concentrations in the hypothalamus and periaqueductal gray matter (PAG). Blood samples were collected to determine corticosterone plasma levels. In both sexes, prolonged EO exposure decreased the time spent in the open arms of the plus-maze apparatus. EO-exposed males and females showed higher thermal nociceptive thresholds than controls when tested with the plantar test apparatus. EO exposure induced female-specific decreases in formalin-induced pain behaviors during the formalin test. β-EP concentrations in the hypothalamus and PAG were affected by EO. Corticosterone was lower in EO-exposed animals of both sexes than in their controls. These results suggest that long-term exposure to lemon EO can induce significant, at times sex-specific, changes in neuronal circuits involved in anxiety and pain.