EEOs have attracted considerable attention due to their wide diversity of potential advantages in several biological applications and therapeutic characteristics (Fayez et al. 2023). These oils include chemical compounds with antibacterial (Elangovan and Mudgil 2023), anti-inflammatory (Salvatori et al. 2023), respiratory (Abbass 2020), pain-relief (Agarwal and Bhargava 2020), wound-healing (Mohammed et al. 2022), and aromatherapy properties (Robinson 2020), emphasizing their significance in supporting health and well-being (Fig. 4).

Biological activities of Eucalyptus essential oils (EEOs)

Essential oils derived from Eucalyptus possess powerful antimicrobial characteristics, rendering them efficacious against an extensive array of bacteria, fungi, and viruses (Ahmad et al. 2023). This action is mostly due to the high cineole concentration (Tine et al. 2020; Polito et al. 2023). EEOs has been proven to suppress the development of a variety of pathogenic microbes, including Staphylococcus aureus (Qasim et al. 2021; Elangovan and Mudgil 2023; Fayez et al. 2023; Iseppi et al. 2023), Escherichia coli (KAREEM et al. 2020; Song et al. 2022), and Candida albicans (da Silva Gündel et al. 2020; Wunnoo et al. 2021; Fayez et al. 2023).

EEOs' anti-inflammatory characteristics make them useful for treating inflammatory conditions, including arthritis (Varkaneh et al. 2022; Ashour et al. 2023; Iqbal et al. 2024), respiratory problems (Smruti 2021; Her et al. 2022), and skin conditions (Almeida et al. 2022; Moreira et al. 2022; Takagi 2024). Moreover, EEOs contains active components such as cineole and alpha-pinene, which contribute to decrease inflammation by suppressing the generation of pro-inflammatory cytokines (Zhao et al. 2023).

The beneficial properties of EEOs on respiratory health are among their most notable effects (Li et al. 2023). Inhaling EEOs can facilitate the clearing of airways, alleviate obstruction, and alleviate the symptoms of respiratory conditions, including sinusitis, colds, and coughing (Sadlon and Lamson 2010; Soleimani et al. 2021; Her et al. 2022). The decongestant properties of cineole facilitate the breakdown of mucus and sputum, thereby facilitate their expulsion (Akkara et al. 2023). Consequently, EEOs are frequently utilized in cough preparations, chest rubs, and inhalation therapies (Abbass 2020; Stinson et al. 2023). Furthermore, the potential of EEOs to mitigate symptoms associated with COVID-19 has been investigated, predominantly due to its antiviral, anti-inflammatory, and decongestant properties. Symptomatic alleviation for individuals afflicted by the virus may be achieved through the inhalation of EEOs, which may alleviate respiratory symptoms such as congestion and wheezing (Abbass 2020; Sharma 2020; Panikar et al. 2021; KHAIRIAH et al. 2022; Lee et al. 2023).

EEOs are also effective in alleviating muscle and joint discomfort. They can mitigate the discomfort associated with conditions such as rheumatism, sprains, and muscle strains when administered topically or incorporated into massage oils (Yin et al. 2020; Varkaneh et al. 2022; Bakó et al. 2023; LO et al. 2024). EEOs 's analgesic properties may be attributed to its ability to desensitize nerve terminals and decrease the perception of pain (Silva et al. 2003). This makes it a favored option among athletes and individuals with chronic pain conditions (Lee et al. 2019; Chandorkar et al. 2021; Ridouh and Hackshaw 2022).

The wound-healing potential of EEOs is another significant application. Their analgesic and anti-inflammatory properties reduce inflammation and pain, while their antimicrobial activity aids in the prevention of infections in incisions (De Luca et al. 2021; Mohammed et al. 2022; Saeedi et al. 2023).

EEOs, particularly their active component eucalyptol, have demonstrated substantial potential in promoting liver health through various mechanisms, such as their antioxidant and anti-inflammatory capacities. Due to these properties, EEOs effectively mitigate hepatotoxicity caused by acetaminophen by significantly decreasing serum levels of hepatic enzymes and oxidative stress markers while increasing antioxidant enzyme activities and reducing inflammatory cytokines (Esmail et al. 2024).

In a lipopolysaccharide-induced inflammation model, EEOs suppressed inflammation by increasing antioxidant enzyme activities such as SOD and decreasing levels of TNF-α and NF-κB. This supports EEOs 's efficacy in treating hepatic inflammation and oxidative stress (Zhao et al. 2021). Additionally, EOs of E. camaldulensis reduced liver damage caused by carbon tetrachloride (CCl4) in Wistar rats. The oils exhibited hepatoprotective potential by preventing elevated serum ALT and AST levels, total cholesterol, triglycerides, and LDL-cholesterol, while significantly increasing plasma HDL-cholesterol levels and antioxidant enzyme activities, underscoring their antioxidant properties (Noumi et al. 2022). The hepatoprotective and nephroprotective effects of α-pinene, a compound found in Eucalyptus, have also been observed in rats exposed to CCl4. By reducing intracellular reactive oxygen species (ROS), α-pinene restored its antioxidant status, highlighting its potential for liver and kidney protection (Udavant et al. 2023).

Eucalyptol has demonstrated protective properties against cisplatin-induced liver injury in rats through the reduction of oxidative stress and DNA damage. Additionally, it enhances the function of antioxidant enzymes, including catalase and glutathione, and lowering MDA levels. Its hepatoprotective effects were further enhanced by the downregulation of iNOS expression (Akcakavak et al. 2023). E. camaldulensis extract protected the livers of mice against Plasmodium chabaudi infection. The extract improved liver histology and enzymatic activity alterations, prevented oxidative damage, and modulated the production of liver cytokines and interleukins, indicating its antioxidant and anti-inflammatory properties (Aljawdah et al. 2022).

In HepG2 cells, α-pinene increased cell viability, decreased oxidative stress indicators, and regulated inflammatory pathways, indicating its potential for controlling hyperglycemia-induced liver damage (Choghakhori et al. 2024). Furthermore, eucalyptol has been shown to lower oxidative stress and ROS generation, thereby downregulating the NF-κB and RIPK1 pathways and reducing cell necroptosis and inflammation in grass carp liver cells caused by chlorpyrifos (Yang et al. 2024). In the same cells, eucalyptol also protected hepatocytes from avermectin-induced injury by alleviating oxidative stress and reducing the expression of NLRP3 inflammasome-related genes (Wang et al. 2023).

EEOs exhibit significant cardioprotective properties through various active constituents, each contributing to cardiovascular health via unique mechanisms. The prominent component, 1,8-cineole (eucalyptol), has been demonstrated to alleviate cardiovascular diseases, including hypertension and type 2 diabetes. Research conducted on rats and H9c2 cardiomyocytes has demonstrated that 1,8-cineole reduces ER stress-related apoptosis by modifying the miR-206-3p/SERP1 trajectory, thereby attenuating cardiac hypertrophy in heart failure. This underscores its potential to manage cardiovascular conditions by targeting specific molecular pathways (Oboh et al. 2013; Wang et al. 2021). Additionally, It ameliorates hypertrophy and enhances cardiac function in models of right ventricular hypertrophy and pulmonary arterial hypertension by reducing mitophagy, restoring mitochondrial respiratory capacity and homeostasis, and enhancing mitochondrial dynamics, all without causing toxicity (Alves-Silva et al. 2022). Furthermore, it shows potential for treating immune-thrombosis in conditions like COVID-19 and sepsis by inhibiting platelet activation and aggregation through activation of the AC-cAMP-PKA pathway. Moreover, it selectively inhibits glycoprotein VI-induced platelet activation and thrombus formation, reduces inflammatory cytokines, and may be useful for controlling excessive platelet reactivity (Alatawi 2021; Petry et al. 2024).

Eucalyptol has been shown to have a variety of cardiovascular benefits. In chronic nicotine-induced hypertension, it decreases plasma levels of MMP-9 and TIMP-1 markedly, suggesting its potential to mitigate cardiovascular complications (Murad 2023). Eucalyptol also enhances renal function and prevents the formation of atheromatous lesions in atherosclerotic models by reducing glycation, oxidative stress, and inflammatory mediators (Mahdavifard and Nakhjavani 2021). Furthermore, eucalyptol has been discovered to decrease myocardial contractility in a concentration-dependent manner. This property can be reversed by Ca2+ and isoproterenol, indicating that it plays a role in the management of myocardial contractility and the reduction of cardiac stress (Soares et al. 2005). Besides, its combined use with nifedipine has demonstrated enhanced effects in vasopressin-induced ischemia models, increasing coronary flow and angina symptoms while lowering oxidative and inflammatory markers (Murad and Alqurashi 2024).

Limonene, an additional significant constituent, provides numerous cardiovascular advantages. ( +)-Limonene is essential for the treatment of conditions such as hypertension and cardiac arrhythmia, as it promotes smooth muscle relaxation in the superior mesenteric artery of rats (de Sousa et al. 2015). The cardioprotective effects of D-limonene have been demonstrated in infarcted hearts of mice by reducing oxidative stress, restoring SOD and GPx activity, and suppressing pro-apoptotic pathways. Additionally, s-limonene mitigates cardiac remodeling in myocardial infarction models by reducing oxidative stress and Ca2+ overload, an observation that is comparable to the effects of well-known antioxidants such as N-acetyl cysteine (Durco et al. 2019; Rhana et al. 2022). D-Limonene has been demonstrated to significantly reduce myocardial infarction injury, primarily through the inhibition of the MAPK/NF-κB pathway, which affects subsequent transcriptional regulation. Furthermore, D-limonene's anti-apoptotic properties enhance its overall cardioprotective pharmacological effects (Younis 2020). Also, D-limonene mitigates cardiac toxicity caused by CCl4 intoxication by enhancing the antioxidant machinery, attenuating lipid peroxidation, and inhibiting inflammatory cascades through its antioxidant and anti-inflammatory properties (AlSaffar et al. 2022). In addition, l-limonene has the potential to enhance the quality of life for diabetic patients by modulating the AMPK/SIRT1/p65 signaling pathway, which also demonstrates anti-atherosclerotic properties in diabetic rats (Han et al. 2023).

Alpha-pinene, contained in EEOs, is also beneficial to cardiovascular health. It has cardioprotective and anti-inflammatory effects in isoproterenol-induced myocardial infarction models by decreasing cardiac marker enzyme levels, lipid peroxidation, and inflammatory mediators while restoring antioxidant status (Zhang et al. 2020). Furthermore, alpha-pinene and its metabolites, myrtenol and verbenol, greatly relax the blood vessels, mediated via endothelial-derived NO and guanylyl cyclase activity, emphasizing its vascular advantages (Jin et al. 2023). Moreover, monoterpenes α- and β-pinene inhibit bacterial growth in endocarditis, though they face resistance from strains such as Staphylococcus aureus (Salehi et al. 2019b).

Furthermore, E. torquata seeds extract (ETS) has demonstrated cardio-preventive properties against myocardial infarction in rats by significantly lowering cardiotoxicity, oxidative stress, and DNA fragmentation while improving lipid levels (Tej et al. 2024). E. globulus leaf extract has been shown to improve cardiac function in diabetic rats by rectifying oxidative stress, dyslipidemia, and cardiomyocyte depletion, as well as enhancing the expression of key cardiac proteins (Akinmoladun et al. 2023).

EEOs contains main components such as 1,8-cineole, α-pinene, and limonene. These compounds have antioxidant, anti-inflammatory, and neuroprotective properties. The central nervous system activities of the oil are primarily attributed to 1,8-cineole (Eucalyptol) and α-pinene (Sebei et al. 2015). Studies suggest that EEOs could be a promising therapy for neurodegenerative diseases such as Alzheimer's and Parkinson's by reducing neuroinflammation, modulating neurotransmitter systems, and promoting neuronal survival. Additionally, EEOs has shown anxiety-reducing and cognitive-enhancing effects (Qneibi et al. 2024). Furthermore, it can easily crosses the blood–brain barrier (BBB), regulating brain receptors and enzymes (Xu et al. 2021).

Memory loss disrupting daily life may indicate early dementia or Alzheimer's disease, marked by difficulty performing tasks and remembering dates. Alzheimer's is linked to amyloid plaques, neurofibrillary tangles, and neural connection loss in the brain (Soares et al. 2021). Alzheimer’s is also associated with decreased acetylcholine levels due to high activity of acetylcholinesterase and cholinergic neuron deterioration, leading to memory loss, a prominent symptom of the disease. E. globulus possesses anti-inflammatory and antimicrobial properties, in addition, it inhibits acetylcholinesterase (AChE), the enzyme that degrades the neurotransmitter acetylcholine into choline and acetate. This inhibition increases acetylcholine levels and prolongs its effects in the central nervous system, enhancing memory as well as preventing and slowing the progression of neurodegenerative diseases like Alzheimer. (Ayaz et al. 2017; Soares et al. 2021; Adedamola et al. 2023).

Experimental models have demonstrated the efficacy of E. globulus in protecting several organs against redox imbalance (Dhibi et al. 2014). Impaired antioxidant system and oxidative stress have been recognized as crucial mechanisms in the pathogenesis of several illnesses. The presence of elevated amounts of free radicals in the system results in the decline of renal function and subsequently gives rise to tubulointerstitial fibrosis (Ganesan et al. 2018). The acute overdose of acetaminophen disrupted the equilibrium between oxidants and antioxidants, therefore disturbing redox homeostasis and inducing oxidative damage in the kidney. Administration of eucalyptus successfully prevented nephrotoxicity caused by acetaminophen by restoring nearly normal levels of superoxide dismutase (SOD), catalase (CAT), and glutathione (GPX) activity (Dhibi et al. 2014).

EEOs with antibacterial qualities obtained from Eucalyptus, contain a significant number of terpenes, especially limonene, that exhibit great potential as bioactive components for optimizing hair and skin health. Studies indicated that the phytochemical components of EEOs, when applied topically, can interfere with the functional capacity of skin cells. Furthermore, these phytochemicals exert advantageous effects on anti-aging, anti-acne, sunscreen, and skin-lightening (Aswandi et al. 2023). EEOs exhibits anti-inflammatory, antioxidant, antibacterial, and antifungal properties, which strengthen the capillary fibers in the hair as well as promote health and cleanliness of the scalp (Zhou et al. 2021).

The antioxidant characteristics of EEOs can mitigate oxidative stress, which is a contributing factor to alopecia. Furthermore, EEOs significantly improve blood flow in the hair follicles as well as preserve the vascularization of hair epidermis papillae (Guzmán and Lucia 2021; Abelan et al. 2022; Aswandi et al. 2023). Incorporating EEOs into anti-dandruff haircare products boosts their effectiveness by combining anti-inflammatory, antifungal, and antioxidant properties, helping to eliminate the root causes of dandruff. Additionally, the use of EEOs benefits hair care by addressing seborrhea, a condition resulting from capillary dysfunction and oily hair fibers. This condition is partially alleviated by essential oils (Abelan et al. 2022).

Effective cosmetic products containing E. globulus essential oils are crucial for improving skin hydration and maintaining overall skin health by supporting the skin barrier function, which can be disrupted by external and internal factors. Frequent use of soaps, detergents, hot water, or alcohol can remove surface lipids, leading to skin barrier damage and increased trans-epidermal water loss (TEWL) (Infante et al. 2022). The dermato-protective properties of E. globulus were investigated, showing notable inhibitory effects on tyrosinase. Moreira et al. (2022) investigation examined the potential protective properties of the essential oil and hydro-distillation residual water extract derived from E. globulus leaves against skin injury. The results revealed a decrease in age-related indicators of aging, such as the increased expression of type I collagen and the stimulation of matrix metalloproteinases and β-galactosidase. Likewise, there was reported suppression of melanin and tyrosinase synthesis (Assaggaf et al. 2022).

Elevated concentrations of pro-inflammatory cytokines and reactive oxygen species have a substantial role in the process of skin aging. A recent study revealed that an ethanolic extract derived from dehydrated commercial E. globulus biomass has a capacity to provide protection against UV-induced photoaging, therefore significantly diminishing the development of wrinkles and mitigating skin dryness. Although the precise chemical mechanisms underlying the anti-inflammatory effect of EEOs are not fully understood, some researchers attributed this activity to the presence of monoterpenes, especially 1,8 cineole, which is a powerful inhibitor of cytokine release (Moreira et al. 2022). Prior studies have illustrated that the main flavonoids in EEOs leaf offer several advantages for skin health (Aswandi et al. 2023).These significant findings strongly advocate for further investigation for anti-aging skincare.

For thousands of years, traditional Aboriginal medicine has used ointments containing EEOs to help in wound healing (Chandorkar et al.