Chemical composition and in vitro evaluation of the antioxidant and antimicrobial activities of Eucalyptus gillii essential oil and extracts

Nanoemulsion and Nanogel Containing Eucalyptus globulus Essential Oil; Larvicidal Activity and Antibacterial Properties

Eucalyptus globulus essential oil (EGEO) possesses many biological effects such as antibacterial, antifungal, and insecticide properties. In the current study, the chemical composition of EGEO was first investigated using GC-MS analysis. Then, a nanoemulsion and nanogel containing EGEO (EGEO-nanoemulsion and EGEO-nanogel) were prepared. After that, the successful loading of EGEO was confirmed using ATR-FTIR analysis. EGEO-nanoemulsion and EGEO-nanogel with LC₅₀ values of 27 and 32 μg/mL showed promising efficacies against Anopheles stephensi larvae. Besides, the efficacy of EGEO-nanogel (IC₅₀ 187 μg/mL) was significantly more potent than EGEO-nanoemulsion (IC₅₀ 3732 μg/mL) against Staphylococcus aureus. However, no significant difference was observed in the efficacy of EGEO-nanoemulsion and EGEO-nanogel against Pseudomonas aeruginosa. Natural components, straightforward preparation, and proper efficacy are some of the advantages of EGEO-nanogel; it could be considered for further consideration against other pathogens and mosquito larvae.

Acute toxicity of eucalyptus leachate tannins to zebrafish and the mitigation effect of Fe3+ on tannin toxicity

Fish ponds polluted by the black water of eucalyptus forests (formed by the complexation of eucalyptus tannins with Fe³⁺) have experienced fish deaths. However, the toxicity of the components of black water is still unclear. To study the acute toxicities of eucalyptus leachate tannins to fish, their changes in the presence of Fe³⁺, and the underlying mechanisms, the static bioassay test method was adopted for acute exposure testing of zebrafish. Zebrafish were exposed to three kinds of tannins, namely, tannic acid (TA), epigallocatechin gallate (EGCG) and tannins from fresh eucalyptus leaf leacheate (TFL), and to solutions of these tannins with different molar ratios of Fe³⁺, under both no-aeration and aeration conditions. The results showed that the 48 h LC50 values of TA, EGCG and TFL were respectively 92, 47, and 186 mg·L^-1, under no aeration, and 171, 86, and 452 mg·L^-1 under aeration. When Fe³⁺ at 2, 1, and 6 times the molar amount of tannin was added to LC100 solutions of TA, EGCG and TFL, zebrafish mortality in 24 h was reduced to 0-33%. Acute fish death in eucalyptus plantation areas is related to high concentrations of eucalyptus tannins in the water. However, with increasing dissolved oxygen and Fe³⁺ levels, the acute toxicity of tannins to fish can be reduced. Thus, the black water in eucalyptus plantation areas reflects a water quality phenomenon that reduces the acute toxicity of eucalyptus tannins to fish. The mechanism of tannin toxicity to fish may be related to the impairment of oxygen delivery by fish blood, but the mechanism needs further study. These results provide a scientific basis for the prevention and control of fish suffering from acute eucalyptus tannin poisoning in eucalyptus plantation areas and for the protection of water resources.

1,8-Cineole: a review of source, biological activities, and application

1,8-Cineole (also known as eucalyptol) is mostly extracted from the essential oils of plants, which showed extensively pharmacological properties including anti-inflammatory and antioxidant mainly via the regulation on NF-κB and Nrf2, and was used for the treatment of respiratory diseases and cardiovascular, etc. Although various administration routes have been used in the application of 1.8-cineole, few formulations have been developed to improve its stability and bioavailability. This review retrospects the researches on the source, biological activities, mechanisms, and application of 1,8-cineole since 2000, which provides a view for the further studies on the application and formulations of 1,8-cineole.

Clove Buds Essential Oil: The Impact of Grinding on the Chemical Composition and Its Biological Activities Involved in Consumer's Health Security

This study is aimed at identifying the chemical composition of the essential oil extracted from the Syzygium aromaticum seeds, as well as investigating its biological activities, insecticide effect, and allelopathic properties. The extraction yield was about 14.3 and 7.14% for grounded and ungrounded seeds, respectively. The GC-MS analysis allowed the identification of 17 heterogeneous compounds, including eugenol (68.7-87.4%), as major compound, cyperene (20.5-7.2%), phenethyl isovalerate (6.4-3.6%), and cis-thujopsene (1.9-0.8%), respectively, for grounded and ungrounded seeds. Concerning the antibacterial activity, the diameter of the inhibition zone reached 35 mm when the essential oil extracted from grounded seeds was applied against Escherichia coli. Regarding the antioxidant activity via the DPPH radical scavenging test, the IC₅₀ varied from 1.2 ± 0.1 to 2.8 ± 0.5 μg/mL. With respect to reducing power, the efficient concentration EC₅₀ ranged from 32 to 50 μg/mL. The essential oil exhibited also an allelopathic effect against seeds of Hyoscyamus niger, as well as an insecticide effect against Sitophilus oryzae with a DL₅₀ value of 252.4 μL/L air. These findings enhance the use of this spice as a natural food preservative and encourage its use in several fields, including pharmaceutical, cosmetics, agriculture, and therapy, that could be a strategic way to guarantee the consumer's health.

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

Eucalyptus grandis × E. urophylla was a unique hybridization in China. However, the chemical and pharmacological properties were rarely reported. Therefore, in this work, we used a steam distillation method to obtain essential oils from leaves of E. grandis × E. urophylla, and further evaluated the antioxidant, antimicrobial, and phytotoxic potential of the essential oil. Gas chromatography mass spectrometry (GC-MS) was applied to investigate the chemical composition of E. grandis × E. urophylla essential oil (EEO) and the results showed that the main components of EEO were monoterpenes followed by sesquiterpenes. Among them, α-pinene accounted about 17.02%. EEO could also well scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals showing a good free radical clearance ability. In addition, EEO efficiently inhibited the growth of six kinds of bacteria as well as seven kinds of plant pathogens, especially Salmonella typhimurium and Colletotrichum gloeosporioides. Moreover, the seedling germination of Raphanus sativus, Lactuca sativa, Lolium perenne, and Bidens pilosa was significantly suppressed by EEO, thus, indicating essential oils from eucalyptus possessed an excellent phytotoxic activity. This study may give a better understanding on EEO and provide a pharmacological activities analysis contributing to the further research of EEO as a functional drug in agronomic and cosmetic industries.

Amelioration of Aflatoxin B1-induced gastrointestinal injuries by Eucalyptus oil in rats

Background Eucalyptus oil (EO), derived from Eucalyptus species, possesses vast remedial and healing properties, although its gut health-promoting properties have not been well investigated. In this study, we investigated the chemical composition of a commercial EO formulation and its potential role in protecting against aflatoxin B1 (AfB1)-induced gastrointestinal damage in rats. Methods Male Wistar rats were divided into six groups with eight rats each. Control rats were administered with the vehicle (1% Tween 80) for 14 days, while another group was exposed to two oral doses of AFB1 on days 12 and 14. Two other groups were pre-treated with oral doses of EO (50 and 100 mg/kg b.w.) for 14 consecutive days, along with two oral doses of AfB1 (5 mg/kg b.w.) on days 12 and 14. The remaining two groups were treated with EO alone at the two doses for 14 days. At the end of the experiment, blood samples, stomach and intestinal tissues were collected for measurement of oxidative stress and antioxidant parameters and light microscopic examination. Results Gas chromatography-mass spectrometry analysis revealed Eucalyptol (1, 8-cineole) as the main constituent (67.48%) of the oil. AfB1 administration induced oxidative and inflammatory disturbances, indicated by significantly (p<0.05) increased serum nitric oxide level and myeloperoxidase activity; increased tissue contents of hydrogen peroxide, malondialdehyde and protein carbonyls, accompanied with corresponding histological alterations. AfB1 also induced significant (p<0.05) reductions in glutathione peroxidase and superoxide dismutase (SOD) activities. Treatment with EO produced significant improvements in the biochemical parameters as well as the appearance of the gastric and intestinal mucosa. EO alone, at the two doses tested did not produce any significant changes in the parameters investigated. Conclusion The findings from this study showed that EO demonstrated protective activity against Aflatoxin-induced toxicity in stomach and intestinal tissues and may thus find application in treatment of gastrointestinal disorders.

Exploring the Insecticidal Potential of Boldo (Peumus boldus) Essential Oil: Toxicity to Pests and Vectors and Non-target Impact on the Microcrustacean Daphnia magna

Every year Chile exports about 2000 tons of boldo folium (Peumus boldus), which is used around the world as a traditional herbal medicinal product (THMP), mostly to relieve gastrointestinal disorders. This biomass may be a resource for the agrochemical industry to manufacture botanical insecticides. In this regard, the insecticidal potential of boldo has been poorly investigated. In the present work, hydrodistillation of a commercial boldo folium gave 1.5% (w/w) of a yellowish essential oil (boldo essential oil, BEO) containing 1,8-cineole (20.7%), p-cymene (18.5%), limonene (9.1%), ascaridole (9.1%) and β-phellandrene (6.4%) as the main constituents, as determined by gas chromatography-mass spectrometry (GC-MS). NMR analysis allowed us to determine that ascaridole was mainly represented by the cis-isomer. BEO was toxic to larvae of the filariasis vector Culex quinquefasciatus and adults of the housefly Musca domestica, showing LC50/LD50 values of 67.9 mg·L-1 and 98.5 µg·adult-1, respectively. On the other hand, lower insecticidal activity was observed against larvae of the moth pest Spodoptera littoralis (LD50 of 268.9 µg·larva-1). It is worth noting that, when tested at LC90 concentration, BEO was significantly less toxic to aquatic microcrustacean Daphnia magna than the conventional insecticide α-cypermethrin. Finally, in the attempt to explore the BEO mode of action, we tested it for acetylcholinesterase (AChE) inhibitory properties using the Ellman method, obtaining negligible effects (IC50 = 0.45 mg·mL-1). Taken together, these results gave new insights into the potential of BEO as a future ingredient of botanical insecticides.

Advances in extraction and analysis of phenolic compounds from plant materials

Phenolic compounds, the most abundant secondary metabolites in plants, have received more and more attention in recent years because of their distinct bioactivities. This review summarizes different types of phenolic compounds and their extraction and analytical methods used in the recent reports, involving 59 phenolic compounds from 52 kinds of plants. The extraction methods include solid-liquid extraction, ultrasound-assisted extractions, microwave-assisted extractions, supercritical fluid extraction, and other methods. The analysis methods include spectrophotometry, gas chromatography, liquid chromatography, thin-layer chromatography, capillary electrophoresis, and near-infrared spectroscopy. After illustrating the specific conditions of the analytical methods, the advantages and disadvantages of each method are also summarized, pointing out their respective suitability. This review provides valuable reference for identification and/or quantification of phenolic compounds from natural products.

Comparative effects of some extraction solvents on the antimicrobial activity of Eucalyptus camaldulensis leaf, bud, capsule and seed crude extracts

Well diffusion method was used to evaluate the antibacterial activity of Eucalyptus camaldulensis, while the antifungal effect was assessed by calculating the reduction percent in the radial growth of mycelia. The inhibition zones exerted by E. camaldulensis crude extracts varied significantly (p ≤ 0.01). The capsule crude extract (acetone 30%) highly inhibited the growth of Acinetobacter baumannii (35 mm clear zone). The highest antifungal activity was against Rhizopus stolonifer with a reduction percent in its radial growth reached to 96%. The bacterial MICs ranged from 20 to 0.5 mg/mL against Escherichia coli and Bacillus subtilis respectively. The MIC values for fungi were between 18 mg/mL (Mucor sp.) and 4 mg/mL (R. stolonifer). Both type and concentration of the solvent greatly affected the antimicrobial potentials of E. camaldulensis. The empty capsule and bud of E. camaldulensis are recognized for the first time as potentially natural resources of effective antimicrobial agents.

Assessment of the antibiofilm and antiquorum sensing activities of Eucalyptus globulus essential oil and its main component 1,8-cineole against methicillin-resistant Staphylococcus aureus strains

Antibacterial resistance is an increasingly serious threat to global public health. The search for new anti-infection agents from natural resources, with different mode of actions and competitive effects became a necessity. In this study, twenty height methicillin-resistant Staphylococcus aureus (MRSA) strains were investigated for their biofilm formation ability. Subsequently, the antibiofilm effects of Eucalyptus globulus essential oil and its main component 1,8-cineole, against MRSA, as well as their antiquorum sensing potential, were evaluated. Our results displayed the potent efficacy of both E. globulus essential oil and 1,8-cineole against the development of biofilms formed by the methicillin-resistant strains. Additionally, E. globulus essential oil showed more potent of anti-QS activity, even at a low concentration, when compared to 1,8-cineole. All these property of tested agents may pave the way to prevent the development of biofilm formation by MRSA and subsequently the spreading of nosocomial infection.

Mechanical and phytochemical protection mechanisms of Calligonum comosum in arid deserts

Unlike animals, plants are sessile organisms, lacking circulating antibodies and specialized immune cells and are exposed to various harsh environmental conditions that make them at risk of being attacked by different pathogens and herbivores. Plants produce chemo-signals to respond to the surroundings and be able to distinguish between harmless and harmful signals. In this study, the production of phytochemicals as plant signaling mechanisms and their defensive roles in disease resistance and repelling herbivores are examined in Calligonum comosum. C. comosum is a leafless standalone perennial shrub widespread in sand dunes. The plant has the ability to survive the drastic environmental conditions of the arid/ hyperarid deserts of the Arabia. Structural anatomy and phytochemicals analyses were used to identify both mechanical and chemical defensive mechanisms in C. comosum. Microscopy-based investigations indicated that stems of this species developed hard structures in its outer layers including sclerenchyma and cluster crystals of calcium oxalate (CaOx). Sclerenchyma and CaOx are difficult to be eaten by herbivores and insects and can harm their mouthparts. On the other hand, the plant developed both short-distance (local) and long-distance (systematic over limited sphere) phytochemicals-producing cells located at its outer regions that is surrounding the inner nutrient-rich vascular system (VS). Local chemical was represented by phenolic idioblasts that were released in response to plant cutting. Systematic chemical was represented by toxic volatile oil containing ~50% benzaldehyde derivative (cuminaldehyde). The oil caused strong killing effect on both mammalian cells and microbial pathogens via either direct addition or indirect exposure to its vapor. The plants lost the oil content and allowed fungal growth once cut and dried. The localization of both defensive mechanisms to the outer region of the plant seemed to protect the inner nutrient-rich VS and hence maintained the plant survival. Surprisingly, in relation to traditional folklore use as medicine, local people use only green parts of the plant and only during the winter, where the plant found devoid of volatile oil and phenolic idioblasts. Moreover, it turns into recommendations for local people to avoid any health problems caused by the plant supply.

Chemical Composition and in-Vitro Evaluation of the Antimicrobial and Antioxidant Activities of Essential Oils Extracted from Seven Eucalyptus Species

Eucalyptus is well reputed for its use as medicinal plant around the globe. The present study was planned to evaluate chemical composition, antimicrobial and antioxidant activity of the essential oils (EOs) extracted from seven Eucalyptus species frequently found in South East Asia (Pakistan). EOs from Eucalyptus citriodora, Eucalyptus melanophloia, Eucalyptus crebra, Eucalyptus tereticornis, Eucalyptus globulus, Eucalyptus camaldulensis and Eucalyptus microtheca were extracted from leaves through hydrodistillation. The chemical composition of the EOs was determined through GC-MS-FID analysis. The study revealed presence of 31 compounds in E. citriodora and E. melanophloia, 27 compounds in E. crebra, 24 compounds in E. tereticornis, 10 compounds in E. globulus, 13 compounds in E. camaldulensis and 12 compounds in E. microtheca. 1,8-Cineole (56.5%), α-pinene (31.4%), citrinyl acetate (13.3%), eugenol (11.8%) and terpenene-4-ol (10.2%) were the highest principal components in these EOs. E. citriodora exhibited the highest antimicrobial activity against the five microbial species tested (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Aspergillus niger and Rhizopus solani). Gram positive bacteria were found more sensitive than Gram negative bacteria to all EOs. The diphenyl-1-picrylhydazyl (DPPH) radical scavenging activity and percentage inhibition of linoleic acid oxidation were highest in E. citriodora (82.1% and 83.8%, respectively) followed by E. camaldulensis (81.9% and 83.3%, respectively). The great variation in chemical composition of EOs from Eucalyptus, highlight its potential for medicinal and nutraceutical applications.

Antimicrobial and antioxidant activities and phenolic profile of Eucalyptus globulus Labill. and Corymbia ficifolia (F. Muell.) K.D. Hill & L.A.S. Johnson leaves

This study was performed to evaluate the in vitro antimicrobial and antioxidant activities and the phenolic profile of Eucalytus globulus Labill. and Corymbia ficifolia (F. Muell.) K.D. Hill & L.A.S. Johnson leaves. Both leave extracts contain significant amounts of phenolic compounds, mainly flavonoids. Qualitative and quantitative analyses of the phenolic compounds were performed using a HPLC/MS method. The main flavonoid was hyperoside and its highest amount was found in E. globulus (666.42 ± 5.02 μg/g dw plant material). Regarding the flavonol profile, myricetin was the dominant compound and its highest amount was found in C. ficifolia leaves (124.46 ± 0.24 μg/g dw plant material). The antioxidant activity was evaluated by DPPH, TEAC, hemoglobin ascorbate peroxidase activity inhibition (HAPX) and inhibition of lipid peroxidation catalyzed by cytochrome c assays, revealing an important antioxidant potential for both species. In the antimicrobial assays, C. ficifolia extract was found to be more active than E. globulus against both Gram-positive and Gram-negative bacterial strains with the exception of Bacillus subtilis. The results of the present study provide new valuable data regarding the bioactivities of these medicinal species.

Chemical composition and antibacterial activities of seven Eucalyptus species essential oils leaves

BACKGROUND

In this paper, we have studied the essential oils chemical composition of the leaves of seven Eucalyptus species developed in Tunisia. Eucalyptus leaves were picked from trees growing in different arboretums in Tunisia. Choucha and Mrifeg arboretums located in Sedjnene, region of Bizerte (Choucha: E. maideni, E. astrengens et E. cinerea; Mrifeg : E. leucoxylon), Korbous arboretums located in the region of Nabeul, North East Tunisia with sub-humid bioclimate, (E. lehmani), Souiniet-Ain Drahem arboretum located in region of Jendouba (E. sideroxylon, E. bicostata). Essential oils were individually tested against a large panel of microorganisms including Staphylococcus aureus (ATCC 6539), Escherichia coli (ATCC 25922), Enterococcus faecalis (ATCC29212), Listeria ivanovii (RBL 30), Bacillus cereus (ATCC11778).

RESULTS

The yield of essential oils ranged from 1.2% to 3% (w/w) for the different Eucalyptus species. All essential oils contain α-pinene, 1,8-cineol and pinocarveol-trans for all Eucalyptus species studied. The 1,8-cineol was the major compound in all species (49.07 to 83.59%). Diameter of inhibition zone of essential oils of Eucalyptus species varied from 10 to 29 mm. The largest zone of inhibition was obtained for Bacillus cereus (E. astrengens) and the lowest for Staphylococcus aureus (E. cinerea). The essential oils from E. maideni, E. astrengens, E. cinerea (arboretum of Bizerte), E. bicostata (arboretum of Aindraham) showed the highest antibacterial activity against Listeria ivanovii and Bacillus cereus.

CONCLUSION

The major constituents of Eucalyptus leaves essential oils are 1,8-cineol (49.07 to 83.59%) and α-pinene (1.27 to 26.35%). The essential oils from E. maideni, E. astrengens, E. cinerea, E. bicostata showed the highest antibacterial activity against Listeria ivanovii and Bacillus cereus, they may have potential applications in food and pharmaceutical products.