A comprehensive and systematic review on potential anticancer activities of eugenol: From pre-clinical evidence to molecular mechanisms of action

An Overview of the Spices Used for the Prevention and Potential Treatment of Gastric Cancer

Gastric cancer (GC) ranks third in terms of cancer-related deaths and is the fifth most commonly diagnosed type of cancer. Its risk factors include Helicobacter pylori infection, Epstein-Barr virus infection, the consumption of broiled and charbroiled animal meats, salt-preserved and smoke-enhanced foods, alcohol drinking, tobacco smoking, exposure to ionizing radiation, and positive family history. The limited effectiveness of conventional therapies and the widespread risk factors of GC encourage the search for new methods of treatment and prevention. In the quest for cheap and commonly available medications, numerous studies focus on herbal medicine, traditional brews, and spices. In this review, we outline the potential use of spices, including turmeric, ginger, garlic, black cumin, chili pepper, saffron, black pepper, rosemary, galangal, coriander, wasabi, cinnamon, oregano, cardamom, fenugreek, caraway, clove, dill, thyme, Piper sarmentosum, basil, as well as the compounds they contain, in the prevention and treatment of GC. We present the potential molecular mechanisms responsible for the effectivity of a given seasoning substance and their impact on GC cells. We discuss their potential effects on proliferation, apoptosis, and migration. For most of the spices discussed, we also outline the unavailability and side effects of their use.

Essential oils and their nanoformulations for breast cancer therapy

Breast Cancer (BC) is the most prevalent type of cancer in the world. Current treatments include surgery, radiation, and chemotherapy but often are associated with high toxicity to normal tissues, chemoresistance, and relapse. Thus, developing novel therapies which could combat these limitations is essential for effective treatment. In this context, phytochemicals are increasingly getting popular due to their safety profile, ability to efficiently target tumors, and circumvent limitations of existing treatments. Essential Oils (EOs) are mixtures of various phytochemicals which have shown potential anticancer activity in preclinical BC models. However, their clinical translation is limited by factors such as high volatility, low stability, and poor solubility. Nanotechnology has facilitated their encapsulation in a variety of nanostructures and proven to overcome these limitations. In this review, we have efficiently summarized the current knowledge on the anticancer effect of EOs and constituents in both in in vitro and in in vivo BC models. Further, we also provide a descriptive account on the potential of nanotechnology in enhancing the anti-BC activity of EOs and their constituents. The papers discussed in this review were selected using the keywords "antiproliferative Essential Oils in breast cancer," "anticancer activity of Essential Oil in breast cancer," and "cytotoxicity of Essential Oils in breast cancer" performed in PubMed and ScienceDirect databases.

Protective role of eugenol against diabetes-induced oxidative stress, DNA damage, and apoptosis in rat testes

Diabetes mellitus, a metabolic disorder alters gonadal development and spermatogenesis, reactive oxygen species production, DNA damage, and apoptosis, which subsequently lead to male subfertility. Eugenol is an antioxidant, traditionally used as medication for digestive disorders and antioxidant therapy, decrease transport of glucose from GIT to systemic circulation. This experiment was aimed to decipher cellular and molecular insights of eugenol in protecting diabetic germ cells in rats. Rats were assigned randomly into five groups: control, eugenol control (Eugenol 400; EUG), diabetic (DIA), diabetic + eugenol 100 (DIA + EUG 100), and diabetic + eugenol 400 (DIA + EUG 400). EUG 400 and DIA + EUG 400 groups received 400 mg/kg eugenol orally. DIA + EUG 100 group received 100 mg/kg eugenol. Treatment was conducted for 4 weeks. Type 1 diabetes was induced by injecting a single i.p. dose of streptozotocin (55 mg/kg). Morphometric, biochemical, sperm parameters, oxidative stress, hormonal levels, histopathology, and fibrosis in the testis and epididymis, were evaluated. DNA damage was evaluated using halo and comet assays; DNA fragmentation and apoptosis using TUNEL assay. Eugenol treatment significantly normalized biochemical parameters, reduced MDA while increased albumin and GSH levels in diabetes. Eugenol significantly increased sperm numbers, motility and attenuated abnormal sperm head morphology in diabetes. Moreover, eugenol significantly reversed diabetes-induced cellular damages, altered spermatogenesis, and collagen deposition in testis and epididymis. It also significantly attenuated diabetes-associated DNA breaks and apoptosis. These findings suggest that 4 weeks treatment with 400 mg/kg of eugenol could be beneficial for diabetic patients to prevent subfertility.

Hyponatremia Promotes Cancer Growth in a Murine Xenograft Model of Neuroblastoma

In cancer patients, hyponatremia is detected in about 40% of cases at hospital admission and has been associated to a worse outcome. We have previously observed that cancer cells from different tissues show a significantly increased proliferation rate and invasion potential, when cultured in low extracellular [Na+]. We have recently developed an animal model of hyponatremia using Foxn1nu/nu mice. The aim of the present study was to compare tumor growth and invasivity of the neuroblastoma cell line SK-N-AS in hyponatremic vs. normonatremic mice. Animals were subcutaneously implanted with luciferase-expressing SK-N-AS cells. When masses reached about 100 mm3, hyponatremia was induced in a subgroup of animals via desmopressin infusion. Tumor masses were significantly greater in hyponatremic mice, starting from day 14 and until the day of sacrifice (day 28). Immunohistochemical analysis showed a more intense vascularization and higher levels of expression of the proliferating cell nuclear antigen, chromogranin A and heme oxigenase-1 gene in hyponatremic mice. Finally, metalloproteases were also more abundantly expressed in hyponatremic animals compared to control ones. To our knowledge, this is the first demonstration in an experimental animal model that hyponatremia is associated to increased cancer growth by activating molecular mechanisms that promote proliferation, angiogenesis and invasivity.

Optimization and Characterization of Phenolic Extraction Conditions and Antioxidant Activity Evaluation of Adenanthera pavonina L. Bark

The presence of high levels of secondary metabolites in medicinal plants can significantly influence the progress of drug development. Here, we aimed to maximize phenolic extraction from Adenanthera pavonina L. stem bark using various solvents such as ethyl acetate, methanol, petroleum ether, and chloroform. A response surface method (RSM) with a central composite design (CCD) statistical technique was applied to optimize the extraction process, employing three important extracting parameters such as extraction time (h), temperature (°C), and solvent composition (% v/v of methanol/water) to obtain the highest phenolic content. Total phenolic content (TPC) and antioxidant activity (IC50 of extract's DPPH radical scavenging activity) were used as response variables to find the influence of these extracting parameters. Among the various solvents used, methanol extract showed the highest contents of phenolics and the maximum level of antioxidant activity with a lower IC50 value. The notable TPC and IC50 value of the extract's DPPH radical scavenging capacity were found to be 181.69 ± 0.20 mg GAE/g dry tissue and 60.13 ± 0.11 mg/mL, respectively, under the optimal conditions with a solvent composition of 71.61% (v/v) of methanol/water, extraction temperature of 42.52 °C, and extraction time of 24 h. The optimized extract of A. pavonina stem bark was further subjected to HPLC analysis, where six phenolic compounds, including coumarin, p-coumaric acid, chlorogenic acid, sinapic acid, gallic acid, and caffeic acid, were identified along with their respective quantities. Overall, the findings of this study uncover a low-cost analytical model for maximizing phenolic extraction from A. pavonina bark with enhanced antioxidant activity.

Phytochemical Profiling and Biological Activities of Quercus sp. Galls (Oak Galls): A Systematic Review of Studies Published in the Last 5 Years

Quercus species have been widely used in traditional medicine, and recently, researchers' attention has focused on galls of the genus Quercus as a source of health-promoting phytochemicals. This review presents a summary of the most recent findings on the phytochemistry and bioactivity of oak galls, following the screening of scientific papers published in two relevant databases, PubMed and Embase, between January 2018 and June 2023. The oak galls are rich in active compounds, mostly gallotannins and phenolic acids. Due to these secondary metabolites, the reviewed studies have demonstrated a wide range of biological activities, including antioxidant and anti-inflammatory actions, antimicrobial properties, tissue-protective effects, and antitumor, anti-aging, and hypoglycemic potential. Thus, oak galls are a promising natural matrix, to be considered in obtaining pharmaceutical and cosmetic preparations used in anti-aging strategies and, together with medications, in the management of age-related diseases. In further evaluations, the valuable functional properties of oak galls, reported mostly in preclinical studies, should be confirmed with clinical studies that would also take into account the potential health risks of their use.

Eugenol: In Vitro and In Ovo Assessment to Explore Cytotoxic Effects on Osteosarcoma and Oropharyngeal Cancer Cells

Cancer is a significant health problem worldwide; consequently, new therapeutic alternatives are being investigated, including those found in the vegetable kingdom. Eugenol (Eug) has attracted attention for its therapeutic properties, especially in stomatology. The purpose of this study was to investigate the cytotoxicity of Eug, in vitro, on osteosarcoma (SAOS-2) and oropharyngeal squamous cancer (Detroit-562) cells, as well as its potential irritant effect in ovo at the level of the chorioallantoic membrane (CAM). The data obtained following a 72 h Eug treatment highlighted the reduction in cell viability up to 41% in SAOS-2 cells and up to 37% in Detroit-562 cells, respectively. The apoptotic-like effect of Eug was indicated by the changes in cell morphology and nuclear aspect; the increase in caspase-3/7, -8 and -9 activity; the elevated expression of Bax and Bad genes; and the increase in luminescence signal (indicating phosphatidylserine externalization) that preceded the increase in fluorescence signal (indicating the compromise of membrane integrity). Regarding the vascular effects, slight signs of coagulation and vascular lysis were observed, with an irritation score of 1.69 for Eug 1 mM. Based on these results, the efficiency of Eug in cancer treatment is yet to be clarified.

Achievement of the Selectivity of Cytotoxic Agents against Cancer Cells by Creation of Combined Formulation with Terpenoid Adjuvants as Prospects to Overcome Multidrug Resistance

Oncological diseases are difficult to treat even with strong drugs due to development the multidrug resistance (MDR) of cancer cells. A strategy is proposed to increase the efficiency and selectivity of cytotoxic agents against cancer cells to engage the differences in the morphology and microenvironment of tumor and healthy cells, including the pH, membrane permeability, and ion channels. Using this approach, we managed to develop enhanced formulations of cytotoxic agents with adjuvants (which are known as efflux inhibitors and as ion channel inhibitors in tumors)-with increased permeability in A549 and a protective effect on healthy HEK293T cells. The composition of the formulation is as follows: cytotoxic agents (doxorubicin (Dox), paclitaxel (Pac), cisplatin) + adjuvants (allylbenzenes and terpenoids) in the form of inclusion complexes with β-cyclodextrin. Modified cyclodextrins make it possible to obtain soluble forms of pure substances of the allylbenzene and terpenoid series and increase the solubility of cytotoxic agents. A comprehensive approach based on three methods for studying the interaction of drugs with cells is proposed: MTT test-quantitative identification of surviving cells; FTIR spectroscopy-providing information on the molecular mechanisms inaccessible to study by any other methods (including binding to DNA, surface proteins, or lipid membrane); confocal microscopy for the visualization of observed effects of Dox accumulation in cancer or healthy cells depending on the drug formulation as a direct control of the correctness of interpretation of the results obtained by the two other methods. We found that eugenol (EG) and apiol increase the intracellular concentration of cytostatic in A549 cells by 2-4 times and maintain it for a long time. However, an important aspect is the selectivity of the enhancing effect of adjuvants on tumor cells in relation to healthy ones. Therefore, the authors focused on adjuvant's effect on the control healthy cells (HEK293T): EG and apiol demonstrate "protective" properties from cytostatic penetration by reducing intracellular concentrations by about 2-3 times. Thus, a combined formulation of cytostatic drugs has been found, showing promise in the aspects of improving the efficiency and selectivity of antitumor drugs; thereby, one of the perspective directions for overcoming MDR is suggested.

Smart pH- and Temperature-Sensitive Micelles Based on Chitosan Grafted with Fatty Acids to Increase the Efficiency and Selectivity of Doxorubicin and Its Adjuvant Regarding the Tumor Cells

The main factors that determine the low effectiveness of chemotherapy are the low target bioavailability of antitumor drugs and the efflux process. In attempts to overcome this problem, several approaches are proposed here. Firstly, the development of polymeric micellar systems based on chitosan grafted by fatty acids (different types to optimize their properties), which, on the one hand, increase the solubility and bioavailability of cytostatics and, on the other hand, effectively interact with tumor cells due to the polycationic properties of chitosan, allowing for more effective penetration of cytostatic drugs into the cells. Secondly, the use of adjuvants-synergists of cytostatics (such as eugenol) included in the same micellar formulation-that selectively enhance the accumulation and retention of cytostatics in the tumor cells. pH- and temperature-sensitive polymeric micelles developed show high entrapment efficiency for both cytostatics and eugenol (EG) >60% and release the drug in a prolonged manner for 40 h in a weakly acidic medium corresponding to the microenvironment of tumors. In a slightly alkaline environment, the drug circulates longer (more than 60 h). The thermal sensitivity of micelles is realized due to an increase in the molecular mobility of chitosan, which undergoes a phase transition at 32-37 °C. The effect of the cytostatic drug doxorubicin (Dox) on cancerous A549 cells and model healthy cells of human embryonic renal epithelium (HEK293T) was studied by FTIR spectroscopy and fluorescence microscopy. Micellar Dox penetrates into cancer cells 2-3 times more efficiently when using EG adjuvant, which inhibits efflux, as demonstrated by a significant increase in the ratio of intra- and extracellular concentrations of the cytostatic. However, here it is worth remembering about healthy cells that they should not be damaged: according to changes in the FTIR and fluorescence spectra, the penetration of Dox into HEK293T when using micelles in combination with EG is reduced by 20-30% compared to a simple cytostatic. Thus, experimental developments of combined micellar cytostatic drugs have been proposed to increase the effectiveness of cancer treatment and overcome multiple drug resistance.

Phytochemical Profiling, Biological Activities, and In Silico Molecular Docking Studies of Causonis trifolia (L.) Mabb. & J.Wen Shoot

Causonis trifolia (L.) Mabb. & J.Wen, commonly known as "fox grape", is an ethnomedicinally important twining herb of the Vitaceae family, and it is used by ethnic communities for its wide range of therapeutic properties. Our research aims to investigate the chemical composition; antioxidant, anti-inflammatory, and antidiabetic activities; and mechanisms of interaction between the identified selective chemical compounds and the target proteins associated with antioxidant, anti-inflammatory, and antidiabetic effects of the optimised phenolic extract of Causonis trifolia (L.) Mabb. & J.Wen, shoot (PECTS) to endorse the plant as a potential drug candidate for a future bioprospecting programme. Here, we employed the response surface methodology (RSM) with a Box-Behnken design to enrich the methanolic extract of C. trifolia shoot with phenolic ingredients by optimising three key parameters: solvent concentration (% v/v, methanol:water), extraction temperature (°C), and extraction duration (hours). From the quantitative phytochemical estimation, it was evident that the PECTS contained good amounts of phenolics, flavonoids, tannins, and alkaloids. During the HPLC analysis, we identified a total of eight phenolic and flavonoid compounds (gallic acid, catechin hydrate, chlorogenic acid, caffeic acid, p-coumaric acid, sinapic acid, coumarin, and kaempferol) and quantified their respective contents from the PECTS. The GC-MS analysis of the PECTS highlighted the presence of 19 phytochemicals. In addition, the bioactivity study of the PECTS showed remarkable potentiality as antioxidant, anti-inflammatory, and antidiabetic agents. In silico molecular docking and computational molecular modelling were employed to investigate the anti-inflammatory, antioxidant, and antidiabetic properties of the putative bioactive compounds derived from the PECTS using the GC-MS technique to understand the drug-receptor interactions, including their binding pattern. Out of the 19 phytocompounds identified by the GC-MS analysis, one compound, ergosta-5,22-dien-3-ol, acetate, (3β,22E), exhibited the best binding conformations with the target proteins involved in anti-inflammatory (e.g., Tnf-α and Cox-2), antioxidant (SOD), and antidiabetic (e.g., α-amylase and aldo reductase) activities. The nontoxic nature of this optimised extract was also evident during the in vitro cell toxicity assay against the Vero cell line and the in vivo acute toxicity study on BALB/c mice. We believe the results of the present study will pave the way for the invention of novel drugs efficacious for several ailments using the C. trifolia plant.

An Update on the Therapeutic Anticancer Potential of Ocimum sanctum L.: "Elixir of Life"

In most cases, cancer develops due to abnormal cell growth and subsequent tumour formation. Due to significant constraints with current treatments, natural compounds are being explored as potential alternatives. There are now around 30 natural compounds under clinical trials for the treatment of cancer. Tulsi, or Holy Basil, of the genus Ocimum, is one of the most widely available and cost-effective medicinal plants. In India, the tulsi plant has deep religious and medicinal significance. Tulsi essential oil contains a valuable source of bioactive compounds, such as camphor, eucalyptol, eugenol, alpha-bisabolene, beta-bisabolene, and beta-caryophyllene. These compounds are proposed to be responsible for the antimicrobial properties of the leaf extracts. The anticancer effects of tulsi (Ocimum sanctum L.) have earned it the title of "queen of herbs" and "Elixir of Life" in Ayurvedic treatment. Tulsi leaves, which have high concentrations of eugenol, have been shown to have anticancer properties. In a various cancers, eugenol exerts its antitumour effects through a number of different mechanisms. In light of this, the current review focuses on the anticancer benefits of tulsi and its primary phytoconstituent, eugenol, as apotential therapeutic agent against a wide range of cancer types. In recent years, tulsi has gained popularity due to its anticancer properties. In ongoing clinical trials, a number of tulsi plant compounds are being evaluated for their potential anticancer effects. This article discusses anticancer, chemopreventive, and antioxidant effects of tulsi.

A Comparative Study on Chemical Compositions and Biological Activities of Four Amazonian Ecuador Essential Oils: Curcuma longa L. (Zingiberaceae), Cymbopogon citratus (DC.) Stapf, (Poaceae), Ocimum campechianum Mill. (Lamiaceae), and Zingiber officinale Roscoe (Zingiberaceae)

Essential oils (EOs) and their vapour phase of Curcuma longa (Zingiberaceae), Cymbopogon citratus (Poaceae), Ocimum campechianum (Lamiaceae), and Zingiber officinale (Zingiberaceae) of cultivated plants grown in an Amazonian Ecuador area were chemically characterised by Gas Chromatography-Flame Ionization Detector (GC-FID), Gas Chromatography-Mass Spectrometry (GC-MS), and Head Space-Gas Chromatograph-Flame Ionization Detector-Mass Spectrometry (HS-GC-FID-MS).figure The EOs analyses led to the identification of 25 compounds for C. longa (99.46% of the total; ar-turmerone: 23.35%), 18 compounds for C. citratus (99.59% of the total; geraniol: 39.43%), 19 compounds for O. campechianum (96.24% of the total; eugenol: 50.97%), and 28 for Z. officinale (98.04% of the total; α-Zingiberene: 15.45%). The Head Space fractions (HS) revealed C. longa mainly characterised by limonene and 1,8-cineole (37.35%) and α-phellandrene (32.33%); Z. officinale and C. citratus showed camphene (50.39%) and cis-Isocitral (15.27%) as the most abundant compounds, respectively. O. campechianum EO revealed a higher amount of sesquiterpenes (10.08%), mainly characterised by E-caryophyllene (4.95%), but monoterpene fraction remained the most abundant (89.94%). The EOs were tested for antioxidant, antimicrobial, and mutagen-protective properties and compared to the Thymus vulgaris EO as a positive reference. O. campechianum EO was the most effective in all the bioactivities checked. Similar results emerged from assaying the bioactivity of the vapour phase of O. campechianum EO. The antioxidant and antimicrobial activity evaluation of O. campechianum EO were repeated through HP-TLC bioautography assay, pointing out eugenol as the lead compound for bioactivity. The mutagen-protective evaluation checked through Ames's test properly modified evidenced a better capacity of O. campechianum EO compared with the other EOs, reducing the induced mutagenicity at 0.1 mg/plate. However, even with differences in efficacy, the overall results suggest important perspectives for the functional use of the four studied EOs.

Eugenol Induces Apoptosis in Tongue Squamous Carcinoma Cells by Mediating the Expression of Bcl-2 Family

Head and neck squamous cell carcinoma is highly aggressive type of cancer for which the available treatment often causes patients severe side effects. Eugenol (Eug) is the major active constituent of clove essential oil and is known to possess antitumor properties. The present study aimed to assess the in vitro cytotoxicity of eugenol in SCC-4, tongue squamous carcinoma cells, and also in HGF, human gingival fibroblasts. Both cell lines were treated with five concentrations of Eug (0.1-1 mM) for 72 h. Cellular viability was assessed, followed by cellular morphological evaluation and by staining of the nuclei and cytoskeleton. RT-PCR was conducted in order to find the effect eugenol had on the expression on Bad, Bax, and Bcl-2 genes. Eugenol induced a dose-dependent decrease in viability in both cell lines, with the SCC-4 cells being significantly more affected. HGF cells detached from the plate at the highest concentrations used, while SCC-4 cells changed their morphology in a dose-dependent manner, with rounding, floating cells, and confluency loss being observed. Apoptotic-like signs such as chromatin and actin filaments condensation were clearly seen in SCC-4 cells, while RT-PCR revealed a significantly increased expression of pro-apoptotic genes Bax and Bad. Therefore, eugenol exerts its cytotoxic effect in tongue squamous cell carcinoma through inducing apoptosis.

Molecular Mechanisms of Action of Eugenol in Cancer: Recent Trends and Advancement

BACKGROUND

Cancer is, at present, among the leading causes of morbidity globally. Despite advances in treatment regimens for cancer, patients suffer from poor prognoses. In this context, the availability of vast natural resources seems to alleviate the shortcomings of cancer chemotherapy. The last decade has seen a breakthrough in the investigations related to the anticancer potential of dietary phytoconstituents. Interestingly, a handsome number of bioactive principles, ranging from phenolic acids, phenylpropanoids, flavonoids, stilbenes, and terpenoids to organosulphur compounds have been screened for their anticancer properties. Among the phenylpropanoids currently under clinical studies for anticancer activity, eugenol is a promising candidate. Eugenol is effective against cancers like breast, cervical, lung, prostate, melanomas, leukemias, osteosarcomas, gliomas, etc., as evident from preclinical investigations.

OBJECTIVE

The review aims to focus on cellular and molecular mechanisms of eugenol for cancer prevention and therapy.

METHODS

Based on predetermined criteria, various scholarly repositories, including PubMed, Scopus, and Science Direct were analyzed for anticancer activities of eugenol.

RESULTS

Different biochemical investigations reveal eugenol inducing cytotoxicity, inhibiting phases of the cell cycles, programmed cell death, and auto-phagocytosis in studied cancer lines; thus, portraying eugenol as a promising anticancer molecule. A survey of current literature has unveiled the molecular mechanisms intervened by eugenol in exercising its anticancer role.

CONCLUSION

Based on the critical analysis of the literature, eugenol exhibits vivid signaling pathways to combat cancers of different origins. The reports also depict the advancement of novel nano-drug delivery approaches upgrading the therapeutic profile of eugenol. Therefore, eugenol nanoformulations may have enormous potential for both the treatment and prevention of cancer.