Volatile Compounds and Biological Activity of the Essential Oil of Aloysia citrodora Paláu: Comparison of Hydrodistillation and Microwave-Assisted Hydrodistillation.

Aromatic plants are a remarkable source of natural products. Aloysia citrodora Paláu (Verbenaceae), commonly known as lemon verbena, is a relevant source of essential oils with potential applications due to its lemony scent and bioactive properties. Studies carried out on this species have focused on the volatile composition of the essential oil obtained by Clevenger hydrodistillation (CHD), with little information available on alternative extraction methodologies or the biological properties of the oil. Therefore, this work aimed to compare the volatile composition, antioxidant activity, cytotoxicity, anti-inflammatory and antibacterial activities of the essential oil extracted by conventional hydrodistillation by Clevenger (CHD) and Microwave-Assisted Hydrodistillation (MAHD). Significant differences (p < 0.05) were observed for some compounds, including the two major ones, geranial (18.7-21.1%) and neral (15.3-16.2%). Better antioxidant activity was exhibited by the MAHD essential oil in DPPH radical scavenging and reducing power assays, while no differences were observed in the cellular antioxidant assay. The MADH essential oil also presented higher inhibition against four tumoral cell lines and exhibited lower cytotoxicity in non-tumoral cells as compared with Clevenger-extracted essential oil. In contrast, the latter showed higher anti-inflammatory activity. Both essential oils were able to inhibit the growth of eleven out of the fifteen bacterial strains tested.

Bioactive Profile of Distilled Solid By-Products of Rosemary, Greek Sage and Spearmint as Affected by Distillation Methods.

By-products of essential oils (EOs) in the industry represent an exploitable material for natural and safe antioxidant production. One representative group of such by-products is distilled solid residues, whose composition is properly modulated by the distillation method applied for the recovery of EOs. Recently, in terms of Green Chemistry principles, conventional extraction and distillation processes are considered outdated and tend to be replaced by more environmentally friendly ones. In the present study, microwave-assisted hydro-distillation (MAHD) was employed as a novel and green method for the recovery of EOs from three aromatic plants (rosemary, Greek sage and spearmint). The method was compared to conventional ones, hydro-distillation (HD) and steam-distillation (SD), in terms of phytochemical composition of distilled solid residues, which was estimated by spectrophotometric and chromatographic methods. Total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity (ABTS, DPPH and FRAP) results highlighted the distilled solid residues as good sources of antioxidants. Moreover, higher antioxidant activity was achieved for MAHD extracts of solid residues in comparison to HD and SD extracts. A metabolomics approach was carried out on the methanolic extracts of solid residues obtained by different distillation methods using LC-MS analysis followed by multivariate data analysis. A total of 29 specialized metabolites were detected, and 26 of them were identified and quantified, presenting a similar phenolic profile among different treatments, whereas differences were observed among different species. Rosmarinic acid was the most abundant phenolic compound in all extracts, being higher in MAHD extracts. In rosemary and Greek sage extracts, carnosol and carnosic acid were quantified in significant amounts, while trimers and tetramers of caffeic acid (salvianolic acids isomers) were identified and quantified in spearmint extracts, being higher in MAHD extracts. The obtained results pointed out that MAHD extracts of distilled solid by-products could be a good source of bioactives with potential application in the food, pharmaceutical and cosmetic industries, contributing to the circular economy.

Extraction of Peppermint Essential Oils and Lipophilic Compounds: Assessment of Process Kinetics and Environmental Impacts with Multiple Techniques.

Consumers are becoming more mindful of their well-being. Increasing awareness of the many beneficial properties of peppermint essential oil (EO) has significantly increased product sales in recent years. Hydrodistillation (HD), a proven conventional method, and a possible alternative in the form of microwave-assisted hydrodistillation (MWHD) have been used to isolate peppermint EO. Standard Soxhlet and alternatively supercritical fluid (SFE), microwave-assisted, and ultrasound-assisted extraction separated the lipid extracts. The distillations employed various power settings, and the EO yield varied from 0.15 to 0.80%. The estimated environmental impact in terms of electricity consumption and CO2 emissions suggested that MWHD is an energy efficient way to reduce CO2 emissions. Different extraction methods and solvent properties affected the lipid extract yield, which ranged from 2.55 to 5.36%. According to the corresponding values of statistical parameters, empiric mathematical models were successfully applied to model the kinetics of MWHD and SFE processes.

Determination and analysis of volatile components from Thymus kotschyanus Boiss with a new solid-phase microextraction fibre and microwave-assisted hydrodistillation by periodic mesoporous organosilica based on alkylimidazolium ionic liquid.

INTRODUCTION: Research on the volatile oil composition of Thymus kotschyanus Boiss was conducted by applying mesoporous organosilica based on alkylimidazolium ionic liquid (PMO-IL) as a fibre coating material via a method referred to as microwave-assisted headspace solid-phase microextraction (MA-HS-SPME). METHODOLOGY: This technique entails microwave irradiation of the sample and collection of the volatile sample components. These components are further introduced into a gas chromatography-mass spectrometry (GC-MS) injection port for further analysis. A simplex method was used for the optimisation of three different parameters affecting the efficiency of the extraction. CONCLUSION: The MA-HS-SPME method proved to be the most suitable technique in oil determination and extraction from Thymus kotschyanus owing to its advantageous aspects of cost effectiveness, simplicity and solvent independence.

Kinetics studies on effects of extraction techniques on bioactive compounds from Vernonia cinerea leaf.

Recently, unconventional methods especially microwave-assisted hydrodistillation extraction (MAHE) is being used as an alternative technique for extracting bioactive compounds from plant materials due to its advantages over conventional methods such as Soxhlet extraction (SE). In this study, bioactive compounds were extracted from Vernonia cinerea leaf using both MAHE and SE methods. In addition, the kinetic study of MAHE and SE methods were carried out using first- and second-order kinetic models. The results obtained showed that MAHE can extract higher yield of bioactive compounds from V. cinerea leaf in a shorter time and reduced used of extracting solvent compared with SE method. Based on the results obtained, second-order kinetic models can actually describe the extraction of bioactive compounds from V. cinerea leaf through MAHE with extraction rate coefficient of 0.1172 L/gmin and extraction capacity of 1.0547 L/g as compared to SE with 0.0157 L/gmin and 1.1626 L/g of extraction rate coefficient and extraction capacity, respectively. The gas chromatography-mass spectrometry analysis of the oil showed the presence of numerous heavy fractions in the oil obtained through MAHE as compared with the SE method. Moreover, the electric consumption and environmental impacts analysis of the oil suggested that MAHE can be a suitable green technique for extracting bioactive compounds from V. cinerea leaf.

Essential Oils from Humulus Lupulus scCO2 Extract by Hydrodistillation and Microwave-Assisted Hydrodistillation.

Two different extraction methods were used for a comparative study of essential oils obtained from the Humulus lupulus scCO2 (sc-supercritical) extract: microwave-assisted hydrodistillation (MAHD) and conventional hydrodistillation (HD). As a result, the best conditions for the maximum essential oil production were determined for the MAHD method at 335 W microwave power for 30 min at water to raw material ratio of 8:3. The obtained essential oils were enriched in ß-myrcene in the amount of 74.13%⁻89.32% (wt%). Moreover, the first application for determination of the above-mentioned volatile compounds by supercritical fluid chromatography (SFC) with photo-diode array detection (PDA) is presented, which in comparison with gas chromatography coupled with mass spectrometry (GC-MS/MS) resulted in similar values for ß-myrcene and α-humulene in obtained samples within less than 1 min.

Profiling of Compositions of Essential Oils and Volatiles of Salvia limbata Using Traditional and Advanced Techniques and Evaluation for Biological Activities of Their Extracts.

In the present work, the essential oils and volatiles from flowers, leaves, and stems of Salvia limbata obtained using microwave-assisted hydrodistillation, solvent-free microwave extraction, headspace-assisted analysis, and headspace-solid phase microextraction have been characterized for the first time. The results have been also compared with those from traditional separation techniques involving hydrodistillation and steam distillation. Regardless of some common compounds in all of the profiles, some dissimilarities were noted due to the use of different extracting approaches. Taking into account the chemical categories, sesquiterpene hydrocarbons were found as the most represented group of natural compounds contributing to the chemical profiles. It was also noted that the methanol extracts obtained from the flowers of Sal. limbata showed a desirable antioxidant activity, comparable to the standard antioxidant butylated hydroxytoluene. Furthermore, using the disc diffusion and broth microdilution methods, all the tested bacteria demonstrated weak to moderate and moderate to strong sensibilities to the MeOH extracts obtained from different plant parts of Sal. limbata.

Microwave-assisted hydrodistillation of essential oil from rosemary.

Effects of microwave assisted hydrodistillation (MAHD) and conventional hydrodistillation (HD) methods on yield, composition, specific gravity, refractive index, and antioxidant and antimicrobial activities of essential oil of Rosmarinus officinalis L were studied. The main aroma compounds of rosemary essential oil were found as 1,8-cineole and camphor. Trolox equivalent antioxidant capacity (TEAC) values for essential oils extracted by MAHD and HD were 1.52 mM/ml oil and 1.95 mM/ml oil, respectively. DPPH radical scavenging activity of the oils obtained by MAHD and HD were found as 60.55% and 51.04% respectively. Inhibitory effects of essential oils obtained by two methods on linoleic acid peroxidation were almost the same. Essential oils obtained by two methods inhibited growth of Esherichia coli O157:H7, Salmonella typhimurium NRRLE 4463 and Listeria monocytogenes Scott A with the same degree. However, inhibitory activity of essential oil obtained by MAHD on Staphylococcus aureus 6538P was stronger than that of obtained by HD (p < 0.05).

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-3ß 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.

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.

Characterization of essential oils and volatiles from the aerial parts of Mentha pulegium L. (Lamiaceae) using microwave-assisted hydrodistillation (MAHD) and headspace solid phase microextraction (HS-SPME) in combination with GC-MS.

Herein, the chemical profiles of the essential oils and volatiles obtained from the aerial parts of Mentha pulegium L. (Lamiaceae) are reported respectively using microwave-assisted hydrodistillation (MAHD) and headspace solid phase microextraction (HS-SPME) approaches associated to gas chromatography-mass spectrometric (GC-MS) quantification. Using MAHD-GC-MS and HS-SPME-GC-MS techniques, 30 and 28 constituents were screened in the essential oils and volatiles of M. pulegium L. aerial parts with high prevalence of oxygenated monoterpenes and non-terpene hydrocarbons, respectively. Accordingly, in the characterized chemical profiles, carvone was found to constitute about 56.0% of the oil using the former technique (MAHD), whereas oleic acid (20.1%), carvone (17.7%) along with limonene (16.1%) were found as the major constituent components of the volatile profile using the latter approach (SPME). The two methods might be used in combination to obtain a wider set of information about the chemical composition of one specific plant sample.

Appraisal on the Wound Healing Potential of Deverra tortuosa DC. and Deverra triradiata Hochst Essential Oil Nanoemulsion Topical Preparation.

Deverra tortuosa (Desf.) DC. and Deverra. triradiata Hochst. ex Bioss are perennial desert shrubs widely used traditionally for many purposes and they are characteristic for their essential oil. The objective of the present study was to investigate the in vivo wound healing activity of the essential oil (EO) of D. tortuosa and D. triradiata through their encapsulation into nanoemulsion. EO nanoemulsion was prepared using an aqueous phase titration method, and nanoemulsion zones were identified through the construction of phase diagrams. The EO was prepared by hydrodistillation (HD), microwave-assisted hydrodistillation (MAHD), and supercritical fluid extraction (SFE) and analyzed using GC/MS. D. tortuosa oil is rich in the non-oxygenated compound, representing 74.54, 73.02, and 41.19% in HD, MADH, and SFE, respectively, and sabinene represents the major monoterpene hydrocarbons. Moreover, D. triradiata is rich in oxygenated compounds being 69.77, 52.87, and 61.69% in HD, MADH, and SFE, respectively, with elemicin and myristicin as major phenylpropanoids. Topical application of the nanoemulsion of D. tortuosa and D. triradiata (1% or 2%) exhibited nearly 100% wound contraction and complete healing at day 16. Moreover, they exhibit significant antioxidant and anti-inflammatory effects and a significant increase in growth factors and hydroxyproline levels. Histopathological examination exhibited complete re-epithelialization accompanied by activated hair follicles and abundant collagen fibers, especially at a concentration of 2%. Therefore, the incorporation of the two Deverra species into nanoemulsion could professionally endorse different stages of wound healing.

Microwave-assisted Natural Deep Eutectic Solvents Pretreatment Followed by Hydrodistillation Coupled with GC-MS for Analysis of Essential Oil from Turmeric (Curcuma longa L.).

In the past decade, natural deep eutectic solvents (NADESs) as green and sustainable extraction solvents with great potential for the efficient extraction of bioactive compounds from the plants are emerging. In this study, a microwave-assisted technology is used to prepare natural deep eutectic solvents. And natural deep eutectic solvents as pretreatment solvents coupled with microwave-assisted hydrodistillation (MAHD) for isolating essential oil (EO) derived from turmeric (Curcuma longa L.) is investigated. To improve the essential oil yield of turmeric (Curcuma longa L.) as a target, various factors affecting extraction efficiency including the type and amount of natural deep eutectic solvents, pretreatment time, pretreatment temperature and hydrodistillation (HD) time are discussed and optimized through central composite design (CCD) of the response surface methodology (RSM). The optimal conditions are as follows: natural deep eutectic solvent composed of choline chloride and oxalic acid (molar ratio with 1:1) as a pretreatment solvent, an amount of 60 g, a pretreatment time of 5 min, a pretreatment temperature of 84 ºC, a hydrodistillation time of 76 min. Under the optimum conditions, the highest essential oil yield of 0.85% is achieved. Additionally, the essential oil is analyzed by using gas chromatography-mass spectrometry (GC-MS), with a total of 49 compounds being identified. Through combining natural deep eutectic solvents with a microwave-assisted hydrodistillation technique, this work provides an eco-friendly extraction way of isolating essential oil, which boosts development in the monitoring other spice quality field.

Microwave-Assisted Hydrodistillation of Hop (Humulus lupulus L.) Terpenes: A Pilot-Scale Study.

Interest in essential oils has consistently increased in recent years. Essential oils have a large variety of applications in multiple fields, including in the food, cosmetics and pharmaceutical industries. The volatile fraction (VF) in hops (Humulus lupulus L.) fits within this domain as it is primarily used in the brewery industry for the aromatization of beer, and is responsible for the floral and fruity tones. This work aims to design an optimized extraction protocol of the VF from hops, using microwaves. Microwave-assisted hydrodistillation (MAHD) has been developed to reduce energy and time consumption in lab-scale reactors up to industrial-scale systems. Hops are principally available in three forms, according to a brewery's applications: (i) fresh (FH); (ii) dried (DH) and (iii) pelletized (PH). In this work, all three forms have therefore been studied and the recovered volatiles characterized by means of GC-MS. The optimized lab-scale MAHD protocol gave the best extraction yield of 20.5 mLVF/kgdry matrix for FH. This value underwent a slight contraction when working at the highest matrix amount (3 kg), with 17.3 mLVF/kgdry matrix being achieved. Further tests were then performed in a pilot reactor that is able to process 30 kg of material. In this case, high yield increases were observed for PH and DH; quadruple and double the lab-scale yields, respectively. In addition, this industrial-scale system also provided marked energy savings, practically halving the absorbed kJ/mLVF.

Deep eutectic solvent-homogenate based microwave-assisted hydrodistillation of essential oil from Litsea cubeba (Lour.) Pers. fruits and its chemical composition and biological activity.

As an important natural product, the sufficient separation of plant essential oil (EO) is helpful to improve its utilization value. In this work, deep eutectic solvent-homogenate based microwave-assisted hydrodistillation (DES-HMAHD) was developed and applied to isolate EO from the fruits of Litsea cubeba (Lour.) Pers. Different types of DES were investigated in terms of the EO kinetics and composition, among which oxalic acid/choline chloride (OA/ChCl) had obvious advantages. Following, molar ratio of OA and ChCl (1:1), water content (50%), liquid-solid ratio (12.5:1 mL/g), homogenate time (2 min), and microwave power (700 W) were found to be the optimum conditions. Gas chromatography-mass spectrometer (GC-MS) analysis showed that the EO isolated from DES-HMAHD contained a large proportion of m-cymene and trans-linalool oxide, which were quite different from the conventionally reported L. cubeba EO. In addition, the proposed DES-HMAHD resulted in higher separation efficiency and economic value, as well as lower environmental impact, as compared with other techniques. Afterwards, the EO isolated by different methods was evaluated from the perspective of biological activity. The EO obtained by DES-HMAHD showed higher antioxidant activity (DPPH and ABTS) but lower antifungal activity, which was related to its chemical composition. In general, DES-HMAHD produced a kind of L. cubeba EO with different components, which provided a scientific foundation for the sufficient isolation of plant EO and its application in the natural products.

Comparison of microwave-assisted hydrodistillation withthe traditional hydrodistillation method in the extractionof essential oils from Thymus vulgaris L.

Microwave-assisted hydrodistillation (MAHD) is an advanced hydrodistillation (HD) technique utilizing a microwave oven in the extraction process. MAHD of essential oils from the aerial parts (tops) of Thymus vulgaris L. (common thyme) was studied and the results were compared with those of the conventional HD in terms of extraction time, extraction yield/efficiency, chemical composition, quality of the essential oils and cost of the operation. MAHD was superior in terms of saving energy and extraction time (75min, compared to 4h in HD). Scanning electron microscopy (SEM) of thyme leaves undergone HD and MAHD provided evidences as to a sudden rupture of essential oil glands with MAHD. Gas chromatography-mass spectrometry analysis of the extracted essential oils indicated that the use of microwave irradiation did not adversely influence the composition of the essential oils. MAHD was found to be a green technology.

Optimization of Microwave-assisted Extraction of Essential Oil from Lavender Using Response Surface Methodology.

A microwave-assisted hydrodistillation (MAHD) method was investigated for extraction of essential oils from lavender. The essential oil extracts at optimized MAHD conditions was compared with hydrodistillation (HD). Response surface methodology coupled with Box-Behnken design was applied to optimize the parameters for MAHD. The optimized MAHD conditions were 500 W microwave power, 17 mL/g liquid-to-solid ratio and 40 min microwave time. The ANOVA results revealed that microwave time had the greatest impact on the essential oil yield followed by liquid-to-solid ratio and microwave power. Under the MAHD optimized conditions, the essential oil yield was 3.19%, approximating the predicted yield (3.20%). MAHD was superior in terms of saving energy and extraction time (40 min, compared to 120 min in HD). The essential oil analyzed by GC-MS, presented 39 compounds constituting 98.37% and 97.51% of the essential oils obtained through MAHD and HD, respectively. No obvious differences were found in composition between MAHD oil and HD oil. Antimicrobial study showed that the lavender essential oil exhibited broad-spectrum antibacterial activity and the MAHD oil showed a higher antimicrobial activity than the HD oil. This study revealed that MAHD could be a good method for extracting essential oil in lavender and other aromatic plants.

A modified approach for isolation of essential oil from fruit of Amorpha fruticosa Linn using microwave-assisted hydrodistillation concatenated liquid-liquid extraction.

In this work, a modified technique was developed to separate essential oil from the fruit of Amorpha fruticosa using microwave-assisted hydrodistillation concatenated liquid-liquid extraction (MHD-LLE). The new apparatus consists of two series-wound separation columns for separating essential oil, one is the conventional oil-water separation column, and the other is the extraction column of components from hydrosol using an organic solvent. Therefore, the apparatus can simultaneously collect the essential oil separated on the top of hydrosol and the components extracted from hydrosol using an organic solvent. Based on the yield of essential oil in the first and second separation columns, the effects of parameters were investigated by single factor experiments and Box-Behnken design. Under the optimum conditions (2mL ethyl ether as the extraction solvent in the second separation column, 12mL/g liquid-solid ratio, 4.0min homogenate time, 35min microwave irradiation time and 540W microwave irradiation power), satisfactory yields for the essential oil in the first separation column (10.31±0.33g/kg) and second separation column (0.82±0.03g/kg) were obtained. Compared with traditional methods, the developed method gave a higher yield of essential oil in a shorter time. In addition, GC-MS analysis of the essential oil indicated significant differences of the relative contents of individual volatile components in the essential oils obtained in the two separation columns. Therefore, the MHD-LLE technique developed here is a good alternative for the isolation of essential oil from A. fruticosa fruit as well as other herbs.