Protective mechanisms of neral as a plant-derived safener against fenoxaprop-p-ethyl injury in rice

BACKGROUND

The use of herbicide safeners effectively minimises crop damage while maintaining the full efficacy of herbicides. The present study aimed to assess the potential protective effects of neral (NR) as a safener, in order to mitigate injury caused by fenoxaprop-p-ethyl (FE) on rice.

RESULTS

The alleviating effect of NR was similar to that of the safener isoxadifen-ethyl (IE). The root elongation of rice was significantly promoted under the FE + NR and FE + IE treatments, as compared to the FE treatment. The transcriptome analysis further suggested that the effects of NR treatment on plant metabolic pathways differed from those of IE treatment. In total, 895 and 47 up-differentially expressed genes induced by NR (NR-inducible genes) and IE (IE-inducible genes) were identified. NR-inducible genes were mainly enriched in phytohormone synthesis and signalling response, including 'response to brassinosteroid', 'response to jasmonic acid', 'response to ethylene', 'brassinosteroid metabolic process', 'brassinosteroid biosynthesis' and 'plant hormone signal transduction'. In contrast, IE-inducible genes were predominantly enriched in glutathione metabolism. The activity of glutathione S-transferase was found to be increased after IE treatment, whereas no significant increase was observed following NR treatment. Moreover, several transcription factor genes, such as those encoding AP2/ERF-ERF and (basic helix-loop-helix) bHLH were found to be significantly induced by NR treatment.

CONCLUSION

This is the first report of the utilisation of NR as an herbicide safener. The results of this study suggest the toxicity of FE to rice is mitigated by NR through a distinct mechanism compared to IE. © 2023 Society of Chemical Industry.

Safety and efficacy of a feed additive consisting of an essential oil derived from the aerial parts of Cymbopogon flexuosus (Nees ex Steud.) Will. Watson (lemongrass oil) for use in all animal species (FEFANA asbl)

Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety and efficacy of lemongrass oil obtained from the aerial parts of Cymbopogon flexuosus (Nees ex Steud.) Will. Watson when used as a sensory additive for all animal species. The FEEDAP Panel concluded that lemongrass oil is safe up to the maximum proposed use levels in complete feed of 125 mg/kg for salmonids; 100 mg/kg for sows and horses; 75 mg/kg for veal calves (milk replacer), cattle for fattening, dairy cows, sheep and goats; and 50 mg/kg for dogs and ornamental fish. For the other species, the calculated safe concentrations in complete feed were 41 mg/kg for chickens for fattening, 61 mg/kg for laying hens, 55 mg/kg for turkeys for fattening, 74 mg/kg for piglets, 88 mg/kg for pigs for fattening, 65 mg/kg for rabbits and 33 mg/kg for cats. These conclusions were extrapolated to other physiologically related species. For any other species, the additive is safe at 33 mg/kg complete feed. The use of lemongrass oil in water for drinking for poultry, pigs, calves and rabbit is safe provided that the total daily intake does not exceed the daily amount considered safe when consumed via feed. No concerns for consumers and the environment were identified following the use of the additive up to the highest safe use level in feed. The essential oil under assessment should be considered as an irritant to skin and eyes and as a dermal and respiratory sensitiser. Since the aerial parts of C. flexuosus and its preparations were recognised to flavour food and its function in feed would be essentially the same as that in food, no further demonstration of efficacy was considered necessary.

Application of RSM Method for Optimization of Geraniol Transformation Process in the Presence of Garnet

This paper presents the results of tests obtained for the transformation of geraniol in the presence of garnet as a catalyst by the response surface method (RSM). The method analyzed the influence of the following parameters: a temperature of 50-150 °C, a catalyst concentration (garnet) of 1.0-10.0 wt% and a reaction time of 0.25-24 h. Response functions included the conversion of geraniol (GA), selectivity for conversion to neral (NE) and selectivity for conversion to citronellol (CL). In addition, the influence of all control parameters on each of the response parameters is presented in the form of second-order polynomials. The optimal parameters of the geraniol transformation process were a temperature of 55 °C, a catalyst concentration of 5 wt% and a reaction time of 2 h, for which high values of the GA conversion function and the selectivity of conversion to NE and CL were obtained. For the GA conversion, the optimum was obtained at 94 mol% at 60 °C, a catalyst concentration of 5.0 wt% and a reaction time of 2 h. For NE selectivity, the optimum value was reached at 49 mol% at 60 °C, a catalyst concentration equal to 2.5 (5.0) wt% mole and a reaction time of almost 2 h. For CL selectivity, the optimum value of 49 mol% was obtained for control factors: a temperature equal to 20 °C, a catalyst concentration equal to 5.0 wt% and a response time equal to 2 h. The optimal set of control factors for all power factors is characterized by a temperature of 55 °C, a catalyst concentration of 5 wt% and a reaction time of 2 h.

Sustainable Extraction, Chemical Profile, Cytotoxic and Antileishmanial Activities In-Vitro of Some Citrus Species Leaves Essential Oils

Anti-leishmanial drugs extracted from natural sources have not been sufficiently explored in the literature. Until now, leishmaniasis treatments have been limited to synthetic and expensive drugs. This study investigated, for the first time, the anti-leishmanial efficacy of essential oils (EOs) from the leaves of Citrus species (C. sinensis, C. limon, and C. clementina). Essential oils were extracted from three species by solvent free microwave extraction (SFME); in addition, lemon oil was also isolated by hydro-distillation (HD). These were investigated using gas chromatography coupled with mass spectrometry (GC–MS) and evaluated against Leishmania species, namely Leishmania major and Leishmania infantum, using a mitochondrial tetrazolium test (MTT) assay. The chemical compositions of Citrus limon EOs obtained by HD and SFME showed some differences. The identified peaks of C. limon (SFME) represented 93.96%, where linalool was the major peak (44.21%), followed by sabinene (14.22%) and ocimene (6.09%). While the hydro-distilled oil of C. limon contained geranial (30.08%), limonene (27.09%), and neral (22.87%) in the identified peaks (96.67%). The identified components of C. clementina leaves oil (68.54%) showed twenty-six compounds, where the predominant compound was geranial (42.40%), followed by neral (26.79%) and limonene (14.48%). However, 89.82% C. sinensis oil was identified, where the major peaks were for neral (27.52%), linalool (25.83%), and geranial (23.44%). HD oil of lemon showed the highest activity against L. major, with moderate toxicity on murine macrophage (RAW 264.7) cells, and possessed the best selectivity index on both Leishmanial species (SI: 3.68; 6.38), followed by C. clementina oil and C. limon using SFME (0.9 ± 0.29, 1.03 ± 0.27, and 1.13 ± 0.3), respectively. C. clementina oil induced the greatest activity on Leishmania infantum, followed by HD lemon and SFME lemon oils (0.32 ± 0.18, 0.52 ± 0.15, and 0.57 ± 0.09, respectively) when compared to Amphotericin B (0.80 ± 0.18 and 0.23 ± 0.13) as a positive control, on both species, respectively. Our study suggests a potent anti-leishmanial activity of lemon oil (HD) on L. major, followed by C. clementina. With the same potency on L. infantum shown by C. clementina oil, followed by HD lemon oil. This effect could be attributed to the major compounds of limonene, citral, and neral, as well as the synergistic effect of other different compounds. These observations could be a starting point for the building of new anti-leishmanial drugs from natural origins, and which combine different EOs containing Citrus cultivars.

Antifungal Activities of cis-trans Citral Isomers against Trichophyton rubrum with ERG6 as a Potential Target

Trichophyton rubrum causes ringworm worldwide. Citral (CIT), extracted from Pectis plants, is a monoterpene and naturally composed of geometric isomers neral (cis-citral) and geranial (trans-citral). CIT has promising antifungal activities and ergosterol biosynthesis inhibition effects against several pathogenic fungi. However, no study has focused on neral and geranial against T. rubrum, which hinders the clinical application of CIT. This study aimed to compare antifungal activities of neral and geranial and preliminarily elucidate their ergosterol biosynthesis inhibition mechanism against T. rubrum. Herein, the disc diffusion assays, cellular leakage measurement, flow cytometry, SEM/TEM observation, sterol quantification, and sterol pattern change analyses were employed. The results showed geranial exhibited larger inhibition zones (p < 0.01 or 0.05), higher cellular leakage rates (p < 0.01), increased conidia with damaged membranes (p < 0.01) within 24 h, more distinct shriveled mycelium in SEM, prominent cellular material leakage, membrane damage, and morphological changes in TEM. Furthermore, geranial possessed more promising ergosterol biosynthesis inhibition effects than neral, and both induced the synthesis of 7-Dehydrodesmosterol and Cholesta-5,7,22,24-tetraen-3β-ol, which represented marker sterols when ERG6 was affected. These results suggest geranial is more potent than neral against T. rubrum, and both inhibit ergosterol biosynthesis by affecting ERG6.

Backhousia citriodora F. Muell. (Lemon Myrtle), an Unrivalled Source of Citral

Lemon oils are amongst the highest volume and most frequently traded of the flavor and fragrance essential oils. Citronellal and citral are considered the key components responsible for the lemon note with citral (neral + geranial) preferred. Of the myriad of sources of citral, the Australian myrtaceous tree, Lemon Myrtle, Backhousia citriodora F. Muell. (Myrtaceae), is considered superior. This review examines the history, the natural occurrence, the cultivation, the taxonomy, the chemistry, the biological activity, the toxicology, the standardisation and the commercialisation of Backhousia citriodora especially in relation to its essential oil.

Safety and efficacy of a feed additive consisting of an essential oil from the fruits of Litsea cubeba (Lour.) Pers. (litsea berry oil) for use in all animal species (FEFANA asbl)

Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety and efficacy of an essential oil from the fruits of Litsea cubeba (Lour.) Pers. (litsea berry oil), when used as a sensory additive (flavouring) in feed and water for drinking for all animal species. The FEEDAP Panel concluded that litsea berry oil is safe up to the maximum proposed use level of 125 mg/kg complete feed for ornamental fish. For the other species, the calculated safe concentration in complete feed are 11 mg/kg for chicken for fattening, 16 mg/kg for laying hen, 14 mg/kg for turkey for fattening, 19 mg/kg for piglet, 23 mg/kg for pig for fattening, 28 mg/kg for lactating sow, 48 mg/kg for veal calf (milk replacer), 43 mg/kg for cattle for fattening, sheep, goat and horse, 28 mg/kg for dairy cow, 17 mg/kg for rabbit, 47 mg/kg for salmon, 50 mg/kg for dog and 8.5 mg/kg for cat. The FEEDAP Panel also concluded that the use of litsea berry oil at the maximum proposed use level in water for drinking of 1 mg/kg is safe for all animal species. Simultaneous use in feed and water for drinking may lead to the maximum safe dose being exceeded. No concerns for consumer safety were identified following the use of the additive up to the highest safe use level in feed for the target animals. The essential oil under assessment should be considered as irritant to skin and eyes, and as a skin and respiratory sensitiser. The use of the additive in animal feed under the proposed conditions was not expected to pose a risk for the environment. Litsea berry oil is recognised to flavour food. Since its function in feed would be essentially the same as that in food, no further demonstration of efficacy was considered necessary.

Repellence of Common Tobacco Flavorants on Lasioderma serricorne (Coleoptera: Anobiidae)

The cigarette beetle, Lasioderma serricorne (F.) (Coleoptera: Anobiidae) is a destructive pest species of tobacco. Olfactory repellents derived from permitted tobacco flavorants have the advantage of not adversely effecting tobacco flavor. Among 12 test compounds, neral exhibited the strongest repellent effect. Among six binary blends prepared, three blends (neral + ethyl cinnamate, neral + cinnamaldehyde, and neral + methyl cinnamate) evoked the strongest repellent response. The interactions between neral and any one of the cinnamic acid derivatives were additive, and the interactions between neral and the cinnamic acid derivatives were antagonistic. In a 32-d tobacco barn bioassay, neral + cinnamaldehyde (embedded in 0.5% agaropectin) showed the strongest repellent effect with a persistence of at least 30 d. The binary blend of two tobacco additives (neral and cinnamaldehyde) appears promising as a repellent for controlling cigarette beetles in tobacco barns.

Composition of essential oil of lemon thyme (Thymus × citriodorus) at different hydrodistillation times

Distillation time can both to optimise the production and to engineer the composition of essential oil in essential oil bearing plants. Purpose of this study was to evaluate the effect of duration of hydrodistillation on composition of essential oil of Thymus × citriodorus, the natural source of commercially important geraniol and citral, a component with valuable biological properties. Essential oils were isolated by hydrodistillation at different distillation times and analysed by GC/MS analytical methods. Increase in percentage of essential oil during all hydrodistillation time gradient was uneven. Elongation of hydrodistillation time decreased percentages of monoterpenes but increased percentages of sesquiterpenes in essential oil. Results showed that the hydrodistillation of essential oil from lemon thyme longer than 60 min is useless.

Volatile Compounds from the Different Organs of Houttuynia cordata and Litsea cubeba (L. citriodora)

The volatile compounds obtained from the different organs of Houttuynia cordata (Saururaceae) and Litsea cubeba (Lauraceae) were analyzed by Gas Chromatography/Mass Spectrometry (GC/MS), Headspace Solid Phase Micro Extraction-Gas Chromatography/Mass Spectrometry (HS-SPME-GC/MS), and GC/olfactometry (GC/O). The major component of all parts of H. cordata is assigned as 4-tridecanone. Each organ produces myrcene as the major monoterpenoid. The major monoterpene in the rhizomes and roots was β-pinene instead of myrcene. 1-Decanal which was responsible for the unpleasant odor of this plant, was the predominant polyketide in both leaves and stems. The presence of 1-decanal was very poor in flowers, stem collected in summer, rhizomes, and roots. GC/MS analyses were very simple in case of the crude extracts of flowers. The content of sesquiterpenoids was extremely poor. (8Z)-Heptadecene, geranial, and neral were detected as the major components in Litsea cubeba. Odor-contributing components by GC/O analysis of the ether extract of the fresh flowers of L. cubeba were neral and geranial which played an important role in sweet-lemon fragrance of the flowers. The role of a high content of (8Z)-heptadecene was still unknown but it might play a significant role in the dispersion of the volatile monoterpene hydrocarbons and aldehydes. The flower volatiles of the Japanese L. cubeba were chemically quite different from those of the Chinese same species.

Composition, anti-quorum sensing and antimicrobial activity of essential oils from Lippia alba

Many Gram-negative pathogens have the ability to produce N-acylhomoserine lactones (AHLs) as signal molecules for quorum sensing (QS). This cell-cell communication system allows them to coordinate gene expression and regulate virulence. Strategies to inhibit QS are promising for the control of infectious diseases or antibiotic resistant bacterial pathogens. The aim of the present study was to evaluate the anti-quorum sensing (anti-QS) and antibacterial potential of five essential oils isolated from Lippia alba on the Tn-5 mutant of Chromobacterium violaceum CV026, and on the growth of the gram-positive bacteria S. aureus ATCC 25923. The anti-QS activity was detected through the inhibition of the QS-controlled violacein pigment production by the sensor bacteria. Results showed that two essential oils from L. alba, one containing the greatest geranial:neral and the other the highest limonene:carvone concentrations, were the most effective QS inhibitors. Both oils also had small effects on cell growth. Moreover, the geranial/neral chemotype oil also produced the maximum zone of growth inhibition against S. aureus ATCC 25923. These data suggest essential oils from L. alba have promising properties as QS modulators, and present antibacterial activity on S. aureus.

Chemical characterization of Lippia alba essential oil: an alternative to control green molds

The essential oil of Lippia alba is reported as an antifungal against human pathogenic microorganisms but few articles report its use as an alternative to synthetic fungicides on green mould control. The objective of this study was to determine chemical characteristics of L. alba essential oil and its antifungal activity against green molds as an alternative to synthetic fungicides. Essential oil was extracted by Clevenger hydrodistillation, characterized by GC-MS analysis, and the structure of the main compounds confirmed by (1)H and (13)C-NMR spectroscopy. Microdilution assays evaluated the essential oil minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC). Commercial fungicides Ketoconazole and Bifonazole were used as control. Essential oil yield is of 0.15% and the major components are neral (33.32%) and geranial (50.94%). The L. alba essential oil has MIC of 0.300-1.250 mg/mL and MFC of 0.600-1.250 mg/mL. Ketoconazole and Bifonazole show MIC ranging from 0.025-0.500 to 0.100-0.200 mg/mL, and MFC ranging from 0.250-0.100 to 0.200-0.250 mg/mL, respectively. L. alba essential oil is classified as citral type and the results indicate that it is a potential alternative to synthetic fungicides.