Composition of peel essential oils from four selected Tunisian Citrus species: Evidence for the genotypic influence

Impact of Solvent Properties of Cold-Pressed and Steam-Distilled Orange Oils on GuttaFlow2 and Gutta-Percha

INTRODUCTION

Root canal retreatment often employs organic solvents like chloroform, eucalyptol, and orange oil. However, studies comparing their effectiveness yield inconsistent results. The quantity of d-limonene, a crucial component in orange oil, varies depending on the oil production method. Cold-pressed orange oil has been observed to contain the highest d-limonene levels. This study investigates the comparative solvent effects of cold-pressed and steam-hydrodistilled orange oils on gutta-percha and GuttaFlow2, typically used components in root canal fillings.

METHODS

Thirty-two discs (10 mm in diameter and 2 mm in thickness) were prepared using GuttaFlow and gutta-percha cones. The samples were weighed and then randomly divided into four groups (n=8) based on the type of solvent used. Each group was immersed in its respective solvent for 10 minutes. After exposure to the solvent, the samples were reweighed to determine the amount of material removed.

RESULTS

The weight loss in the group treated with cold-pressed orange oil on gutta-percha was significantly higher than in other groups (GuttaFlow2 + cold-pressed orange oil, gutta-percha + steam hydrodistilled orange oil, GuttaFlow2 + steam hydrodistilled orange oil) (p<0.001, p<0.001, and p<0.001).

CONCLUSION

According to the study findings, cold-pressed orange oil demonstrated a higher solvent effect on both GuttaFlow2 and traditional gutta-percha compared to steam-hydrodistilled orange oil. This indicates the significant impact of the production method of orange oil on its efficacy as a solvent in root canal therapy retreatment.

Preparation, Characterization and Application of Active Food Packaging Films Based on Sodium Alginate and Twelve Varieties of Mandarin Peel Powder

The industrial processing of mandarin fruits yields a large amount of peel waste, resulting in economic losses and environmental pollution. The peels of mandarin fruits are a good source of biomass and active substances that can be used to produce food packaging systems. In this study, active food packaging films were prepared based on sodium alginate and twelve varieties of mandarin peel powder. The structures, properties, and corn oil packaging performance of the films were compared. Results showed that the twelve varieties of mandarin peel powder differed in pectin, lipid, protein, crude fiber, and total phenol contents. The prepared films all exhibited a yellow color, 117.73-152.45 μm thickness, 16.39-23.62% moisture content, 26.03-90.75° water contact angle, 5.38-8.31 × 10-11 g m-1 s-1 Pa-1 water vapor permeability, 5.26-12.91 × 10-20 m2 s-1 Pa-1 oxygen permeability, 4.87-7.90 MPa tensile strength, and 13.37-24.62% elongation at break. Notably, the films containing mandarin peel powder with high pectin and lipid contents showed high moisture/oxygen barrier ability and mechanical properties. The films containing mandarin peel powder with high total phenol content exhibited high antioxidant- and antimicrobial-releasing abilities and good performance in delaying corn oil oxidation. Overall, the results suggested that the films have good application potential in active food packaging.

The effects of different extraction methods on essential oils from orange and tangor: From the peel to the essential oil

Citrus fruits are largely consumed due to their unique and pleasant aromas. Citrus hybrids have been developed to enhance their flavors and bioactivities. Citrus aroma depends on the composition of the volatile compounds in citrus essential oils (CEOs), which are mostly located in the peels. During the extraction of CEOs, a specific series of chemical reactions occurred depending on the extraction methods (CP, cold pressing; HD, hydrodistillation), leading to variations in the composition of volatile compounds. In this study, the orange and the tangor which is a hybrid between C. reticulata × C. sinensis were investigated to compare the changes in volatile compounds based on the extraction methods. Results showed that the CP-specific volatile compounds were sesquiterpenes, oxygenated monoterpenes, and fatty acid derivatives, while the HD-specific volatile compounds were terpinyl cation derivatives, limonene, and 4-vinylguaiacol. On the other hand, the contents of some volatile compounds ((E)-ocimene, α-terpinene, and α-terpinolene) were affected by the Citrus species rather than by the extraction methods. In particular, during HD, terpinene-4-ol and 4-vinylguiacol, known as off-flavor compounds in citrus juice, were formed more abundantly in the orange than in the tangor. In conclusion, these results provide comprehensive data on essential oils, especially those derived from oranges and tangors, for selecting the appropriate extraction method for obtaining a higher yield and quality of citrus flavor.

Essential oil composition and antioxidant activity of citron fruit (Citrus medica var. macrocarpa Risso.) peel as relation to ripening stages

Stages of maturity have decisive roles in determining the quality and quantity of essential oil (EO). In this regard, EO yield and composition and their antioxidant activity of citron fruit at four fruit maturity stages, i.e. the green mature (GM), intermediate (INT), yellow ripe (MAT) and overripe stage (OR) were studied. Obtained results showed significant effect of fruit maturity on most measured properties. The concentration of EO varied between 0.60 and 0.77% (v/w). The highest amount of limonene was 89.39% related to GM stage. The limonene decreased significantly during maturity. The highest antioxidant activity (76.08%) was measured at the OR stage, which is probably due to the presence of specific compounds in the EO and their synergistic effects. The phytochemical behaviors of this citron variety were different as relation to stages of fruit maturity. We can determine the ideal harvest period for maximum bioactive substances by recognizing these actions.

Identification of Polymethoxyflavones (PMFs) from Orange Peel and Their Inhibitory Effects on the Formation of Trimethylamine (TMA) and Trimethylamine-N-oxide (TMAO) Using cntA/B and cutC/D Enzymes and Molecular Docking

This study investigates the inhibitory effects of polymethoxyflavones (PMFs) on enzymes involved in the production of trimethylamine (TMA) and trimethylamine-N-oxide (TMAO). PMFs were isolated from Valencia orange peel and identified using column separation and NMR techniques. The findings reveal that nobiletin and 3,6,7,8,2',5'-hexamethoxyflavone significantly suppress cntA/B and cutC/D, respectively. Furthermore, 3,6,7,8,2',5'-hexamethoxyflavone decreases the level of TMAO formation by suppressing the FMO3 mRNA level. This study elucidates that specific structural features of PMFs can contribute to their interactions with enzymes. Our study represents the first demonstration of the ability of PMFs to mitigate the risk of cardiovascular disease (CVD) by inhibiting enzymes responsible for TMA production, which are generated by gut microbiomes. Furthermore, we introduce a novel model system utilizing TMA-induced HepG2 cells to assess and compare the inhibitory effects of PMFs on TMAO production. These findings could pave the way for the development of novel therapeutic approaches to manage CVD.

Nutritional and volatile profiles of pulp and flavedo from four local pummelo cultivars grown in Fujian province of China

The nutritional and volatile profiles of pulp and flavedo samples from four distinct local pummelo landraces ("Siji," "Pingshan," "Wendan," and "Guanxi") cultivated in Fujian province of China were investigated. "Guanxi" pummelo exhibited relatively high contents of vitamin C (42.01 mg/100 mL) and phenols (360.61 mg/L) and displayed a robust antioxidant capacity (41.15 mg/100 mL). Conversely, the red pulp from "Pingshan" demonstrated relatively high values of carotenoids (55.96 µg/g) and flavonoids (79.79 mg/L). Considerable differences were observed in volatile compositions between the two fruit tissues and among the four genotypes. A total of 166 and 255 volatile compounds were detected in the pulp and flavedo samples, respectively. Notably, limonene and β-myrcene were identified as the principal volatile compounds in flavedo, whereas hexanal was highly abundant in the pulp of "Siji," "Pingshan," and "Guanxi." "Wendan" displayed distinct separation from the other three pummelo cultivars in principal component analysis based on the pulp volatile compositions. This distinction was attributed to the higher number and content of volatile compounds in "Wendan" pulp, particularly the remarkable enrichment of β-myrcene. The newly characterized pummelo landraces and genotype/tissue-dependent variations in volatiles provide essential information for the genetic improvement of pummelo aroma, as well as for fruit processing and utilization.

Application of Essential Oils Extracted from Peel Wastes of Four Orange Varieties to Control Anthracnose Caused by Colletotrichum scovillei and Colletotrichum gloeosporioides on Mangoes

A huge amount of orange peel waste is annually discharged into the environment. Processing of this waste for the control of post-harvest fruit diseases can reduce environmental pollution. Essential oils (EOs) from fruit peels of Citrus reticulata × sinensis (Sanh cultivar) and Citrus sinensis (Xoan, Mat and Navel cultivar) were investigated for their ability to control anthracnose caused by Colletotrichum gloeosporioides and Colletotrichum scovillei on mangoes. EOs were extracted by hydro-distillation and analyzed by GC-MS and GC-FID. The antifungal activity of the EOs was determined by in vitro and in vivo assays. The Mat cultivar had the highest extraction yield of 3% FW, followed by Xoan (2.9%), Sanh (2.2%), and Navel (1%). The chemical composition of the EOs was similar, with limonene as the main compound (around 96%). The antifungal activity of EOs was not different, with a minimum fungicidal concentration of 16% for both fungi. The disease inhibition of EOs increased with their concentration. The highest inhibition of anthracnose caused by both fungi on mangoes was achieved at 16% EO. EOs had no adverse effect on mango quality (pH, total soluble solids, total acidity, color and brightness of mangoes), except firmness and weight loss at high concentrations (16%). Orange EOs can be used as bio-fungicides to control mango anthracnose at high concentrations.

Preliminary Study on Insecticidal Potential and Chemical Composition of Five Rutaceae Essential Oils against Thrips flavus (Thysanoptera: Thripidae)

To meet the demand for novel pest management strategies to combat the development of insecticide resistance, plant essential oils may be a promising alternative source. This study investigated the insecticidal activity of five essential oils from the Rutaceae plant family against Thrips flavus Schrank (Thysanoptera: Thripidae) under laboratory conditions. The plant essential oils were citrus oil (Citrus reticulata Blanco), Chuan-shan pepper oil (Zanthoxylum piasezkii Maxim.), zanthoxylum oil (Zanthoxylum bungeanum Maxim.), pomelo peel oil (Citrus maxima (Burm.) Merr.) and orange leaf oil (Citrus sinensis (L.) Osbeck). Among the essential oils evaluated, orange leaf oil (LC50 = 0.26 g/L), zanthoxylum oil (LC50 = 0.27 g/L), and pomelo peel oil (LC50 = 0.44 g/L) resulted in a higher gastric toxicity under laboratory conditions. The results of the pot experiment also showed that orange leaf oil (93.06 ± 3.67% at 540.00 g a.i.·hm−2, 97.22 ± 1.39% at 720 g a.i.·hm−2, 100.00% at 900.00 g a.i.·hm−2) zanthoxylum oil (98.73 ± 1.27% at 900 g a.i.·hm−2), and pomelo peel oil (100.00% at 900 g a.i.·hm−2) exhibited a higher control efficacy, being the most effective against T. flavus after 7 days of treatment. The essential oil components were then identified by gas chromatography–mass spectrometry (GC–MS). The insecticidal activity of orange leaf oil, pomelo peel oil, and zanthoxylum oil could be attributed to their main constituents, such as methyl jasmonate (50.92%), D-limonene (76.96%), and linalool (52.32%), respectively. In the olfactory test, adult T. flavus were attracted by zanthoxylum oil and Chuan-shan pepper oil. We speculated that linalool might be the key signaling compound that attracts T. flavus. These results showed that orange leaf oil, zanthoxylum oil, and pomelo peel oil exhibited insecticidal activities under controlled conditions. They can be implemented as effective and low-toxicity botanical insecticides and synergistic agents against T. flavus.

Evaluation of Cryogen-Free Thermal Modulation-Based Enantioselective Comprehensive Two-Dimensional Gas Chromatography for Stereo-Differentiation of Monoterpenes in Citrus spp. Leaf Oils

This study evaluates the applicability of enantioselective gas chromatography (eGC) and enantioselective comprehensive two-dimensional gas chromatography (eGC×GC) coupled with flame ionization detection for the stereospecific analysis of designated chiral monoterpenes within essential oils distilled from the leaves of Citrus hystrix (CH), C. limon (CL), C. pyriformis (CP), and C. microcarpa (CM). A cryogen-free solid-state modulator with a combination of enantioselective first-dimension and polar second-dimension column arrangements was used to resolve potential interferences in Citrus spp. leaf oils that can complicate the accurate determination of enantiomeric compositions. Interestingly, considerable variations were observed for the enantiomeric fractions (EFs) of the chiral terpenes. (+)-limonene was identified as the predominant enantiomer (60.3-98.9%) in all Citrus oils, (+)-linalool was the major enantiomer in CM (95.9%), (-)-terpenin-4-ol was the major isomer in CM (66.4%) and CP (61.1%), (-)-α-pinene was the dominant antipode in CL (55.5%) and CM (92.1%). CH contained (-)-citronellal (100%) as the pure enantiomer, while CL and CP have lower proportions (9.0-34.6%), and citronellal is absent in CM. The obtained enantiomeric compositions were compared and discussed with results from eGC using the same enantioselective column. To our knowledge, this work encapsulates the first report that details the EFs of these chiral monoterpenes in Citrus spp. leaf oil.

Citrus sinensis Essential Oils an Innovative Antioxidant and Antipathogenic Dual Strategy in Food Preservation against Spoliage Bacteria

The present study evaluates the chemical compositions and antioxidant and antipathogenic properties of commercial orange (Citrus sinensis (L.) Osbeck) essential oils obtained using the cold-press method (EOP) and the cold-press method followed by steam distillation (EOPD). The chemical compositions of the volatilizable fractions, determined by gas chromatography-mass spectrometry, were similar in both samples. A relatively large amount of γ-terpinene was found in the EOPD (1.75%) as compared to the EOP (0.84%). Monoterpene hydrocarbons with limonene (90.4-89.8%) followed by myrcene (3.2-3.1%) as the main compounds comprised the principal phytochemical group. The non-volatile phenolics were eight times higher in the EOP than in the EOPD. Several assays with different specificity levels were used to study the antioxidant activity. Although both essential oils presented similar reducing capacities, the radical elimination ability was higher for the EOP. Regarding the antipathogenic properties, the EOs inhibited the biomass and cell viability of Staphylococcus aureus and Pseudomonas aeruginosa biofilms. Furthermore, both EOs similarly attenuated the production of elastase, pyocyanin, and quorum-sensing autoinducers as assessed using Gram-negative bacteria. The EOP and EOPD showed important antioxidant and antipathogenic properties, so they could represent natural alternatives to extend the shelf life of food products by preventing oxidation and contamination caused by microbial spoilage.

Phytochemical Composition, Antioxidant and Antiproliferative Activities of Citrus hystrix, Citrus limon, Citrus pyriformis, and Citrus microcarpa Leaf Essential Oils against Human Cervical Cancer Cell Line

The essential oil derived from Citrus plants has long been used for medicinal purposes, due to its broad spectrum of therapeutic characteristics. To date, approximately 162 Citrus species have been identified, and many investigational studies have been conducted to explore the pharmacological potential of Citrus spp. oils. This study investigated the volatile constituents of essential oil distilled from the leaves of C. hystrix, C. limon, C. pyriformis, and C. microcarpa, using gas chromatography-quadrupole mass spectrometry. A total of 80 secondary compounds were tentatively identified, representing 84.88-97.99% of the total ion count and mainly comprising monoterpene (5.20-76.15%) and sesquiterpene (1.36-27.14%) hydrocarbons, oxygenated monoterpenes (3.91-89.52%) and sesquiterpenes (0.21-38.87%), and other minor chemical classes (0.10-0.52%). In particular, 27 compounds (1.19-39.06%) were detected across all Citrus species. Principal component analysis of the identified phytoconstituents and their relative quantities enabled differentiation of the Citrus leaf oils according to their species, with the loading variables contributing to these metabolic differences being identified. The Citrus leaf oils were tested for their antioxidant and antiproliferative activities using 2,2-diphenyl-1-picryl-hydrazylhydrate (DPPH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. The results indicated that C. limon displayed the highest DPPH radical scavenging ability (IC₅₀ value of 29.14 ± 1.97 mg/mL), while C. hystrix exhibited the lowest activity (IC₅₀ value of 279.03 ± 10.37 mg/mL). On the other hand, all the Citrus oils exhibit potent antiproliferative activities against the HeLa cervical cancer cell line, with IC₅₀ values of 11.66 μg/mL (C. limon), 20.41 μg/mL (C. microcarpa), 25.91 μg/mL (C. hystrix), and 87.17 μg/mL (C. pyriformis).

Impact of orange essential oil on enteric methane emissions of heifers fed bermudagrass hay

In this study, the effects of orange essential oil (OEO) on the rumen fermentation, nutrient utilization, and methane (CH₄) emissions of beef heifers fed a diet of bermudagrass (Cynodon dactylon) were examined. In addition, in vitro and in situ experiments were conducted. The in vitro experiment consisted of three treatments: control (CTL, no OEO), OEO1 (0.25% OEO), and OEO2 (0.5% OEO). The forage to concentrate ratio was 70:30 (dry matter [DM] basis) in all treatments. No changes in pH, proportions of volatile fatty acids, and the acetate:propionate ratio were observed (P > 0.05). The addition of 0.25% OEO resulted in a reduction in CH₄ production (mL/g) relative to the control (P < 0.05). In the in situ experiment, 5 g of total mixed ration (CTL, OEO1, and OEO2) were incubated for 6, 12, 24, 48, and 72 h. Potential and effective degradability were not affected by OEO supplementation (P > 0.05). In the in vivo study, six crossbred beef heifers (Bos indicus × Bos taurus), fitted with rumen cannulas, were assigned to three different treatments: no additive (CTL), 0.25% OEO (OEO1), and 0.5% OEO (OEO2) in a replicated 3 × 3 Latin square (21-day periods). Heifers were fed at 2.8% body weight. In vivo CH₄ production was measured in open-circuit respiration chambers. Reductions in gross energy consumption, apparent total tract digestibility, and rumen valerate concentration were observed for OEO2 compared to the control (P < 0.05). Additionally, decreases in CH₄ emissions (g/day; P < 0.05) and CH₄ (MJ gross energy intake/day; P < 0.05) were observed in response to supplementation of 0.5% OEO as compared to the CTL treatment. Thus, supplementation of 0.5% OEO reduced CH₄ emissions (g/day) by 12% without impacting the DM intake of heifers fed bermudagrass hay as a basal ration.

Impact of Storage Condition on Chemical Composition and Antifungal Activity of Pomelo Extract against Colletotrichum gloeosporioides and Anthracnose in Post-harvest Mango

Anthracnose caused by Colletotrichum leads to a tremendous post-harvest mango loss. While chemical fungicides are applied to control anthracnose, natural alternatives are preferred due to food safety and environmental concerns. Pomelo extract (PE) exhibits a broad spectrum of antimicrobial activities; however, its effect against anthracnose is unknown. Here we investigated the chemical profile of PE using GC-MS and the anti-anthracnose activity of PE using in vitro and in vivo assays. We also evaluated the impact of storage temperature (0°, 5°, 10°, 20°, -20°, and -80 °C) and light conditions on the composition and antifungal activity of PE. We found that PE inhibited C. gloeosporioides in vitro with an IC₅₀ of 3.2 mL L^-1. Applying chitosan-based coating incorporated with 20 mL L^-1 PE significantly suppressed anthracnose in post-harvest 'Keitt' mango. A storage temperature below 5 °C substantially preserved major compounds and the antifungal activity of PE after 6 m of storage. Finally, we showed that applying d-limonene, the key constituent of PE, inhibited C. gloeosporioides in vitro (IC₅₀: 10.9 mM) and suppressed anthracnose in vivo. In conclusion, we demonstrated that the application of PE and d-limonene are sustainable methods for anthracnose control in post-harvest crops and established the preservation protocol for PE.

Citrus maxima (Brum.) Merr. (Rutaceae): Bioactive Chemical Constituents and Pharmacological Activities

Citrus maxima (Burm). Merr. (family Rutaceae), commonly known as Pomelo, is an ethnomedicinally, pharmacologically, and phytochemically valued species. Various ethnomedicinal reports have revealed the use of C. maxima for cough, fever, asthma, diarrhea, ulcer, and diabetes and as a sedative. Numerous phytochemicals have been reported from C. maxima such as polyphenols, terpenoids, sterols, carotenoids, vitamins, and amino acids. The plant possesses significant bioactivities like antioxidant, antimicrobial, anti-inflammatory, analgesic, anticancer, antidiabetic, anti-Alzheimer's disease, insecticidal, anxiolytic, hepatoprotective, antimalarial, and antiobesity. Extensive research is necessary to explore the detailed mechanism of action of extracts and compounds to design effective medicines, herbal products, and functional foods.

Detection of Volatiles by HS-SPME-GC/MS and Biological Effect Evaluation of Buddha's Hand Fruit

The present work aimed to chemically characterize and evaluate the antiradical power and biological effects of Citrus medica var. sarcodactylus essential oil (EO) and hydrolate (Hy) from exocarp as well as methanol extracts, from both exocarp and mesocarp (EEX and MEX). The whole fresh fruit was also investigated by SPME-GC/MS to describe its volatile composition. EO and Hy were analyzed by GC/MS and HS-GC/MS techniques, respectively. Limonene and γ-terpinene were found to be the most abundant compounds both in the fresh parts of the fruit and in the EO, while α-terpineol and terpinen-4-ol were in the Hy. The extracts were also rich in furan and coumarin derivatives. A good antiradical activity of all samples except Hy was detected both against ABTS·+ than DPPH·, removed up to about 50%. The antibacterial activity against Bacillus cereus and Escherichia coli was evaluated by microwell dilution method to determine MIC and MBC values. EEX and MEX showed efficacy at very high concentrations against both tested bacteria. The MIC value of EO against B. cereus was 0.5% v/v, while Hy was not able to inhibit the bacterial growth at the tested concentrations. Cytotoxicity investigated on the HL60 leukemia cell line by MTT assay provided an EC₅₀ of 1.24% v/v for EO. Interesting activity of Hy was also observed.

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 β-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, β-myrcene, and β-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.

Volatile Compounds and Antioxidant and Antimicrobial Activities of Selected Citrus Essential Oils Originated from Nepal

Citrus species of plants are among the most commercially cultivated crops, mainly for their fruit. Besides, the generally consumed flesh inside the fruit, the peel is quite important too. Essential oils extracted from the peel have a history of being used by humankind for centuries. These essential oils are rich in antioxidants and antimicrobial agents. Comparative investigation of volatile constituents, and antioxidant and antimicrobial activities were undertaken. The essential oils were evaluated through gas chromatography-mass spectrometry (GC-MS), and enantiomeric composition by chiral GC-MS. Similarly, the antioxidant properties were evaluated by 2,2-diphenyl-1-picrylhydrazyl scavenging assay, and antimicrobial activities were assayed using the disk diffusion method. The highest extraction yield of 1.83% was observed in Citrus sinensis Osbeck. GC-MS analysis showed limonene (63.76-89.15%), γ-terpinene (0.24-6.43%), β-pinene (0.15-6.09%), linalool (0.35-3.5%), sabinene (0.77-2.17%), myrcene (0.74-1.75%), α-terpineol (0.28-1.15%), and α-pinene (0.2-0.58%) as the major constituents of the essential oil of the Citrus species studied. For the first time, through our study, chiral terpenoids have been observed from Citrus grandis Osbeck essential oil. The order of antioxidant activity is as follows: Citrus grandis Osbeck red flesh > Citrus reticulata Blanco > Citrus sinensis Osbeck > Citrus grandis Osbeck white flesh. Except for Citrus grandis Osbeck white flesh (52.34 µL/mL), all samples demonstrated stronger antioxidant activities than those of the positive control, quercetin (5.60 µL/mL). Therefore, these essential oils can be used as a safe natural antioxidant to prevent product oxidation. Likewise, citrus peel essential oil showed antimicrobial activity against tested bacterial strains, albeit marginal.

Citrus aurantium L. Active Constituents, Biological Effects and Extraction Methods. An Updated Review

Citrus genus is a prominent staple crop globally. Long-term breeding and much hybridization engendered a myriad of species, each characterized by a specific metabolism generating different secondary metabolites. Citrus aurantium L., commonly recognized as sour or bitter orange, can exceptionally be distinguished from other Citrus species by unique characteristics. It is a fruit with distinctive flavor, rich in nutrients and phytochemicals which possess different health benefits. This paper presents an overview of the most recent studies done on the matter. It intends to provide an in-depth understanding of the biological activities and medicinal uses of active constituents existing in C. aurantium. Every plant part is first discussed separately with regards to its content in active constituents. All extraction methods, their concepts and yields, used to recover these valuable molecules from their original plant matrix are thoroughly reported.

Effects of Molecular Distillation on the Chemical Components, Cleaning, and Antibacterial Abilities of Four Different Citrus Oils

Essential oils (EOs) from citrus fruits are excellent aromatic resources that are used in food, cosmetics, perfume, and cleaning products. EOs extracted from four citrus varieties, sweet orange, grapefruit, mandarin, and lemon, were separated into two fractions by molecular distillation. The composition, physicochemical properties, cleaning ability, and antimicrobial activity of each EO were then systematically evaluated. The relationships between each of the aforementioned characteristics are also discussed. In keeping with the principle of “like dissolves like,” most citrus EOs show better cleaning ability than acetone and all tend to dissolve the fat-soluble pigment. The key components of citrus EOs are 1-Decanol, α-terpineol, geraniol, and linalool for the inhibition of Staphylococcus aureus, Escherichia coli, Candida albicans, and Vibrio parahaemolyticus, respectively. The findings of this study will be of significant importance for the effective utilization of citrus peel resources and in the development of future applications for citrus EOs.

Chemical Compounds Studied in This Article: (+)-α-Pinene (PubChem CID: 6654); β-Phellandrene (PubChem CID: 11142); 3-Carene (PubChem CID: 26049); β-Myrcene (PubChem CID: 31253); D-Limonene (PubChem CID: 440917); γ-Terpinene (PubChem CID: 7461); Octanal (PubChem CID: 454); Decanal (PubChem CID: 8175); Linalool (PubChem CID: 6549); 1-Octanol (PubChem CID: 957); β-Citral (PubChem CID: 643779); α-Terpineol (PubChem CID: 17100); Hedycaryol (PubChem CID: 5365392); α-Citral (PubChem CID: 638011); 1-Decanol (PubChem CID: 8174); Geraniol (PubChem CID: 637566).

A review of chemical constituents and health-promoting effects of citrus peels

Citrus is one of the main fruits processed worldwide, producing a lot of industrial by-products. As the main part of citrus "residue", citrus peels have a wide application prospect. They could not only be directly used to produce various food products, but also be used as promising biofuels to produce ethanol and methane. Additionally, functional components (flavonoids, limonoids, alkaloids, essential oils and pectin) extracted from citrus peels have been related to the improvement of human health against active oxygen, inflammatory, cancer and metabolic disorders. Therefore, it is clear that the citrus peels have great potential to be developed into useful functional foods, medicines and biofuels. This review systematically summarizes the recent advances in current uses, processing, bioactive components and biological properties of citrus peels. A better understanding of citrus peels may provide reference for making full use of it.

Essential Oils from Citrus reticulata cv. Shatangju Peel: Optimization of Hydrodistillation Extraction by Response Surface Methodology and Evaluation of Their Specific Adhesive Effect to Polystyrene

Essential oil (Eo) from the Citrus reticulata peel has been widely used, and its adhesive effect on polystyrene (PS) was found accidentally. To analyze the essential oils of C. reticulata cv. Shatangju (CrspEos), the extraction of these oils by steam distillation was optimized using the response surface method. The chemical composition of CrspEos was analyzed by gas chromatography-mass spectrometry. Then, the adhesive effect of these essential oils on PS was evaluated. The adhesion area, the influence of adhesion on the thickness of the essential oil on the materials, the effect of adhesion on the transmittance of PS, the strength of adhesion point, and specificity of adhesion were determined. The optimum extraction conditions resulting in the extraction yield of 47.37 μL g^-1 were a ratio of liquid-to-solid of 8.94:1, a soaking time of 199.45 min, and an extraction time of 138.71 min. The major component in the essential oils was d-limonene (56.66%), followed by myrcene (6.62%). CrspEos presented a specific adherence effect on PS without influencing the thickness and transmittance of PS but with stronger tenacity than the parent material. CrspEos can be used as an environmentally friendly specific adhesive for PS.

Relationship among Agroclimatic Variables, Soil and Leaves Nutrient Status with the Yield and Main Composition of Kaffir Lime (Citrus hystrix DC) Leaves Essential Oil

Previous studies revealed the impact growing location has on the quantity and quality of essential oils derived from numerous Citrus spp., except on the kaffir lime. This study aims to analyze the relationship shared by agroclimatic variables and soil-plant nutrient status to kaffir lime leaves essential oil yield and main composition. The experiment was conducted between February and April 2019 in four growing locations, namely Bogor (6°36'36″ S, 106°46'47″ E), West Bandung (6°48'12″ S, 107°39'16″ E), Pasuruan (7°45'5″ S, 112°40'6″ E) and Tulungagung (8°6'27″ S, 112°0'35″ E). The highest essential oil yield was obtained from Bogor (1.5%), while the lowest one was from Tulungagung (0.78%). The yield was positively and significantly correlated with the rainfall, soil organic carbon, soil pH, and macronutrient levels, i.e., nitrogen, phosphorus, and magnesium. Citronellal, the major component in metabolites' profile of kaffir lime leaves essential oils, was significantly affected by the growing location. The absolute content of citronellal was positively and significantly correlated with the actual soil pH and leaf Ca content; furthermore, it negatively correlated with the leaf content of Fe, Mn, Zn, Cu. Pearson correlation analysis also showed (i) a negative significant correlation between the relative percentage of citronellol and annual rainfall intensity; (ii) a negative significant correlation between altitude and relative percentage of caryophyllene, and (iii) a positive significant correlation between the relative percentage of linalool and leaf K content.

Recent developments in extraction and encapsulation techniques of orange essential oil

Orange production is constantly growing. The main orange by-product, the orange peel, is a usable source of essential oils with a lot of health benefits. Because of that, it is important to find the best recovery and encapsulation techniques in order to get the best bioavailability for human and to ensure the highest quality for food applications. Thus, the aim of this work is to summarize the complete process needed to obtain orange essential oil, from the pre-treatments to the encapsulation steps, carried out in the last years. This review is focused on the comparison of new and more innovative techniques in front of the most conventional ones used for extracting and encapsulating the orange essential oil.

Tangerine, banana and pomegranate peels valorisation for sustainable environment: A review

Over the last decade the world has been generating a high quantity of tangerine peel waste (TPW), pomegranate peel waste (PPW) and banana peel waste (BPW). These peels have several economic benefits but there is mismanagement or inappropriate valorisation that could present risks to environment and public health. In the current review, we discussed the use of TPW, PPW and BPW directly for animal feed, soil fertilization, specific compost production and bio-adsorbent. We also discussed the valorisation of these peels for manufacturing the value-added products including enzymes, essential oil and other products that can be used in human food, in medical and cosmetic industry. Additionally, recent studies concerning the valorisation of these peels by biorefinery for bioethanol, biogas and biohydrogen production have been discussed. In the same context some other recent studies about valorisation of microorganisms isolated from these peels for medical, agronomic and industrial interests have been also discussed.

Insights into the chemical composition and bioactivities of citrus peel essential oils

Citrus peel (CP), a by-product of the citrus fruit processing, comprises nearly forty to fifty percent of the fruit portion. Interestingly, the essential oil (EO) is primarily concentrated in the peel portion of the citrus fruit. Extraction of CP essential oil (CPEO) is an effective way of utilizing the citrus fruit processing waste. The CPEO can be more efficiently recovered from CP waste by improving the efficiency of conventional extraction processes. The main components of CPEO include monoterpenes, sesquiterpenes and their oxygenated derivatives. Specifically, limonene is the major oil component identified in the peel of different citrus species. The health promoting biological activities of CPEO are functioning as antioxidant, anti-inflammatory, analgesic, antimicrobial and anticancer agents, thereby can be used as a source of functional components and preservatives for the development of nutritionally safe newer food products. This paper provides an in-depth knowledge about the chemical constituents and bioactivities of EOs extracted from peels of different citrus species.

Pomelo peel oil alleviates cerebral NLRP3 inflammasome activation in a cardiopulmonary resuscitation rat model

The NLR family pyrin domain-containing 3 (NLRP3) inflammasome, which is composed of NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC) and pro-caspase-1 protein complexes, is activated by the reactive oxygen species (ROS) that are associated with ischemia-reperfusion (I/R) and are involved in brain damage. Pomelo peel oil (PPO) exhibits antioxidant activity. However, it is unclear whether PPO is able to attenuate NLRP3 inflammasome-induced inflammation and pyroptosis. Healthy male Sprague-Dawley rats were subjected to 7 min of cardiac arrest via trans-esophageal electrical stimulation, followed by cardiopulmonary resuscitation (CPR). The rats were then treated with PPO prior to reperfusion for 24 h. Hematoxylin and eosin staining was used to evaluate brain tissue and cell damage. In the brain tissues, reactive oxygen species (ROS) were assayed, immunofluorescence was used to analyze the expression of NLRP3 and western blotting was performed to determine the expression levels of neuroenolase (NSE), NF-κB, interleukin-1β (IL-1β), gasdermin D (GSDMD) and the NLRP3 inflammasome. Treatment of the rats with PPO significantly decreased the pathological damage of the brain tissue and reduced the expression of NSE, production of ROS and secretion of NF-κB, NLRP3, IL-1β and GSDMD. In conclusion, these results demonstrate the ability of PPO to protect the brain against I/R injury in rats after CPR by a mechanism involving inhibition of the inflammation and pyroptosis mediated by NLRP3 inflammasome activation.

Monoterpenes as a perspective for the treatment of seizures: A Systematic Review

BACKGROUND

Epilepsy affects more than 65 million people worldwide. Treatment for epileptic seizures is ineffective and has many adverse effects. For this reason, the search for new therapeutic options capable of filling these limitations is necessary.

HYPOTHESIS/PURPOSE

In this sense, natural products, such as monoterpenes, have been indicated as a new option to control neurological disorders such as epilepsy.

STUDY DESIGN

Therefore, the objective of this study was to review the monoterpenes that have anticonvulsive activity in animal models.

METHODS

The searches were performed in the PubMed, Web of Science and Scopus databases in September, 2020 and compiled studies using monoterpenes as an alternative to seizure. Two independent reviewers performed the study selection, data extraction and methodological quality assessment using the Syrcle tool.

RESULTS

51 articles that described the anticonvulsant activity of 35 monoterpenes were selected with action on the main pharmacological target, including GABAA receptors, glutamate, calcium channels, sodium and potassium. In addition, these compounds are capable of reducing neuronal inflammation and oxidative stress caused by seizure.

CONCLUSION

These compounds stand out as a promising alternative for acting through different pharmacological mechanisms, which may not only reduce seizure, but also promote neuroprotective effect by reducing toxicity in brain regions. However, further studies are needed to determine the mechanism of action and safety assessment of these compounds.

Odoriferous Therapy: A Review Identifying Essential Oils against Pathogens of the Respiratory Tract

This review explores the body of scientific information available on the antimicrobial properties of essential oils against pathogens responsible for respiratory infections and critically compares this to what is recommended in the Layman's aroma-therapeutic literature. Essential oils are predominantly indicated for the treatment of respiratory infections caused by bacteria or viruses (total 79.0 %), the efficacy of which has not been confirmed through clinical trials. When used in combination, they are often blended for presumed holistic synergistic effects. Of the essential oils recommended, all show some degree of antioxidant activity, 50.0 % demonstrate anti-inflammatory effects and 83.3 % of the essential oils showed antihistaminic activity. Of the essential oils reviewed, 43.8 % are considered non-toxic while the remaining essential oils are considered slightly to moderately toxic (43.7 %) or the toxicity is unknown (12.5 %). Recommendations are made for further research into essential oil combinations.

Citrus Essential Oils (CEOs) and Their Applications in Food: An Overview

Citrus is a genus belonging to the Rutaceae family and includes important crops like orange, lemons, pummelos, grapefruits, limes, etc. Citrus essential oils (CEOs) consist of some major biologically active compounds like α-/β-pinene, sabinene, β-myrcene, d-limonene, linalool, α-humulene, and α-terpineol belonging to the monoterpenes, monoterpene aldehyde/alcohol, and sesquiterpenes group, respectively. These compounds possess several health beneficial properties like antioxidant, anti-inflammatory, anticancer, etc., in addition to antimicrobial properties, which have immense potential for food applications. Therefore, this review focused on the extraction, purification, and detection methods of CEOs along with their applications for food safety, packaging, and preservation. Further, the concerns of optimum dose and safe limits, their interaction effects with various food matrices and packaging materials, and possible allergic reactions associated with the use of CEOs in food applications were briefly discussed, which needs to be addressed in future research along with efficient, affordable, and "green" extraction methods to ensure CEOs as an ecofriendly, cost-effective, and natural alternative to synthetic chemical preservatives.

Effects of Citrus sinensis Essential Oil and Intrinsic and Extrinsic Factors on the Growth and ToxinProducing Ability of Clostridium botulinum Type A

Background: Considering the high fatality of botulism, the control of Clostridium botulinum and its neurotoxins has clinical importance. In this regard, using chemical preservatives, natural essential oils (Eos), and changes in the growth predisposing factors of bacteria are suitable methods to control the growth and toxin producing of C. botulinum in foods. Objective: The current survey was done to assess the effects of Citrus sinensis EO and intrinsic and extrinsic factors on the growth and toxin producing of C. botulinum type A. Materials and Methods: In this experiment with a factorial design, C. sinensis EO (0.0%, 0.015%, 0.03%, and 0.045%), nisin (0, 500, and 1500 IU/mL), nitrite (0, 20, and 60 ppm), pH (5.5 and 6.5), storage temperature (25 and 35° C), and sodium chloride (NaCl, 0.5% and 3%) were used to assess bacterial growth in the brain heart infusion medium. Finally, the mouse bioassay method was also used to assess toxicity. Results: Clostridium sinensis EO with a concentration of 0.045%, as well as the reduction of pH and temperature could significantly delay the growth of bacteria (P≤0.05) in contrast to the use of NaCl and nisin alone. However, all concentrations of sodium chloride (NaCl), nisin, and C. sinensis EO (< 0.045%) in interaction with each other, especially in combination with nitrite, showed good synergistic effects. Conclusion: These results suggested that using certain concentrations of C. sinensis EO and nisin, along with other suboptimal factors caused a significant decrease in the nitrite contents of foods with a significant reduction in the growth and toxin-producing ability of C. botulinum.

Phenolic composition, antioxidant potential and health benefits of citrus peel

Citrus peel (CP) forms around 40-50% of the total fruit mass but is generally thought to be a waste. However, it is a substantial source of naturally occurring health enhancing compounds, particularly phenolic compounds and carotenoids. Phenolic compounds in CP mainly comprise phenolic acids (primarily caffeic, p-coumaric, ferulic and sinapic acid), flavanones (generally naringin and hesperidin) and polymethoxylated flavones (notably nobiletin and tangeretin). It has also been noted that CP's contain more amounts of these compounds than corresponding edible parts of the fruits. Phenolic compounds present in CP act as antioxidants (by either donation of protons or electrons) and protect cells against free radical damage as well as help in reducing the risk of many chronic diseases. Owing to the more abundance of polyphenols in CP's, their antioxidant activity is also higher than other edible fruit parts. Therefore, peels from citrus fruits can be used as sources of functional compounds and preservatives for the development of newer food products, that are not only safe but also have health-promoting activities. The present review provides in-depth knowledge about the phenolic composition, antioxidant potential and health benefits of CP.

Variations of peel essential oils during fruit ripening in four lemon (Citrus limon (L.) Burm. F.) cultivars

BACKGROUND

Lemon processing procedures yield a significant amount of waste as peels, which are 57% of processed lemons and represent a possible source of bioactive compounds (essential oils, EOs). EOs were extracted from lemon fruits belonging to four cultivars harvested at four different sampling times (25 October, 23 November, 20 December, 1 February), characterized, and quantified through gas chromatography-mass spectrometry.

RESULTS

The chemical composition of EOs highlighted that 26 compounds of the four lemon cultivars at the different ripening stages were clearly identified. The compounds analysed belonged to four chemical classes: monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpenes, and fatty alcohol esters. Among the monoterpene hydrocarbons, d-limonene, β-pinene, and γ-terpinene were the most abundant; and among the oxygenated monoterpenes, α-terpineol, nerol, and geraniol were the most abundant. Quantitative gas chromatography-mass spectrometry analysis of the most abundant monoterpene hydrocarbons (α-pinene, β-pinene, myrcene, d-limonene, and γ-terpinene) highlighted that the amount of EOs decreased during ripening stages. 'Ovale di Sorrento' and 'Sfusato Amalfitano' showed the highest level of EOs in December, whereas in 'Femminello Cerza' and 'Femminello Adamo' this occurred in November. EOs, as well as the phenolic compounds, were positively correlated with the antioxidant activity (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid).

CONCLUSIONS

EOs reached the highest level in the four lemon cultivars at different ripening stages. Campanian cultivars ('Ovale di Sorrento' and 'Sfusato Amalfitano') showed the greatest EO content in November, whereas in Sicilian cultivars ('Femminello Cerza' and 'Femminello Adamo') this occurred in December. Besides phenolic compounds, measured in lemon peel extracts, EOs can contribute to antioxidant activity, as demonstrated by the positive correlation. © 2019 Society of Chemical Industry.

Peel oils from three Citrus species: volatile constituents, antioxidant activities and related contributions of individual components

In the present study, peel oils were extracted through hydrodistillation and cold pressing from three Citrus species (Valencia orange, Ponkan and Eureka lemon) to investigate their volatile constituents and antioxidant activities. A total of 47 volatile components were identified by GC-MS, and then grouped by principal component analysis. The extraction methods were found to have an obvious effect on the proportion of terpenes and oxygenated compounds in the six Citrus oils, especially for Eureka lemon oils. The major fractions in the Citrus oils were found to be monoterpenes (78.65-96.57%), with limonene occupying a dominant percentage (51.22-86.65%). Furthermore, γ-terpinene and terpinolene displayed strong DPPH (1,1-diphenyl-2-picrylhydrazyl) scavenging abilities and efficient inhibition of lipid peroxidation, while oxygenated compounds of α-terpineol and terpinen-4-ol showed poor DPPH radical-scavenging abilities. Therefore, hydrodistillated Eureka lemon oil with high levels of α-terpineol (9.11%) and terpinen-4-ol (4.69%) presented low radical scavenging capability. Citral displayed a high pro-oxidant ability against thiobarbituric acid reactive species formation, which might lead to the decreased ability of the Eureka lemon oils in inhibition of lipid peroxidation, since citral was significantly high in Eureka lemon oils. This study facilitated the understanding of volatile constituents and antioxidant activities in different Citrus peel oils.

Effects of Controlled Atmosphere on the Storage Quality and Aroma Compounds of Lemon Fruits Using the Designed Automatic Control Apparatus

‘Eureka' lemon fruits were stored under four controlled atmosphere- (CA-) combinations at 8°C for 20 days to investigate the effects on weight loss (WL), total soluble solids (TSS), titratable acidity (TA), vitamin C (VC), total phenolic content (TPC), sodium carbonate-soluble pectin (SSP), malondialdehyde (MDA), and volatile compounds. Results showed that the contents of TSS, TA, VC, and SSP in the stored fruits reduced during the storage period, while the WL and MDA increased. Fruit stored under CA2-combination (6 % O₂+8 % CO₂) showed the lower contents of WL and MDA and the higher content of TSS, TA, TPC, and VC than that of other treated fruits. The main volatile compounds present in the lemons were terpenoids, aldehydes, alcohols, and esters. In addition, both the terpenoid and aldehyde content are substantially higher in lemons exposed to CA2 conditions. In contrast, the alcohols and esters displayed elevated levels in the regular air (RA) stored fruit. In conclusion, CA with the suitable conditions proves to be better than RA as a storage regimen to keep the quality of lemons. These results indicated that the application of 6% O₂+8% CO₂ CA conditions could maintain the quality of ‘Eureka' lemon fruit during the storage time of 20 days and should be the optimal storage environment for postharvest Eureka lemons.

Antifungal Effect of Essential Oils from Five Kinds of Rutaceae Plants - Avoiding Pesticide Residue and Resistance

Panax notoginseng root is a traditional Chinese herb, of which the yield and quality have been seriously affected by microorganisms, and is commonly used to treat various kinds of bleeding. In this experiment, the effects of the antifungal properties of essential oils (EOs) from five kinds of Rutaceae plants on the growth of three kinds of pathogens were studied to develop natural, environmentally friendly antifungal agents. Citrus medica EO was found to have stronger inhibitory effects on the growth of pathogenic fungi in vitro than other EOs with the Oxford cup method, of which the chemical composition was further investigated by GC/MS. The major components were d-limonene (22.79 %) and γ-terpinene (9.71 %). The antifungal activities were evaluated by MIC and FIC assays. In these assays, C. medica EO, d-limonene and γ-terpinene were effective against three pathogens of P. notoginseng with MIC values ranging from 0.12 to 12.05 mg/mL. The association between hymexazol and C. medica EO showed a high synergistic effect with lower FIC index values (FICi=0.31-2.00). Furthermore, C. medica EO was further assessed in P. notoginseng planted in a continuous cropping soil (CCS) and was found to reduce the disease incidence and disease severity compared with P. notoginseng planted in CCS only without EO addition. This finding suggested that C. medica EO has potential as a natural environmentally antifungal agent against pathogens of P. notoginseng, ensuring its safety.