Antifungal activity of the volatile oil of Eucalyptus citriodora

Antimicrobial, Herbicidal and pesticidal potential of Tunisian eucalyptus species: Chemoprofiling and biological evaluation

The Eucalyptus genus, characterized by its imposing stature and fragrant foliage, has been a source of fascination for humanity over the centuries. The focus of the present investigation was directed towards the essentials oils (EOs) of five Eucalyptus trees cultivated in Tunisia. The GC-MS analysis unveiled unique compositional profiles, a finding substantiated by both Hierarchical Clustering Analysis (HCA) and Principal Component Analysis (PCA) conducted on the leaves EOs. These analyses resulted in the formation of discrete HCA clades, delineating 23 significant components. Notably, the percentage of eucalyptol emerged as the pivotal factor demarcating the separation between three distinct groups. The statistical analysis revealed a dose-dependent relationship in both phytotoxicity evaluation and antibacterial activity. The EOs from Eucalyptus loxophleba and E. salubris exhibited the highest phytotoxicity, inhibiting radical elongation and germination of various seeds, especially Sinapis arvensis and Raphanus sativus. The antimicrobial assessment demonstrated significant inhibitory effects of the EOs on bacterial strains, with MIC values spanning from 14 to exceeding 50 mg/ml. The EOs also affected biofilm formation and cellular metabolism, displaying varied efficacy among different Eucalyptus species against some bacterial strains. The EOs exhibited selective inhibition against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), α-amylase, and α-glucosidase. E. campaspe EO showed the highest AChE activity, while E. loxophleba and E. salubris EOs were most potent toward α-amylase. E. loxophleba EO demonstrated notable activity against α-glucosidase. Overall, these findings provide important data about the diverse biological activities of Eucalyptus EOs, suggesting potential applications in agriculture, medicine, and pharmacy.

The Ethnopharmacology, Phytochemistry and Bioactivities of the Corymbia Genus (Myrtaceae)

Plants have been vital to human survival for aeons, especially for their unique medicinal properties. Trees of the Eucalyptus genus are well known for their medicinal properties; however, little is known of the ethnopharmacology and bioactivities of their close relatives in the Corymbia genus. Given the current lack of widespread knowledge of the Corymbia genus, this review aims to provide the first summary of the ethnopharmacology, phytochemistry and bioactivities of this genus. The Scopus, Web of Science, PubMed and Google Scholar databases were searched to identify research articles on the biological activities, phytochemistry and ethnomedical uses of Corymbia species. Of the 115 Corymbia species known, 14 species were found to have ethnomedical uses for the leaves, kino and/or bark. Analysis of the references obtained for these 14 Corymbia spp. revealed that the essential oils, crude extracts and compounds isolated from these species possess an array of biological activities including anti-bacterial, anti-fungal, anti-protozoal, anti-viral, larvicidal, insecticidal, acaricidal, anti-inflammatory, anti-oxidant, anti-cancer and anti-diabetic activities, highlighting the potential for this under-studied genus to provide lead compounds and treatments for a host of medical conditions.

Insulin Secretory Actions of Ethanol Extract of Eucalyptus citriodora Leaf, including Plasma DPP-IV and GLP-1 Levels in High-Fat-Fed Rats, as Well as Characterization of Biologically Effective Phytoconstituents

Due to the numerous adverse effects of synthetic drugs, researchers are currently studying traditional medicinal plants to find alternatives for diabetes treatment. Eucalyptus citriodora is known to be used as a remedy for various illnesses, including diabetes. This study aimed to explore the effects of ethanol extract of Eucalyptus citriodora (EEEC) on in vitro and in vivo systems, including the mechanism/s of action. The methodology used involved the measurement of insulin secretion from clonal pancreatic β-cells, BRIN BD11, and mouse islets. Other in vitro systems further examined EEEC’s glucose-lowering properties. Obese rats fed a high-fat-fed diet (HFF) were selected for in vivo evaluation, and phytoconstituents were detected via RP-HPLC followed by LC-MS. EEEC induced insulin secretion in a concentration-dependent manner with modulatory effects, similar to 1 µM glucagon-like peptide 1 (GLP-1), which were partly declined in the presence of Ca^2+-channel blocker (Verapamil), K_ATP-channel opener (Diazoxide), and Ca²⁺ chelation. The insulin secretory effects of EEEC were augmented by isobutyl methylxanthine (IBMX), which persisted in the context of tolbutamide or a depolarizing concentration of KCl. EEEC enhanced insulin action in 3T3-L1 cells and reduced glucose absorption, and protein glycation in vitro. In HFF rats, it improved glucose tolerance and plasma insulin, attenuated plasma DPP-IV, and induced active GLP-1 (7-36) levels in circulation. Rhodomyrtosone B, Quercetin-3-O-β-D-glucopyranoside, rhodomyrtosone E, and quercitroside were identified as possible phytoconstituents that may be responsible for EEEC effects. Thus, these findings revealed that E. citriodora could be used as an adjunct nutritional supplement to manage type 2 diabetes.

In vitro and in silico Evaluation of ACE2 and LOX Inhibitory Activity of Eucalyptus Essential Oils, 1,8-Cineole, and Citronellal

Eucalyptus essential oils are well-known and used especially in upper respiratory tract pathologies or diseases as herbal drug preparations. In the present study, the in vitro angiotensin-converting enzyme 2 (ACE2) and lipoxygenase (LOX) enzyme inhibitory potentials of commercial Eucalyptus globulus Labill. and Eucalyptus citriodora Hook. essential oils were evaluated for their potential anti-coronavirus disease 2019 (COVID-19), and anti-inflammatory effects. In addition, the major components, 1,8-cineole and citronellal, were evaluated for their ability to bind at the active site of either human ACE2 or human 5-LOX using an in silico setting. Before activity evaluation, Eucalyptus globulus and E citriodora essential oils were analysed by GC/FID and GC/MS, where 1,8-cineole (30%), and citronellal (80%) were identified as the major components, respectively. The in vitro ACE2 inhibition was calculated as 94.9% for E globulus, and that of E citriodora essential oil as 83.4%. In vitro LOX inhibition experiments for essential oils in the same order showed inhibitions of 71.3 and 91.4%, respectively, at 20 µg/mL test concentrations in microplate-based fluorometric assays. In addition, protein–ligand docking, and interaction profiling was used to gain structural and mechanistic insights into the in silico ACE2 and LOX inhibitory potentials of the major Eucalyptus essential oil constituents, 1,8-cineole as well as citronellal. The resulting data supported the in vitro findings; however, further in vivo studies are needed to confirm the activity.

Development, Optimization, and Evaluation of Luliconazole Nanoemulgel for the Treatment of Fungal Infection

The present study aimed to optimize luliconazole nanoemulsion using Box–Behnken statistical design, which was further incorporated into the polymeric gel of Carbopol 934. The formulation was characterized for its size, entrapment efficiency, ex vivo permeation, and mechanism of release. The size of the dispersed globules of the optimized drug-loaded nanoemulsion was found to be 17 ± 3.67 nm with a polydispersity index (PDI) less than 0.5. Although the surface charge was recorded at –9.53 ± 0.251, the stability was maintained by the polymeric matrix that prevented aggregation and coalescence of the dispersed globules. The luliconazole-nanoemulgel (LUL-NEG) was characterized for drug content analysis, viscosity, pH, and refractive index, where the results were found to be 99.06 ± 0.59%, 9.26 ± 0.08 Pa.s, 5.65 ± 0.17, and 1.31 ± 0.08, respectively. The permeation across the rat skin was found to be significantly higher with LUL-NEG when compared with LUL gel. Furthermore, the skin irritation test performed in experimental animals revealed that the blank NEG, as well as the LUL-NEG, did not produce any signs of erythema following 48 h exposure. In addition, the histopathological findings of the experimental skins reported no abnormal signs at the formulation application site. Finally, the NEG formulation was found to create a statistically significant zone of inhibition ( $P$  < 0.05) when compared to all other test groups. Overall, it could be summarized that the nanoemulgel approach of delivering luliconazole across the skin to treat skin fungal infections could be a promising strategy.

Effectiveness of Oil-Based Denture Dentifrices-Organoleptic Characteristics, Physicochemical Properties and Antimicrobial Action

Denture dentifrices must be effective and not deleterious to prosthetic devices. This study formulated and evaluated dentifrices based on oils of Copaifera officinalis, Eucalyptus citriodora, Melaleuca alternifolia, Pinus strobus, and Ricinus communis. Organoleptic characteristics (appearance, color, odor, taste), physicochemical properties (pH, density, consistency, rheological, abrasiveness, weight loss, and surface roughness) and antimicrobial (Hole-Plate Diffusion–HPD)/anti-biofilm (Colony Forming Units–CFU) action against Staphylococcus aureus, Streptococcus mutans, and Candida albicans were evaluated. Formulations were compared with water (negative control) and a commercial dentifrice (positive control). The data were analyzed by Kruskal-Wallis and Dunn tests (α = 0.05). The organoleptic and physicochemical properties were adequate. All dentifrices promoted weight losses, with high values for C. officinalis and R. communis, and an increase in surface roughness, without differing from each other. For antimicrobial action, C. officinalis and E. citriodora dentifrices were similar to positive control showing effectiveness against S. mutans and C. albicans and no dentifrice was effective against S. aureus; regarding the anti-biofilm action, the dentifrices were not effective, showing higher CFU counts than positive control for all microorganisms. The dentifrices presented satisfactory properties; and, although they showed antimicrobial action when evaluated by HPD, they showed no effective anti-biofilm action on multispecies biofilm.

Green and Efficient Processing of Wood with Supercritical CO2: A Review

Wood processing is a crucial step of wood utilization, but the adding of environmentally hazardous feedstocks and the use of unreasonable technology allow it to harm the environment and human health. Supercritical CO2 (scCO2) is a non-toxic, odorless, and safe solvent, which is widely used in studies and industrial production, but there is no review summarizing wood processing with scCO2. The unique structure and chemical properties of wood combined with scCO2 technology produce positive results. In this paper, wood processing with scCO2 is summarized, including wood impregnation, wood drying, wood thermochemical conversion, and wood extraction. The green and efficient characteristics of wood processing with scCO2 are explained in detail for researchers, engineers, and investors to provide a clean wood processing method. Further study is needed to reduce its energy consumption and commercialize it eventually.

Mass Spectroscopic Analysis, MNDO Quantum Chemical Studies and Antifungal Activity of Essential and Recovered Oil Constituents of Lemon-Scented Gum against Three Common Molds

The present study described the possibility of using wood-treated oil-fungicide of lemon-scented gum (Corymbia citriodora) from newly emerged leaves and unripened fruits against the infestation of Fusarium culmorum, Rhizoctonia solani and Penicillium chrysogenum. Air-dried wood samples of Melia azedarach were treated with the extracted oils from leaves and unripened fruits from C. citriodora. The main chemical constituents identified in the essential oil (EO) from leaves were citronellal (55.31%), citronellol (21.03%) and isopulegol (10.79%), while in unripened fruits were α-pinene (17.86%), eudesmol (13.9%), limonene (9.19%), γ-terpinen (8.21%), and guaiol (7.88%). For recovered oils (ROs), the major components from leaves were D-limonene (70.23%), γ-terpinene (13.58%), β-pinene (2.40%) and isopregol (2.23%), while, 4-terpineol (21.35%), cis-β-terpineol, (19.33%), D-limonene (14.75%), and γ-terpinene (7.42%) represented the main components in fruits. EOs from leaves and fruits at the amounts of 100, 50 and 25 µL showed the highest inhibition percentage (IP) of 100% against F. culmorum and P. chrysogenum compared to control treatment, while at the amounts of 100, and 50 µL showed 100% IP of R. solani. Wood treated with ROs from leaves and fruits showed IPs of 96.66% and 93.33%, respectively, against the growth of R. solani. The mass spectra of the main components of C. citriodora leaves and fruits’ EOs have been recorded in electron ionization mode at 70 eV and fragmentation has been reported and discussed. On the other hand, different quantum parameters such as the heat of formation, ionization energy total energy, binding energy, electronic energy and dipole moment using the modified neglect of diatomic overlap (MNDO) semi-empirical method have been calculated.

A Strategy Based on GC-MS/MS, UPLC-MS/MS and Virtual Molecular Docking for Analysis and Prediction of Bioactive Compounds in Eucalyptus Globulus Leaves

The discovery of medicinal plants is crucial for drug development. Eucalyptus globulus leaves are used as a traditional medicine in many areas of world due to herbicidal and insecticidal activity. While natural products are difficult to be separated and activity assayed, a new approach is needed to predict the active ingredients therein. In this study, a new method for screening active compounds extracted from E. globulus leaves was developed by GC-MS/MS and UPLC-MS/MS combined with molecular docking technology. Predicted compounds with high activity were proposed. Firstly, 35 volatile compounds and 34 aqueous extracted compounds were extracted from E. globulus leaves, and identified by GC-MS/MS and UPLC-MS/MS. The herbicidal receptor (1BX9) was then docked with the identified compounds by docking software, evaluated by docking models and seven scoring functions. The results showed that gallic acid had a strong inhibitory activity of 1BX9, which was speculated to be the main reason for the inhibitory effect of E. globulus leaves. Finally, allelopathic tests of gallic acid, citric acid, and isopulegol were carried out on grass seeds to verify its inhibitory activity against herbicide receptor 1BX9. The results show that the method can screen compounds with specific activity from a complex system of medicinal plants, which is very important for the screening of new active ingredients, confirmation of new medicinal ingredients, and the in-depth development of animal and plant medicines.

Effect of essential oils of Myrtaceae plants on the Penicillium commune

The aim of this research was to determine the inhibitory effect of vapor phase of five essential oils (EOs) on the growth of seven strains of Penicillium commune isolated from moldy milk products. Another objective was to determine the minimum inhibitory doses (in vitro and probit analyses) of EOs, which at concentration 625 μL.L-1 of air completely inhibited the growth of all strains. The antifungal activity was evaluated by the micro-atmosphere method. The essential oils used in this study were extract of plants from family Myrtaceae. Only one essential oil – clove (from Syzygium aromaticum L.; leaves) completely inhibited the growth of all strains during cultivation at 25 °C and 5 °C. Eucalyptus essential oil (from Eucaliptus globulus; leaves), tea tree essential oil (from Melaleuca alternifolia Cheel; leaves), cajeput essential oil (from Melaleuca leucadendra L.; leaves and twigs), niaouli essential oil (from Melaleuca quinquenervia (Cav.) S.T.Blake; leaves) have different effects on the growth of P. commune strains. The order of tested essential oils according to the inhibition effect on the growth of the strains of P. commune (from the strongest to the weakest effect) was: clove > tea tree > cajeput > niaouli > eucalyptus. Clove EO that completely inhibited the growth of all strains was used to determine minimum inhibitory doses (MIDs). The MIDs were 125 µL.L-1 of air for two strains of P. commune and 250 µL.L-1 of air for five strains of P. commune on the 7th and 14th day of cultivation, also. Using probit analysis, predicted MIDs90 and MIDs50 were calculated. The MIDs90 were determined from 104.93 to 301.37 µL.L-1 of air.

Inhibition of Alternaria stem canker on tomato by essential oils from Baccharis species

The toxicity of four essential oils extracted from Baccharis articulata, Baccharis ochracea, Baccharis psiadioides and Baccharis trimera was tested against the phytopathogen Alternaria alternata, which causes Alternaria stem canker on tomatoes. Diseases caused by Alternaria fungi are responsible for great economic losses in terms of production and are controlled by synthetic fungicides; however, essential oils offer an alternative, since they have been proven to be effective for controlling against various plant pathogens. In this way, the antifungal activity of Baccharis essential oils was tested using potato dextrose agar medium with concentrations ranging from 0.1 to 20.0 µL mL^-1. Baccharis trimera and Baccharis ochracea essential oils presented 100% mycelial growth inhibition of A. alternata and were also able to control Alternaria stem canker disease under greenhouse conditions. Tomato plants treated with these essential oils exhibited area under the disease progress curve (AUDPC) values of 230.10 and 241.42, differing from the control condition, which showed an AUDPC value of 268.92. The essential oils of B. trimera and B. ochracea can be an alternative for controlling Alternaria stem canker disease of tomatoes and should be formulated as a potential fungicide against the A. alternata pathogen.

Antibacterial activity of three essential oils and some monoterpenes against Ralstonia solanacearum phylotype II isolated from potato

The present study describes the possibility of using some essential oils and monoterpens as bioagents against the growth of Ralstonia solanacearum, a causal bacterium of potato brown rot disease. Eight isolates of the bacterium were recovered from infected potato tubers, showing typical symptoms of the disease, Isolates were identified as R.solanacearum phylotype II, based on biochemical and physiological characteristics, as well as, at the molecular level through PCR analysis. Three essential oils extracted from Corymbia citriodora (leaves), Cupressus sempervirens (aerial parts), and Lantana camara (aerial parts) were evaluated for their antibacterial activity against eight isolates of R. solanacearum phylotype II. Results demonstrated that L. camara essential oil (concentration 5000 μg/mL) had the highest effects against the RsMo2, RsSc1 and Rs48, with inhibition zone (IZ) values of 17.33, 16.33, and 17.50 mm, respectively, also against Rs2 (IZ 14.33 mm), and RsIs2 (IZ 16 mm). C. citriodora oil showed the highest activity against RsBe2 (IZ 14 mm), RsFr4 (IZ 13.66 mm) and RsNe1 (IZ 13.66 mm). Gas Chromatography-Mass Spectrometry (GC-MS-FID) analyzed the chemical composition of these essential oils. It was proved that L. camara leaves contains mainly trans-caryophyllene (16.24%) and α-humulene (9.55%), in C. citriodora oil were α-citronellal (56.55%), α-citronellol (14.89%), and citronellol acetate (13.04%), and in Cup. sempervirens aerial parts were cedrol (22.17%), and Δ3-carene (18.59%). Five monoterpenes were evaluated against the most resistance Ralstonia isolate RsFr5 to the three studied essential oils and found that limonene had the highest effect against it compared with the lowest thymol. The results proved the strong bio effects of the essential oil from L. camara leaves as a natural product contained monoterpenes that can inhibit the growth of tested R. solanacearum phylotype II isolates.

GC-MS and HS-SPME-GC×GC-TOFMS Determination of the Volatile Composition of Essential Oils and Hydrosols (By-Products) from Four Eucalyptus Species Cultivated in Tuscany

Essential oils are widely used as functional ingredients for potential multi-purpose functional uses. Hydrosols, co-products of the distillation of plant material, are used in food and cosmetic industries and in biological agriculture, but their volatile composition is poorly investigated. The volatile fractions of essential oils and hydrosols from four less-studied 1,8-cineol-rich Eucalyptus species (E. parvula L.A.S. Johnson & K.D. Hill, E. cinerea F. Muell, E. pulverulenta Sims and E. pulverulenta baby blue Sims), cultivated in Tuscany in a system of organic farming, were characterized by solvent dilution (essential oils) or extraction (hydrosols) followed by GC-MS and by HS-SPME-GC×GC-TOFMS analysis. GC-MS analysis showed that essential oils were mainly constituted by oxygenated monoterpenes, particularly 1,8-cineole, with monoterpenes hydrocarbons up to 10.8%. Relative differences in the abundance of minor terpenes as limonene, α-pinene, γ-terpinene, p-cymene, terpinen-4-ol, α-terpineol, and alloaromandrene were pointed out and seem to be suitable for differentiation among EOs of the four different Eucalyptus species. Hydrosols of these species were characterized for the first time: they were mainly constituted by oxygenated monoterpenes (97.6–98.9%), with 1,8-cineole up to 1.6 g/L, while monoterpene and sesquiterpene hydrocarbons were detected only in traces. HS-SPME-GC×GC-TOFMS analysis also allowed providing metabolic profiling of hydrosols for the direct comparison and visualization of volatile components, pointing out the potentially different uses of these products as functional ingredients in food, beverage, and cosmetic industries.

Antifungal activity of essential oils on two Venturia inaequalis strains with different sensitivities to tebuconazole

The antifungal activity of seven essential oils (eucalyptus, clove, mint, oregano, savory, tea tree, and thyme) was studied on Venturia inaequalis, the fungus responsible for apple scab. The composition of the essential oils was checked by gas chromatography-mass spectrometry. Each essential oil had its main compound. Liquid tests were performed to calculate the IC₅₀ of essential oils as well as their majority compounds. The tests were made on two strains with different sensitivities to tebuconazole: S755, the sensitive strain, and rs552, the strain with reduced sensitivity. Copper sulfate was selected as the reference mineral fungicidal substance. IC₅₀ with confidence intervals were calculated after three independent experiments. The results showed that all essential oils and all major compounds had in vitro antifungal activities. Moreover, it was highlighted that the effectiveness of four essential oils (clove, eucalyptus, mint, and savory) was higher than copper sulfate on both strains. For each strain, the best activity was obtained using clove and eucalyptus essential oils. For clove, the IC₅₀ obtained on the sensitive strain (5.2 mg/L [4.0-6.7 mg/L]) was statistically lower than the IC₅₀ of reduced sensitivity strain (14 mg/L [11.1-17.5 mg/L]). In contrast, for eucalyptus essential oil, the IC₅₀ were not different with respectively 9.4-13.0 and 12.2-17.9 mg/L for S755 and rs552 strains. For mint, origano, savory, tea tree, and thyme, IC₅₀ were always the best on rs552 strain. The majority compounds were not necessarily more efficient than their corresponding oils; only eugenol (for clove) and carvacrol (for oregano and savory) seemed to be more effective on S755 strain. On the other hand, rs552 strain seemed to be more sensitive to essential oils than S755 strain. In overall, it was shown that essential oils have different antifungal activities but do not have the same antifungal activities depending on the fungus strain used.

Effects of isopulegol in acute nociception in mice: Possible involvement of muscarinic receptors, opioid system and l-arginine/NO/cGMP pathway

Previous studies have shown that isopulegol has anxiolytic, anticonvulsant, gastro-protective and antioxidant activities in rodents, but until now there are no studies showing activity of isopulegol in animal models of nociception and inflammation. The objective of this study was to evaluate the antinociceptive effect of isopulegol and to propose possible mechanisms involved in its effects observed in mice. Groups of male and female Swiss mice (20-35 g, n = 5-8) were used in this test under the authorization of Ethics Committee on Animal Experimentation (CEEA/UFPI N° 82/2014). In order to evaluate the antinociceptive activity of isopulegol, nociception was induced using formalin test, capsaicin and glutamate in hind paw licking model, followed by the investigation of the involvement of opioid mechanisms, K + ATP channels, muscarinic, L arginine-nitric oxide and cGMP. The oral administration of isopulegol showed antinociceptive effect in both phases of the formalin test at doses from 0.78 to 25 mg/kg (first phase) and 1.56-25 mg/kg (second phase) and also produced significant results before capsaicin test at doses from 1.56 to 12.5 mg/kg and glutamate test at doses from 3.12 to 6.25 mg/kg with a dose-dependent effect. The antinociception activity of isopulegol was inhibited in the presence of naloxone (2 mg / kg, ip), glibenclamide (3 mg/kg, ip), atropine (1 mg/kg, ip), l-arginine (600 mg/kg, ip) and methylene blue (20 mg/kg, ip). The results suggested that acute antinociceptive action of opioid isopulegol seems to be related to the K + ATP channels system, through the involvement of muscarinic receptors, inhibiting nitric oxide and cGMP.

Chloroplast variation is incongruent with classification of the Australian bloodwood eucalypts (genus Corymbia, family Myrtaceae)

Previous molecular phylogenetic analyses have resolved the Australian bloodwood eucalypt genus Corymbia (~100 species) as either monophyletic or paraphyletic with respect to Angophora (9-10 species). Here we assess relationships of Corymbia and Angophora using a large dataset of chloroplast DNA sequences (121,016 base pairs; from 90 accessions representing 55 Corymbia and 8 Angophora species, plus 33 accessions of related genera), skimmed from high throughput sequencing of genomic DNA, and compare results with new analyses of nuclear ITS sequences (119 accessions) from previous studies. Maximum likelihood and maximum parsimony analyses of cpDNA resolve well supported trees with most nodes having >95% bootstrap support. These trees strongly reject monophyly of Corymbia, its two subgenera (Corymbia and Blakella), most taxonomic sections (Abbreviatae, Maculatae, Naviculares, Septentrionales), and several species. ITS trees weakly indicate paraphyly of Corymbia (bootstrap support <50% for maximum likelihood, and 71% for parsimony), but are highly incongruent with the cpDNA analyses, in that they support monophyly of both subgenera and some taxonomic sections of Corymbia. The striking incongruence between cpDNA trees and both morphological taxonomy and ITS trees is attributed largely to chloroplast introgression between taxa, because of geographic sharing of chloroplast clades across taxonomic groups. Such introgression has been widely inferred in studies of the related genus Eucalyptus. This is the first report of its likely prevalence in Corymbia and Angophora, but this is consistent with previous morphological inferences of hybridisation between species. Our findings (based on continent-wide sampling) highlight a need for more focussed studies to assess the extent of hybridisation and introgression in the evolutionary history of these genera, and that critical testing of the classification of Corymbia and Angophora requires additional sequence data from nuclear genomes.

Biological, medicinal and toxicological significance of Eucalyptus leaf essential oil: a review

The genus Eucalyptus L'Heritier comprises about 900 species, of which more than 300 species contain volatile essential oil in their leaves. About 20 species, within these, have a high content of 1,8-cineole (more than 70%), commercially used for the production of essential oils in the pharmaceutical and cosmetic industries. However, Eucalyptus is extensively planted for pulp, plywood and solid wood production, but its leaf aromatic oil has astounding widespread biological activities, including antimicrobial, antiseptic, antioxidant, chemotherapeutic, respiratory and gastrointestinal disorder treatment, wound healing, and insecticidal/insect repellent, herbicidal, acaricidal, nematicidal, and perfumes, soap making and grease remover. In the present review, we have made an attempt to congregate the biological ingredients of leaf essential oil, leaf oil as a natural medicine, and pharmacological and toxicological values of the leaf oil of different Eucalyptus species worldwide. © 2017 Society of Chemical Industry.

Bioactivity of essential oils extracted from Cupressus macrocarpa branchlets and Corymbia citriodora leaves grown in Egypt

BACKGROUND

Cupressus macrocarpa Hartw and Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson, widely grown in many subtropical areas, are used for commercial purposes, such as in perfumery, cosmetics, and room fresheners. Their potential as a source of antimicrobial compounds may be useful in different applications.

METHODS

The chemical composition of essential oils (EOs) from C. macrocarpa branchlets and C. citriodora leaves was analyzed by using gas chromatography-mass spectrometry (GC/MS). Antibacterial and antifungal activities were assessed by the micro-dilution method to determine the minimum inhibitory concentrations (MICs), and minimum fungicidal concentrations (MFCs), and minimum bactericidal concentrations (MBCs). Further, the antioxidant capacity of the EOs was determined via 2,2'-diphenypicrylhydrazyl (DPPH) and β-carotene-linoleic acid assays.

RESULTS

Terpinen-4-ol (23.7%), α-phellandrene (19.2%), α-citronellol (17.3%), and citronellal were the major constituents of EO from C. macrocarpa branchlets, and α-citronellal (56%), α-citronellol (14.7%), citronellol acetate (12.3%), isopulegol, and eucalyptol were the primary constituents of EO from C. citriodora leaves. Antibacterial activity with MIC values of EO from C. citriodora leaves was ranged from 0.06 mg/mL to 0.20 mg/mL, and MBC from 0.12 mg/mL against E. coli to 0.41 mg/mL. EO from C. macrocarpa branchlets showed less activity against bacterial strains. The MIC values against tested fungi of the EO from C. citriodora ranged from 0.11 to 0.52 mg/mL while for EO from C. macrocarpa from 0.29 to 3.21 mg/mL. The MIC and MFC values of EOs against P. funiculosum were lower than those obtained from Ketoconazole (KTZ) (0.20; 0.45; 0.29 and 0.53 mg/mL, respectively, vs 0.21 and 0.41 mg/mL. Antioxidant activity of the EO from C. citriodora was higher than that of the positive control but lower than that of the standard butylhydroxytoluene (BHT) (IC50 = 5.1 ± 0.1 μg/mL).

CONCLUSION

The results indicate that the EO from Egyptian trees such as C. citriodora leaves may possesses strong bactericidal and fungicidal activities and can be used as an agrochemical for controlling plant pathogens and in human disease management which will add crop additive value.

Antifungal Activity of Eucalyptus Oil against Rice Blast Fungi and the Possible Mechanism of Gene Expression Pattern

Eucalyptus oil possesses a wide spectrum of biological activity, including anti-microbial, fungicidal, herbicidal, acaricidal and nematicidal properties. We studied anti-fungal activities of the leaf oil extracted from Eucalyptus. grandis × E. urophylla. Eleven plant pathogenic fungi were tested based on the mycelium growth rates with negative control. The results showed that Eucalyptus oil has broad-spectrum inhibitory effects toward these fungi. Remarkable morphological and structural alterations of hypha have been observed for Magnaporthe grisea after the treatment. The mRNA genome array of M. grisea was used to detect genes that were differentially expressed in the test strains treated by the Eucalyptus oil than the normal strains. The results showed 1919 genes were significantly affected, among which 1109 were down-regulated and 810 were up-regulated (p < 0.05, absolute fold change >2). According to gene ontology annotation analysis, these differentially expressed genes may cause abnormal structures and physiological function disorders, which may reduce the fungus growth. These results show the oil has potential for use in the biological control of plant disease as a green biopesticide.

Antitumor effect of 1, 8-cineole against colon cancer

Several essential oils possess pharmacological effects. Among the various constituents of essential oils, 1, 8-cineole has been shown to possess pharmacological effects such as anti-bacterial and anti-inflammatory effects. The effect of 1, 8-cineole on human colorectal cancer cells, however, has not reported previously. In this study, we have investigated the anti-proliferative effect of 1, 8-cineole on human colon cancer cell lines HCT116 and RKO by WST-8 and BrdU assays. The cytotoxicity of 1, 8-cineole was investigated by LDH activity and TUNEL staining. The mechanism of apoptosis by 1, 8-cineole was determined by western blot analyses. In in vivo study, RKO cells were injected into the SCID mice and the effect of 1, 8-cineole was investigated. Specific induction of apoptosis, not necrosis, was observed in human colon cancer cell lines HCT116 and RKO by 1, 8-cineole. The treatment with 1, 8-cineole was associated with inactivation of survivin and Akt and activation of p38. These molecules induced cleaved PARP and caspase-3, finally causing apoptosis. In xenotransplanted SCID mice, the 1, 8-cineole group showed significantly inhibited tumor progression compared to the control group. These results indicated 1, 8-cineole suppressed human colorectal cancer proliferation by inducing apoptosis. Based on these studies 1, 8-cineole would be an effective strategy to treat colorectal cancer.

Effect of Echinophora platyloba, Stachys lavandulifolia, and Eucalyptus camaldulensis plants on Trichomonas vaginalis growth in vitro

BACKGROUND

Trichomonas vaginalis is a protozoan parasite which causes vaginitis in women worldwide. Metronidazole with vast side effects is drug of choice for this infection. In search for an alternative drug, in this study the effect of three plants on Trichomonas vaginalis has been investigated in vitro.

MATERIALS AND METHODS

Alcoholic and watery extracts of Echinophora platyloba, Stachys lavandulifolia, and Eucalyptus camaldulensis were prepared. In TYIS culture medium containing alive Trichomonas vaginalis different concentrations of extracts of three plants were added. Following, 24, 48, and 72 h incubation the number of parasite in each test tube was counted.

RESULTS

Eucalyptus camaldulensis showed a strong effect on Trichomonas vaginalis growth. However, no significant effect was observed with Echinophora platyloba or Stachys lavandulifolia extracts.

CONCLUSION

Eucalyptus camaldulensis can be considered as an alternative drug for treatment of infective vaginitis which is caused by bacteria, fungi and parasites.

Fumigant antifungal activity of Myrtaceae essential oils and constituents from Leptospermum petersonii against three Aspergillus species

Commercial plant essential oils obtained from 11 Myrtaceae plant species were tested for their fumigant antifungal activity against Aspergillus ochraceus, A. flavus, and A. niger. Essential oils extracted from Leptospermum petersonii at air concentrations of 56 × 10(-3) mg/mL and 28 × 10(-3) mg/mL completely inhibited the growth of the three Aspergillus species. However, at an air concentration of 14 × 10(-3) mg/mL, inhibition rates of L. petersonii essential oils were reduced to 20.2% and 18.8% in the case of A. flavus and A. niger, respectively. The other Myrtaceae essential oils (56 × 10(-3) mg/mL) only weakly inhibited the fungi or had no detectable affect. Gas chromatography-mass spectrometry analysis identified 16 compounds in L. petersonii essential oil. The antifungal activity of the identified compounds was tested individually by using standard or synthesized compounds. Of these, neral and geranial inhibited growth by 100%, at an air concentration of 56 × 10(-3) mg/mL, whereas the activity of citronellol was somewhat lover (80%). The other compounds exhibited only moderate or weak antifungal activity. The antifungal activities of blends of constituents identified in L. petersonii oil indicated that neral and geranial were the major contributors to the fumigant and antifungal activities.

Chemical composition of 8 eucalyptus species' essential oils and the evaluation of their antibacterial, antifungal and antiviral activities

BACKGROUND

In 1957, Tunisia introduced 117 species of Eucalyptus; they have been used as fire wood, for the production of mine wood and to fight erosion. Actually, Eucalyptus essential oil is traditionally used to treat respiratory tract disorders such as pharyngitis, bronchitis, and sinusitis. A few investigations were reported on the biological activities of Eucalyptus oils worldwide. In Tunisia, our previous works conducted in 2010 and 2011 had been the first reports to study the antibacterial activities against reference strains. At that time it was not possible to evaluate their antimicrobial activities against clinical bacterial strains and other pathogens such as virus and fungi.

METHODS

The essential oils of eight Eucalyptus species harvested from the Jbel Abderrahman, Korbous (North East Tunisia) and Souinet arboreta (North of Tunisia) were evaluated for their antimicrobial activities by disc diffusion and microbroth dilution methods against seven bacterial isolates: Haemophilus influenzae, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pneumoniae and Streptococcus pyogenes. In addition, the bactericidal, fungicidal and the antiviral activities of the tested oils were carried out.

RESULTS

Twenty five components were identified by GC/FID and GC/MS. These components were used to correlate with the biological activities of the tested oils. The chemical principal component analysis identified three groups, each of them constituted a chemotype. According to the values of zone diameter and percentage of the inhibition (zdi, % I, respectively), four groups and subgroups of bacterial strains and three groups of fungal strains were characterized by their sensitivity levels to Eucalyptus oils. The cytotoxic effect and the antiviral activity varied significantly within Eucalyptus species oils.

CONCLUSIONS

E. odorata showed the strongest activity against S. aureus, H. influenzae, S. agalactiae, S. pyogenes, S. pneumoniae and against all the tested fungal strains. In addition, E. odorata oil showed the most cytotoxic effect. However, the best antiviral activity appeared with E. bicostata. Virus pretreatment with E. bicostata essential oil showed better antiviral activity (IC(50) = 0.7 mg/ml, SI = 22.8) than cell-pretreatment (IC(50) = 4.8 mg/ml, SI = 3.33). The essential oil of E. astringens showed antiviral activity only when incubated with virus prior to cell infection. This activity was dose-dependent and the antiviral activity diminished with the decreasing essential oil concentration.

Chromatographic evaluation and anthelmintic activity of Eucalyptus globulus oil

In world Helminthes infections are the most widespread of all the infections in humans. The morbidity due to parasitic diseases has been increasing in our population. The gastrointestinal helminthes become resistant to the currently available anthelmintic drugs. Anthelmintic substances having considerable toxicity to human beings are present in foods derived from livestock, posing a serious threat to human health. Due to this, there is a need to derive new chemical substances from natural sources, for helminthes control. In this study, volatile oil isolated from Eucalyptus globulus Labill was evaluated for its anthelmintic activity on adult Indian earthworms, Pheretima posthuma, which have anatomical and physiological resemblance with the intestinal roundworm parasites of human beings. In concentrations of 0.05, 0.01 and 0.15 ml/ml, respectively, all the oil samples showed potent anthelmintic activity as compared to that of the standard drug albendazole at a concentration of 10 mg/ml.

Antibacterial activity of essential oils from Eucalyptus and of selected components against multidrug-resistant bacterial pathogens

CONTEXT

Eucalyptus globulus Labill (Myrtaceae) is the principal source of eucalyptus oil in the world and has been used as an antiseptic and for relieving symptoms of cough, cold, sore throat, and other infections. The oil, well known as 'eucalyptus oil' commercially, has been produced from the leaves. Biological properties of the essential oil of fruits from E. globulus have not been investigated much.

OBJECTIVE

The present study was performed to examine the antimicrobial activity of the fruit oil of E. globulus (EGF) and the leaf oils of E. globulus (EGL), E. radiata Sieber ex DC (ERL) and E. citriodora Hook (ECL) against multidrug-resistant (MDR) bacteria. Furthermore, this study was attempted to characterize the oils as well as to establish a relationship between the chemical composition and the corresponding antimicrobial properties.

MATERIALS AND METHODS

The chemical composition of the oils was analyzed by GLC-MS. The oils and isolated major components of the oils were tested against MDR bacteria using the broth microdilution method.

RESULTS

EGF exerted the most pronounced activity against methicillin-resistant Staphylococcus aureus (MIC ~ 250 µg/ml). EGF mainly consisted of aromadendrene (31.17%), whereas ECL had citronellal (90.07%) and citronellol (4.32%) as the major compounds. 1,8-cineole was most abundant in EGL (86.51%) and ERL (82.66%).

DISCUSSION AND CONCLUSION

The activity of the oils can be ranked as EGF > ECL > ERL ~ EGL. However, all the oils and the components were hardly active against MDR Gram-negative bacteria. Aromadendrene was found to be the most active, followed by citronellol, citronellal and 1,8-cineole.

Evaluation of Eucalyptus citriodora essential oil on goat gastrointestinal nematodes

Phytotherapy may be an alternative strategy for controlling gastrointestinal parasites. This study evaluated the anthelmintic efficacy of Eucalyptus citriodora essential oil (EcEO). The in vitro effects of EcEO were determined through testing the inhibition of egg hatching and larval development of Haemonchus contortus. EcEO was subjected to acute toxicity testing on mice, orally and intraperitoneally. The in vivo effects of EcEO were determined by the fecal egg count reduction test (FECRT) in goats infected with gastrointestinal nematodes. The results showed that 5.3 mg.mL-1 EcEO inhibited egg hatching by 98.8% and 10.6 mg.mL-1 EcEO inhibited H. contortus larval development by 99.71%. The lethal doses for 50% of the mice were 4153 and 622.8 mg.kg-1, for acute toxicity orally and intraperitoneally. In the FECRT, the efficacy of EcEO and ivermectin was 66.25 and 79.16% respectively, on goat gastrointestinal nematodes eight days after treatment. EcEO showed in vitro and in vivo anthelmintic activity.

Synergistic properties of the terpenoids aromadendrene and 1,8-cineole from the essential oil of Eucalyptus globulus against antibiotic-susceptible and antibiotic-resistant pathogens

The aim of the present study was to investigate the chemical composition of the essential oil of the fruits of Eucalyptus globulus and to examine the potential application of the fruit oil against multidrug-resistant bacteria. GLC/MS analysis in the fruit oil showed that aromadendrene was the main compound followed by 1,8-cineole and globulol. The three most abundant components of the fruit oil were also tested individually against microorganisms. In addition, the synergistic effects of combinations of the major constituents (aromadendrene and 1,8-cineole) of the fruit oil were also investigated. All Gram-positive bacteria were susceptible to the fruit oil with different degrees of susceptibility as determined by microdilution method. The oil exerted a marked inhibition against multidrug-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) Enterococcus faecalis. The results indicated that aromadendrene might be responsible for the antimicrobial properties, whereas 1,8-cineole and globulol exhibited low activities. The checkerboard assay demonstrated that combinations of 1,8-cineole and aromadendrene reduce the MIC in most cases in an additive way, whereas the time-kill assay indicates a synergistic effect.

Anthelmintic effect of Eucalyptus staigeriana essential oil against goat gastrointestinal nematodes

The aim of this study was to evaluate the anthelmintic efficacy of Eucalyptus staigeriana essential oil (EsEO). The in vitro effects of EsEO were determined through the egg hatching test and the inhibition of larval development of Haemonchus contortus. The oil was subjected to acute and subacute toxicity rodents. The in vivo effects were determined through fecal egg count reduction test in goats. 1.35 and 5.4 mgml(-1) EsEO inhibited 99.27 and 99.20% H. contortus egg hatching and larval development. In subacute toxicity of EsEO, all parameters were found to be in the normal range, and histopathological analysis of organs did not present alterations. EsEO efficacy against goat gastrointestinal nematodes was 76.57% at 15th day after treatment. E. staigeriana essential oil showed in vitro and in vivo anthelmintic activity.

Bioactive monoterpene glycosides conjugated with gallic acid from the leaves of Eucalyptus globulus

Two monoterpene glycosides, conjugated with gallic acid [globulusin A (1) and B (2)], together with four known compounds, cypellocarpin A (3), eucaglobulin (4), cuniloside (5) and (1S, 2S, 4R)-trans-2-hydroxy-1,8-cineole beta-d-glucopyranoside (6), were isolated from hot-water extracts of the leaves of Eucalyptus globulus. The structures of compounds 1 and 2 were determined by 1D, 2D NMR and MS spectroscopic analyses. The absolute stereochemistry of 1 was determined by correlating the spectroscopic data with those of synthetic compound 6 with a known configuration. Globulusin A (1) and B (2), cypellocarpin A (3) and eucaglobulin (4), scavenged DPPH free radicals and globulusin A (1) showed a higher antioxidant activity than the other tested compounds, with an IC50 of 3.8microM. Globulusin A (1) and eucaglobulin (4) concentration-dependently suppressed inflammatory cytokine production, tumor-necrosis factor-alpha and interleukin-1beta in cultured human myeloma THP-1 cells co-stimulated with phorbol myristate acetate. These compounds also inhibited melanogenesis in cultured murine melanoma B16F1 cells, without any significant cytotoxicity. These results suggested that globulusin A (1) and eucaglobulin (4), which were isolated as antioxidants from E. globulus, also had anti-inflammatory as well as anti-melanogenesis activity.

Chemical composition and antimicrobial activity of the essential oils from two species ofEucalyptus

The leaf-essential oil from Eucalyptus robusta and E. saligna, the latter in two phenologic stages, were analysed by gas chromatography coupled to mass spectrometry (GC-MS). The major constituent in E. robusta oil was the monoterpene alpha-pinene (73.0% of the total amount). The oil composition of the E. saligna was dependent of the phenologic stage. In the vegetative phase, the major constituents were p-cymene (54.2%) and gamma-terpinene (43.8%), while during the blossoming alpha-pinene became the major constituent followed by p-cymene (22.5%). Additionally, the antimicrobial activity for all three oils was evaluated against Staphylococcus aureus, Escherichia coli and Candida albicans. The E. robusta oil presented the highest growth inhibition for all the microorganisms tested.