Geraniol modulates tongue and hepatic phase I and phase II conjugation activities and may contribute directly to the chemopreventive activity against experimental oral carcinogenesis

Essential Oils: Chemistry and Pharmacological Activities-Part II

The importance of essential oils and their components in the industrial sector is attributed to their chemical characteristics and their application in the development of products in the areas of cosmetology, food, and pharmaceuticals. However, the pharmacological properties of this class of natural products have been extensively investigated and indicate their applicability for obtaining new drugs. Therefore, this review discusses the use of these oils as starting materials to synthesize more complex molecules and products with greater commercial value and clinic potential. Furthermore, the antiulcer, cardiovascular, and antidiabetic mechanisms of action are discussed. The main mechanistic aspects of the chemopreventive properties of oils against cancer are also presented. The data highlight essential oils and their derivatives as a strategic chemical group in the search for effective therapeutic agents against various diseases.

Potential Effects of Geraniol on Cancer and Inflammation-Related Diseases: A Review of the Recent Research Findings

Geraniol (GNL), a natural monoterpene, is found in many essential oils of fruits, vegetables, and herbs, including lavender, citronella, lemongrass, and other medicinal and aromatic plants. GNL is commonly used by the cosmetic and food industries and has shown a wide spectrum of pharmacological activities including anti-inflammatory, anticancer, antimicrobial, antioxidant, and neuroprotective activities. It represents a potential anti-inflammatory agent and a promising cancer chemopreventive agent, as it has been found to be effective against a broad range of cancers, including colon, prostate, breast, lung, skin, kidney, liver, and pancreatic cancer. Moreover, GNL scavenges free radicals and preserves the activity of antioxidant enzymes. In addition, GNL induces apoptosis and cell cycle arrest, modulates multiple molecular targets, including p53 and STAT3, activates caspases, and modulates inflammation via transcriptional regulation. In the present study, different modes of action are described for GNL's activity against cancer and inflammatory diseases. This compound protects various antioxidant enzymes, such as catalase, glutathione-S-transferase, and glutathione peroxidase. Experiments using allergic encephalomyelitis, diabetes, asthma, and carcinogenesis models showed that GNL treatment had beneficial effects with low toxicity. GNL has been shown to be effective in animal models and tumor cell lines, but there have not been any clinical studies carried out for it. The aim of the present review is to provide updated data on the potential effects of GNL on cancer and inflammation, and to enhance our understanding of molecular targets, involved pathways, and the possible use of GNL for clinical studies and therapeutic purposes in the treatment of cancer and inflammation-related diseases.

Conversion of Geraniol into Useful Value-Added Products in the Presence of Catalysts of Natural Origin: Diatomite and Alum

This article presents research related to the transformation of geraniol (GA), leading to the formation of products with very valuable properties. In the planned method, heterogeneous catalysts of natural origin in the form of alum and diatomite were used as catalysts. Initially, the process which we investigated was the process of isomerization of GA, but it turned out during the studies that GA is also transformed in other reactions. Before catalytic tests, these two minerals were subjected to detailed instrumental analyses using the following methods: XRD, SEM/EDX, XRF and FTIR, which allowed to obtain their full morphological characteristics. During the catalytic tests, the influence of such relevant parameters on the GA transformations was determined: temperature from 80 to 150 °C, catalyst content from 5 to 15% by weight and the reaction time from 15 min to 24 h. The tests presented in the article were carried out under atmospheric pressure (in air) as well as without the use of a solvent. The optimal conditions for the transformations of GA were determined on the basis of its conversion and selectivities of transformation to the main products in the form of: beta-pinene (BP), 6,11-dimethyl-2,6,10-dodecatriene-1-ol (DC) and thumbergol (TH). The above products were formed with the highest selectivity, respectively: 100 mol%, 50 mol% and 52 mol%. The results of the syntheses showed that for GA the best transformation results were obtained at the temperature of 80 °C (for both tested catalysts), with the catalyst content of 1 wt % (for both tested catalysts) and for the reaction time of 1 h (for diatomite)) and 3 h (for alum).

Potential anticancer effects of cyclo(-Pro-Tyr) against N-diethyl nitrosamine induced hepatocellular carcinoma in mouse through PI3K/AKT signaling

The oceans are considered as magnificent source of bioactive metabolites, of which marine sponges associated organisms are being the most effective producers of various bioactive molecules. We previously reported that cyclo(-Pro-Tyr) (CPT), a dipeptide from marine sponge Callyspongia fistularis associated Bacillus pumilus AMK1 bacteria for its anti-proliferative activity through down regulating PI3K signaling and inducing mitochondrial mediated apoptosis in HepG2 cells. Further we emphasize to study the role of CPT against hepatocellular carcinoma (HCC) induced by N-diethylnitrosamine (DEN) in male swiss albino mice in vivo. In this study, HCC was induced by the administration of DEN (75 mg/kg b.wt) dissolved in saline once/week for 3 weeks, then 100 mg/kg b.wt for another successive 3 weeks and observed for 18 weeks. CPT (100 mg/kg b.wt) treatment was started after 14 weeks of DEN induction. The obtained results demonstrated that CPT altered DEN induced oxidative stress by decreasing serum SGOT and SGPT followed increment in the antioxidants such as superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase. This was accompanied by decreased accumulation of glycoconjugates and argyophilic nucleolar organizing regions in the treatment groups. Further, CPT significantly reduced the levels of phospho-PI3Kinase p85 and phospho-AKT and upregulation of PTEN compared with DEN induced group. Besides this, decreased expression of Bcl-2 and increased expression of Bax, Caspase 3, and p53 was observed in CPT treated mice. Therefore, the anticancer mechanism of CPT against DEN induced HCC may be associated with the regulation of the PI3K/AKT signaling pathway, which ultimately stimulates apoptosis.

Geraniol exerts its antiproliferative action by modulating molecular targets in lung and skin carcinoma cells

Geraniol, an acyclic monoterpene present in several plant species' essential oils, is utilized as a food additive. It possesses potent antiproliferative and antitumor effects ascribed to its antiinflammatory, and antioxidant properties. The study aimed to understand geraniol's mechanism in human lung and skin cancer cells by employing molecular and cell target-based assays. SRB, NRU, MTT assays, qRT-PCR, molecular docking, and EAC model were used. Geraniol inhibits the proliferation of PC-3, A431, and A549 cells (~50%) and suppresses the activity of ornithine decarboxylase (15.42 ± 0.61 μM) and hyaluronidase (57.61 ± 8.53 μM) in A549 cells; LOX-5 (25.44 ± 3.50 μM) and hyaluronidase (90.71 ± 2.38 μM) in A431 cells. The qRT-expression analysis of the targeted gene depicts non-significant change at the transcriptional level of LOX-5 in A431 cells. A robust binding interaction of geraniol with molecular targets was observed in the molecular docking studies. In Ehrlich Ascites Carcinoma model, geraniol inhibit tumor growth by 50.08% at 75 mg/kg bw and was found to be safe up to 1,000 mg/kg bw in a toxicity study. Geraniol has two prenyl units allied head-to-tail and functionalized with one hydroxyl group at its tail end could be responsible for the antiproliferative activity. These observations provide evidence for geraniol to be used as a new prototype to develop a novel anticancer agent.

One Hundred Faces of Geraniol

Geraniol is a monoterpenic alcohol with a pleasant rose-like aroma, known as an important ingredient in many essential oils, and is used commercially as a fragrance compound in cosmetic and household products. However, geraniol has a number of biological activities, such as antioxidant and anti-inflammatory properties. In addition, numerous in vitro and in vivo studies have shown the activity of geraniol against prostate, bowel, liver, kidney and skin cancer. It can induce apoptosis and increase the expression of proapoptotic proteins. The synergy of this with other drugs may further increase the range of chemotherapeutic agents. The antibacterial activity of this compound was also observed on respiratory pathogens, skin and food-derived strains. This review discusses some of the most important uses of geraniol.

Reactive oxygen species generation and mitochondrial dysfunction for the initiation of apoptotic cell death in human hepatocellular carcinoma HepG2 cells by a cyclic dipeptide Cyclo(-Pro-Tyr)

Cyclic dipeptides are increasingly gaining importance as considering its significant biological and pharmacological activities. This study was aimed to investigate the anticancer activity of a dipeptide Cyclo(-Pro-Tyr) (DP) identified from marine sponge Callyspongia fistularis symbiont Bacillus pumilus AMK1 and the underlying apoptotic mechanisms in the liver cancer HepG2 cell lines. MTT assay was done to demonstrate the cytotoxic effect of DP in HepG2 cells and mouse Fibroblast McCoy cells. Initially, apoptosis inducing activity of DP was identified using propidium iodide (PI) and acridine orange/ethidium bromide (AO/EB) dual staining, then it was confirmed by DNA fragmentation assay and western blotting analysis of apoptosis related markers Bax, Bcl-2, cytochrome c, caspase-3 and cleaved poly (ADP-ribose) polymerase (PARP). Rhodamine 123 staining was performed to observe DP effects on the mitochondrial membrane potential (MMP) and DCFH-DA (Dichloro-dihydro-fluorescein diacetate) staining was done to measure the intracellular reactive oxygen species (ROS) levels. The MTT results revealed that DP initiated dose-dependent cytotoxicity in HepG2 cells, but no significant toxicity in mouse Fibroblast McCoy cells treated with DP at the specified concentrations. DP induced apoptosis, which is confirmed by the appearance of apoptotic bodies with PI and AO/EB dual staining, and DNA fragmentation. DP significantly elevated the Bax/Bcl-2 ratio, disrupted the mitochondrial membrane potential (MMP), enhanced cytochrome c release from mitochondria, increased caspase-3 activation, the cleavage of PARP and increased intracellular reactive oxygen species (ROS) levels. Besides this, DP successfully inhibited the phosphorylation of PI3K, AKT and increased PTEN expression. These results suggested DP might have anti-cancer effect by initiating apoptosis through mitochondrial dysfunction and downregulating PI3K/Akt signaling pathway in HepG2 cells with no toxicity effect on normal fibroblast cells. Therefore, DP may be developed as a potential alternative therapeutic agent for treating hepatocellular carcinoma.

The Potential of Isoprenoids in Adjuvant Cancer Therapy to Reduce Adverse Effects of Statins

The mevalonate pathway provides sterols for membrane structure and nonsterol intermediates for the post-translational modification and membrane anchorage of growth-related proteins, including the Ras, Rac, and Rho GTPase family. Mevalonate-derived products are also essential for the Hedgehog pathway, steroid hormone signaling, and the nuclear localization of Yes-associated protein and transcriptional co-activator with PDZ-binding motif, all of which playing roles in tumorigenesis and cancer stem cell function. The phosphatidylinositol-4,5-bisphosphate 3-kinase-AKT-mammalian target of rapamycin complex 1 pathway, p53 with gain-of-function mutation, and oncoprotein MYC upregulate the mevalonate pathway, whereas adenosine monophosphate-activated protein kinase and tumor suppressor protein RB are the downregulators. The rate-limiting enzyme, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), is under a multivalent regulation. Sterol regulatory element binding protein 2 mediates the sterol-controlled transcriptional downregulation of HMGCR. UbiA prenyltransferase domain-containing protein-1 regulates the ubiquitination and proteasome-mediated degradation of HMGCR, which is accelerated by 24, 25-dihydrolanosterol and the diterpene geranylgeraniol. Statins, competitive inhibitors of HMGCR, deplete cells of mevalonate-derived intermediates and consequently inhibit cell proliferation and induce apoptosis. Clinical application of statins is marred by dose-limiting toxicities and mixed outcomes on cancer risk, survival and mortality, partially resulting from the statin-mediated compensatory upregulation of HMGCR and indiscriminate inhibition of HMGCR in normal and tumor cells. Tumor HMGCR is resistant to the sterol-mediated transcriptional control; consequently, HMGCR is upregulated in cancers derived from adrenal gland, blood and lymph, brain, breast, colon, connective tissue, embryo, esophagus, liver, lung, ovary, pancreas, prostate, skin, and stomach. Nevertheless, tumor HMGCR remains sensitive to isoprenoid-mediated degradation. Isoprenoids including monoterpenes (carvacrol, L-carvone, geraniol, perillyl alcohol), sesquiterpenes (cacalol, farnesol, β-ionone), diterpene (geranylgeranyl acetone), “mixed” isoprenoids (tocotrienols), and their derivatives suppress the growth of tumor cells with little impact on non-malignant cells. In cancer cells derived from breast, colon, liver, mesothelium, prostate, pancreas, and skin, statins and isoprenoids, including tocotrienols, geraniol, limonene, β-ionone and perillyl alcohol, synergistically suppress cell proliferation and associated signaling pathways. A blend of dietary lovastatin and δ-tocotrienol, each at no-effect doses, suppress the growth of implanted murine B16 melanomas in C57BL6 mice. Isoprenoids have potential as adjuvant agents to reduce the toxicities of statins in cancer prevention or therapy.

Deficiency of IL-18 Aggravates Esophageal Carcinoma Through Inhibiting IFN-γ Production by CD8+T Cells and NK Cells

To investigate the potential role of interleukin-18 (IL-18) in immunomodulation during tumorigenesis of esophageal carcinoma and elucidate the underlying molecular mechanism, we employed IL-18 knockout mice for this purpose. Carcinogen 4-nitroquinoline 1-oxide (4NQO) was administrated in drinking water to induce occurrence of esophageal squamous cell carcinoma (ESCC). T cell activation as indicated by the surface CD molecules was analyzed with flow cytometry. The serous content of interferon-γ (IFN-γ) along with other cytokines was determined by inflammatory human cytokine cytometric bead array. The cytotoxicity assay was performed by co-culture of tumor cells with immune cells and relative cell viability was determined by lactate dehydrogenase (LDH) assay. Apoptotic cells were stained with Annexin-V/propidium iodide (PI) and analyzed by flow cytometry. Cell proliferation was measured with Cell Counting Kit-8 (CCK-8) assay. Our data demonstrated that deficiency of IL-18 promoted the progression and development of 4NQO-induced ESCC. Loss of IL-18 suppressed the activation of T cells in the esophagus. Deficiency of IL-18 inhibited the IFN-γ production by CD8+ T cells and natural killer (NK) cells. Absence of IL-18 inhibited the cytotoxicity of CD8+ T cells and NK cell in vitro. Moreover, deficiency of IL-18 promoted the apoptosis of CD8+ T cells and inhibited the proliferation of CD8+ T cells in vitro. Our data elucidated the immunomodulatory role of IL-18 during tumorigenesis of ESCC, whose deficiency compromised antitumor immunity and contributed to immune escape of esophageal carcinoma. Our results also indicated the therapeutic potential of exogenous IL-18 against ESCC, which warrants further investigations.

Geraniol Pharmacokinetics, Bioavailability and Its Multiple Effects on the Liver Antioxidant and Xenobiotic-Metabolizing Enzymes

Geraniol is a natural monoterpene showing anti-inflammatory, antioxidant, neuroprotective and anticancer effects. No pharmacokinetic and bioavailability data on geraniol are currently available. We therefore performed a systematic study to identify the permeation properties of geraniol across intestinal cells, and its pharmacokinetics and bioavailability after intravenous and oral administration to rats. In addition, we systematically investigated the potential hepatotoxic effects of high doses of geraniol on hepatic phase I, phase II and antioxidant enzymatic activities and undertook a hematochemical analysis on mice. Permeation studies performed via HPLC evidenced geraniol permeability coefficients across an in vitro model of the human intestinal wall for apical to basolateral and basolateral to apical transport of 13.10 ± 2.3 × 10^-3 and 2.1 ± 0.1⋅× 10^-3 cm/min, respectively. After intravenous administration of geraniol to rats (50 mg/kg), its concentration in whole blood (detected via HPLC) decreased following an apparent pseudo-first order kinetics with a half-life of 12.5 ± 1.5 min. The absolute bioavailability values of oral formulations (50 mg/kg) of emulsified geraniol or fiber-adsorbed geraniol were 92 and 16%, respectively. Following emulsified oral administration, geraniol amounts in the cerebrospinal fluid of rats ranged between 0.72 ± 0.08 μg/mL and 2.6 ± 0.2 μg/mL within 60 min. Mice treated with 120 mg/kg of geraniol for 4 weeks showed increased anti-oxidative defenses with no signs of liver toxicity. CYP450 enzyme activities appeared only slightly affected by the high dosage of geraniol.

Molecular effects of hesperetin, a citrus flavanone on7,12-dimethylbenz(a)anthracene induced buccal pouch squamous cell carcinoma in golden Syrian hamsters

In recent years, researchers have been focused on citrus flavanone, a naturally occurring bioactive substance of hesperetin. To investigate the molecular mechanism based chemopreventive efficacy of hesperetin on 7,12-dimethylbenz(a)anthracene (DMBA) induced hamster buccal pouch (HBP) squamous cell carcinoma (SCC). The oral tumour was provoked by painted with 0.5% DMBA on left buccal pouch thrice a week for 10 consecutive weeks developed well-differentiated SCC and tumour formation was 100% in DMBA alone. We evaluated the chemopreventive potential of hesperetin by assessing the lipid peroxidation (LPO) by-products, status of enzymatic, non-enzymatic antioxidants, detoxifying agents etc. Moreover, modulating expression of apoptotic and cell proliferation markers were observed in HBP SCC experimental hamsters. Oral administration of hesperetin (20 mg/kg b.w.) to DMBA painted hamsters significantly reversed the stages of oral SCC. Our findings indicate that hesperetin possesses a chemopreventive effect in DMBA-induced oral SCC by exerting anti-carcinogenic property.

Geraniol promotes functional recovery and attenuates neuropathic pain in rats with spinal cord injury

Geraniol, a plant-derived monoterpene, has been extensively studied and showed a wide variety of beneficial effects. The aim of this study was to investigate the therapeutic effect of geraniol on functional recovery and neuropathic pain in rats with spinal cord injury (SCI). Rats received a clip-compression SCI and were treated with geraniol 6 h following SCI. Treatment of SCI rats with geraniol markedly improved locomotor function, and reduced sensitivity to the mechanical allodynia and thermal hyperalgesia. Treatment of SCI rats with geraniol increased NeuN-positive cells, suppressed expression of glial fibrillary acidic protein, and reduced activity of caspase-3 in the injured region. Treatment of SCI rats with geraniol reduced levels of malondialdehyde and 3-nitrotyrosine, upregulated protein expression of nuclear factor-erythroid 2-related factor 2 and heme oxygenase 1, and suppressed expression of inducible nitric oxide synthase in the injured region. In addition, treatment of SCI rats with geraniol downregulated protein expression of N-methyl-d-aspartate receptor 1 and reduced the number of CD68-positive cells and protein levels of TNF-α in the injured region. In conclusion, geraniol significantly promoted the recovery of neuronal function and attenuated neuropathic pain after SCI.

The antitumor effects of geraniol: Modulation of cancer hallmark pathways (Review)

Geraniol is a dietary monoterpene alcohol that is found in the essential oils of aromatic plants. To date, experimental evidence supports the therapeutic or preventive effects of geraniol on different types of cancer, such as breast, lung, colon, prostate, pancreatic, and hepatic cancer, and has revealed the mechanistic basis for its pharmacological actions. In addition, geraniol sensitizes tumor cells to commonly used chemotherapy agents. Geraniol controls a variety of signaling molecules and pathways that represent tumor hallmarks; these actions of geraniol constrain the ability of tumor cells to acquire adaptive resistance against anticancer drugs. In the present review, we emphasize that geraniol is a promising compound or chemical moiety for the development of a safe and effective multi-targeted anticancer agent. We summarize the current knowledge of the effects of geraniol on target molecules and pathways in cancer cells. Our review provides novel insight into the challenges and perspectives with regard to geraniol research and to its application in future clinical investigation.

Geraniol Suppresses Angiogenesis by Downregulating Vascular Endothelial Growth Factor (VEGF)/VEGFR-2 Signaling

Geraniol exerts several direct pharmacological effects on tumor cells and, thus, has been suggested as a promising anti-cancer compound. Because vascularization is a major precondition for tumor growth, we analyzed in this study the anti-angiogenic action of geraniol. In vitro, geraniol reduced the migratory activity of endothelial-like eEND2 cells. Western blot analyses further revealed that geraniol downregulates proliferating cell nuclear antigen (PCNA) and upregulates cleaved caspase-3 (Casp-3) expression in eEND2 cells. Moreover, geraniol blocked vascular endothelial growth factor (VEGF)/VEGFR-2 signal transduction, resulting in a suppression of downstream AKT and ERK signaling pathways. In addition, geraniol significantly reduced vascular sprout formation in a rat aortic ring assay. In vivo, geraniol inhibited the vascularization of CT26 tumors in dorsal skinfold chambers of BALB/c mice, which was associated with a smaller tumor size when compared to vehicle-treated controls. Immunohistochemical analyses confirmed a decreased number of Ki67-positive cells and CD31-positive microvessels with reduced VEGFR-2 expression within geraniol-treated tumors. Taken together, these findings indicate that geraniol targets multiple angiogenic mechanisms and, therefore, is an attractive candidate for the anti-angiogenic treatment of tumors.

Antitumor activity of monoterpenes found in essential oils

Cancer is a complex genetic disease that is a major public health problem worldwide, accounting for about 7 million deaths each year. Many anticancer drugs currently used clinically have been isolated from plant species or are based on such substances. Accumulating data has revealed anticancer activity in plant-derived monoterpenes. In this review the antitumor activity of 37 monoterpenes found in essential oils is discussed. Chemical structures, experimental models, and mechanisms of action for bioactive substances are presented.

Geraniol ameliorates the motor behavior and neurotrophic factors inadequacy in MPTP-induced mice model of Parkinson's disease

Many experiments affirm the notion that augmentation of neurotrophic factors (NTFs) activity, especially brain-derived neurotrophic factors and glial cell-derived neurotrophic factors, could prevent or halt the progress of neurodegeneration in Parkinson's disease (PD). In this study, we investigated the therapeutic accomplishment of geraniol (GE 100 mg/kg) on 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mice model of PD. Current investigation proved that pretreatment with GE ameliorates the MPTP-induced alterations in behavioral, biochemical, immunohistochemical, and immunoblotting manifestations in mice. Systematically, the loss of dopaminergic neurons and reduced NTFs mRNA expressions induced by MPTP was ameliorated to a significant extent by pretreatment with GE. We found that GE confers a potent neuroprotective agent against MPTP-induced dopaminergic denervation and may become a potential therapeutic agent for PD and/or its progression.