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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.

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.

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 β-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 β-myrcene and α-humulene in obtained samples within less than 1 min.

Conventional hydrodistillation (HD) and microwave-assisted hydrodistillation (MAHD) methods has been compared and evaluated for their effectiveness in the isolation of essential oils (EOs) from patchouli (Pogostemon cablin) leaves. The MAHD method offers important advantages over HD, viz. shorter extraction time (126 min vs. 417 min for HD); better yields (2.7227 % v/w vs. 2.6132 % v/w for HD); environmental impact (energy cost is appreciably higher for performing HD than that required for rapid MAHD extraction); and provides a more valuable EO (with high amounts of oxygenated compounds). It also offers the possibility for better reproduction of the natural aroma of the EO from patchouli leaves than that obtained using HD. The extraction of patchouli consisted of an initial, fast oil distillation followed by a slow oil distillation. Based on the experimental kinetic results, a semi-empirical model was fitted. The experimental investigation shows also that the operation time for MAHD in opposite to classical HD, for the same product quantity, was shorter. Higher yield results from higher extraction rates by microwave and could be due to a synergy of two transfer phenomena: mass and heat acting in the same way.

Aromatic plants are reported to display pharmacological properties, including anti-aging. This work aims to disclose the anti-aging effect of the essential oil (EO) of Thymbra capitata (L.) Cav., an aromatic and medicinal plant widely used as a spice, as well as of the hydrodistillation residual water (HRW), a discarded by-product of EO hydrodistillation. The phytochemical characterization of EO and HRW was assessed by GC-MS and HPLC-PDA-ESI-MSn, respectively. The DPPH, ABTS, and FRAP assays were used to disclose the antioxidant properties. The anti-inflammatory potential was evaluated using lipopolysaccharide-stimulated macrophages by assessing NO production, iNOS, and pro-IL-1β protein levels. Cell migration was evaluated using the scratch wound assay, and the etoposide-induced senescence was used to assess the modulation of senescence. The EO is mainly characterized by carvacrol, while the HRW is predominantly characterized by rosmarinic acid. The HRW exerts a stronger antioxidant effect in the DPPH and FRAP assays, whereas the EO was the most active sample in the ABTS assay. Both extracts reduce NO, iNOS, and pro-IL-1β. The EO has no effect on cell migration and presents anti-senescence effects. In opposition, HRW reduces cell migration and induces cellular senescence. Overall, our study highlights interesting pharmacological properties for both extracts, EO being of interest as an anti-aging ingredient and HRW relevant in cancer therapy.

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.

This study aimed to optimize the process of extracting essential oil from Eucalyptus citriodora leaves using either conventional hydrodistillation (CHD) or microwave-pretreatment hydrodistillation (MPHD), and to compare the two methods. The response surface methodology was utilized to optimize two techniques. The essential oil yield was quantified in terms of eucalyptol, and the highest yields of eucalyptol in CHD and MPHD were 2.72% and 3.50%, respectively. For CHD, the optimum conditions for extraction of eucalyptol from E. citriodora leaves were 700 mL/100 g solvent-to-solid ratio and a 4 h extraction time with a 2.64 mg/100 g eucalyptol predicted yield. For MPHD, the optimum conditions were the solvent-to-solid ratio of 555 mL/100 g, extraction time of 4 h, irradiation time of 30 s, and power of 466 W, giving a 2.24 mg/100 g eucalyptol predicted yield. The validation study verified the efficacy of the optimized models. Gas chromatography-mass spectrometry (GC-MS) showed eucalyptol as the most abundant chemical constituent of both the CHD and MPHD distillates. In conclusion, MPHD had a lower solvent requirement, consuming less water for a slightly lower yield than CHD. In terms of efficiency, both techniques worked almost equally well for extracting eucalyptol from E. citriodora leaves, but MPHD was more environmentally sustainable in terms of water consumption.

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. 

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.

Pomelo (Citrus grandis .Linn Osbeck) oils is becoming more and more popular for everyone because it has great benefits. However, the efficiency of essential oil extraction process depends on the method and is influenced by a number of factors. Microwave-assisted hydro-distillation and Response Surface Methodology are selected for extracting and optimizing the factors affect the yield of the pomelo oil. The pomelo oil has the optimum yield was 4.5% when extracted with a water and peels ratio of 3,119: 1 (ml/g) for time extraction of 117.336 (minutes) at a microwave power of 403.115 (W) with high reliability (R2 = 0.9831)