Extracellular phospholipase production by Malassezia pachydermatis strains and its inhibition by selected antimycotics and plant essential oil components.

Extracellular phospholipase (EPL) plays an important role in the pathogenesis of the yeast Malassezia pachydermatis. Currently, the attention of researchers is focused on studying the virulence factors involved in this process and searching solutions to reduce their activity. One of the options is the use of natural remedies as anti-virulence agents. This study is aimed at investigating the production of extracellular phospholipase in M. pachydermatis strains (18 samples) and followed by the time-dependent inhibitory effect of selected azole antifungals (itraconazole, posaconazole and voriconazole) and plant essential oil components (terpinen-4-ol, thymol, carvacrol, eugenol and geraniol), evaluated by Egg Yolk Agar plate method. Almost all strains (17 isolates, (94.4%) were found to be intense EPL producers. A significant, time-dependent inhibition of EPL was noted after 1-, 3- and 6-h exposure of Malassezia cells to itraconazole (26.4%, 47.2% and 50.9%, respectively) compared to exposure to posaconazole (26.4%, 28.3% and 28.3%, respectively) and voriconazole (18.8%, 20.8% and 35.8%, respectively). After one-hour exposure to plant essential oil components, the best inhibitory effect was recorded for eugenol (62.3%), followed by terpinen-4-ol and thymol (56.6%), geraniol (41.5%) and carvacrol (26.4%). A 3-h exposure revealed that thymol retained the best inhibitory effect (88.7%) on EPL production, followed by carvacrol (73.6%), eugenol (56.6%), terpinen-4-ol (52.8%) and geraniol (49.1%). After 6-h exposure, no growth of M. pachydermatis strains exposed to carvacrol was observed, and the inhibitory efficiency for the other tested essential oil (EO) components achieved 88.7%. The obtained results indicate the promising efficacy of plant essential oils components in the inhibition of virulence factors such as EPL production.

Effect of Eucalyptus globulus and Ferula assafoetida essential oils and their nanoformulations on the life table parameters of Tetranychus urticae (Acari: Tetranychidae).

One of the most damaging pests of agricultural crops across the globe is the two-spotted spider mite, Tetranychus urticae Koch. A wide variety of arthropods and plant pathogens can be controlled by essential oils, which are secondary metabolites produced by plants. It is possible to enhance the stability as well as the anti-pest efficiency of plant essential oils by encapsulation. Water distillation was used to extract the essential oils from Eucalyptus globulus and Ferula assafoetida. The chitosan nanoparticles were used to load both essential oils into nanoformulations. Studies were conducted on T. urticae life table characteristics under experimental circumstances to determine the sublethal impacts of essential oils and their nanoformulations. Intrinsic growth rate (r) for population exposed to E. globulus, F. assafoetida essential oils, their nanoformulations and the control were 0.1, 0.069, 0.051, 0.018 and 0.21 per day, respectively. F. assafoetida and E. globulus nanoformulations resulted the lowest fecundity compared to the other treatments. According the result of the lethal and sublethal effects of purified essential oils and nanoformulations of F. assafoetida and E. globulus, they would be recommended for controlling the two-spotted spider mites, T. urticae.

Effects of different combinations of antibacterial compound supplements in calf pellets on growth performance, health, blood parameters, and rumen microbiome of dairy calves.

This study investigated the effects of different combinations of antibacterial compounds (attapulgite, plant essential oils, and chitosan oligosaccharides) on growth performance, blood biochemical parameters, and rumen microbiome of calves. A total of 48 preweaning calves were randomly divided into four groups (n = 12 per group), and fed the following full mixed-ration granule diets for the 67-d-feeding trial: (1) basal diet (control group); (2) basal diet +1,000 g/t attapulgite, plant essential oils, and chitosan oligosaccharide (AEOCO group); (3) basal diet +1,000 g/t attapulgite and chitosan oligosaccharide (ACO group); and (4) basal diet +1,000 g/t attapulgite and plant essential oil (AEO group). The results showed that the daily weight gain of the AEOCO and AEO groups significantly increased (p < 0.05), whereas the feed conversion ratio decreased compared with that of the control group. Among the three treatment groups, AEO group showed the most positive effect, with the diarrhea rate reduced by 68.2% compared with that of the control group. Total protein and globulin levels were lower in the AEO group than in the control group. Albumin levels were higher in the AEOCO and AEO groups than in the control group. Immunoglobulin A, immunoglobulin G, and immunoglobulin M concentrations were higher in the AEOCO group (p < 0.05) than in the control group. The interleukin-6 concentration was lower in the AEOCO and AEO groups than in the control group (p < 0.05). The Chao 1 richness and ACE indices were higher in the AEOCO group than in the control group (p < 0.05). The ACO group had a significantly lower (p < 0.05) relative abundance of Firmicutes than the control group. The relative abundance of Bacteroidetes was the lowest in the control group, whereas that of Spirochaetota and Fibrobacteriota was the highest (p < 0.05). The relative abundance of Succiniclasticum was higher in the ACO and AEO groups (p < 0.05). These findings indicate that the combination of attapulgite, plant essential oils, and chitosan oligosaccharides has ameliorative effects on the growth performance, blood parameters, and rumen microbiome of calves.

[Hologram quantitative structure-activity relationship on the gas chromatographic retention index of plant essential oil constituents].

The gas chromatography retention index (RI) is an important parameter for the identification of different types of compounds in the field of chromatographic analysis; however, the experimental collection of RI values is a extremely cumbersome process. Thus, there is an urgent need for the establishment of a simple, efficient, and accurate model for the prediction of the RI values of compounds. In this study, first, the experimental RI values for 60 plant essential oil constituents were obtained. Next, a model describing the hologram quantitative structure-activity relationship (HQSAR) between the structural properties of the essential oil constituents and their RI values was investigated and constructed. The optimal HQSAR model was established by setting the model parameters "fragment size", "fragment distinction", "hologram length" and "principal components" to "1-4", "C, Ch", "199", and "4", respectively. Finally, the predictive ability of the model was verified using external test set validation and leave-one-out cross-validation (LOO-CV). The experimental results were as follows, the root mean square error of prediction (RMSEP), predictive determination coefficient ([Formula: see text]), concordance correlation coefficient (CCC), and mean relative error (MRE) for external test set validation were 40.45, 0.984, 0.968, and 2.20%, respectively. Meanwhile, the root mean square error of cross validation (RMSECV) and MRE for LOO-CV were 72.56 and 4.17%, respectively. These findings demonstrate that the established HQSAR model has a good predictive ability and can accurately predict the RI values of plant essential oil constituents. In addition, the molecular contribution maps of the HQSAR model revealed that the RI values of aromatic compounds increase when hydroxyl groups are connected to their alkyl chains. Aliphatic compounds feature long chain alkyl groups, which can lead to an increase in RI values. The above phenomena highlight the promising application prospects of HQSAR for studying the RI values of plant essential oil constituents. Therefore, this study provides a reliable theoretical basis for predicting the RI values of other essential oil constituents.

Plant Essential Oils: Dual Action of Toxicity and Egg-Laying Inhibition on Tetranychus urticae (Acari: Tetranychidae), Unveiling Their Potential as Botanical Pesticides.

Tetranychus urticae, a prominent pest mite in strawberry and vegetable cultivation in China, has developed escalating resistance due to extensive chemical pesticide application. Consequently, there is an urgent need to identify safe and efficacious methods to reduce resistance development. In this study, 38 commercially available plant essential oils (EOs) were screened for their acaricidal potential and ability to inhibit oviposition. The findings revealed that 13 EOs exhibited notable acaricidal activity, with lemon EO demonstrating the highest toxicity, followed by sage, patchouli, frankincense, lemongrass, palmarosa, and oregano EOs. In addition, 18 EOs displayed significant inhibitory effects on oviposition, with lemon EO exhibiting the highest inhibition rate (99.15%) and inhibition index (0.98). Subsequently, sage, frankincense, clove, lemongrass, oregano, patchouli, myrrh, black pepper, palmarosa, and geranium EOs also showed inhibition rates exceeding 50%. Despite black pepper, clove, myrrh, and oregano EOs demonstrating relatively low toxicity against T. urticae, they exhibited heightened efficacy in inhibiting oviposition and suppressing population expansion. This study conducted a comparative assessment of the acaricidal and oviposition inhibition activities of EOs and their principal constituents, thus providing a theoretical basis for the development of botanical acaricides against T. urticae.

Effect of diets supplemented with coated plant essential oil on the growth performance, immunity, antioxidant activity, and fecal microbiota of weaned piglets.

Introduction: This trial was conducted to compare the effect of diets supplemented with plant essential oil (PEO) and coated plant essential oil (CEO) on growth performance, immunity, antioxidant activity, and fecal microbiota of weaned piglets. Methods: A total of 360 21-day-old weaned piglets were randomly allocated into three groups, namely, CON, PEO, and CEO (basal diets supplemented with 0, 500 mg/kg PEO, and 500 mg/kg CEO, respectively) for a 4-week feeding trial. Results and discussion: The results showed that dietary supplementation with CEO improved the average final weight and average daily gain, decreased the diarrhea rate, increased antioxidant enzyme activities, enhanced immunoglobulin concentrations, and decreased concentrations of pro-inflammatory cytokines in the serum of weaned piglets (p < 0.05). In addition, CEO addition increased the fecal concentrations of propionic acid and isovaleric acid of piglets (p < 0.05). Spearman correlation analysis showed that fecal microorganisms at the genus level were closely correlated with the volatile fatty acid concentrations. The present study indicated that PEO and CEO could improve growth performance, enhance immunity, and increase antioxidant capacity by modulating the microbial flora in weaned piglets. Moreover, CEO addition seemed to offer more positive results than of PEO addition.

Comparison of Emulsion Stabilizers: Application for the Enhancement of the Bioactivity of Lemongrass Essential Oil.

Recent focus on cellulose nanomaterials, particularly biodegradable and biocompatible cellulose nanocrystals (CNCs), has prompted their use as emulsion stabilizers. CNCs, when combined with salt, demonstrate enhanced emulsion stabilization. This study explored three emulsion stabilizers: Tween 80, soybean CNCs with salt (salted CNCs), and a combination of salted CNCs with Tween 80. Soybean CNCs, derived from soybean stover, were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Antifungal testing against Aspergillus flavus revealed increased bioactivity in all lemongrass essential oil (EO)-loaded emulsions compared to pure essential oil. In addition, all three emulsions exhibited a slight reduction in antifungal activity after 30 days of room temperature storage. The release experiment revealed that the EO-loaded nanoemulsion exhibited a slow-release profile. The nanoemulsion stabilized by salted CNCs and Tween 80 exhibited significantly lower release rates when compared to the nanoemulsion stabilized solely by Tween 80, attributed to the gel network formed by salted CNCs. The findings of this study highlight the efficacy of cellulose nanocrystals procured from soybean byproducts in conjunction with synthetic surfactants to create nanoencapsulated essential oils, resulting in improved antimicrobial efficacy and the achievement of sustained release properties.

Tea Tree Oil Improves Energy Metabolism, Non-Specific Immunity, and Microbiota Diversity via the Intestine-Hepatopancreas Axis in Macrobrachium rosenbergii under Low Fish Meal Diet Administration.

Tea tree oil (TTO) is an essential plant oil with diverse antibacterial and antioxidant properties; however, whether the role played by TTO in low fish meal (LF) diets induced the observed effects in the farmed crustaceans remains unclear. Therefore, this study used Macrobrachium rosenbergii as the model crustacean, and an 8-week feeding experiment with NF (normal fish meal), LF (soybean meal replacing 40% fish meal), and LFT (LF with 200 mg/kg TTO) diets was conducted to evaluate the positive effects of TTO under the LF diet. Compared to the NF diet, the LF diet reduced hemolymph antioxidant capacity and non-specific immunity, and induced hepatopancreas apoptosis and damage. However, in comparison with LF, LTF significantly ameliorated morphological impairment in the hepatopancreas, improved hepatopancreas energy metabolism by upregulating the Bcl-2/Bax and Akt/mTOR pathways, and enhanced antioxidant and non-specific immune capacity by activating the NF-κB/NO pathway. In addition, LFT repaired intestinal barrier injury and the imbalance of intestinal microbiota induced by the LF diet. Moreover, the Pearson correlation revealed the variations of the above indicators, which were related to the abundance changes of Klebsiella, Clostridium sensu stricto 12, Thermobifida, Bifidobacterium, and Alistipes, indicating that these microbes might serve as prospective targets for the intestine-hepatopancreas axis to affect hepatopancreas apoptosis, metabolism, and non-specific immunity. In summary, 200 mg/kg TTO supplementation mediated gut microbiota and positively improved energy metabolism and non-specific immunity, thereby alleviating hepatopancreas dysplasia and damage induced by the LF diet in M. rosenbergii.

Fumigant activity and transcriptomic analysis of two plant essential oils against the tea green leafhopper, Empoasca onukii Matsuda.

Introduction: The tea green leafhopper, Empoasca (Matsumurasca) onukii Matsuda, R., 1952 (Hemiptera: Cicadellidae), is currently one of the most devastating pests in the Chinese tea industry. The long-term use of chemical pesticides has a negative impact on human health, impeding the healthy and sustainable development of the tea industry in this region. Therefore, there is a need for non-chemical insecticides to control E. onukii in tea plants. The essential oils from plants have been identified for their potential insecticidal ability; however, there is a lack of knowledge regarding the effect of plant essential oils on E. onukii and its gene expression. Methods: In order to address these knowledge gaps, the components of Pogostemon cablin and Cinnamomum camphora essential oils were analyzed in the present study using gas chromatography-mass spectrometry. The fumigation toxicity of two essential oils on E. onukii was tested using sealed conical flasks. In addition, We performed comparative transcriptome analyses of E. onukii treated with or without P. cablin essential oil. Results: The 36-h lethal concentration (LC50) values for E. onukii treated with P. cablin and C. camphora essential oils were 0.474 and 1.204 µL mL-1 respectively. Both essential oils exhibited the potential to control E. onukii, but the fumigation activity of P. cablin essential oil was more effective. A total of 2,309 differentially expressed genes were obtained by transcriptome sequencing of E. onukii treated with P. cablin essential oil. Conclusion: Many of differentially expressed genes were found to contain detoxifification genes, indicating that these families may have played an important role when E. onukii was exposed to essential oil stress. We also found differential expression of genes related to redox-related gene families, suggesting the upregulation of genes associated with possible development of drug and stress resistance. This work offers new insights for the prevention and management of E. onukii in the future.

The efficient activity of plant essential oils for inhibiting Botrytis cinerea and Penicillium expansum: Mechanistic insights into antifungal activity.

Botrytis cinerea and Penicillium expansum produce deterioration in fruit quality, causing losses to the food industry. Thus, plant essential oils (EOs) have been proposed as a sustainable alternative for minimizing the application of synthetic fungicides due to their broad-spectrum antifungal properties. This study investigated the efficacy of five EOs in suppressing the growth of B. cinerea and P. expansum and their potential antifungal mechanisms. EOs of Mentha × piperita L., Origanum vulgare L., Thymus vulgaris L., Eucalyptus globules Labill., and Lavandula angustifolia Mill., were screened for both fungi. The results showed that the EO of T. vulgaris and O. vulgare were the most efficient in inhibiting the growth of B. cinerea and P. expansum. The concentration increase of all EO tested increased fungi growth inhibition. Exposure of fungi to EOs of T. vulgaris and O. vulgare increased the pH and the release of constituents absorbing 260 nm and soluble proteins, reflecting membrane permeability alterations. Fluorescence microscopic examination revealed that tested EOs produce structural alteration in cell wall component deposition, decreasing the hypha width. Moreover, propidium iodide and Calcein-AM stains evidenced the loss of membrane integrity and reduced cell viability of fungi treated with EOs. Fungi treated with EOs decreased the mitochondria activity and the respiratory process. Therefore, these EOs are effective antifungal agents against B. cinerea and P. expansum, which is attributed to changes in the cell wall structure, the breakdown of the cell membrane, and the alteration of the mitochondrial activity.

Fumigant toxicity and behavioral alterations of six plant essential oils against the red fire ant (Solenopsis invicta Buren).

The red imported fire ant (RIFA), Solenopsis invicta Buren (Hymenoptera: Formicidae), is an invasive species that is considered to be among the 100 most dangerous species to human health and the environment. RIFA is currently controlled primarily by chemical insecticides. However, human health concerns and environmental problems require environment friendly, green insect pest control technology. In this study, the HS-SPME-GC/MS method was used to determine the volatile components of six essential oils, namely Illicium verum Burm, Blumea balsamifera (L.) DC., Citrus limon Burm, Acorus tatarinowii Schott, Mosla chinensis Maxim, and Cinnamomum cassia Presl, as well as their fumigation activity against RIFA. D-Limonene was identified as a core volatile in all six essential oils. The effects of volatile substances from essential oils on the fumigation activity and behavior of RIFA workers were studied by closed fumigation method. Except for C. limon essential oil, all other five plant essential oils exhibit excellent fumigation activity under the treatment of a concentration at 10 µL/ cm3 within 24 h. All plant essential oils are capable of causing the death of all red fire ants, while C. limon essential oil exhibited the lowest fumigation activity at 63.25%. Significant reductions in RIFA aggregation, aggressiveness, and gripping abilities were observed with all plant essential oils, and antenna sensilla appeared to bend or break. Moreover, after treating red ant fire ants with essential oil for 24 h, three protective enzyme activities were assessed. All six plant essential oils were shown to have enhanced enzyme activities for superoxide dismutase (SOD), glutathione S-transferase (GST), and catalase (CAT). It has been shown that plant essential oils have the capability of reducing the viability of red fire ants via receptor and behavioral factors, ultimately causing them to die off. As a conclusion, plant oils were demonstrated to be negatively affecting RIFA and providing a green and environmentally sustainable control method in this study.

Vapours from plant essential oils to manage tomato grey mould caused by Botrytiscinerea.

Tomato grey mould has been a great concern during tomato production. The in vitro antifungal activity of vapours emitted from four plant essential oils (EOs) (cinnamon oil, fennel oil, origanum oil, and thyme oil) were evaluated during in vitro conidial germination and mycelial growth of Botrytis cinerea, the causal agent of grey mould. Cinnamon oil vapour was the most effective in suppressing conidial germination, whereas the four EOs showed similar activities regarding inhibiting mycelial growth in dose-dependent manners. The in planta protection effect of the four EO vapours was also investigated by measuring necrotic lesions on tomato leaves inoculated by B. cinerea. Grey mould lesions on the inoculated leaves were reduced by the vapours from cinnamon oil, origanum oil and thyme oil at different levels, but fennel oil did not limit the spread of the necrotic lesions. Decreases in cuticle defect, lipid peroxidation, and hydrogen peroxide production in the B. cinerea-inoculated leaves were correlated with reduced lesions by the cinnamon oil vapours. The reduced lesions by the cinnamon oil vapour were well matched with arrested fungal proliferation on the inoculated leaves. The cinnamon oil vapour regulated tomato defence-related gene expression in the leaves with or without fungal inoculation. These results suggest that the plant essential oil vapours, notably cinnamon oil vapour, can provide eco-friendly alternatives to manage grey mould during tomato production.

Complex of Lauric Acid Monoglyceride and Cinnamaldehyde Ameliorated Subclinical Necrotic Enteritis in Yellow-Feathered Broilers by Regulating Gut Morphology, Barrier, Inflammation and Serum Biochemistry.

This experiment investigated the benefits of plant essential oil (EO) composed with lauric acid monoglyceride and cinnamaldehyde on necrotic enteritis-challenged broilers. A total of 180 1-day-old healthy yellow-feathered broilers were randomly divided into 4 groups with 3 replicates of 15 chicks each. The experimental groups were as follows: the control group (CON) was fed with the basal diet and was not challenged by Eimeria acervulina (EA) and Clostridium perfringens (CP); CPEA group was also fed with a basal diet, but infected with CP and EA; CPEA_EO350 group and CPEA_EO500 group were fed with a basal diet supplemented with 350 and 500 mg/kg EO, respectively, and all infected with CP and EA. On the 7th day, each bird in the CPEA group, CPEA_EO350 group and CPEA_EO500 group was orally administrated with 1 mL Eimeria acervulina containing 5000 oocytes/mL, and the birds of the CON group were orally administrated with 1 mL normal saline. From the 15th day, 1 mL of CP type A CVCC-2030 strain (about 5 × 108 cfu/mL) was orally inoculated into each bird of the CPEA, CPEA_EO350 and CPEA_EO500 groups for three consecutive days. Similarly, the CON group was orally given 1 mL of normal saline. The CPEA stimulation reduced the average daily gain (ADG) of broilers, increased the feed-to-gain ratio (F:G), and increased the intestinal lesions of the broilers (p < 0.01), indicating that CPEA stimulation was clinically successful. Compared with the CPEA group, the ADG of CPEA_EO350 and CPEA_EO500 increased, the F:G decreased (p < 0.01), and the intestinal score of CPEA_EO500 decreased (p < 0.01). The expression of the tight junction protein of the jejunum and ileum on 21d was upregulated (p < 0.01), and the expression of jejunum inflammation factors TNF-α on 21d and jejunum and ileum inflammatory factor IL-6 on 28d were also downregulated. The CPEA_EO350 and CPEA_EO500 increased antioxidant capacity. To sum up, 350 and 500 mg/kg of lauric acid monoglyceride and cinnamaldehyde complex plant essential oils can improve ADG and F:G, improve intestinal morphology and the body's antioxidant capacity, and downregulate the expression of inflammatory factors. The concentration of 500 mg/kg performed even better.

Synergistic modes of interaction between the plant essential oils and the respiratory blocker chlorfenapyr.

Plant essential oils are widely acknowledged for their insecticidal activities and synergistic interaction with conventional insecticides, but their insecticidal modes of action and the mechanism of synergy remain less understood. In this study, electrophysiological screenings on the larval central nervous system (CNS) of the common fruit fly, Drosophila melanogaster, and the housefly, Musca domestica, were conducted to identify the neurophysiological effects of the oils and their major constituents. Several oils changed the firing rate of the central motor neurons, and four oils were selected to determine their major active compounds. Eugenol and thymol (87.2% and 31.1% in clove bud and thyme oils, respectively) were inhibitory to the nerve firing rates of the CNS, and exhibited synergistic toxicity to the housefly when blended with a respiratory blocking pyrrole insecticide, chlorfenapyr. On the other hand, trans-cinnamaldehyde and terpinen-4-ol (74.6% and 52.0% in cinnamon and teatree oils) seemed excitatory to the nerves, and displayed antagonistic interaction to chlorfenapyr in their insecticidal activity. Chlorfenapyr led to ATP depletion in the insects, and the inhibitory compounds accelerated the process. On the other hand, nerve-excitatory compounds seemed to nullify the depletion. This was further confirmed with the two CNS-excitatory synthetic insecticides, permethrin and chlorpyrifos, that they exhibited antagonistic toxicity when mixed with chlorfenapyr. Meanwhile, the synergy between the inhibitory compounds and chlorfenapyr was diminished when ATP was artificially injected, indicating that the bioenergetic effects of neuroinhibitors are responsible for their synergistic interactions.

Co-treatment with Origanum Oil and Thyme Oil Vapours Synergistically Limits the Growth of Soil-borne Pathogens Causing Strawberry Diseases.

Vapours from origanum oil (O) and thyme oil (T) were applied to the four soil-borne strawberry pathogens Fusarium oxysporum f. sp. fragariae, Colletotrichum fructicola, Lasiodiplodia theobromae, and Phytophthora cactorum, causing Fusarium wilt, anthracnose, dieback, and Phytophthora rot, respectively. Increasing T vapour doses in the presence of O vapour strongly inhibited mycelial growths of the four pathogens and vice versa. When mycelia of F. oxysporum f. sp. fragariae and P. cactorum exposed to the combined O + T vapours were transferred to the fresh media, mycelial growth was restored, indicating fungistasis by vapours. However, the mycelial growth of C. fructicola and L. theobromae exposed to the combined O + T vapours have been slightly retarded in the fresh media. Prolonged exposure of strawberry pathogens to O + T vapours in soil environments may be suggested as an alternative method for eco-friendly disease management.

Preparation Process Optimization and Performance Characterization of Feed Plant Essential Oil Microcapsules.

The exploration of safe antibiotic substitutes is one of the research hotspots in animal husbandry. Adding suitable plant essential oils into feed could improve the growth performance and immune capacity of animals. In order to make plant essential oil play a better role in feed application, sodium alginate and chitosan were used as the wall materials, and blended plant essential oils (BEO) as the core material to prepare BEO microcapsules by the sharp-hole condensation method. On the basis of single-factor experiments, the optimal preparation conditions for BEO microcapsules were obtained by response surface experiments. The physicochemical properties were characterized and analyzed by Fourier-transform infrared spectroscopy (FTIR) and field scanning electron microscope (FSEM). Meanwhile, the release mechanism was studied by simulating a gastrointestinal sustained-release experiment. The results showed that under the optimal preparation conditions, the encapsulation efficiency of BEO microcapsules could reach 80.33 ± 2.35%. FTIR and SEM analysis displayed that the microcapsules obtained had uniform color and size and a complete and compact structure. In vitro study indicated that the release amount of BEO microcapsules in the simulated intestinal fluid is higher than that in the simulated intestinal fluid, which was consistent with animal digestive and absorptive characteristics.

Anesthetic and sedative efficacy of essential oil of Hesperozygis ringens and the physiological responses of Oreochromis niloticus after biometric handling and simulated transport.

This study aimed to evaluate different concentrations of the essential oil of Hesperozygis ringens (EOHR) and its effects on anesthesia and transport of Oreochromis niloticus. Experiment I evaluated the concentrations of 0, 150, 300, 450, and 600 µL L-1 EOHR for times of induction and recovery from anesthesia and ventilatory frequency (VF) of O. niloticus (26 g), with 10 repetitions each in a completely randomized design. Based on the results of Experiment I, Experiment II submitted fish (25 g) to three treatments-control (clean water), ethanol (5 mL ethyl alcohol), and 600 µL L-1 EOHR-and then handling for biometry. Blood was collected 1 and 24 h after exposure and handling to analyze hematological and biochemical parameters in a completely randomized design in a factorial arrangement (3 × 2). Experiment III submitted fish (35 g) to simulated transport (4.5 h) with 0, 10, or 20 µL L-1 EOHR and determined the effects on blood variables. Concentrations of 450 and 600 µL L-1 EOHR provoked deep anesthesia in juvenile O. niloticus and provided induction and recovery times within the limits considered ideal for fish. However, this essential oil was not able to attenuate the effects of stress caused by biometric handling. EOHR was able to attenuate the effects of stress from simulated transport, with 10 µL L-1 EOHR being responsible for causing a decrease in protein, triglycerides, and cholesterol values immediately after transport of O. niloticus.

Research on the Bioactivity of Plant Essential Oils on Armyworm [Mythimna separata (Walker)] Larvae.

In order to find out the biological activity of plant essential oils on armyworm [Mythimna separata (Walker, 1865)] larvae and provide a theoretical basis for the biological control of armyworms, in this study, the antifeedant activity, repellent activity, fumigation activity, contact activity, and synergistic effect on indoxacarb of nine kinds of plant essential oils on armyworm larvae were determined. The results showed that lavender and citronella essential oils had the greatest impact on the antifeedant activity on armyworm larvae, and the antifeedant rate reached 100.00%. Meanwhile, rosemary essential oil revealed the best repellent activity on armyworm larvae with an average dwell time of 0 s at the content of 0.2%. Moreover, tea tree essential oil and lemon essential oil at the content of 2.0% had the best fumigation and contact activity against armyworm larvae, and the corrected mortality rates at 120 h were 86.67 and 66.67%, respectively. In addition, the combination of citronella essential oil and indoxacarb with the ratio of 5:1 had the best synergistic effect on armyworm larvae at 96 h, and the synergistic ratio was reached 100.00%. These findings will guide the development of new insecticides for controlling armyworm larvae.

Guaiacol as a natural melanin biosynthesis inhibitor to control northern corn leaf blight.

BACKGROUND: The natural 1,8-dihydroxynaphthalene (DHN) melanin biosynthesis inhibitors (MBIs) are one of the promising approaches to the integrated management of plant diseases but have received scarce attention until now. Herein, to explore the natural DHN MBIs used in the control of northern corn leaf blight (NCLB), a library of 53 essential oil compounds was used to screen the MBIs against Exserohilum turcicum, the causal pathogen of NCLB, using tricyclazole as a reference compound. RESULTS: The results of morphological change in the colony, thermogravimetric analysis, ultraviolet-visible spectroscopy, and transmission electron microscopy confirmed that guaiacol could effectively inhibit the melanin production at 50 µg/mL under in vitro conditions. The in vitro bioassay results indicated that this inhibition effect was concentration-dependent and the minimum inhibition concentration of guaiacol was 50 µg/mL. The in vivo experimental results demonstrated that guaiacol significantly inhibited appressorium formation and penetration on corn leaf sheaths at the concentration of 500 µg/mL. The pot experiment results revealed that there were no differences between guaiacol (500 µg/mL) and tricyclazole (100 µg/mL) in control efficacy. The enzymatic assay suggested that guaiacol might exert the activity through inhibiting DHN polymerization to form melanins, which was distinct from tricyclazole. CONCLUSIONS: Taken together, this study screened out guaiacol as a natural MBI from 53 essential oil compounds and verified its effectiveness in the control of NCLB at 500 µg/mL. Above all, this research opened an avenue for exploring natural DHN MBIs in the integrated management of plant diseases. © 2022 Society of Chemical Industry.

Antifungal activities and mechanisms of trans-cinnamaldehyde and thymol against food-spoilage yeast Zygosaccharomyces rouxii.

Due to hydrophobicity, plant essential oil components trans-cinnamaldehyde and thymol exert broad-spectrum antimicrobial activities by interfering with the structures and functions of microbial cell membranes, yet their antifungal properties against food-spoilage yeast Zygosaccharomyces rouxii are still unclear. This work aimed to elucidate their antifungal activities and mechanisms against Z. rouxii. Minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were measured using broth dilution method to evaluate the antifungal activities. Membrane permeability, potential and integrity, intracellular ATP content, and intracellular pH (pHin ) were determined, and membrane damage was observed by scanning electron microscope (SEM) to investigate the antifungal mechanisms. The MICs of trans-cinnamaldehyde and thymol were 0.3125 and 0.0625 mg/ml, respectively, and the MFCs were 1.25 and 0.125 mg/ml, respectively. Increased membrane permeability, membrane hyperpolarization, decreased membrane integrity, reduced intracellular ATP content, and lowered pHin were found after trans-cinnamaldehyde or thymol treatment at the MIC and MFC levels, and thymol exhibited more severe influence on cell membrane. SEM observation further confirmed that trans-cinnamaldehyde caused cell membrane shrinkage and invagination, while thymol resulted in perforation in cell membrane. These results suggest that trans-cinnamaldehyde and thymol exert anti-Z. rouxii activities by inducing cell membrane damage and subsequent intracellular homeostasis disruption. Cellular contents leakage and intracellular homeostasis disruption probably proceed more rapidly after thymol inducing perforation in the cell surface, thereby thymol exerting better anti-Z. rouxii activity. PRACTICAL APPLICATION: The addition of a small amount of thymol (0.125 mg/ml) is sufficient to effectively inhibit the growth of Z. rouxii in apple juice concentrate. Based on our previous work, the addition of thymol (0.125 mg/ml) in apple juice concentrate did not significantly affect the organoleptic property of the diluted apple juice (5°Brix) used for producing commercial apple juice products. Therefore, thymol is practical for application at the effective concentration (0.125 mg/ml) in apple juice concentrate.