Antiviral Activities of Eucalyptus Essential Oils: Their Effectiveness as Therapeutic Targets against Human Viruses

Given the limited therapeutic management of infectious diseases caused by viruses, such as influenza and SARS-CoV-2, the medicinal use of essential oils obtained from Eucalyptus trees has emerged as an antiviral alternative, either as a complement to the treatment of symptoms caused by infection or to exert effects on possible pharmacological targets of viruses. This review gathers and discusses the main findings on the emerging role and effectiveness of Eucalyptus essential oil as an antiviral agent. Studies have shown that Eucalyptus essential oil and its major monoterpenes have enormous potential for preventing and treating infectious diseases caused by viruses. The main molecular mechanisms involved in the antiviral activity are direct inactivation, that is, by the direct binding of monoterpenes with free viruses, particularly with viral proteins involved in the entry and penetration of the host cell, thus avoiding viral infection. Furthermore, this review addresses the coadministration of essential oil and available vaccines to increase protection against different viruses, in addition to the use of essential oil as a complementary treatment of symptoms caused by viruses, where Eucalyptus essential oil exerts anti-inflammatory, mucolytic, and spasmolytic effects in the attenuation of inflammatory responses caused by viruses, in particular respiratory diseases.

Effect of process variables on heating profiles and extraction mechanisms during hydrodistillation of eucalyptus essential oil

The effect of different process variables, such as solid/liquid ratio (1: 1, 1: 3, or 1: 5 g/ml) and stirring speeds (0, 200, or 400 rpm), was studied on the extraction mechanisms of eucalyptus essential oil obtained by hydrodistillation (HD). Different performance parameters such as obtained yield, energy requirements, and environmental impact were compared to those obtained by steam distillation (SD). Two different mathematical models were used to describe the process behavior. The obtained results indicate that the system with a solid/liquid ratio of 1:5 g/ml using a stirring speed of 400 rpm yielded maximum for HD (1.19% ± 0.01%). The environmental impact expressed as Ecopoints (EI99) ranged between 50.87 ± 13.18 and 78.17 ± 13.82 mPT/g essential oil (EO) for systems with steam injection, whereas for HD took values between 16.9 ± 0.3 and 19.24 ± 1.4 mPT/g EO at optimal operating conditions. The model parameters allowed us to identify that large amounts of steam at lower heating velocities induce a high accumulation of EO in the aqueous layer (vapor-liquid equilibrium at the interface), favoring the extraction process.

In Vitro Cytotoxicity and Apoptotic Assay of Eucalyptus globulus Essential Oil in Colon and Liver Cancer Cell Lines

PURPOSE

Toxic effects of vegetables have been the subject of numerous investigations in recent years. Eucalyptus globulus of the Myrtaceae family has been traditionally used in the treatment of various infectious disorders. This study aims to assay the potential anticancer effect of Eucalyptus globulus essential oil, in vitro, and compare its cytotoxic effects on cancerous and non-cancerous cell lines.

METHODS

The cytotoxicity of the Eucalyptus globulus essential oil was evaluated in colon cancer cell line SW48, liver cancer cell line HepG2, HEK293t, and skin fibroblast using the MTT assay. We used 5-FU as the control treatment for cancer. The essential oil was diluted by phosphate buffer saline in cell culture.

RESULTS

Eucalyptus globulus essential oil with the concentration of 0.01% did not reduce the cell viability of SW48 (IC50 = 0.2%) and fibroblast cells (IC50 = 5%) after a 48-h treatment period. Eucalyptus globulus essential oil did not also exhibit any toxic effects on HEK293t and HEPG2 cell lines, except in high dose (0.5%) with IC50 = 0.2% for both of the cell lines.

CONCLUSION

Eucalyptus essential oil showed some side effects and might not be safe to use for treatment at high doses (0.5% and 5%). Moreover, the findings of the present study show that eucalyptus essential oil suppressed the proliferation of human colon cancer cells by inducing apoptosis. Eucalyptus essential oil might be a good candidate for the treatment of colon cancer.

Antibacterial polysaccharide-based hydrogel dressing containing plant essential oil for burn wound healing

BACKGROUND

Polysaccharide-based hydrogels have been developed for many years to treat burn wounds. Essential oils extracted from aromatic plants generally exhibit superior biological activity, especially antibacterial properties. Studies have shown that antibacterial hydrogels mixed with essential oils have great potential for burn wound healing. This study aimed to develop an antibacterial polysaccharide-based hydrogel with essential oil for burn skin repair.

METHODS

Eucalyptus essential oil (EEO), ginger essential oil (GEO) and cumin essential oil (CEO) were employed for the preparation of effective antibacterial hydrogels physically crosslinked by carboxymethyl chitosan (CMC) and carbomer 940 (CBM). Composite hydrogels were prepared and characterized using antimicrobial activity studies, Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, gas chromatography-mass spectrometery, rheological analysis, viscosity, swelling, water loss rate and water vapor transmission rate studies. In addition, the biocompatibility of hydrogels was evaluated in vivo by cytotoxicity and cell migration assays and the burn healing ability of hydrogels was tested in vivo using burn-induced wounds in mice.

RESULTS

The different essential oils exhibited different mixing abilities with the hydrogel matrix (CMC and CBM), which caused varying levels of reduction in essential oil hydrogel viscosity, swelling and water vapor transmission. Among the developed hydrogels, the CBM/CMC/EEO hydrogel exhibited optimal antibacterial activities of 46.26 ± 2.22% and 63.05 ± 0.99% against Staphylococcus aureus and Escherichia coli, respectively, along with cell viability (>92.37%) and migration activity. Furthermore, the CBM/CMC/EEO hydrogel accelerated wound healing in mouse burn models by promoting the recovery of dermis and epidermis as observed using a hematoxylin-eosin and Masson's trichrome staining assay. The findings from an enzyme-linked immunosorbent assay demonstrated that the CBM/CMC/EEO hydrogel could repair wounds through interleukin-6 and tumor necrosis factor-α downregulation and transforming growth factor-β, vascular endothelial growth factor (VEGF) and epidermal growth factor upregulation.

CONCLUSIONS

This study successfully prepared a porous CBM/CMC/EEO hydrogel with high antibacterial activity, favorable swelling, optimal rheological properties, superior water retention and water vapor transmission performance and a significant effect on skin repair in vitro and in vivo. The results indicate that the CBM/CMC/EEO hydrogel has the potential for use as a promising burn dressing material for skin burn repair.

A strategy of rapidly screening out herbicidal chemicals from Eucalyptus essential oils

BACKGROUND

To enhance discovering efficiency of new herbicidal compounds, a strategy for rapidly screening out strongly herbicidal chemical components from natural resources is necessary.

RESULTS

Seventeen essential oils selected from 14 Eucalyptus species and hybrids were evaluated for their herbicidal activities on annual ryegrass. A feasible strategy was established for rapidly pinpointing the chemicals contributing to strong herbicidal activities without the process of isolation and purification of individual compounds. This strategy was based on gas chromatography-mass spectrometry (GC-MS) coupled with principal component analysis (PCA) and verified by the bioassay results using several individual compounds. Two strong herbicidal compounds trans-pinocarveol and α-terpineol were screened out using the strategy. The strong herbicidal activity of trans-pinocarveol was discovered for the first time.

CONCLUSION

The established strategy of screening herbicidal compounds from natural resources is simple, feasible and reliable. © 2019 Society of Chemical Industry.

Evaluation the Effects of Eucalyptus Essential Oil and Hypertonic Saline as Scolicidal Agents in Induction of Sclerosing Cholangitis in Rabbits

Background

There are several scolicidal agents for inactivation of hydatid cyst protoscolices during surgery, but most of them are associated with adverse side effects such as sclerosing cholangitis (SC) and liver necrosis. The present study aimed to evaluate the adverse effects of Eucalyptus essential oil to induce SC in animal models.

Materials and Methods

Eighteen rabbits weighting 2000-3500 g were included in three groups for this study. About 0.3 ml of Eucalyptus essential oil (1%), or 5% hypertonic saline, or normal saline was injected for 5 min in the gallbladder. After 4 months, the liver, common bile duct, and duodenum were resected and immediately sent for cholangiography and pathologic studies.

Results

According to pathological studies, inflammation is more common in Eucalyptus and hypertonic saline groups. Due to cholangiographic studies, stricture was slightly higher in the hypertonic saline group than the Eucalyptus group.

Conclusion

Thus, 1% Eucalyptus essential oil is at least as safe as 5% hypertonic saline, but for clinical uses, it must be confirmed with further studies.