Chemical Composition, Antioxidant, Antimicrobial, and Phytotoxic Potential of Eucalyptus grandis × E. urophylla Leaves Essential Oils

GC-MS profiling, antifeedant, nematicidal and phytotoxic effects of essential oils of two subspecies of Eucalyptus flocktoniae (Maiden) Maiden

This work presents the biocidal effects and chemical compositions of two essential oils (EOs) obtained by hydrodistillation of Eucalyptus flocktoniae subsp. flocktoniae and E. flocktoniae subsp. hebes. The two subspecies studied had different chemical composition, when analysed by gas chromatography coupled to mass spectrometry with 1,8-cineole (56.98%), trans-pinocarveol (20.38%) and α-pinene (5.86%) being the major components of E. flocktoniae subsp. flocktoniae and spathulenol (25.09%), p-cymene (21.20%), 1,8-cineole (10.74%) and α-pinene (8.93%) are the major components of E. flocktoniae subsp. hebes. These oils were evaluated for their insect antifeedant, nematicidal and phytotoxic activities. The biocidal tests showed that E. flocktoniae subsp. hebes was the most active against Myzus persicae and Rhopalosiphum padi. While, E. flocktoniae subsp. flocktoniae was not antifeedant. None of the investigated EOs were active against both Spodoptera littoralis and Meloidogyne javanica root-knot nematode. Moreover, the EOs extracted from these two subspecies showed a significant phytotoxic effect.

Chemical Composition of Litsea pungens Essential Oil and Its Potential Antioxidant and Antimicrobial Activities

Litsea pungens is a plant with medicinal and edible properties, where the fruits are edible and the leaves have medicinal properties. However, there is limited research on the chemical and pharmacological activities of the plant. In this study, essential oils were extracted by steam distillation and their antioxidant and antibacterial activities were further evaluated. Gas chromatography-mass spectrometry (GC-MS) was used to identify the chemical components of L. pungens fresh fruit essential oil (FREO) and L. pungens fresh flower essential oil (FLEO), rapeseed oil (RO) and commercial Litsea oil (CEO). The results showed that 12 chemical components were identified in FREO. Twelve chemical components were identified from FLEO, four chemical components were identified from CEO, and thirteen chemical components were identified from RO. Except for RO, the other three oils were mainly composed of terpenes, among which limonene is the main chemical component. In terms of antioxidant activity, FREO, FLEO, CEO and RO have antioxidant capacity, mainly reflected in the scavenging DPPH free radicals and the iron ion chelating ability, and the antioxidant activity shows a certain dose effect, but the antioxidant activity of FLEO is the weakest among the four oils. Meanwhile, under the stress of hydrogen peroxide, CEO demonstrated a significant antioxidant protective effect on cells. It is worth mentioning that compared with the positive control, the FREO exhibited a better antibacterial rate. When the concentration of essential oil is 20 mg/mL, the bacteriostatic rate can reach 100%. Therefore, it could be a promising candidate among medicinal and edible plants.

Antimicrobial activity of essential oils against Staphylococcus aureus and Staphylococcus chromogenes isolated from bovine mastitis

Staphylococcus aureus and Staphylococcus chromogenes are pathogens frequently detected in bovine mastitis. Treatment and prevention of this disease have been usually carried on with antimicrobials. However, the emergence of bacterial isolates with antimicrobial resistance has aroused interest in new therapeutic alternatives. Plant essential oils (EOs) have been largely studied as antibacterial treatments. In the present study, EOs from five plants were evaluated for their antibacterial activities against S. aureus and S. chromogenes. Bacterial isolates were obtained in a previous study of clinical cases of bovine mastitis. EOs from lemongrass, eucalyptus, lavender, peppermint, and thyme were obtained by hydrodistillation and their chemical compositions were evaluated by gas chromatography (GC). Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were evaluated for all EOs. The results demonstrated that citral (40.9%), myrcene (24.7%), and geraniol (1.9%) were detected in lemongrass EO; 1,8-cineole (76.9%), α-pinene (8.2%), and ledene (5.1%) in eucalyptus EO; 1,8-cineole (45.2%), camphor (18.2%), and fenchone (14.6%) in lavender EO; L-menthol (38.5%), menthofuran (16.3%), and citronellal (10.6%) in peppermint EO; and thymol (44.2%), p-cymene (24.6%) and 1,8-cineole (9.9%) in thyme EO. More effective antibacterial activities were observed only with the use of lemongrass (MIC and MBC ranging from 0.39 to 3.12 mg/mL and 0.39 to 6.35 mg/mL, respectively) and thyme (MIC and MBC ranging from 0.39 to 1.56 mg/mL and 0.39 to 3.12 mg/mL, respectively). Peppermint, lavender and eucalyptus EOs did not show bactericidal activities. In conclusion, lemongrass and thyme EOs are promising antibacterial alternatives against Staphylococcus species associated with bovine mastitis.

Volatile Components, Antioxidant and Phytotoxic Activity of the Essential Oil of Piper acutifolium Ruiz & Pav. from Peru

Piper acutifolium Ruiz & Pav is known as "matico" and belongs to the Piperaceae family, and in Peru it is traditionally used as an infusion or decoction to ameliorate wound healings or ulcers. In this study, the aim was to investigate the volatile components, the antioxidant profile, and the phytotoxic activity of the essential oil (EO) of P. acutifolium from Peru. To identify the phytoconstituents, the EO was injected into a Gas Chromatography-Mass Spectrometry (GC-MS) to obtain the chemical profile of the volatile components, followed by the antioxidant activity carried out by the reaction with three organic radicals (2,2-diphenyl-1-picrylhydrazyl (DPPH); 2,2'-azinobis-(3-ethylbenzothiazoline)-6- sulfonic acid (ABTS); ferric reducing/antioxidant power (FRAP)). Finally, the phytotoxic capabilities of the EO were tested on two model plants, Lactuca sativa seeds and Allium cepa bulbs. As a result, the analysis identified α-phellandrene as its main volatile chemical at 38.18%, followed by β-myrcene (29.48%) and β-phellandrene (21.88%). Regarding the antioxidant profile, the half inhibitory concentration (IC₅₀) in DPPH was 160.12 ± 0.30 µg/mL, for ABTS it was 138.10 ± 0.06 µg/mL and finally in FRAP it was 450.10 ± 0.05 µg/mL. The phytotoxic activity demonstrated that the EO had high activity at 5% and 10% against L. sativa seed germination, the inhibition of root length, and hypocotyl length. Additionally, in A. cepa bulbs, the inhibition root length was obtained at 10%, both comparable to glyphosate, which was used as a positive control. The molecular docking on 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) revealed that α-phellandrene had -5.8 kcal/mol, being near to glyphosate at -6.3 kcal/mol. The conclusion shows that the EO of P. acutifolium presented antioxidant and phytotoxic activity and might be useful as a bioherbicide in the future.

Essential Oils and Biological Activities of Eucalyptus falcata, E. sideroxylon and E. citriodora Growing in Tunisia

Many plants are able to synthesize essential oils (EOs), which play key roles in defense against weeds, fungi and pests. This study aims to analyze the chemical composition and to highlight the antioxidant, antimicrobial and phytotoxic properties of the EOs from Eucalyptus falcata, E. sideroxylon and E. citriodora growing in Tunisia. EOs were analyzed by gas chromatography coupled to mass spectrometry (GC/MS) and their antioxidant properties were determined by total antioxidant capacity (TAC), DPPH and ABTS assays. The phytotoxic potential was assessed against weeds (Sinapis arvensis, Phalaris canariensis) and durum wheat crop (Triticum durum) and compared to chemical herbicide glyphosate. The antifungal activity was investigated in vitro against eight target fungal strains. All EOs displayed a specific richness in oxygenated monoterpenes (51.3-90%) and oxygenated sesquiterpenes (4.8-29.4%), and 1,8-cineole, citronellal, citronellol, trans-pinocarveol, globulol, spathulenol and citronellyl acetate were the main constituents. Eucalyptus EOs exhibited remarkable antioxidant activity and E. citriodora oil exhibited significant activity when compared with E. falcata and E. sideroxylon EOs. The phytotoxic potential of the tested oils had different efficacy on seed germination and the growth of seedlings and varied among tested herbs and their chemical composition variability. Their effectiveness was better than that of glyphosate. At the post-emergence stage, symptoms of chlorosis and necrosis were observed. Furthermore, a decrease in chlorophyll and relative water content, electrolyte leakage and high levels of MDA and proline were indicators of the oxidative effects of EOs and their effectiveness as bioherbicides. Moreover, all the EOs exhibited moderate fungitoxic properties against all the tested fungal strains. Therefore, according to the obtained results, Eucalyptus EOs could have potential application as natural pesticides.

Chemical Composition and Phytotoxic and Antibiofilm Activity of the Essential Oils of Eucalyptus bicostata, E. gigantea, E. intertexta, E. obliqua, E. pauciflora and E. tereticornis

Eucalyptus species are characterized by their richness in essential oils (EOs) with a great diversity of biological activities. This study reports the chemical composition and the phytotoxic and antibiofilm activities of the EOs of six Eucalyptus species growing in Tunisia: E. bicostata, E. gigantea, E. intertexta, E. obliqua, E. pauciflora and E. tereticornis. Four EOs were rich above all in oxygenated monoterpenes (25.3-91.4%), with eucalyptol as the main constituent. However, in the EOs of E. pauciflora and E. tereticornis, sesquiterpene hydrocarbons (28.8-54.0%) were the main class of constituents; piperitone was the main constituent of both EOs. The phytotoxicity of the EOs was tested against germination and radicle elongation of the weeds Sinapis arvensis and Lolium multiflorum and the crop Raphanus sativus, resulting in the different inhibition of seed germination and radicle elongation depending on both chemical composition and the seed tested, with remarkable phytotoxicity towards S. arvensis and R. sativus. Furthermore, almost all EOs showed antibacterial potential, resulting in significant inhibition of bacterial biofilm formation and the metabolism of Gram-positive (Staphylococcus aureus subsp. aureus and Listeria monocytogenes) and Gram-negative (Acinetobacter baumannii, Pseudomonas aeruginosa and Escherichia coli) bacterial strains, in addition to acting on mature biofilms. The EOs were inhibitory against all bacterial strains tested and usually reluctant to undergo the action of conventional antibiotics. Therefore, these EOs may be considered for applications both as herbicides and in food and health fields.

Eucalyptus cinerea and E. nicholii by-Products as Source of Bioactive Compounds for Agricultural Applications

The cultivation of different species of Eucalyptus has recently expanded in Liguria (Italy) due to the growing demand of the North European floricultural market. Eucalyptus tree branches are cut and selected for their quality, resulting in large amounts of waste biomass to be disposed of. The aim of our study was to evaluate the phytotoxic and antimicrobial activities of essential oils (EOs) from pruning wastes of E. cinerea (EC) and E. nicholii (EN), for potential applications in agriculture. Phytochemical analyses showed eucalyptol (1,8-cineole) as the major component in both EOs, but the EO yield of EN was higher than that of EC, in agreement with a significantly higher oil gland density on EN leaves. EOs from both species showed phytotoxicity on both weeds tested, but no significant inhibition on horticultural crop seed germination, except for Raphanus sativus. The EO from EC showed the strongest antibacterial activity, while the EO from EN showed the strongest antifungal activity. Concluding, EOs from Eucalyptus pruning may be used as possible alternatives to synthetic herbicides and pesticides, acting as antimicrobial and antifungal agents, thus representing a safe strategy for crop management programs.

Chemistry and Bioactivities of Six Tunisian Eucalyptus Species

The complex taxonomy of Eucalyptus genus, the renewed interest in natural compounds able to combat microbial strains, the overuse of synthetic pesticides, the consequent request for alternative control methods were the reasons for this research. The essential oils (Eos) of Eucalyptus bosistoana, Eucalyptus melliodora, Eucalyptus odorata, Eucalyptus paniculata, Eucalyptus salmonopholia, and Eucalyptus transcontinentalis were analyzed by GC/MS and their potential phytotoxic activity was evaluated against the germination and radicle elongation of Sinapis arvensis, Raphanus sativus and Lolium multiflorum. The antibiofilm activity was assayed against both Gram-positive (Staphylococcus aureus and Listeria monocytogenes) and Gram-negative (Pseudomonas aeruginosa, Escherichia coli, and Acinetobacter baumannii) bacteria. Monoterpenoids were the most representative constituents in all EOs and eucalyptol was the dominant component except in E. melliodora EO, in which p-cymene was the most abundant. In phytotoxic assays, the EOs from E. odorata and E. paniculata were the most active against germination and radical elongation of the tested seeds. Finally, the Eucalyptus EOs proved their capacity to effectively inhibit the adhesion process of all five pathogen strains, with percentages often reaching and exceeding 90%. These Eucalytpus EOs could have possible employments in the food, health and agricultural fields.

Chemical Composition and Phytotoxic, Antibacterial and Antibiofilm Activity of the Essential Oils of Eucalyptus occidentalis, E. striaticalyx and E. stricklandii

The Eucalyptus genus (Myrtaceae) is characterized by a richness in essential oils (EO) with multiple biological activities. This study reports the chemical composition and the phytotoxic and antimicrobial activities of the EOs from Tunisian E.occidentalis, E.striaticalyx and E.stricklandii. The EOs were analyzed using GC/MS and their phytotoxicities were assessed against the germination and seedling growth of Sinapis arvensis, Trifolium campestre and Lolium rigidum. Antimicrobial activity was investigated against both Gram-negative (Pseudomonas aeruginosa, Escherichia coli and Acinetobacter baumannii) and Gram-positive (Staphylococcus aureus and Listeria monocytogenes) bacteria. The inhibition of biofilm formation and its metabolism was determined at different times. All EOs were rich in oxygenated monoterpenes (36.3-84.8%); the EO of E.occidentalis was rich in sesquiterpenes, both oxygenated and hydrocarbon (40.0% and 15.0%, respectively). Eucalyptol was the main constituent in all samples. The EOs showed phytotoxic activity on seed germination and seedling growth, depending both on chemical composition and weed. The EOs show a remarkable antibacterial potential resulting in a significant inhibition of the formation of bacterial biofilm and its metabolism, depending on the EO and the strain, with activity on the mature biofilm as well. Therefore, these Eucalyptus EOs could have potential applications both in the food and health fields.

Potential Action Mechanism and Inhibition Efficacy of Morinda citrifolia Essential Oil and Octanoic Acid against Stagonosporopsis cucurbitacearum Infestations

The use of plant-based products has been shown to efficiently inhibit fungi-mediated diseases in agricultural crops. Here, we extracted and evaluated the composition of noni, Morinda citrifolia L., essential oil and assessed its activities against Stagonosporopsis cucurbitacearum in Cucumis melo L. Using in silico molecular approaches, potential interactions between the essential oil major components and S. cucurbitacearum tyrosine-tRNA ligase were predicted. Finally, we also measured the potential interference of plant physiology (the stomatal conductance and net photosynthesis) mediated by the application of the M. citrifolia essential oil. Chromatographic analysis revealed that octanoic acid (75.8%), hexanoic acid (12.8%), and isobutyl pent-4-enyl carbonate (3.1%) were the major essential oil compounds. Octanoic acid and noni essential oil, when used as preventive measures, reduce fungal mycelial growth at a concentration of 5 mg/mL without causing significant damage to the treated leaves, which reinforces their efficacies as preventive tools against S. cucurbitacearum. Molecular docking analyses predicted very stable interactions between the major essential oil constituents and S. cucurbitacearum tyrosine-tRNA ligase, suggesting the interference of these plant-based molecules upon enzyme activation. Octanoic acid and M. citrifolia essential oil at concentrations of 20 mg/mL decreased the stomatal conductance and net photosynthesis rate of melon plants, resulting in robust phytotoxicity. Collectively, our findings indicated that despite the phytotoxicity risks at higher concentrations, M. citrifolia essential oil and octanoic acid, have potential as alternative tools for the integrative management of S. cucurbitacearum.

Phytochemical Profile and Herbicidal (Phytotoxic), Antioxidants Potential of Essential Oils from Calycolpus goetheanus (Myrtaceae) Specimens, and in Silico Study

The essential oil (EO) of Calycolpus goetheanus (Myrtaceae) specimens (A, B, and C) were obtained through hydrodistillation. The analysis of the chemical composition of the EOs was by gas chromatography coupled with mass spectrometry CG-MS, and gas chromatography coupled with a flame ionization detector CG-FID. The phytotoxic activity of those EOs was evaluated against two weed species from common pasture areas in the Amazon region: Mimosa pudica L. and Senna obtusifolia (L.) The antioxidant capacity of the EOs was determined by (DPPH•) and (ABTS•+). Using molecular docking, we evaluated the interaction mode of the major EO compounds with the molecular binding protein 4-hydroxyphenylpyruvate dioxygenase (HPPD). The EO of specimen A was characterized by β-eudesmol (22.83%), (E)-caryophyllene (14.61%), and γ-eudesmol (13.87%), while compounds 1,8-cineole (8.64%), (E)-caryophyllene (5.86%), δ-cadinene (5.78%), and palustrol (4.97%) characterize the chemical profile of specimen B’s EOs, and specimen C had α-cadinol (9.03%), δ-cadinene (8.01%), and (E)-caryophyllene (6.74%) as the majority. The phytotoxic potential of the EOs was observed in the receptor species M. pudica with percentages of inhibition of 30%, and 33.33% for specimens B and C, respectively. The EOs’ antioxidant in DPPH• was 0.79 ± 0.08 and 0.83 ± 0.02 mM for specimens A and B, respectively. In the TEAC, was 0.07 ± 0.02 mM for specimen A and 0.12 ± 0.06 mM for specimen B. In the results of the in silico study, we observed that the van der Waals and hydrophobic interactions of the alkyl and pi-alkyl types were the main interactions responsible for the formation of the receptor–ligand complex.

Efficacy and Mechanism of Thymol/KGM/LG Edible Coating Solution on Inhibition of Mucor circinelloides Isolated From Okra

With the increasing demand and quality requirement for the natural nutritious food in modern society, okra has attracted much attention because of its high nutritional value and remarkable functionality. However, the occurrence of postharvest diseases of fresh okra severely limited the application and the value of okra. Therefore, in this study, the dominant pathogens causing postharvest diseases such as soft rot were isolated from naturally decaying okra. It was identified as Mucor circinelloides by its morphological characteristics and standard internal transcribed spacer ribosomal DNA sequence. Furthermore, the biological characteristics of M. circinelloides were studied, and the inhibitory effect of thymol/KGM/LG (TKL) edible coating solution on M. circinelloides and its possible mechanism was discussed. In addition, TKL edible coating solution had a dose-dependent inhibitory effect on M. circinelloides, with a 50% inhibitory concentration (EC50) of 113.55 mg/L. The TKL edible coating solution at 960 mg/L of thymol completely inhibited mycelial growth and spore germination of M. circinelloides. The results showed that the best carbon source of M. circinelloides was maltose, the best nitrogen source was beef extract and potassium nitrate, the best pH was 6, the best temperature was 28°C, the best NaCl concentration was 0.5%, and the light was conducive to the growth of M. circinelloides. It was also observed by scanning electron microscope (SEM) that TKL was more likely to destroy the cell wall integrity of M. circinelloides, inhibit spore morphology and change mycelium structure. Meanwhile, the activity of chitinase (CHI), an enzyme related to cell wall synthesis of M. circinelloides, was significantly decreased after being treated by TKL with thymol at 100 mg/L (TKL100). The content of Malondialdehyde (MDA) in M. circinelloides decreased significantly from 12 h to 48 h, which may cause oxidative damage to the cell membrane. The activity polygalacturonase (PG), pectin methylgalacturonase (PMG), and cellulase (Cx) of M. circinelloides decreased significantly. Therefore, the results showed that TKL had a good bacteriostatic effect on okra soft rot pathogen, and the main bacteriostatic mechanism might be the damage of cell membrane, degradation of the cell wall, inhibition of metabolic activities, and reduction of metabolites, which is helpful to further understand the inhibitory effect of TKL on okra soft rot pathogen and its mechanism.

Pesticidal Activity and Mode of Action of Monoterpenes

Synthetic pesticides are often associated with issues such as pest resistance, persistent residue, nontarget toxicity, and environmental issues. Therefore, the research and development of novel, safe, and effective pesticides has become a focus in pesticide discovery. Monoterpenes are secondary plant metabolites that commonly have multiple action targets and have been used in aromatherapy, alternative medicine, and food industries. Some are highly potent and stereoselective. They can potentially be botanical pesticides and serve as lead candidates for the design and synthesis of new monoterpenoid pesticides for agricultural applications. This article reviews publications and patents found in SciFinder Scholar between 2000 and May 2021 on monoterpenes and mainly focuses on pesticidal activities of frequently studied monoterpenes and their modes of action. The presented information and our views are hopefully useful for the development of monoterpenes as biopesticides and monoterpenoid pesticides.

Significance of Chromatographic Techniques in Pharmaceutical Analysis

This work presents an overview of the modern approaches embracing advanced equipment and validation parameters of both liquid and gas chromatography techniques, including thin-layer chromatography (TLC), column liquid chromatography (CLC), and gas chromatography (GC), suitable for the identification and quantitative determination of various bioactive compounds occurring in pharmaceutical products and medicinal plants in the time from 2020 to 2021 (November). This review confirmed that HPLC is an incredibly universal tool, especially when combined with different detectors, such as UV-Visible spectroscopy, mass spectrometry (MS), and fluorescence detection for numerous active ingredients in different pharmaceutical formulations without interferences from other excipients. TLC, in combination with densitometry, is a very efficient tool for the determination of biologically active substances present in pharmaceutical preparations. In addition, TLC coupled to densitometry and mass spectrometry could be suitable for preliminary screening and determination of the biological activity (e.g., antioxidant properties, thin layer chromatography (TLC) by 2,2-diphenyl-1-picrylhydrazyl (DPPH) method) of plant materials. Gas chromatography, coupled with a mass spectrometer (GC-MS, GC-MS/MS), is of particular importance in the testing of any volatile substances, such as essential oils. LC, coupled to NMR and MS, is the best solution for identifying and studying the structure of unknown components from plant extracts, as well as degradation products (DPs). Thanks to size-exclusion chromatography, coupled to multi-angle light scattering, the quality control of biological pharmaceuticals is possible.

Cinnamon and Eucalyptus Oils Suppress the Inflammation Induced by Lipopolysaccharide In Vivo

Inflammation caused by bacterial lipopolysaccharide (LPS) disrupts epithelial homeostasis and threatens both human and animal health. Therefore, the discovery and development of new anti-inflammatory drugs is urgently required. Plant-derived essential oils (EOs) have good antioxidant and anti-inflammatory activities. Thus, this study aims to screen and evaluate the effects of cinnamon oil and eucalyptus oil on anti-inflammatory activities. The associated evaluation indicators include body weight gain, visceral edema coefficient, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), nitrogen monoxide (NO), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor alpha (TNF-α), Urea, Crea, ALT, TLR4, MyD88, NF-κB, IκB-α, iNOS, and Mn-SOD. In addition, tissue injury was determined by H&E staining. The results revealed that cinnamon oil and eucalyptus oil suppressed inflammation by decreasing SOD, TNF-α, and NF-κB levels. We also found that cinnamon oil increased the level of GSH-Px, MDA, and Mn-SOD, as well as the visceral edema coefficient of the kidney and liver. Altogether, these findings illustrated that cinnamon oil and eucalyptus oil exhibited wide antioxidant and anti-inflammatory activities against LPS-induced inflammation.