Composition of the essential oil of Citrus tamurana Hort. ex Tanaka (Hyuganatsu)

p-Synephrine Indicates Internal Maturity of Citrus grandis (L.) Osbeck cv. Mato Peiyu-Reclaiming Functional Constituents from Nonedible Parts

The processing of Citrus grandis Osbeck cv. Mato Peiyu (CGMP) fruits generates a considerable amount of waste, mainly the flavedo, albedo, and segment membrane; the generated waste yields severe environmental and economic challenges. In this study, we tried to reclaim some functional chemicals from the waste. Our data indicated that the essential oil content in the flavedo was 0.76-1.34%, with the major component being monoterpenes (93.75% in August, declining to 85.56% in November, including mainly limonene (87.08% to 81.12%) and others such as β-myrcene). p-Synephrine (mg/100 g dry weight) declined accordingly (flavedo, 10.40 to 2.00; albedo, 1.80 to 0.25; segment membrane, 0.3 in August, 0.2 in September, and none since October). Polyphenols (in μg/g) included gallic acid (70.32-110.25, 99.27-252.89, and 105.78-187.36, respectively); protocatechuic acid (65.32-204.94, 26.35-72.35, and 214.98-302.65, respectively), p-coumaric acid (30.63-169.13, 4.32-17.00, and 6.68-34.32, respectively), ferulic acid (12.36-39.36, 1.21-10.25, and 17.07-39.63, respectively), and chlorogenic acid (59.19-199.36, 33.08-108.57, and 65.32-150.14, respectively). Flavonoids (in μg/g) included naringin (flavedo, 89.32-283.19), quercetin (181.05-248.51), nobiletin (259.75-563.7), hesperidin, and diosmin. The phytosterol content (mg/100 g) was 12.50-44.00 in the flavedo. The total dietary fiber in the segment membrane was 57 g/100 g. The antioxidant activity against the DPPH^• and ABTS^+• free radicals was moderately high. In conclusion, the waste of CGMP fruits is worth reclaiming for essential oil, p-synephrine, polyphenolics, and dietary fiber. Notably, p-synephrine content (flavedo: <8 mg/100 g dry weight, albedo: <2.0, or segment membrane: <0.4 mg) can serve as a marker of the internal maturation of CGMP fruits.

Essential Oils in Citrus Fruit Ripening and Postharvest Quality

Citrus essential oils (EOs) are widely used as flavoring agents in food, pharmaceutical, cosmetical and chemical industries. For this reason, their demand is constantly increasing all over the world. Besides industrial applications, the abundance of EOs in the epicarp is particularly relevant for the quality of citrus fruit. In fact, these compounds represent a natural protection against postharvest deteriorations due to their remarkable antimicrobial, insecticidal and antioxidant activities. Several factors, including genotype, climatic conditions and cultural practices, can influence the assortment and accumulation of EOs in citrus peels. This review is focused on factors influencing variation of the EOs’ composition during ripening and on the implications on postharvest quality of the fruit.

A New Sesquiterpene Essential Oil from the Native Andean Species Jungia rugosa Less (Asteraceae): Chemical Analysis, Enantiomeric Evaluation, and Cholinergic Activity

As part of a project devoted to the phytochemical study of Ecuadorian biodiversity, new essential oils are systematically distilled and analysed. In the present work, Jungia rugosa Less (Asteraceae) has been selected and some wild specimens collected to investigate the volatile fraction. The essential oil, obtained from fresh leaves, was analysed for the first time in the present study. The chemical composition was determined by gas chromatography, coupled to mass spectrometry (GC-MS) for qualitative analysis, and to flame ionization detector (GC-FID) for quantitation. The calculation of relative response factors (RRF), based on combustion enthalpy, was carried out for each quantified component. Fifty-six compounds were identified and quantified in a 5% phenyl-polydimethylsiloxane non-polar column and 53 compounds in a polyethylene glycol polar column, including four undetermined compounds. The main feature of this essential oil was the exclusive sesquiterpenes content, both hydrocarbons (74.7% and 80.4%) and oxygenated (8.3% and 9.6%). Major constituents were: γ-curcumene (47.1% and 49.7%) and β-sesquiphellandrene (17.0% and 17.9%), together with two abundant undetermined oxygenated sesquiterpenes, whose abundance was 6.7-7.2% and 4.7-3.3%, respectively. In addition, the essential oil was submitted to enantioselective evaluation in two β-cyclodextrin-based enantioselective columns, determining the enantiomeric purity of a minor component (1S,2R,6R,7R,8R)-(+)-α-copaene. Finally, the AChE inhibition activity of the EO was evaluated in vitro. In conclusion, this volatile fraction is suitable for further investigation, according to two main lines: (a) the purification and structure elucidation of the major undetermined compounds, (b) a bio-guided fractionation, intended to investigate the presence of new sesquiterpene AChE inhibitors among the minor components.

Exploring the multisensory perception of terpene alcohol and sesquiterpene rich hop extracts in lager style beer

Understanding the contribution of hop essential oil to the multisensory profile of beer is known to be challenging because of its chemical and sensory complexity. Limited research has been conducted investigating hop-derived volatiles' role in the modulation of taste and mouthfeel sensations. Supercritical CO₂ can be used to extract specific fractions from hop oil, thereby enabling the localisation of compounds responsible for different sensory impressions. Terpene alcohol and sesquiterpene fractions were extracted from a Magnum hop oil and further fractionated into seven sub-fractions and individual compounds. All extracts were evaluated in lager (4.5% v/v) by a trained panel (n = 10) using a newly developed attribute lexicon and following a sensory descriptive analysis approach. The sensory data was analysed using ANOVA, followed by Tukey's test (HSD) and correlated with chemical profile data obtained by gas chromatography-mass spectrometry (GC-MS) by Principal Component Analysis. The study revealed evidence for hop extracts to impart multisensory characteristics to beer due to sensory interactions within and across modalities. The monoterpene alcohols-rich fractions and particularly geraniol, added fruity- and floral aromas and flavours, modified the sweetness and induced a smooth bitterness in the beer matrix. Flavouring the beer with sesquiterpene fractions resulted in a harsh bitterness sensation. Contrary to previous findings, the humulene epoxides fraction appeared to have limited effects on lingering bitterness and astringency, illustrating the need for temporal sensory assessments in future studies. This research shows that splitting hop oil into fractions and sub-fractions provides a source of natural, sustainable flavouring preparations with distinct sensory characteristics.

Yield, Phytochemical Constituents, and Antibacterial Activity of Essential Oils from the Leaves/Twigs, Branches, Branch Wood, and Branch Bark of Sour Orange (Citrus aurantium L.)

In the present work, essential oils (EOs) extracted from different parts of sour orange Citrus aurantium (green leaves/twigs, small branches, wooden branches, and branch bark) were studied through gas chromatography coupled with mass spectrometry (GC/MS). Furthermore, the EOs in the amounts of 5, 10, 15, 20, and 25 µL were studied for their antibacterial activity against three pathogenic bacteria, Agrobacterium tumefaciens, Dickeya solani, and Erwinia amylovora. The main EO compounds in the leaves/twigs were 4-terpineol (22.59%), D-limonene (16.67%), 4-carvomenthenol (12.84%), and linalool (7.82%). In small green branches, they were D-limonene (71.57%), dodecane (4.80%), oleic acid (2.72%), and trans-palmitoleic acid (2.62%), while in branch bark were D-limonene (54.61%), γ-terpinene (6.68%), dodecane (5.73%), and dimethyl anthranilate (3.13%), and in branch wood were D-limonene (38.13%), dimethyl anthranilate (8.13%), (-)-β-fenchol (6.83%), and dodecane (5.31%). At 25 µL, the EO from branches showed the highest activity against A. tumefaciens (IZ value of 17.66 mm), and leaves/twigs EO against D. solani and E. amylovora had an IZ value of 17.33 mm. It could be concluded for the first time that the wood and branch bark of C. aurantium are a source of phytochemicals, with D-limonene being the predominant compound in the EO, with potential antibacterial activities. The compounds identified in all the studied parts might be appropriate for many applications, such as antimicrobial agents, cosmetics, and pharmaceuticals.

Comparative analysis of three Australian finger lime (Citrus australasica) cultivars: identification of unique citrus chemotypes and new volatile molecules

The volatile constituents of the peel of three cultivars of Australian finger lime (Citrus australasica) were investigated: Alstonville, Judy's Everbearing and Durham's Emerald. Both qualitative and quantitative GC-MS analyses were performed on their peel solvent extract. The results showed that the unique phenotypes of finger lime are also correlated to unique molecular compositions. Each cultivar revealed a different chemotype: limonene/sabinene for cv. Alstonville, limonene/citronellal/isomenthone for cv. Judy's Everbearing, and limonene/citronellal/ citronellol for cv. Durham's Emerald. To the best of our knowledge, these chemotypes have never been reported in any other citrus species. Furthermore, the amounts of some volatile constituents (γ-terpinene, α-pinene, β-pinene, citral), which are generally the major constituents besides limonene in lime species, were surprisingly low in the three cultivars. Comparative GC-MS analysis also showed that some volatile molecules tended to be specific to one cultivar and could therefore be considered as markers. Moreover six molecules were reported for the first time in a citrus extract and confirmed by synthesis. Heart-cutting enantioselective two-dimensional GC-MS was performed to determine the enantiomeric distribution of the major chiral constituents. The combined data on three finger lime cultivars gives evidence of their divergence from other citrus species.

Identification of aroma active compounds in orange essence oil using gas chromatography-olfactometry and gas chromatography-mass spectrometry

Using GC-MS and GC-flame ionization detection (FID)/olfactometry, 95 volatile components were detected in orange essence oil, of which 55 were aroma active. In terms of FID peak area the most abundant compounds were: limonene, 94.5%; myrcene, 1%; valencene, 0.8%; linalool, 0.7%, and octanal, decanal, and ethyl butyrate, 0.3% each. One hundred percent of the aroma activity was generated by slightly more than 4% of the total volatiles. The most intense aromas were produced by octanal, wine lactone, linalool, decanal, beta-ionone, citronellal, and beta-sinensal. Potent aroma components reported for the first time in orange essence oil include: E-2-octenal, 1-octen-3-ol, Z-4-decenal, E,E-2,4-nonadienal, guaiacol, gamma-octalactone, and m-cresol. Over 20 compounds were identified for the first time in orange essence oil using MS, however, most did not exhibit aroma activity.