D-Limonene reduces depression-like behaviour and enhances learning and memory through an anti-neuroinflammatory mechanism in male rats subjected to chronic restraint stress.

D-limonene is a widely used flavouring additive in foods, beverages and fragrances due to its pleasant lemon-like odour. This study aimed to investigate the effects of D-limonene on the central nervous system when subjected to chronic restraint stress in rats for 21 days. Forty rats were randomly divided into five groups: i) control, ii) D-limonene, iii) restraint stress, iv) restraint stress+D-limonene and v) restraint stress+fluoxetine. Following the induction of restraint stress, the sucrose preference test, the open field test, the novel object recognition test and the forced swimming test were performed. The levels of BDNF, IL-1ß, IL-6 and caspase-1 were measured from hippocampal tissue using the ELISA method. Sucrose preference test results showed an increase in consumption rate in the stress+D-limonene and a decrease in the stress group. The stress+D-limonene group reversed the increased defensive behaviour observed in the open-field test compared to the stress group. In the novel object recognition test, the discrimination index of the stress+D-limonene group increased compared to the stress group. BDNF levels increased in the stress+limonene group compared to the stress group. In contrast, IL-1ß and caspase-1 levels increased in the stress group compared to the control and decreased in the stress+limonene group compared to the stress group. In this study, D-limonene has been found to have antidepressant-like properties, reducing anhedonic and defensive behaviours and the impairing effects of stress on learning and memory tests. It was observed that D-limonene showed these effects by alleviating neuroinflammation induced by chronic restraint stress in rats.

D-limonene inhibits peritoneal adhesion formation in rats via anti-inflammatory, anti-angiogenic, and antioxidative effects.

The aim of this research was to investigate the effects of D-limonene on decreasing post-operative adhesion in rats and to understand the mechanisms involved. Peritoneal adhesions were induced by creating different incisions and excising a 1 × 1 cm section of the peritoneum. The experimental groups included a sham group, a control group in which peritoneal adhesions were induced without any treatment, and two treatment groups in which animals received D-limonene with dosages of 25 and 50 mg/kg after inducing peritoneal adhesions. Macroscopic examination of adhesions showed that both treatment groups had reduced adhesion bands in comparison to the control group. Immunohistochemical assessment of TGF-ß1, TNF-α, and VEGF on day 14 revealed a significant increment in the level of immunopositive cells for the mentioned markers in the control group, whereas administration of limonene in both doses significantly reduced levels of TGF-ß1, TNF-α, and VEGF (P < 0.05). Induction of peritoneal adhesions in the control group significantly increased TGF-ß1, TNF-α, and VEGF on days 3 and 14 in western blot evaluation, while treatment with limonene significantly reduced TNF-α level on day 14 (P < 0.05). Moreover, VEGF levels in both treatment groups significantly reduced on days 3 and 14. In the control group, a significant increment in the levels of MDA and NO and a notable decline in the levels of GPX, CAT was observed (P < 0.05). Limonene 50 group significantly reduced MDA level and increased GPx and CAT levels on day 14 (P < 0.05). In summary, D-limonene reduced adhesion bands, inflammatory cytokines, angiogenesis, and oxidative stress.

D-Limonene Inhibits Pichia kluyveri Y-11519 in Sichuan Pickles by Disrupting Metabolism.

The Pichia kluyveri, a proliferation commonly found in Sichuan pickles (SCPs), can accelerate the growth and reproduction of spoilage bacteria, causing off-odor development and decay. Although D-limonene, a common natural preservative, effectively restricts P. kluyveri, its inhibitory mechanism remains unclear. This study aimed to elucidate this molecular mechanism by investigating the impact on basic P. kluyveri metabolism. The findings revealed that D-limonene inhibited P. kluyveri growth and disrupted the transcription of the genes responsible for encoding the enzymes involved in cell wall and membrane synthesis, oxidative phosphorylation, glycolysis, and the tricarboxylic acid (TCA) cycle pathway. The results indicated that these events disrupted crucial metabolism such as cell wall and membrane integrity, adenosine triphosphate (ATP) synthesis, and reactive oxygen species (ROS) balance. These insights provided a comprehensive understanding of the inhibitory effect of D-limonene on the growth and reproduction of P. kluyveri while highlighting its potential application in the SCP industry.

d-Limonene complexed with cyclodextrin attenuates cardiac arrhythmias in an experimental model of doxorubicin-induced cardiotoxicity: Possible involvement of calcium/calmodulin-dependent protein kinase type II.

BACKGROUND: Arrhythmias are one manifestation of the cardiotoxicity that results from doxorubicin (Doxo) administration. Although cardiotoxicity is an anticipated outcome in anticancer therapies, there is still a lack of treatment options available for its effective management. This study sought to evaluate the possible cardioprotective effect of complex d-limonene (DL) plus hydroxypropyl-ß-cyclodextrin (HßDL) during treatment with Doxo, focusing on the arrhythmic feature. METHODS: Cardiotoxicity was induced in Swiss mice with Doxo 20 mg/kg, with 10 mg/kg of HßDL being administered 30 min before the Doxo. Plasma CK-MB and LDH levels were analyzed. Cellular excitability and susceptibility to cardiac and cardiomyocyte arrhythmias were evaluated using in vivo (pharmacological cardiac stress) and in vitro (burst pacing) ECG protocols. Ca2+ dynamics were also investigated. The expression of CaMKII and its activation by phosphorylation and oxidation were evaluated by western blot, and molecular docking was used to analyze the possible interaction between DL and CaMKII. RESULTS: Electrocardiograms showed that administration of 10 mg/kg of HßDL prevented Doxo-induced widening of the QRS complex and QT interval. HßDL also prevented cardiomyocyte electrophysiological changes that trigger cellular arrhythmias, such as increases in action potential duration and variability; decreased the occurrence of delayed afterdepolarizations (DADs) and triggered activities (TAs), and reduced the incidence of arrhythmia in vivo. Ca2+ waves and CaMKII overactivation caused by phosphorylation and oxidation were also decreased. In the in silico study, DL showed potential inhibitory interaction with CaMKII. CONCLUSION: Our results show that 10 mg/kg of ßDL protects the heart against Doxo-induced cardiotoxicity arrhythmias, and that this is probably due to its inhibitory effect on CaMKII hyperactivation.

Comparative study of zinc oxide nanoparticles synthesized through biogenic and chemical route with reference to antibacterial, antibiofilm and anticancer activities.

The present focused on comparative study on synthesis of ZnO nanoparticles (ZnO NPs) using chemical method via alkaline precipitation method (ZnO(A) NPs) using NaOH and biogenic method using termite mound extract (ZnO(B) NPs). GC-MS analysis revealed that D-limonene present in termite mound extract might be responsible for the synthesis of ZnO(B) NPs. XRD patterns confirmed hexagonal crystalline structure of ZnO(A) and (B) NPs. Results of antibacterial activity illustrated that ZnO(B) NPs showed its potential against Pseudomonas aeruginosa, ESBL-1, ESBL-2 and EBSL-3. Antibiofilm studies revealed that ZnO(B) NPs exhibited optimum decline in MRSA biofilm formation than ZnO(A) NPs. In addition, ZnO(B) NPs showed potent cytotoxic effect against lung cancer cell lines A549 with IC50 of 35.16 ± 0.10 µg/mL in comparison with ZnO(A) NPs (IC50- 55.09 ± 0.30 µg/mL). Overall, the results revealed that biogenic synthesis of ZnO NPs ensures its biosafety level and enhanced biological activity when compared to chemical synthesis method.

A Comparative GC/MS Analysis of Citrus Essential Oils: Unveiling the Potential Benefits of Herb-Drug Interactions in Preventing Paracetamol-Induced Hepatotoxicity.

Our study aimed to test the potential of Citrus oils in protecting against paracetamol (PAR)-induced hepatotoxicity. The essential oils of Pineapple sweet orange (OO), Murcott mandarin (MO), Red grapefruit (GO), and Oval kumquat (KO) were investigated using gas chromatography coupled with mass spectrometry (GC/MS). Twenty-seven compounds were identified, with monoterpene hydrocarbons being abundant class. d-Limonene had the highest percentage (92.98 %, 92.82 %, 89.75 %, and 94.46 % in OO, MO, GO, and KO, respectively). Hierarchical cluster analysis (HCA) and principal components analysis (PCA) revealed that octanal, linalool, germacrene D, and d-limonene were the principal discriminatory metabolites that segregated the samples into three distinct clusters. In vitro antioxidant capacities were ranged from 1.2-12.27, 1.79-5.91, and 235.05-585.28 µM Trolox eq/mg oil for 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic (ABTS), ferric-reducing antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC), respectively. In vivo, citrus oils exhibited a significant reduction in alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), and nitric oxide (NO). Additionally, there was an increase in glutathione reductase (GSH), and the liver architecture was nearly normal. Molecular docking revealed that d-limonene exhibited a good inhibitory interaction with cytochrome P450 (CYP450) isoforms 1A2, 3A4, and 2E1, with binding energies of -6.17, -4.51, and -5.61 kcal/mol, respectively.

Development of an ultrasound-assisted pre-treatment strategy for the extraction of D-Limonene toward the production of bioethanol from citrus peel waste (CPW).

Citrus is one of the world's most abundant fruits containing vitamins, pigments, and fragrances, making it vital for several industries. However, these fruits contain about 45-50% residues (peels), which often end up as waste and can be harmful to the environment if not properly treated. Bioethanol production from citrus peel waste offers a potential solution to this problem. Hence, this study explores the potential of using ultrasound-assisted pre-treatment method as a novel strategy to extract D-Limonene (essential oil in the residue), and further demonstrates bioethanol production. This was done by investigating ultrasonication's optimal effect on pre-treatment of the citrus residue, followed by bioethanol production. The results show that, optimum values for D-Limonene extraction were obtained at a temperature of 14.6 °C and an ultrasound intensity of 25.81 W/cm2 with a validation yield of 134 ± 4.24 mg/100 g dry CPW. With optimal ultrasonic parameters, the study went further to demonstrate the effect of the essential oil on bioethanol production which is hindered by the oils present. Key findings show better bioethanol yield once the essential oil was extracted (treated) from the citrus waste as opposed to it not extracted (untreated), with a 66 and a 29% increase when comparing simultaneous saccharification and fermentation (SSF) and sequential hydrolysis and fermentation (SHF) respectively. Based on this result, ultrasound-assisted extraction as a pretreatment method was found suitable for bioethanol production from citrus residue and could be utilized as a biorefinery pre-treatment approach to scale bioethanol production.

Long-Term Ingestion of Sicilian Black Bee Chestnut Honey and/or D-Limonene Counteracts Brain Damage Induced by High Fat-Diet in Obese Mice.

Obesity is linked to neurodegeneration, which is mainly caused by inflammation and oxidative stress. We analyzed whether the long-term intake of honey and/or D-limonene, which are known for their antioxidant and anti-inflammatory actions, when ingested separately or in combination, can counteract the neurodegeneration occurring in high fat diet (HFD)-induced obesity. After 10 weeks of HFD, mice were divided into: HFD-, HFD + honey (HFD-H)-, HFD + D-limonene (HFD-L)-, HFD + honey + D-limonene (HFD-H + L)-fed groups, for another 10 weeks. Another group was fed a standard diet (STD). We analyzed the brain neurodegeneration, inflammation, oxidative stress, and gene expression of Alzheimer's disease (AD) markers. The HFD animals showed higher neuronal apoptosis, upregulation of pro-apoptotic genes Fas-L, Bim P27 and downregulation of anti-apoptotic factors BDNF and BCL2; increased gene expression of the pro-inflammatory IL-1ß, IL-6 and TNF-α and elevated oxidative stress markers COX-2, iNOS, ROS and nitrite. The honey and D-limonene intake counteracted these alterations; however, they did so in a stronger manner when in combination. Genes involved in amyloid plaque processing (APP and TAU), synaptic function (Ache) and AD-related hyperphosphorylation were higher in HFD brains, and significantly downregulated in HFD-H, HFD-L and HFD-H + L. These results suggest that honey and limonene ingestion counteract obesity-related neurodegeneration and that joint consumption is more efficacious than a single administration.

Pharmacokinetic and Permeation Studies in Rat Brain of Natural Compounds Led to Investigate Eugenol as Direct Activator of Dopamine Release in PC12 Cells.

Eugenol, cinnamaldehyde and D-limonene, the main components of natural essential oils, are endowed with antioxidant and anti-inflammatory properties which allow them to induce beneficial effects on intestinal, cardiac and neuronal levels. In order to characterize their pharmacokinetic profiles and aptitude to permeate in the central nervous system after intravenous and oral administration to rats, new analytical procedures, easily achievable with HPLC-UV techniques, were developed. The terminal half-lives of these compounds range from 12.4 ± 0.9 (D-limonene) and 23.1 ± 1.6 min (cinnamaldehyde); their oral bioavailability appears relatively poor, ranging from 4.25 ± 0.11% (eugenol) to 7.33 ± 0.37% (cinnamaldehyde). Eugenol evidences a marked aptitude to permeate in the cerebrospinal fluid (CSF) of rats following both intravenous and oral administrations, whereas cinnamaldehyde appears able to reach the CSF only after intravenous administration; limonene is totally unable to permeate in the CSF. Eugenol was therefore recruited for in vitro studies of viability and time-/dose-dependent dopamine release in neuronal differentiated PC12 cells (a recognized cellular model mimicking dopaminergic neurons), evidencing its ability to increase cell viability and to induce dopamine release according to a U-shaped time-course curve. Moreover, concentration-response data suggest that eugenol may induce beneficial effects against Parkinson's disease after oral administration.

Development of invaethosomes and invaflexosomes for dermal delivery of clotrimazole: optimization, characterization and antifungal activity.

The objective of this study was to develop novel invaethosomes (I-ETS) and invaflexosomes (I-FXS) to enhance the dermal delivery of clotrimazole (CZ). Twenty model CZ-loaded I-ETS and I-FXS formulations were created according to a face-centered central composite experimental design. CZ-loaded vesicle formulations containing a constant concentration of 0.025% w/v CZ and various amounts of ethanol, d-limonene, and polysorbate 20 as penetration enhancers were prepared using the thin film hydration method. The physicochemical characteristics, skin permeability, and antifungal activity were characterized. The skin permeability of the experimental CZ-loaded I-ETS/I-FXS was significantly higher than that of conventional ethosomes, flexosomes, and the commercial product (1% w/w CZ cream). The mechanism of action was confirmed to be skin penetration of low ethanol base vesicles through the disruption of the skin microstructure. The optimal I-ETS in vitro antifungal activity against C. albicans differed significantly from that of ETS and the commercial cream (control). The response surface methodology predicted by Design Expert® was helpful in understanding the complicated relationship between the causal factors and the response variables of the 0.025% w/v CZ-loaded I-ETS/I-FXS formulation. Based on the available information, double vesicles seem to be promising versatile carriers for dermal drug delivery of CZ.

D-Limonene inhibits the occurrence and progression of LUAD through suppressing lipid droplet accumulation induced by PM2.5 exposure in vivo and in vitro.

BACKGROUND: PM2.5 exposure is associated with lung adenocarcinoma (LUAD), but the mechanism is unclear. The lack of understanding impedes our effort on prevention. This study examined a possible mechanism of lung cancer caused by PM2.5 exposure, and aimed to find a potential intervention for people living in PM2.5 polluted regions. METHODS: Electron microscopy and oil-red staining were conducted to examine the lipid droplet accumulation. Masson's trichrome staining, colony forming, scratch assay and transwell experiment were conducted to evaluate the effect of PM2.5 exposure and D-limonene intervention on the occurrence and progression of LUAD. Potential intervention targets were found by RNA-Seq and verified by luciferase reporter assay. MiR-195 KO mice constructed with CRISPR/Cas9 technology were used to investigate the pivotal role of D-limonene-miR-195-SREBP1/FASN axis. Cohort analysis of lung cancer patients, human LUAD tissues staining and human intervention trial were also conducted to validate the results of cell and animal experiments. RESULTS: Our results showed that PM2.5 exposure induced accumulation of lipid droplets in LUAD cells which accompanied by increased malignant cellular behaviors. PM2.5 exposure led to cleaved N-SREBP1 translocation into nucleus, which activated the de novo lipogenesis pathway. Same changes were also observed in normal lung epithelial cells and normal lung tissue, and mice developed pulmonary fibrosis after long-term exposure to PM2.5. Furthermore, in a cohort of 11,712 lung cancer patients, significant lipid metabolism disorders were observed in higher PM2.5 polluted areas. In view of that, D-limonene was found to inhibit the changes in lipid metabolism through upregulating the expression of miR-195, which inhibited the expression of lipogenic genes (SREBF1/FASN/ACACA) specifically. And a small human intervention trial showed that serum miR-195 was upregulated after oral intake of D-limonene. CONCLUSION: Our findings reveal a new mechanism of pulmonary fibrosis and LUAD that is related to PM2.5 exposure-induced lipid droplet accumulation. We also demonstrate that D-limonene-miR-195-SREBP1/FASN axis is a potential preventive intervention for mediating the progression and development of LUAD induced by PM2.5 exposure. Trial registration Chinese Clinical Trial Registry, ChiCTR2000030200. Registered 25 February 2020, http://www.chictr.org.cn/showproj.aspx?proj=48013.

Natural essential oils efficacious in internal organs fibrosis treatment: Mechanisms of action and application perspectives.

Internal organs fibrosis (IOF) is the leading cause of morbidity and mortality in most chronic inflammatory diseases, which is responsible for 45% of deaths due to disease. However, there is a paucity of drugs used to treat IOF, making it urgent to find medicine with good efficacy, low toxic side effects and good prognosis. Essential oils (EOs) extracted from natural herbs with a wide range of pharmacological components, multiple therapeutic targets, low toxicity, and broad sources have unique advantages and great potential in the treatment of IOF. In this review, we summarized EOs and their monomeric components with anti-IOF, and found that they work mainly through inhibiting TGF-ß-related signaling pathways, modulating inflammatory cytokines, suppressing NF-κB, and anti-oxidative stress. The prognostic improvement of natural EOs on IOF was further discussed, as well as the quality and safety issues in the current development of natural EOs. This review hopes to provide scientific basis and new ideas for the development and application of natural medicine EOs in anti-IOF.

Allergic contact dermatitis from ("hypoallergenic") adhesives containing D-limonene.

BACKGROUND: Besides being a potential component of (some species of) colophonium, D-limonene is also used as a tackifier in the production of adhesives. Hydroperoxides of limonene are well-known skin sensitizers. OBJECTIVES: To show that D-limonene may be present in colophonium-containing but also colophonium-free ("hypoallergenic") adhesives, and that patients suffering from allergic contact dermatitis (ACD) from both types of adhesives might display positive patch test reactions to limonene hydroperoxides in this regard. METHODS: Five patients with suspected ACD from adhesives were patch tested to the baseline series (containing limonene hydroperoxides 0.3 and 0.2% pet.), additional series and, if available, to the culprit adhesives. The adhesives labelled as containing colophonium (n = 3) or free from it (n = 2) were analysed with gas chromatography - mass spectrometry (GC-MS) for the presence of D-limonene. RESULTS: All five patients sensitised to adhesives had (strong) positive patch test reactions to limonene hydroperoxides. The presence of D-limonene, and/or related components, could be demonstrated in all three colophonium-containing and, surprisingly, also in two colophonium-free ("hypoallergenic") tapes. CONCLUSIONS: D-limonene may be present in both regular and "hypoallergenic" adhesives, with limonene hydroperoxides potentially contributing to ACD from such medical devices. The use of fragrance chemicals in adhesives deserves further research.

Food-grade D-limonene enhanced a green biocide in the mitigation of carbon steel biocorrosion by a mixed-culture biofilm consortium.

Microbiologically influenced corrosion (MIC), or microbial biocorrosion, is caused directly by microbial metabolic activities/products or induced by microbial biofilm's damage of a protective film that exposes a solid surface to a pre-existing corrosive environment. MIC causes billions of dollars of losses in various industrial processes, especially in oil and gas and water utilities. The mitigation of problematic industrial microbes typically relies on biocides whose discharges can cause environmental problems. Thus, more effective biocide applications are desired to minimize environmental impact. D-Limonene, a citrus peel oil, generally regarded as safe (GRAS), was used to enhance the popular biodegradable tetrakis hydroxymethyl phosphonium sulfate (THPS) biocide. An oilfield mixed-culture biofilm was grown anaerobically in enriched artificial seawater containing C1018 carbon steel coupons for 7 days at 37 °C. One hundred ppm (w/w) D-limonene reduced general heterotrophic bacteria (GHB) and acid-producing bacteria (APB) effectively, leading to 5.4-log and 6.0-log reductions in sessile GHB and APB cell counts, respectively, compared to no treatment control. The combination of 100 ppm D-limonene + 100 ppm THPS achieved extra 1.0-log SRB, 0.6-log GHB and 0.5-log APB reductions in sessile cell counts, which led to extra 58% reduction in microbial corrosion mass loss (1.2 vs. 0.5 mg/cm2) and extra 30% reductions in maximum pit depth (11.5 vs. 8.1 µm), compared to 100 ppm THPS-only treatment. Linear polarization resistance and potentiodynamic polarization (PDP) corrosion data supported mass loss and pitting data. Mixed-culture biofilms on carbon steel coupons after 7 day incubation at 37 °C showing enhanced biocide treatment outcome using D-limonene + THPS: A no treatment, B 100 ppm D-limonene, C 100 ppm THPS, D 100 ppm D-limonene + 100 ppm THPS.

Effect of D-Limonene Nanoemulsion Edible Film on Banana (Musa sapientum Linn.) Post-Harvest Preservation.

D-limonene (4-isopropenyl-1-methylcyclohexene) is an important compound in several citrus essential oils (such as orange, lemon, tangerine, lime, and grapefruit). It has been used as a flavoring agent and as a food preservative agent, with generally recognized as safe (GRAS) status. D-limonene has been well-studied for its anti-inflammatory, antioxidant, anti-cancer, and antibacterial properties. The antibacterial activity of D-limonene against food-borne pathogens was investigated in this study by preparing a D-limonene nanoemulsion. The D-limonene solution and nanoemulsion have been prepared in six concentrations, 0.04%, 0.08%, 0.1%, 0.2%, 0.4%, and 0.8% (v/v), respectively, and the antibacterial activity was tested against four food-borne pathogens (Staphylococcus aureus, Listeria monocytogenes, Salmonella enterica, and Escherichia coli). The results showed that the D-limonene nanoemulsion had good nanoscale and overall particle size uniformity, and its particle size was about 3~5 nm. It has been found that the D-limonene solution and nanoemulsion have a minimal inhibitory concentration of 0.336 mg/mL, and that they could inhibit the growth of microorganisms efficiently. The data indicate that the D-limonene nanoemulsion has more antibacterial ability against microorganisms than the D-limonene essential oil. After bananas are treated with 1.0% and 1.5% D-limonene nanoemulsion coatings, the water loss of the bananas during storage and the percentage of weight loss are reduced, which can inhibit the activity of pectinase. The application of a biocoating provides a good degree of antibacterial activity and air and moisture barrier properties, which help with extending the shelf life of bananas.

Chemical Compositions and Antioxidant Activities of Essential Oils, and Their Combinations, Obtained from Flavedo By-Product of Seven Cultivars of Sicilian Citrus aurantium L.

In this work, seven Citrus aurantium essential oils (EOs) derived from flavedo of cultivars 'Canaliculata', 'Consolei', 'Crispifolia', 'Fasciata', 'Foetifera', 'Listata', and 'Bizzaria' were investigated. EOs were also combined in 1:1 (v/v) ratio to identify possible synergism or antagonism of actions. GC-MS analysis was done to investigate Eos' phytochemical profiles. The antioxidant activity was studied by using a multi-target approach based on FRAP, DPPH, ABTS, and ß-carotene bleaching tests. A great difference was observed in EOs' phytochemical profiles. d-limonene (33.35-89.17%) was the main monoterpene hydrocarbon, and α-Pinene, ß-myrcene, and ß-linalool were identified in almost all samples. Among EOs, only C3 showed high quantitative and qualitative variability in its chemical composition. The chemical diversity of EOs was also demonstrated by PCA and HCA statistical analysis. Samples C2, C4, C5, C6, and C7 were statistically similar to each other, while C1 and C3 were characterized as having a different amount of other compounds and oxygenated monoterpenes, respectively, with respect to the other EOs mentioned. The global antioxidant score (GAS) revealed that among the tested EOs, C. aurantium 'Fasciata' EO had the highest antioxidant potential, with a GAS value of -0.47, whereas among combinations, the EO obtained by mixing 'Canaliculata' + 'Bizzaria' was the most active. Comparison by theoretical and real data on inhibitory concentration (IC50) and FRAP values did not reveal any significant effect of synergism or antagonism of actions to be valid in all biological applied tests. These findings, considered together, represent an important starting point to understand which compounds are responsible for the activities and their future possible industrial application.

Effect of d-limonene and its derivatives on breast cancer in human trials: a scoping review and narrative synthesis.

BACKGROUND: D-limonene and its derivatives have demonstrated potential chemopreventive and anticancer activity in preclinical and clinical studies. The aim of this scoping review was to assess and critically appraise current literature on the effect of these bioactive citrus peel compounds on breast cancer in human trials and to identify knowledge gaps for exploration in future studies. METHODS: This study followed a scoping review framework. Peer-reviewed journal articles were included if they reported the effect of d-limonene or its derivatives on breast cancer in human subjects. Articles were retrieved from academic databases - PubMed, EMBASE, CINAHL, Web of Science, and Cochrane reviews - and iteratively through review of bibliographies of relevant manuscripts. Titles and abstracts were appraised against the aforementioned inclusion criteria in a first round of screening. Through consensus meetings and full article review by authors, a final set of studies were selected. Results were reported according to the PRISMA extension for scoping reviews. RESULTS: Our search strategy yielded 367 records. Following screening and adjudication, five articles reporting on phase 1(n = 2), phase 2 (n = 2) and both trial phases (n = 1) were included as the final dataset for this review. Trials evaluating the effect of d-limonene (n = 2) showed it was well tolerated in subjects. One study (n = 43 participants) showed d-limonene concentrated in breast tissue (mean 41.3 µg/g tissue) and reduction in tumor cyclin D1 expression, which is associated with tumor proliferation arrest. This study did not show meaningful change in serum biomarkers associated with breast cancer, except for a statistically significant increase in insulin-like growth factor-1 (IGF-I) levels. While elevation of IGF-I is associated with increased cancer risk, the clinical implication of this study remains uncertain given its short duration. Trials with perillyl alcohol (n = 3) showed low tolerance and no effect on breast cancer. CONCLUSION: This review demonstrated a dearth of clinical studies exploring the effect of d-limonene and its derivatives on breast cancer. Limited literature suggests d-limonene is safe and tolerable in human subjects compared to its derivative, perillyl alcohol. Our review demonstrates the need for additional well-powered placebo-controlled trials that assess d-limonene's efficacy on breast cancer compared to other therapies.

Design of multicomponent indomethacin-paracetamol and famotidine loaded nanoparticles for sustained and effective anti-inflammatory therapy.

Indomethacin is one of the nonsteroidal anti-inflammatory drugs (NSAIDs) that are widely prescribed drug for pain and inflammation. However, its notoriety of causing gastrointestinal effect, low water solubility, and its short half-life would affect patient compliance and its oral absorption and accordingly justify the need to develop a formula with a controlled and sustained release manner in combination with anti-ulcer drugs. Herein, we synthesized indomethacin-paracetamol co-drug loaded in nanoemulsion and encapsulated in famotiditine loaded polycaprolactone (PCL) nanoparticles. The synthesis of the co-drug was achieved by the formation of a hydrolyzable ester between the indomethacin and paracetamol. The synthesized co-drug was preloading in nanoemulsion (Co-NE), which encapsulated into famotidine PCL nanoparticles utilizing the nanoprecipitation approach. The developed nanosystem showed hydrodynamic size less than 200 nm and the zeta potential value above -30 mV. TEM images confirmed the morphological structure of the formed nanoemulsion and the loaded PCL nanoparticles. Stability studies revealed that the developed nanosystem was stable at different temperatures and pHs over 1 month. Moreover, improvement of the solubilities of these three drugs leading to have a controlled-release multicomponent system of both co-drug and famotidine over 3 days. This multicomponent nanoparticle might be a potential platform to overcome the obstacles of NSAIDs, synergize drugs with different mechanisms of actions by co-encapsulating a small-sized nanoemulsion into PCL nanoparticles for reaching the goal of effective anti-inflammatory therapy.

[Prediction of Q-markers of Citri Reticulatae Pericarpium volatile oil and GC-MS based quantitative analysis].

This study was designed to predict the Q-markers of Citri Reticulatae Pericarpium volatile oil and conduct quantitative analysis by GC-MS. The common components of Citri Reticulatae Pericarpium volatile oil were detected by GC-MS. The network pharmacology approaches were utilized for constructing the component-target network and protein-protein interaction(PPI) network, followed by the GO and KEGG pathway enrichment analysis to clarify the pharmacological effects of common components. Molecular docking was conducted to observe the biological activities of common components, thus identifying the Q-markers of Citri Reticulatae Pericarpium volatile oil. The obtained Q-markers were subjected to quantitative analysis by GC-MS. The GC-MS analysis of 19 batches of Citri Reticulatae Pericarpium volatile oil revealed three common components, namely, D-limonene, γ-terpinene, and myrcene. The common components were analyzed based on network pharmacology, and the results showed that Citri Reticulatae Pericarpium volatile oil mainly acted on the core targets GABRA1, GABRA6, GABRA5, GABRA3, and GABRA2 through D-limonene and γ-terpinene, with five important pathways such as nicotine addiction and GABAergic synapse involved. The core targets were mainly distributed in olfactory region, cerebral cortex, cerebellum, basal ganglia, hippocampus, and amygdala to exert the pharmacological effects. As revealed by molecular docking, D-limonene and γ-terpinene exhibited good biological activities, so they were identified as the Q-markers of Citri Reticulatae Pericarpium volatile oil. The results of quantitative analysis showed that the volume fraction of D-limonene was within the range of 0.77-1.03 µL·mL~(-1), and that of γ-terpinene within the range of 0.04-0.13 µL·mL~(-1). The prediction of D-limonene and γ-terpinene as the Q-markers of Citri Reticulatae Pericarpium volatile oil has laid an experimental foundation for the establishment of the quality evaluation standard for Citri Reticulatae Pericarpium volatile oil.

Effects of the autophagy modulators d-limonene and chloroquine on vimentin levels in SH-SY5Y cells.

The molecular target and mechanism by which d-limonene induces LC3 lipidation and autophagosome formation remain elusive. Here, we report that this monoterpene rapidly enhances Ca2+ levels in SH-SY5Y cells; yet this effect does not lead to calpain- or caspase-mediated proteolysis of α-spectrin, nor calpain activity is required for the established enhancement of LC3-II levels by d-limonene. However, d-limonene rapidly reduced vimentin levels, an unexpected effect also induced by the autophagy inhibitor chloroquine (CQ). The magnitude of vimentin reduction parallels accumulation of LC3-II caused by a brief incubation with d-limonene or CQ. For longer exposure (48 h), d-limonene does not reduce vimentin, nor it increases LC3-II levels; conversely, a clear reduction of vimentin along with a massive accumulation of LC3-II is evident in cells treated with CQ. Vimentin participates in organelle positioning and in other cellular processes that have linked this intermediate filament protein to various diseases, including cancer, inflammatory and autoimmune disorders, and to virus replication and internalization. Our findings suggest an inverse relationship between vimentin reduction and LC3-II accumulation, whose causal link needs to be examined. Further experiments are needed to dissect the role of vimentin reduction in the mechanisms through which CQ impairs fusion of autophagosome with lysosomes as well as in other effects of this drug.