Automated HPLC-HRGC: A powerful method for essential oils analysis. Part V. identification of terpene hydrocarbons of bergamot, lemon, mandarin, sweet orange, bitter orange, grapefruit, clementine and mexican lime oils by coupled HPLC-HRGC-MS(ITD)

Valorization of Sweet Lime Peel for the Extraction of Essential Oil by Solvent Free Microwave Extraction Enhanced with Ultrasound Pretreatment

Essential oils of sweet lime peel, a waste by-product in the juice industry, were extracted using the vacuum assisted solvent free microwave extraction (VASFME) method. The effects of microwave output power (500–1000 W) and extraction time (20–30 min) on the essential oils yield and antimicrobial property were investigated. Optimal conditions were observed at 797.844 W microwave output power and 30 min extraction time. The essential oils yield and antimicrobial property under these conditions were 0.792 ± 0.03% and 18.25 ± 1.45 mm, respectively, which agrees with the predicted values of 0.757% and 16.50 mm. The essential oils were extracted at optimized conditions and analyzed through GCMS for compound identification. A total of 49 compounds were identified, with limonene content (43.47%) being the highest among all sweet lime peel oil compounds. Moreover, the sweet lime peels were subjected to ultrasound pre-treatment before microwave extraction. The ultrasound pre-treatment helped to increase the essential oils yield from 0.84 to 1.06% as the treatment time increased from 30 to 90 min. The increase in yield was 37.66% more compared to VASFME at 90 min treatment time.

Modification of brain waves and sleep parameters by Citrus reticulata Blanco. cv. Sai-Nam-Phueng essential oil

Background

Citrus essential oil (EO) has been used for mood elevation and sedative hypnotic purposes. However, scientific proofs of its central nervous system (CNS) action remained largely unexplored. This study investigated chemotypes, electrical brain waves and sleep-wake effects of the essential oil from Citrus reticulata in rat model.

Methods

Chemical contents of citrus EO were analyzed using gas chromatography-mass spectrometry (GC–MS). Male Wistar rats implanted with electrodes on the frontal and parietal skulls were used for electroencephalographic (EEG) recording while inhaling the citrus EO (200 μl on cotton wool). Diazepam (10 mg/kg, p.o.) was used as a standard anxiolytic drug. EEG frequency analyses were performed by using Fast Fourier transform. All data were statistical analyzed using One-way ANOVA followed by Tukey's test.

Results

GC–MS analysis revealed d-limonene (95.7%) as a major constituent of citrus EO. The EEG results showed that overall EEG patterns of citrus EO effects were relatively similar to that of diazepam. However, significant differences between treatments were seen from sleep-wake analyses. Diazepam significantly increased episode numbers of awake and non-rapid eye movement (REM) sleep and reduced averaged episode duration. On the other hand, the citrus EO significantly decreased REM sleep latency and increased total time and episode numbers of REM sleep.

Conclusion

These findings demonstrated unique CNS effects of C. reticulata EO with EEG fingerprints and sleep-wake profiles. The data might be useful for citrus essential oil sub-classification and clinical application.

Evaluation of Physical and Chemical Properties of Pomelo (Citrus grandis L.) Essential Oil using Steam Distillation Process

This study attempted the extraction of essential oils from the peels of pomelo (Citrus grandis L.) grown in Ben Tre province, Vietnam through hydrodistillation method. In addition, the chemical composition and physio-chemical properties of the essential oils were reported. The results showed that the extraction yield of the extraction process achieved about 1.67%. The physico-chemical index of essential oils is determined by specific gravity (0.8572 g/cm3), acid index (0.3556 mg KOH/g), ester index (2.4216 mg KOH/g), and refractive index (1.476). The GC-MS analyses of the oil indicated the component with highest content in the oil was α-limonene (96.491%), followed by α-pinene (0.686%), β-pinene (0.248%), β-myrcene (1.644%), α-phellandrene (0.793%) and β-cis-ocimene (0.138%). These results suggested that wastes from fruit peeling process can be converted into a new material source with great potential for industrial use.

Anxiolytic Terpenoids and Aromatherapy for Anxiety and Depression

In our society, anxiety and depression are serious health issues that affect a large proportion of the population. Unfortunately, drug therapies are not always effective and can lead to drug abuse, delay of therapeutic effect, dependence, and tolerance. Traditionally, aromatherapy has also been used for anxiety relief and mood improvement. The use of essential oils, in relieving anxiety and depression, does not have the disadvantages associated with currently used drug therapies. In-vivo studies on animal models have verified the anxiolytic effects of these essential oils and the interactions of their major components with central nervous system receptors. Therefore, it seems reasonable to argue that the modulation of glutamate and GABA neurotransmitter systems are likely to be the critical mechanisms responsible for the sedative, anxiolytic, and anticonvulsant proprieties of linalool and essential oils containing linalool in significant proportions. Popular anxiolytic essential oils are generally rich in terpenoid alcohols like linalool, geraniol and citronellol, and the monoterpene limonene (or citral). Therefore, other essential oils or formulations that contain these terpenoids as major components may serve as important aromatherapeutics for relief of anxiety.

In-Depth Qualitative Analysis of Lime Essential Oils Using the Off-Line Combination of Normal Phase High Performance Liquid Chromatography and Comprehensive Two-Dimensional Gas Chromatography-Quadrupole Mass Spectrometry

The present research is focused on the in-depth qualitative analysis of three types of lime essential oil (EO), viz., Key (A and B) and Persian, using the off-line combination of normal phase high performance liquid chromatography (NP-HPLC) and comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC × GC-QMS). The first analytical dimension (NP-HPLC) was exploited for the isolation of the hydrocarbon constituents from the oxygenated ones. Each fraction was then reduced in volume and analyzed using (cryogenic modulation) GC × GC-QMS. Peak assignment was carried out through the combined use of mass spectral database and linear retention index matching processes. The powerful four-dimensional technology enabled the separation and identification of a very high number (153) of lime essential oil volatile compounds.

Anxiolytic-Like Effects of Bergamot Essential Oil Are Insensitive to Flumazenil in Rats

Anxiety disorders are one of the most common mental disorders, and benzodiazepines (BDZs), acting on gamma-aminobutyric acid type A (GABA-A) receptor complex, represent the most common antianxiety medications in the world. However, chronic BDZ use elicits several adverse reactions. Reportedly, aromatherapy is safer for the management of anxiety. Bergamot essential oil (BEO) extracted from Citrus bergamia Risso et Poiteau fruit, like other essential oils, is widely used in aromatherapy to relieve symptoms of stress-induced anxiety. Interestingly, preclinical data indicate that BEO induces anxiolytic-like/relaxant effects in animal behavioural tasks not superimposable to those of benzodiazepine diazepam. To better elucidate the involvement of GABAergic transmission, the present study examines the effects of pretreatment with flumazenil (FLZ), a benzodiazepine site antagonist, on BEO effects using open-field task (OFT) in rats. The data yielded show that FLZ does not significantly affect behavioural effects of the phytocomplex. These results demonstrate the lack of overlapping between BEO and BDZ behavioural effects, contributing to the characterization of the neurobiological profile of the essential oil for its rational use in aromatherapy.

Classification of Bitter Orange Essential Oils According to Fruit Ripening Stage by Untargeted Chemical Profiling and Machine Learning

The quality and composition of bitter orange essential oils (EOs) strongly depend on the ripening stage of the citrus fruit. The concentration of volatile compounds and consequently its organoleptic perception varies. While this can be detected by trained humans, we propose an objective approach for assessing the bitter orange from the volatile composition of their EO. The method is based on the combined use of headspace gas chromatography–mass spectrometry (HS-GC-MS) and artificial neural networks (ANN) for predictive modeling. Data obtained from the analysis of HS-GC-MS were preprocessed to select relevant peaks in the total ion chromatogram as input features for ANN. Results showed that key volatile compounds have enough predictive power to accurately classify the EO, according to their ripening stage for different applications. A sensitivity analysis detected the key compounds to identify the ripening stage. This study provides a novel strategy for the quality control of bitter orange EO without subjective methods.

Role of D-Limonene in autophagy induced by bergamot essential oil in SH-SY5Y neuroblastoma cells

Bergamot (Citrus bergamia, Risso et Poiteau) essential oil (BEO) is a well characterized, widely used plant extract. BEO exerts anxiolytic, analgesic and neuroprotective activities in rodents through mechanisms that are only partly known and need to be further investigated. To gain more insight into the biological effects of this essential oil, we tested the ability of BEO (0.005–0.03%) to modulate autophagic pathways in human SH-SY5Y neuroblastoma cells. BEO-treated cells show increased LC3II levels and appearance of dot-like formations of endogenous LC3 protein that colocalize with the lysosome marker LAMP-1. Autophagic flux assay using bafilomycin A1 and degradation of the specific autophagy substrate p62 confirmed that the observed increase of LC3II levels in BEO-exposed cells is due to autophagy induction rather than to a decreased autophagosomal turnover. Induction of autophagy is an early and not cell-line specific response to BEO. Beside basal autophagy, BEO also enhanced autophagy triggered by serum starvation and rapamycin indicating that the underlying mechanism is mTOR independent. Accordingly, BEO did not affect the phosphorylation of ULK1 (Ser757) and p70^S6K (Thr389), two downstream targets of mTOR. Furthermore, induction of autophagy by BEO is beclin-1 independent, occurs in a concentration-dependent manner and is unrelated to the ability of BEO to induce cell death. In order to identify the active constituents responsible for these effects, the two most abundant monoterpenes found in the essential oil, d-limonene (125–750 µM) and linalyl acetate (62.5–375 µM), were individually tested at concentrations comparable to those found in 0.005–0.03% BEO. The same features of stimulated autophagy elicited by BEO were reproduced by d-limonene, which rapidly increases LC3II and reduces p62 levels in a concentration-dependent manner. Linalyl acetate was ineffective in replicating BEO effects; however, it greatly enhanced LC3 lipidation triggered by d-limonene.

Natural bioactive compounds of Citrus limon for food and health

Citrus genus is the most important fruit tree crop in the world and lemon is the third most important Citrus species. Several studies highlighted lemon as an important health-promoting fruit rich in phenolic compounds as well as vitamins, minerals, dietary fiber, essential oils and carotenoids. Lemon fruit has a strong commercial value for the fresh products market and food industry. Moreover, lemon productive networks generate high amounts of wastes and by-products that constitute an important source of bioactive compounds with potential for animal feed, manufactured foods, and health care. This review focuses on the phytochemistry and the analytical aspects of lemon compounds as well as on the importance for food industry and the relevance of Citrus limon for nutrition and health, bringing an overview of what is published on the bioactive compounds of this fruit.

Prevention of Glutamate Accumulation and Upregulation of Phospho-Akt may Account for Neuroprotection Afforded by Bergamot Essential Oil against Brain Injury Induced by Focal Cerebral Ischemia in Rat

The effects of bergamot essential oil (BEO; Citrus bergamia, Risso) on brain damage caused by permanent focal cerebral ischemia in rat were investigated. Administration of BEO (0.1-0.5 ml/kg but not 1 ml/kg, given intraperitoneally 1 h before occlusion of the middle cerebral artery, MCAo) significantly reduced infarct size after 24 h permanent MCAo. The most effective dose (0.5 ml/kg) resulted in a significant reduction of infarct extension throughout the brain, especially in the medial striatum and the motor cortex as revealed by TTC staining of tissue slices. Microdialysis experiments show that BEO (0.5 ml/kg) did not affect basal amino acid levels, whereas it significantly reduced excitatory amino acid, namely aspartate and glutamate, efflux in the frontoparietal cortex typically observed following MCAo. Western blotting experiments demonstrated that these early effects were associated, 24 h after permanent MCAo, to a significant increase in the phosphorylation and activity of the prosurvival kinase, Akt. Indeed, BEO significantly enhanced the phosphorylation of the deleterious downstream kinase, GSK-3beta, whose activity is negatively regulated via phosphorylation by Akt.

Cell signaling pathways in the mechanisms of neuroprotection afforded by bergamot essential oil against NMDA-induced cell death in vitro

BACKGROUND AND PURPOSE

The effects of bergamot essential oil (BEO; Citrus bergamia, Risso) on excitotoxic neuronal damage was investigated in vitro.

EXPERIMENTAL APPROACH

The study was performed in human SH-SY5Y neuroblastoma cells exposed to N-methyl-D-aspartate (NMDA). Cell viability was measured by dye exclusion. Reactive oxygen species (ROS) and caspase-3 activity were measured fluorimetrically. Calpain I activity and the activation (phosphorylation) of Akt and glycogen synthase kinase-3beta (GSK-3beta) were assayed by Western blotting.

KEY RESULTS

NMDA induced concentration-dependent, receptor-mediated, death of SH-SY5Y cells, ranging from 11 to 25% (0.25-5 mM). Cell death induced by 1 mM NMDA (21%) was preceded by a significant accumulation of intracellular ROS and by a rapid activation of the calcium-activated protease calpain I. In addition, NMDA caused a rapid deactivation of Akt kinase and this preceded the detrimental activation of the downstream kinase, GSK-3beta. BEO (0.0005-0.01%) concentration dependently reduced death of SH-SY5Y cells caused by 1 mM NMDA. In addition to preventing ROS accumulation and activation of calpain, BEO (0.01%) counteracted the deactivation of Akt and the consequent activation of GSK-3beta, induced by NMDA. Results obtained by using specific fractions of BEO, suggested that monoterpene hydrocarbons were responsible for neuroprotection afforded by BEO against NMDA-induced cell death.

CONCLUSIONS AND IMPLICATIONS

Our data demonstrate that BEO reduces neuronal damage caused in vitro by excitotoxic stimuli and that this neuroprotection was associated with prevention of injury-induced engagement of critical death pathways.

Pharmaceutical and therapeutic Potentials of essential oils and their individual volatile constituents: a review

Essential oils and their volatile constituents are used widely to prevent and treat human disease. The possible role and mode of action of these natural products is discussed with regard to the prevention and treatment of cancer, cardiovascular diseases including atherosclerosis and thrombosis, as well as their bioactivity as antibacterial, antiviral, antioxidants and antidiabetic agents. Their application as natural skin penetration enhancers for transdermal drug delivery and the therapeutic properties of essential oils in aroma and massage therapy will also be outlined.

On-line reversed–phase liquid chromatography-gas chromatography coupled to mass spectrometry for enantiomeric analysis of chiral compounds in fruit beverages

A method based on the on-line coupling of reversed phase liquid chromatography with gas chromatography/mass spectrometry (RPLC-GC-MS) for the chiral evaluation of characteristic constituents of fruit beverage aroma was investigated. The consideration of a variety of parameters involved in the transfer step allowed to achieve relative standard deviations ranging from 0.4 to 10% in most cases and detection limits from 0.2 to 2.5 mg/l. By applying the developed method to fruit beverages, racemic mixtures of ethyl 2-methylbutanoate and gamma-nonalactone were found. This fact suggests the eventual addition of artificial aromas. The method proposed in the present work can be useful to assess reliably the authenticity of aqueous samples, such as fruit beverages.

Biochemical characterization of blood orange, sweet orange, lemon, bergamot and bitter orange

This paper reports on the composition of aroma compounds and fatty acids and some physico-chemical parameters (juice percentage, acidity and total sugars) in five varieties of citrus: blood orange, sweet orange, lemon, bergamot and bitter orange. Volatile compounds and methyl esters have been analyzed by gas chromatography. Limonene is the most abundant compound of monoterpene hydrocarbons for all of the examined juices. Eighteen fatty acids have been identified in the studied citrus juices, their quantification points out that unsaturated acids predominate over the saturated ones. Mean concentration of fatty acids varies from 311.8 mg/l in blood orange juice to 678 mg/l in bitter orange juice.

Gas chromatographic technologies for the analysis of essential oils

Essential oil analysis has basically had one technical goal: to achieve the best possible separation performance by using the most effective, available technology of the day. The result achieved from this may then be used to answer the research or industrial analysis questions which necessitated the analysis. This may be for comparative purposes, where one oil is contrasted with other(s) for quality control or investigation of adulteration, to discover new components, or to characterise the chemical classes of compounds present. Clearly, today the analyst turns to chromatography as the provider of separation and then may supplement that with mass spectrometry to aid identification. The power of GC-MS means that advances in both the separation technique, and improvements in mass spectrometry detection - along with improved data handling tools - will immediately be relevant to the essential oil area. This present review outlines the developmental nature of instrumental approaches to essential oil analysis using gas chromatography. Mass spectrometry will be included to the extent that it represents the hyphenation of choice for most analysts when analysing essential oils. Thus single-column and multi-dimensional analysis will be covered, as will sample handling or introduction techniques prior to the analysis step, where these techniques provide some measure of separation. The recent demonstration of comprehensive gas chromatography will be discussed as the potentially most powerful separation method for essential oils. This brief review is not intended to be a comprehensive dissertation on the field of essential oil analysis since that would require sufficient space to occupy a book in its own right. Rather, it will outline selected considerations and developments, to help explain where new technology has been applied to advantage in this field.

Chemical variability of peel and leaf essential oils of 15 species of mandarins

Peel and leaf oils of 58 mandarin cultivars, belonging to 15 different species were obtained from fruits and leaves collected on mandarin-trees submitted to the same pedoclimatic and cultural conditions. Their chemical composition was investigated by capillary GC, GC/MS and 13C NMR and the results were submitted to a cluster analysis and a discriminant analysis. Three major chemotypes, limonene, limonene/gamma-terpinene and linalyl acetate/limonene, were distinguished for peel oils while three other chemotypes, sabinene/linalool, gamma-terpinene/linalool and methyl N-methylanthranilate, were observed for leaf oils.