Microwave-assisted Hydrodistillation Research Articles

Extraction, Characterization, and Encapsulation of Cinnamon Hydrosol Obtained via Microwave-Assisted Hydrodistillation: Analysis of Antioxidant and Antimicrobial Activities

Microwave-assisted hydrodistillation (MAHD) method was employed to extract cinnamon oil and hydrosol (a byproduct). The total polyphenol content (TPC) of the cinnamon hydrosol (CH) was determined using the Folin-Ciocalteu method, and its antioxidant power was assessed through the DPPH radical reduction method. Gas chromatography was utilized to quantify the main bioactive compound (cinnamaldehyde). The disc agar diffusion method was applied to evaluate the inhibition of pathogenic microorganisms. To protect the bioactive compound, an encapsulation method involving cross-linking with calcium alginate was utilized. The capsules were examined using environmental scanning electron microscopy (ESEM). The TPC content was found to be 15.63 ± 0.21 mg gallic acid/g dry matter, and the DPPH radical inhibition rate was 84.26 ± 1.35%. CH exhibited a significant inhibitory effect against Escherichia coli, and a moderate inhibition effect against Shigella flexneri, Salmonella spp., Salmonella typhimurium, and Escherichia coli EPEC. Finally, successful encapsulation of CH was achieved using sodium alginate, resulting in bead sizes ranging between 1.75 and 2.75 mm.

Investigation of Antioxidant and Enzyme Inhibitory Activities of Echinophora chrysantha: Microwave-assisted Hydrodistillation and SPME Analysis of its Essential Oils.

Echinophora genus is represented by six species in Türkiye, including three endemics. The objective of this study was to ascertain the antioxidant, tyrosinase, and collagenase inhibitory activities and to analyse the volatile oil and extracts derived from E. chrysantha using GC/MS/SPME. The antioxidant and enzyme inhibition activities were evaluated using spectrophotometric methods. The findings indicated that the methanol extract of E. chrysantha exhibited the highest antioxidant activity. Furthermore, both the methanol extract and volatile oil of the plant demonstrated potent inhibitory effects on tyrosinase and collagenase. A total of 84 volatile compounds were identified from the hydrodistilled oil obtained using a microwave oven, and 23 compounds were detected by the solid-phase microextraction (SPME) method. The most frequently occurring volatile components were α-Phellandrene, o-Cymene, p-Cymene, E-β-Farnesene, Carotol, trans-Caryophyllene, and β-Phellandrene. The results of this study indicate that E. chrysantha has the potential to be developed for the treatment of hyperpigmentation issues and anti-aging applications. Furthermore, it may also have applications in pharmacology, cosmetics and the food industry.

Characterization and antimicrobial activity of essential oils extracted from lemongrass (Cymbopogon flexuosus) using microwave-assisted hydro distillation.

Lemongrass (Cymbopogon flexuosus) essential oil (LGEO) contains α-citral, β-citral and other phytochemicals extracted using various methods. This research extracted essential oils using steam distillation (SD) and microwave-assisted hydro distillation (MAHD) to maximize quantity and purity. LGEO was tested for antibacterial properties. LGEO was extracted using SDand compared to MAHD output based on oil production andchemical composition. We performed GCMS to characterize LGEO. Fourier transform infrared spectroscopy (FTIR) used for quantum chemical analysis. Spectroscopic analysis showed that SD extracted secondary metabolites (ethyl-linalool, isogeranial, β-citral, α-citral, geranyl acetate, and caryophyllene) yielded 9.7 %, 11.5 %, 35.4 %, 13.4 %, 6.4 %, and 6.4 %, respectively, while MAHD yielded 10.2 %, 13.4 %, 43.2 %, 17.3 %, 6.9 %, and 7.3 %. MAHD extracted α and β citral content was better than SD extraction technique. FTIR spectroscopy and quantum chemistry analysis showed extracted oil chemical composition, electronic structure of α and β citral isomers. In the disc-diffusion experiment, both extracts were effective against Gram-positive and Gram-negative bacteria and harmful fungi. LGEO from SDand MAHD extraction (30 mg/mL) demonstrated disc diffusion assay antibacterial efficacy against microorganisms. The two extracts effectively inhibited microorganisms with MIC values of 3.75 and 7.5 μg/mL. It can be concluded that, LGEO have greater antimicrobial activity in MAHD extraction.

Evaluation of lavender essential oils and by-products using microwave hydrodistillation and conventional hydrodistillation

This study investigated the impact of two extraction methods, traditional hydrodistillation (TDH) and microwave-assisted hydrodistillation (MAH), on the essential oil yield and chemical profile of Lavandula angustifolia L., as well as the bioactive potential of the resulting wastewater. Essential oil composition was analyzed via GC–MS, revealing similar qualitative and quantitative profiles for both methods, with α-terpinolene and (–)borneol as major constituents. Wastewater analysis via LC–MS/MS and spectrophotometric assays demonstrated the presence of significant total phenolic content (3.29–1.78 mg GAE/g) and 32 individual phenolics (463.1 µg/kg for TDH; 479.33 µg/kg for MAH). These findings suggest that both essential oil and wastewater obtained by either method possess considerable bioactive potential, with the MAH method potentially offering advantages over TDH for essential oil extraction. Further exploration of wastewater applications in various industrial sectors is warranted.

Influence of the Extraction Method on the Biological Potential of Solidago virgaurea L. Essential Oil and Hydrolates.

Solidago virgaurea L., or European goldenrod, has a long tradition in folk medicine due to the wide range of its biological activity. This paper aimed to investigate the antimicrobial and antioxidative potential of S. virgaurea essential oil and hydrolates obtained by traditional and novel extraction techniques. For that purpose, hydrodistillation, microwave-assisted hydrodistillation and solvent-free extraction were performed. Analysis of the composition of essential oils indicated the presence of 59 different compounds with cyclocolorenone, germacrene D and spathulenol being the dominant in all essential oil samples. Antimicrobial activity was detected in all the analyzed samples, with higher effect on Gram-positive microorganisms compared to Gram-negative. Regarding the type of performed extraction process, the introduction of microwaves induced higher antimicrobial and antioxidative potential in both essential oils and hydrolates. Hydrolates obtained in microwave-assisted processes had pronounced antioxidative activity, which creates a good basis for further investigation of this side product's potential use in the food, cosmetic and pharmaceutical industries.

Artemisia monosperma essential oil nanoformulations alleviate imiquimod-induced psoriasis-like dermatitis in mice

Psoriasis is an inflammatory immune-mediated skin disease that affects nearly 2–3 % of the global population. The current study aimed to develop safe and efficient anti-psoriatic nanoformulations from Artemisia monosperma essential oil (EO). EO was extracted using hydrodistillation (HD), microwave-assisted hydrodistillation (MAHD), and head-space solid-phase microextraction (HS–SPME), as well as GC/ MS was used for its analysis. EO nanoemulsion (NE) was prepared using the phase inversion method, while the biodegradable polymeric film (BF) was prepared using the solvent casting technique. A.monosperma EO contains a high percentage of non-oxygenated compounds, being 90.45 (HD), 82.62 (MADH), and 95.17 (HS–SPME). Acenaphthene represents the major aromatic hydrocarbon in HD (39.14 %) and MADH (48.60 %), while sabinene as monoterpene hydrocarbon (44.2 %) is the primary compound in the case of HS–SPME. The anti-psoriatic Effect of NE and BF on the successful delivery of A.monosperma EO was studied using the imiquimod (IMQ)-induced psoriatic model in mice. Five groups (n = 6 mice) were classified into control group, IMQ group, IMQ+standard group, IMQ+NE group, and IMQ+BF group. NE and BF significantly alleviated the psoriatic skin lesions and decreased the psoriasis area severity index, Baker’s score, and spleen index. Also, they reduced the expression of Ki67 and attenuated the levels of tumor necrosis factor-alpha, interleukin 6, and interleukin 17. Additionally, NE and NF were able to downregulate the NF-κB and GSK-3β signaling pathways. Despite the healing properties of BF, NE showed a more prominent effect on treating the psoriatic model, which could be referred to as its high skin penetration ability and absorption. These results potentially contribute to documenting experimental and theoretical evidence for the clinical uses of A.monosperma EO nanoformulations for treating psoriasis.

Metabolic profiling and enzyme inhibitory activity of the essential oil of citrus aurantium fruit peel

BackgroundBitter orange (Citrus aurantium) is a fruiting shrub native to tropical and subtropical countries around the world and cultivated in many regions due to its nutraceutical value. The current study investigated the metabolic profiling and enzyme inhibitory activities of volatile constituents derived from the C. aurantium peel cultivated in Egypt by three different extraction methods.MethodsThe volatile chemical constituents of the peel of C. aurantium were isolated using three methods; steam distillation (SD), hydrodistillation (HD), and microwave-assisted hydrodistillation (MAHD), and then were investigated by GC-MS. The antioxidant potential was evaluated by different assays such as DPPH, ABTS, FRAP, CUPRAC, and phosphomolybdenum and metal chelating potential. Moreover, the effect of enzyme inhibition of the three essential oils was tested using BChE, AChE, tyrosinase, glucosidase, as well as amylase assays.ResultsA total of six compounds were detected by GC/MS analysis. The major constituent obtained by all three extraction methods was limonene (98.86% by SD, 98.68% by HD, and 99.23% by MAHD). Differences in the composition of the compounds of the three oils were observed. The hydrodistillation technique has yielded the highest number of compounds, notably two oxygenated monoterpenes: linalool (0.12%) and α-terpineol acetate (0.1%).ConclusionIn our study differences in the extraction methods of C. aurantium peel oils resulted in differences in the oils’ chemical composition. Citrus essential oils and their components showed potential antioxidant, anticholinesterase, antimelanogenesis, and antidiabetic activities. The presence of linalool and α-terpineol acetate may explain the superior activity observed for the oil isolated by HD in both radical scavenging and AChE inhibition assays, as well as in the enzyme inhibition assays.

Study on the Upgrading Citronella (Cymbopogon nardus L.) Oil Isolation Using Microwave Assisted Hydro-distillation Method

Isolation of essential oil using microwave-assisted hydro-distillation (MAHD) method could enhance the yield compared to steam-distillation or conventional hydro-distillation methods. This study explored the isolation of essential oil from Citronella (Cymbopogon nardus L.) using the MAHD method with several parameters, such as solid-to-liquid ratio, power of the microwave, and extraction time. The essential oils produced were evaluated based on yield, density, refractive index, and composition. The result showed that the density of the essential oil product was in the range of 0.866–0.902 g/mL, while the refractive index was in the range of 1.470–1.475, which met the ISO standard. Chemical compounds were identified using Gas Chromatography-Mass Spectrometry (GC-MS) analysis. It was found that the total amount of citronellal, citronellol, and geraniol in the product obtained by MAHD is higher than the one from conventional methods. This study aims to identify the most efficient operating conditions to maximize yield while analyzing energy consumption to determine the most cost-effective conditions.

Extraction of Bioactive Compound-Rich Essential Oil from Cistus ladanifer L. by Microwave-Assisted Hydrodistillation: GC-MS Characterization, In Vitro Pharmacological Activities, and Molecular Docking

Cistus ladanifer L. is an aromatic and resinous perennial shrub commonly used in Moroccan folk medicine against a range of illnesses including skin problems, diabetes, diarrhea, and inflammation. The current investigation aims to determine the bioactive compounds of C. ladanifer essential oil (CL-Eo) extracted by microwave-assisted hydrodistillation and their biological properties using in vitro and molecular docking approaches. The GC-MS analysis identified linderol (17.76%), gamma-terpinene (17.55%), and borneol (13.78%) as main bioactive compounds. CL-Eo significantly inhibited α-amylase (IC50 = 0.41 ± 0.009 mg/mL), α-glucosidase (IC50 = 0.49 ± 0.002 mg/mL) and lipase (IC50 = 0.45 ± 0.004 mg/mL) enzymes. Moreover, CL-Eo showed significant hemoglobin glycation as well as antioxidant capacity as indicated by DPPH, ABTS, Frap and beta-carotene tests. The antimicrobial evaluation used disc-diffusion and microdilution tests in vitro. The results showed that CL-Eo had significant antibacterial activity, particularly against P. mirabilis (17.16 ± 1.04 mm), and moderate effects against L. innocua (13.48 ± 1.65 mm) and E. coli (12.47 ± 0.61 mm). In addition, it demonstrated potent antifungal activity against C. albicans (18.01 ± 0.91 mm) and C. tropicalis (16.45 ± 0.32 mm). The MIC and MBC tests provided confirmation that CL-Eo exhibited potent growth inhibition. The MIC ranged from 0.25 to 8.0% v/v and the MBC or MFC ranged from 0.25 to 16.0% v/v Eo. The tolerance level ratio showed bactericidal and fungicidal effects against tested microbial strains in varying degrees. According to these data, CL-Eo might be suggested as a promising candidate for drug development, specifically for combating candidiasis and diabetes.

Optimization of a novel Renealmia ligulata (Zingiberaceae) essential oil extraction method through microwave-assisted hydrodistillation

Renealmia is a tropical plant genus within the Zingiberaceae family. In tropical South America, Renealmia plants are known for their therapeutic uses against bone and muscle pain, colds, and to counteract snake bite symptoms. Despite the biomedical importance of Renealmia metabolites, the components of their essential oils (EO) have been scarcely studied, and a cause thereof is the lack of local efficient, inexpensive, and environmentally friendly EO extraction methods. This work addressed the optimization of an EO extraction method from the aerial parts and rhizomes of Renealmia ligulata plants based on microwave-assisted hydrodistillation (MAHD) with an ultrasound-assisted extraction (UAE) pretreatment. Three MAHD extraction variables (radiation power, radiation exposure length, and solvent volume) were studied on their own and in combination using a response surface analysis to determine the value combinations leading to optimal EO yields. The results showed that the best average extraction duration time was 42.5 min, combined with a radiation power of 765 W and a solvent volume 225.9 mL for 30 g of aerial part plant material or 799 W and 145 mL of solvent for 20 g of plant rhizomes. A GC-MS analysis of the obtained R. ligulata EOs revealed that their main component was epi-Eudesmol (28% in plant aerial parts and 13% in rhizomes), which is a molecule of interest considering its reported neuro-protective properties.

Profiling of seized Cannabis sativa L. flowering tops by means of microwave-assisted hydro distillation and gas chromatography analyses

This research aimed to support police forces in their battle against illicit drug trafficking by means of a multi-technique approach, based on gas chromatography. In detail, this study was focused on the profiling of volatile substances in narcotic Cannabis sativa L. flowering tops. For this purpose, the Scientific Investigation Department, RIS Carabinieri of Messina, provided 25 seized samples of Cannabis sativa L. The content of Δ9-tetrahydrocannabinol (THC), useful to classify cannabis plant as hemp (≤ 0.2 %) or as marijuana (> 0.2 %), was investigated. Essential oils of illicit drug samples were extracted using a microwave-assisted hydro-distillation (MAHD) system; GC–MS and GC-FID analytical techniques were used for the characterization of the terpenes and terpenoids fingerprint. Furthermore, the enantiomeric and carbon isotopic ratios of selected chiral compounds were investigated using a heart-cutting multidimensional GC (MDGC) approach. The latter exploited a combination of an apolar column in the first dimension, and a chiral cyclodextrin-based column in the second one, prior to parallel isotope-ratio mass spectrometry (C-IRMS) and MS detection. Finally, all the data were gathered into a statistical model, to demonstrate the existence of useful parameters to be used for the classification of seized samples.

Ultrasonic Pretreatment Combined with Microwave-Assisted Hydrodistillation for Extraction of Essential Oil from Melaleuca bracteata ‘Revolution Gold’ Leaves Scales Induced by Cellulase-Inorganic Salt and Its Anti-Fungal Activity

In order to further develop the commercial use of Melaleuca bracteata (F. Muell), this report studied the extraction of essential oil from Melaleuca bracteata (F. Muell) leaves using ultrasonic pretreatment, cellulase-inorganic salt soaked and combined with microwave-assisted hydrodistillation. To optimize the primary contributing parameters, the Box–Behnken design (BBD) was applied. The optimum yield of essential oil was 9.61 mL/kg DW at a microwave power of 510.77 W, lithium chloride dose of 63.56 μmol, and microwave irradiation period of 46.97 min. The essential oil included a total of 41 compounds, and methyl eugenol (76.53%) and methyl cinnamate (12.62%) were the main compounds. The inhibitory impact was notable when the essential oil concentration was 1.6 mg/mL. Therefore, it has the potential to replace chemical pesticides. When the concentration of the essential oil solution was 1.6 mg/mL, the three pathogenic species of fungus (Pseudocercospora psidii, Colletotrichum eriobotryae, and Colletotrichum siamense) were greatly affected; at this dose, the fungus was unable to develop and its growth diameter was 0 mm. Additionally, the fungus’s inhibition rate reached 100%.

Essential Oil of Glycosmis stenocarpa (Drake) Leaves Grown in Hai Duong Province, Vietnam

In this study, the extraction of essential oil of Vietnamese Glycosmis stenocarpa leaves was conducted using two different methods such as conventional microwave-assisted hydrodistillation (MAHD) and hydrodistillation (HD). The obtained products were analyzed by gas chromatography-mass spectrometry (GC-MS). The essential oil quality was attained in a comparable manner in both samples respectively. In addition, the GC-MS analysis showed that the hydrodistillation essential oil contains a total of 29 chemical compounds, whereas the MAHD essential oil contained 28 constituents. Moreover, the chemical constitutes of the two essential oils were similar, with the major components being citronellal, neryl acetate, citronellyl acetate and geranyl acetate.

The effect of using some extraction techniques on the physical and chemical properties of essential oils of citrus peels

The aim of the current study was to determine how extraction techniques affected the physical and chemical properties of the essential oils from citrus peels, specifically C.bitter orange and C.lemon. The results of the study were summarized as follows:1- The extraction method using microwave-assisted hydrodistillation without solvents was the best in terms of yield, time, and energy savings compared to the extraction method by pre-treatment with ultrasound and then hydro-distillation and hydro-distillation extraction .2- The essential oil extracted from dried bitter orange peels gave the best extraction yield using microwave-assisted hydro-distillation without solvents, reaching 4.21%, followed by lemon, which reached 2.21%.3- No significant effect was observed between the extraction methods used and the physical properties. While observed, there is a slight significant effect between the extraction methods used and the chemical properties of the C. bitter orange peel essential oil.4-It is noted that there is a slight significant effect between the extraction methods used and the physical and chemical properties of the C. Limon peel essential oil.

Exploring the essence of celery seeds (Apium graveolens L.): Innovations in microwave-assisted hydrodistillation for essential oil extraction using in vitro, in vivo and in silico studies

This study presents the composition analysis of essential oils extracted from celery seeds (Apium graveolens L.) collected from Morocco. Essential oil of A. graveolens (AG-EO), were obtained through microwave-assisted hydro-distillation, and its composition was characterized using gas chromatography/mass spectrometry (GC/MS). antimicrobial properties were assessed utilizing disc diffusion and microdilution assay methods, while antioxidant activities were evaluated through spectrophotometric techniques. Additionally, in vivo anti-inflammatory effects were investigated. The molecular docking technique, a computational approach utilized to predict the binding of small molecules to specific proteins, was employed to elucidate the antioxidative and antibacterial characteristics of the constituent molecules. The physicochemical and pharmacokinetic features of absorption, distribution, metabolism, excretion, and toxicity (ADME-Tox) tests were anticipated to provide insights into the drug likeness, pharmacokinetic characteristics, and expected safety profiles upon ingestion and the potential pharmacological activity of the identified compounds. Fifteen constituent compounds representing 99.99% of AG-EO were identified and quantified by the use of GC/MS. The main constituent, comprising 64.58% of AG-EO was limonene. AG-EO demonstrated a significant DPPH free radical scavenging activity, showing estimated scavenging rates of 8.49±0.00 µg/mL, and 5.09±0.04 µg/mL for ABTS+. AG-EO exhibited reducing Power (RP) and total antioxidant activity (TAC) of 3.42±0.01 µg/mL and 245.93±0.04 mg AAE/mL, respectively. AG-EO exhibited significant antimicrobial activity against all tested microorganisms. Additionally, the anti-inflammatory activity demonstrated the remarkable efficacy of AG-EO. Taken together, the essential oil derived from celery seeds holds promise for large-scale utilization as an environmentally friendly preservative within the food and agriculture industries, effectively countering fungal growth and aflatoxin contamination in stored commodities. Additionally, it exhibits potential as a suitable candidate for the development of pharmaceutical drugs.

Ionic liquid microwave-assisted hydrodistillation extraction of Angelica sinensis essential oil and its own anti-inflammatory and antioxidant activities

In this study, ionic liquid microwave-assisted hydrodistillation (IL-MAHD) was employed to overcome the challenges of substantial emulsification and low extraction yield which occur in the extraction process of Angelica sinensis essential oil (AEO). Additionally, an online detection system was introduced into the AEO extractor to enable real-time monitoring during the extraction process. Optimal conditions were determined as follows: material-to-liquid of 1:10, ionic liquid concentration of 0.5%, microwave power of 400 W, extraction time of 4 h, condensation temperature of 20 °C, and cooling temperature of 40 °C. Under these optimized conditions, the AEO yield reached 0.7707%, marking a 1.4066-fold increase compared to microwave-assisted hydrodistillation (MAHD) and a 3.7615-fold increase compared to hydrodistillation (HD). Meanwhile, IL-MAHD exhibited the highest relative content of (Z)-ligustilide (73.424%), and the corresponding AEO displayed significant anti-inflammatory and antioxidant effects at concentrations of 7.8125, 15.625, and 31.25 µg/g. The results of extraction kinetics and online monitoring suggested that the IL-MAHD achieved the fastest extraction yield of AEO. This study provides a new perspective on exploring a potential cost-efficient technology for the industrial extraction of essential oils.

Ultrasonic pretreatment combined with microwave-assisted hydrodistillation for the situ extraction of essential oil from Pinus koraiensis seed scales induced by tea saponin: Functional activity, composition, thermal stability and material characterization

In this work, in situ extraction of essential oil from Pinus koraiensis seed scales using tea saponin-induced ultrasonic pretreatment-microwave-assisted hydrodistillation (UP-MAHD) was studied. By fitting the extraction kinetic curves with different factors, a first-order kinetic model was determined to be more suitable. The key factors were screened and optimized via PlackettBurman Design (PBD) and BOX-Behnken Design (BBD). Under the optimization parameters of a liquid material ratio of 14 mL/g, power of 100 W, time of 15 min, temperature of 50 °C, and tea saponin dose of 0.4% for the ultrasonication and then microwave at 458 W for 18 min, the actual yield was 8.02 μL/g± 0.35% and was highly consistent with the theoretical yield of 8.21 μL/g. UP-MAHD-treated Pinus koraiensis seed scales essential oil (PKSSEO) had good inhibition functional activity of α-amylase. In addition, the chemical composition of the PKSSEO were determined using Gas chromatographymass spectrometry (GCMS) and Fourier transform infrared spectroscopy (FT IR), thermal gravimetry (TG), and differential scanning calorimetry (DSC), and its spatial structure characterization (SSC) obtained via UP-MAHD treatment was enhanced. In summary, this extraction method efficiently extracted PKSSEO with a lower effect on its activity and composition and could have solid future development prospects. Our study provided effective theoretical data support for the reuse and development of abandoned Pinus koraiensis seed scales resources.

Essential oil was extraction from Cinnamomum camphor peel using microwave as an aid and study of their inhibitory effect on Pseudocercospora psidii fungi

To apply the natural ingredients of plants in the field of food preservation, the essential oil of Cinnamomum camphor peel was isolated by salt-out pretreatment and microwave-assisted hydrodistillation. Using the single-factor mixed response surface approach, the extraction yield was optimized. A total of 14.98 mL/kg DW (dry weight: DW) was the greatest essential oil yield recorded. By using GC–MS analysis, a total of 29 compounds were found in the essential oil, with methyl eugenol (12.66 %) and safrole (10.36 %) being the two predominant compounds. However, the essential oil had a clear inhibitory effect on Pseudocercospora psidii at a concentration of 10 mg/mL. In conclusion, Cinnamomum camphora pericarp essential oil is anticipated to be a green natural pesticide that significantly inhibits pathogenic bacteria in crops.

The Flavor Characterization of ‘Huyou’ (Citrus changshanensis) Essential Oils Extracted by Conventional and Novel Methods

The aroma of citrus is among the most appealing natural flavors. ‘Huyou’ (HY) is a hybrid citrus with a unique flavor compared to grapefruit (GF), but few studies have analyzed its characteristic flavor comprehensively. In this study, we extract six essential oils (EOs) from HY and GF peels by cold pressing (CP) and microwave-assisted hydrodistillation (MADH) and spinning cone column (SCC). Further, the flavor of six EOs was investigated by using flavoromics analysis, including e-nose, GC-MS and GC-O combined with chemometric approaches. The results showed that CP EOs exhibited a stronger citrus characteristic flavor, while MADH and SCC EOs contained more diverse volatiles. A total of 23 key odorants were identified in the GC-O-MS analysis, 12 of which were specific to HY. The flavor wheel and partial least squares regression (PLSR) revealed that floral, sweet and fruity odors were positively correlated with linalool, α-terpineol and geraniol, while fatty, green and woody odors with germacrene D, germacrene B and nootkatone. Additionally, based on orthogonal partial least squares discriminant analysis (OPLS-DA), six aroma-active compounds were screened as aroma markers to distinguish HY from GF; i.e., γ-terpinene, D-limonene, germacrene D, nootkatone, germacrene B and terpinolene. The extraction methods and citrus varieties both impact the flavor characterization of citrus EOs, and our study provides guidance on the extraction and application for citrus EOs.

Enhanced extraction of clove essential oil by ultrasound and microwave assisted hydrodistillation and their comparison in antioxidant activity

Clove essential oil (CEO) is recognized for its variety of bioactivities and is widely used in the fields of food and pharmaceuticals. Eugenol is the main component that causes the oil's effectiveness. This study included a bibliometric analysis to demonstrate the novelty of the CEO extraction method. A combination of ultrasound and microwave techniques was utilized to enhance the efficiency of hydrodistillation (HD) extraction of essential oil from clove bud in terms of extraction yield, extraction rate, and eugenol composition, which is a strong antioxidant agent. Meanwhile, the effects of ultrasonic extraction temperature and time, microwave distillation power and time, and the ratio of clove to water were also investigated. The optimum conditions were as follows: ultrasonic extraction was at 40 °C for 45 min, microwave distillation power was 400 W for 45 min, and the clove to water ratio was 1:20 (g/mL). The ultrasound pretreatment prior to microwave-assisted hydrodistillation (U-MHD) method obtained the CEO, which had a significantly higher extraction yield (16.80 ± 0.26 %) and a greater amount of eugenol (78.49 %) than the CEOs obtained by traditional HD and MHD methods. Corresponding to the antioxidant activity of CEO from U-MHD, it possessed the strongest DPPH radical scavenging activity with an IC50 value of 2.79 ± 0.05 μg/mL, and it was comparable to the activity of eugenol. This is the first occurrence of CEO extraction employing the U-MHD procedure. This process could be used to enhance the bioactivity of CEO as well as its extraction efficiency, easy operation, rapid extraction, and eco-friendly technique. In terms of cost-analysis, MHD stands out as the most economically viable extraction method, boasting the lowest cost per 100 g product. The obtained results serve as fundamental data for implementing the scaling up of extraction processes to an industrial level.