Bitter Orange Essential Oils Research Articles

Variation of the essential oil components of Citrus aurantium leaves upon using different distillation techniques and evaluation of their antioxidant, antidiabetic, and neuroprotective effect against Alzheimer’s disease

Citrus fruit essential oil is considered one of the widely studied essential oils while its leaves attract less attention although being rich in nearly the same composition as the peel and flowers. The leaves of bitter orange or sour orange (Citrus aurantium L.) were extracted using three different techniques namely; hydrodistillation (HD), steam distillation (SD), and microwave-assisted distillation (MV) to compare their chemical composition. The three essential oil samples were analyzed through GC/FID and GC/MS analyses. The samples were tested in vitro using different antioxidant techniques (DPPH, ABTS, CUPRAC, FRAP, PBD, and MCA), neuroprotective enzyme inhibitory activities (acetylcholine and butyl choline enzymes), and antidiabetic activities (α-amylase and α-glucosidase). The results showed that thirty-five volatile ingredients were detected and quantified. Monoterpenes represented the most abundant class in the three essential oils followed by sesquiterpenes. C. aurantium essential oil carried potential antioxidant activity where SD exhibited the highest antioxidant activity, with values arranged in the following order: FRAP (200.43 mg TE/g), CUPRAC (138.69 mg TE/g), ABTS (129.49 mg TE/g), and DPPH (51.67 mg TE/g). SD essential oil also presented the most potent α-amylase (0.32) inhibition while the MV essential oil showed the highest α-glucosidase inhibition (2.73 mmol ACAE/g), followed by HD (2.53 mmol ACAE/g), and SD (2.46 mmol ACAE/g). The SD essential oil exhibited the highest BChE and AChE inhibitory activities (3.73 and 2.06 mg GALAE/g), respectively). Thus, bitter orange essential oil can act as a potential source of potent antioxidant, antidiabetic, and neuroprotective activities for future drug leads.

Make the Quality Control of Essential Oils Greener: Fast Enantioselective GC-MS Analysis of Sweet and Bitter Orange as a Case Study.

Quality control of essential oils is fundamental for verifying their authenticity and conformity with quality standards, ensuring their safety and regulatory compliance, and monitoring their consistency. Companies that produce or market essential oils routinely evaluate the quality and authenticity of their products. However, they also must deal with increasing attention to environmental sustainability as well as practical considerations such as productivity, cost, and simplicity of methods. In this study, enantioselective gas chromatography (GC) was adopted to evaluate the quality of sweet and bitter orange essential oils, used as a case study. The analytical conditions were optimized and translated to fast GC to evaluate the impact of this approach on the environmental footprint of the analyses. The greenness of fast GC, compared with conventional GC, was quantitatively evaluated using a dedicated metric tool (AGREE), and important improvements have been calculated. The developed methods were applied to a set of commercial essential oils, and the data about the enantiomeric composition and relative percentage abundance were elaborated through multivariate statistics (principal component analysis). The results showed that fast chiral gas chromatography enables the classification of citrus essential oil samples and can be considered an environmentally friendly and sustainable approach for evaluating their quality.

Evaluation of Leaf, Flower and Peel Bitter Orange Essential Oils and their Constituents in Response to Various Planting Locations of Egypt

Bitter orange essential oils have biological characteristics that make them suitable for many purposes, the most important of which are food, agricultural and pharmaceutical industries. Cultivation of bitter oranges in different locations leads to change in the essential oil compositions, and thus their biological effects. Leaves, flowers and fruit peels of bitter orange were collected from three locations of Egypt (north, midst and south); essential oils were isolated and analyzed. Results were statistically analyzed according to ANOVA-1. The maximum contents of essential oils were recorded with samples collected from south location. The major component of leaf (33.9–41.9%) and flower (47.2–51.5%) essential oils was linalool; while, the main component of peel essential oil (70.5–74.7%) was limonene. Detected components of various parts noteworthy the presence of sesquiterpene hydrocarbons in leaf and peel essential oils which was completely omitted in flower essential oil. Oxygenated monoterpenes was the main fraction in leaf and flower essential oils; but monoterpene hydrocarbon was the major fraction in peel essential oil. Samples collected from south location resulted in the maximum values of major component from leaf (41.9%) and flower (51.5%) essential oils; while those harvested from north one produced the greatest amount of main component of peel essential oil (74.7%). Fractions of essential oil were varied due to different locations. This study concluded that it is possible in the future to expand the cultivation of Bitter orange at new reclamation sites of Egypt to increase the sources of natural essential oils; also this trial serves as a reference for selecting the suitable location to produce bitter orange essential oils because of the target compounds.

Influence of eight chosen essential oils in the vapor phase on the growth of Rhizopus stolonifer and Rhizopus lyococcus

This study aimed to evaluate the fungicidal effect of eight essential oils against five strains of the genus Rhizopus. Strains were obtained from various moldy foods, namely Rhizopus stolonifer KMi 383 from chestnut, R. stolonifer KMi 510 from strawberry, R. stolonifer KMi 511 from nectarine, R. stolonifer KMi 524 from cherry tomatoes, and R. lyococcus KMi 512 from blackberry. The essential oils (EO) used in this study were jasmine EO (extract from Jasminum officinale L.), bergamot EO (Mentha aquatica L. var. citrata (Her.) Fresen), bitter orange EO (from Citrus aurantium L.), grapefruit EO (Citrus paradisi Macfady), sweet flag EO (East Asian Calamus, from Acorus calamus L. var. angustatus Bes), star anise EO (from Illicium verum J.D.Hook), geranium EO (from Pelargonium graveolens), and lemongrass EO (from Cymbopogon citratus DC). The semi-quantitative composition of the essential oil samples was determined by gas chromatography coupled with mass spectrometry (GC-MS). The antifungal activity of essential oils against the strains of R. stolonifer and R. lyococcus was determined during 7 days, using the micro-atmosphere method (0.625 μL.mL-1 of air). Two essential oils, geranium and lemongrass, completely inhibited the growth of all isolates. Bitter orange essential oil inhibited the growth of all isolates of Rhizopus stolonifer, but isolate of Rhizopus lyococcus began to grow after four days of cultivation. In conclusion, certain essential oils are highly effective in the vapor phase. These could be used in further tests of their antifungal activity and could be used in the control of Rhizopus spp. or other fungal pathogens.

Bitter orange peel essential oil: A review of the different factors and chemical reactions influencing its composition

AbstractThis review summarizes the findings and discusses the results on the different factors that can influence the bitter orange peel oil composition. Small changes in composition can result in noticeable modifications of the odour profile of the essential oil. The analysis method appears to have a crucial effect on the number of compounds identified in the essential oil. Growing location, cultivar, ripening stage, storage conditions and extraction methods are reported to impact the bitter orange essential oil. Bitter orange peel oil should be stored at −21°C to prevent changes in the composition and formation of artefacts when storing for a period of several months. The influence of cultivars should not be neglected, since a few cultivars differ a lot from the main cluster of Citrus aurantium L. The geranyl pyrophosphate forms most of the terpenes present in the bitter orange, especially limonene which is the majority compound, by the action of the terpene synthases during growing of the fruit. The extraction method can also be responsible for some differences in the composition due to the absence of water‐soluble compounds in cold‐pressed oils and to acid‐catalysed reactions in hydrodistilled oils such as the decomposition of the linalyl acetate forming many different terpene derivatives.

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.

Effect of essential oil from Citrus aurantium in maternal reproductive outcome and fetal anomaly frequency in rats.

Citrus aurantium L., commonly known as bitter orange, is widely used in folk medicine, but there is little data in the literature about the effects on pregnancy. The aim of the present study was to evaluate the influence of essential oil obtained from fruits of Citrus aurantium on the maternal reproductive outcome and fetal anomaly incidence in rats. Pregnant Wistar rats were randomized into four groups (n minimum = 12 animals/group): G1 = control, G2 to G4 = treated with essential oil from C. aurantium at dose 125, 250 and 500 mg/kg, respectively. Rats were orally treated, by gavage, with plant essential oil or vehicle during pre-implantation and organogenic period (gestational day 0-14). On gestational day 20 the rats were anaesthetized and the gravid uterus was weighed with its contents and the fetuses were analyzed. Results showed that the treated group with 500 mg/kg presented decreased placental weights and placental index, although the treatment with bitter orange essential oil did not show any alteration in maternal reproductive performance, toxicological effect, changes in ossification sites, and malformation index. In conclusion, the treatment of Citrus aurantium essential oil was not teratogenic and did not alter the maternal reproductive outcome.

Classification of commercial bitter orange essential oils (Citrus aurantium L.), based on a combination of chemical and sensory analyses of specific odor markers

Ten commercial cold-pressed Citrus aurantium L. essential oils (EOs) were previously classified according to their content in twenty-seven key odorants as measured by gas chromatography–mass spectrometry (GC–MS). Principal component analysis and hierarchical cluster analysis performed on odor markers and composition data made it possible to distinguish five EO groups. In addition to chemical measurements, thirty-one subjects participated in a sensory analysis of the sample odors and classified the ten EO samples by means of a free-sorting task. The very good correlation found between chemical and sensory measurements made it possible to confirm that the odor markers previously identified using GC–olfactometry were effective indicators of the EO overall odor. This method combining instrumental and sensory analyses thus appears promising for discriminating and classifying EOs from a given botanical species.

Vapor–Liquid Equilibria Measurements of Bitter Orange Aroma Compounds Highly Diluted in Boiling Hydro-Alcoholic Solutions at 101.3 kPa

In this work, experimental vapor-liquid equilibria (VLE) of water + ethanol + five aroma compound (two monoterpene hydrocarbons, alpha-pinene and D-limonene, and three oxygenated compounds, linalool, citral, and linalool oxide) mixtures were measured at boiling point at 101.3 kPa for ethanol molar fractions ranging from 0.0140 to 0.8389. The five aroma compounds were selected for their strong contribution to the aroma of the distillate of bitter orange essential oil. First, the thermodynamic consistency of the experimental VLE data was validated. Then the NRTL and Henry's law type models were tested to correlate the experimental data. Good agreement was obtained with both models to predict the phase equilibrium of the oxygenated compounds, and a better agreement was obtained with Henry's law type models for the monoterpene hydrocarbons in this kind of mixture.

Toxicity of citrus essential oils against Ceratitis capitata (Diptera: Tephritidae) larvae

AbstractCitrus peel essential oils are considered to constitute the most important resistance factor of citrus fruits against fruit flies. Essential oils were obtained from three sweet orange varieties, one bitter orange and one lemon variety. Yield, chemical composition and toxicity against neonates of the Mediterranean fruit fly were determined. Based on chemical analysis, the toxicity of commercially purchased major and minor components (monoterpenes and sesquiterpenes) of essential oils was determined. In addition, fractions were prepared to evaluate the role of minor components in the toxicity of crude essential oils. Limonene was by far the most abundant ingredient (96.2–97.4%) in all sweet orange varieties and in bitter orange, while the concentration of limonene was much lower in lemon essential oils (74.3%). Orange and bitter orange essential oils were more toxic than lemon essential oils. The toxicity of orange and bitter orange essential oils was similar to that of their major component limonene. In tests of commercially purchased chemicals, the oxygenated components of essential oils were more toxic than hydrocarbons but their low concentration in citrus essential oils could not affect the toxic activity of essential oils. The presence of α‐pinene and β‐pinene seems to account for the lower toxicity of lemon essential oils in relation to other citrus essential oils. The importance of understanding the toxicity of essential oils in relation to their composition and their role regarding the resistance of citrus fruits to Ceratitis capitata infestation is discussed.

Comparative investigation of the sweet and bitter orange essential oil (Citrus sinensis and Citrus aurantium)

The volatile fraction composition of commercially produced sweet and bitter orange oil from fruit peels was studied using GC-MS. More than fifty components were identified in the oils using their mass spectra and linear retention indices. The monoterpene limonene was the most abundant component even though not in a quantity expected for a fresh orange essential oil. Aldehydes, followed by alcohols and esters, were the main components in the oxygenated fraction. Aldehydes were the major oxygenated components in the sweet orange oil, whereas alcohols and esters were present in higher amounts in the bitter orange oil. Among them, nonanal, decanal and linalool are the most important components for the flavour of sweet orange oil and carvon is the most important ketone for the flavour of bitter orange oil in combination with the other components. The amount of carvon gives a good indication about the freshness of the oil and the quantities of α-pinene and β-pinene, sabinene and myrcene give an indication about the natural or artificially changed composition of the essential oils.

On the Genuineness of Citrus Essential Oils. 51. Oxygen Heterocyclic Compounds of Bitter Orange Oil (Citrus aurantium L.)

The composition of the oxygen heterocyclic fraction of bitter orange essential oil, obtained by normal-phase HPLC with two on-line coupled columns (μ-Porasil and Zorbax), is reported. Genuine, industrial, cold-pressed Italian and Spanish essential oils, commercial oils, laboratory hand-extracted oils, and mixtures of bitter orange oil with sweet orange, lemon, lime, and grapefruit oils were analyzed. Four coumarins (osthol, meranzin, isomeranzin, and meranzin hydrate), three psoralens (bergapten, epoxybergamottin, and epoxybergamottin hydrate), and four polymethoxyflavones (tangeretin, 3,3‘,4‘,5,6,7,8-heptamethoxyflavone, nobiletin, and tetra-O-methylscutellarein) were identified. In addition, three unknown coumarins were found. Meranzin was the main component isolated. Meranzin hydrate, the formation of which was probably due to the hydration of meranzin during the industrial extraction, was not found in the laboratory hand-extracted samples. Meranzin was not present in some industrial samples, probably ...

On the genuineness of citrus essential oils. Part XLI. Italian bitter orange essential oil: Composition and detection of contamination and additions of oils and terpenes of sweet orange and of lemon

AbstractThe composition of the volatile fraction of Italian bitter orange essential oil, carried out by LC, HRGC and GC–MS, is reported: 60 components have been identified. The results obtained are compared with those in the literature for Italian and Spanish bitter orange oils.Two methods are suggested which allows the detection of contamination or possible additions of terpenes and oils of sweet orange and of lemon to genuine bitter orange oil. One is based upon the content of δ‐3‐carene and the value of the ratios δ‐3‐carene/camphene and δ‐3‐carene/terpinolene which permits the detection of the additions of 5% of sweet orange terpenes and oils; the second is based upon the content of α‐terpinene and the value of the ratios α‐terpinene/camphene and α‐terpinene/cis‐β‐ocimene and allows the detection of the addition of even 3% of lemon terpenes and oils.