A Comparative Evaluation of the Antimicrobial Activities of the Essential Oils of Three Salvia Species Growing in Egypt, Obtained by Hydrodistillation and Microwave-Assisted Hydro-distillation

In the current study, both the essential oil composition and biological activity of Saussurea lappa and Ligusticum sinensis were investigated by means of microwave-assisted hydrodistillation (MAHD) and characterized by Gas chromatography/mass spectrometry (GC/MS), whereas the antimicrobial efficiency of MAHD essential oils was examined against four pathogens: Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Candida albicans responsible for microbial infections. The goal was to spot synergy and a favorable method that gives essential oils to possibly use as alternatives to common antimicrobial agents for the treatment of bacterial infections using a microdilution assay. S. lappa's 21 compounds were characterized by MAHD extraction. Sesquiterpene lactones (39.7 % MAHD) represented the major components, followed by sesquiterpene dialdehyde (25.50 % MAHD), while L. sinensis's 14 compounds were identified by MAHD extraction. Tetrahydroisobenzofurans (72.94 % MAHD) was the predominant compound class. S. lappa essential oil collection showed the strongest antimicrobial activity with MIC values of 16 μg/ml against all pathogens tested, while L. sinensis showed strong antibacterial activity and moderate antifungal activity with MIC values of 32 μg/ml and 500 μg/ml, respectively. The principal components of both oils, (velleral, eremanthin and neocnidilide), were docked into the bacterial histidine kinase (HK) and the fungal heat shock protein 90 (Hsp90).

The present study aimed to evaluate the chemical analysis and antimicrobial effects of the Thamnobryum alopecurum (Hedw.) Gangulee essential oils were obtained by different distillation methods (Clevenger apparatus hydrodistillation (HD) and microwave-assisted hydrodistillation (MD)). In this study obtained volatile oils were analyzed by gas chromatography-mass spectrometry which revealed the presence of forty-five compounds present in the essential oil obtained by HD method representing 99.48 % of the total identified compounds and thirty-four compounds were identified in the essential oil extracted by MD method representing 95.39 % of the total identified compounds. 3-octanone was the major constituent of the essential oils extracted by both HD (14.28 %) and MD (20.07 %). Terpenes were the major constituents in the essential oil extra-cted by both methods (54.41 % in HD and 52.21 % in MD) followed by oxygenated terpenoids (17.16 % in HD and 14.94 % in MD). The other major compounds of the essential oil in HD was limonene (9.65 %) followed by β-pinene (9.13 %), cuparene (6.04 %), gymnomitrone (5.72 %) and 4-epi-abietal (5.59 %). While in MD essential oil the other major compounds were β-pinene (12.20 %) followed by limonene (8.56 %), α-pinene (9.01 %), cupa-rene (6.44 %), abietadiene (5.97 %). The antimicrobial effects of the essential oils were determined tested quantitatively in respective broth media by using double microdilution and the minimal inhibition concentration (MIC) values (μg/mL). The isolated essential oils of T. alopecurum showed effective antimicrobial activities against Escherichia coli, Yersinia pseudotuberculosis, Staphylococcus aureus, Enterococcus faecalis, Bacillus cereus, Mycobacterium smegmatis and Candida albicans. However, no activity was not observed against Pseudomonas aeruginosa. The hydrodistillation method was found to be more effective than the microwave method in iden-tifying the chemical composition of the structure of T. alopecurum essential oil. While for antimicrobial study MD method was found to be more effective in terms of antimicrobial effect. The T. alopecurum thus is a potential source of an antimicrobial agent with a wide range of chemical compounds that could be responsible for their activity.

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.

Comparative study of chemical composition, antibacterial and antioxidant activity of essential oils isolated from the seeds of Amomum subulatum by using microwave extraction and hydro-distillation methods

In this study, the essential oils obtained from the fruits of Amomum villosum var. xanthioides by three different extraction methods (hydrodistillation, steam distillation, and microwave-assisted hydrodistillation) were reported for their yield, chemical composition and antimicrobial activity. The oils obtained were analysed using gas chromatography and gas chromatography-mass spectrometry. Furthermore, the antimicrobial activity of essential oils was evaluated using a microdilution broth assay. The results revealed that the microwave-assisted hydrodistillation produced 2.02% (w/w) yield of oil compared to 1.77% from hydrodistillation and 1.50% from steam distillation. There were significant differences in the content of main components in the essential oils obtained from the different extraction methods. Overall, bornyl acetate (30.01% - 38.18%), camphor (17.53% - 20.91%), borneol (9.21% - 14.68%), D-limonene (6.61% - 9.67%), camphene (4.14% - 8.51%), and β-myrcene (3.85% - 5.16%) were the main components in all the oil samples. The highest amounts of borneol, bornyl acetate, and camphor were obtained from the microwave-assisted hydrodistilled oil. In addition, the essential oil samples were tested for antimicrobial activity and were shown to inhibit the growth of Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus, and Pseudomonas aeruginosa, with minimum inhibitory concentration (MIC) ranging from 100 to 200 μg/mL, and the microwave-assisted hydrodistilled oil exhibited higher antimicrobial activity. In summary, this research revealed that microwave-assisted hydrodistillation is an outstanding method of extracting essential oils from the fruits of A. villosum var. xanthioides.

ABSTRACTDracocephalum kotschyi essential oils obtained by hydrodistillation (HD), microwave-assisted hydrodistillation (MAHD), and solvent-free microwave extraction (SFME) were investigated by GC-FID (Gas Chromatography-Flame Ionization Detector) and GC-MS (Gas Chromatography-Mass Spectrometry). The percentage of oxygenated compounds was significantly increased from 62.52% in HD to 76.47% in MAHD, and 84.52% in SFME. Conversely, the monoterpene hydrocarbons were decreased from 30.84% in HD to 13.71% in MAHD, and 5.85% in SFME. The main compound in the essential oil obtained by HD is limonene, which accounted for more than 30% of the oil, while the percentage of this compound was reduced to 9.52% in MAHD, and 5.60% in SFME. The percents of other oxygenated compounds such as neral, geranial, geraniol, geranyl acetate, α-terpineol, trans-verbenol, carvon, and trans-carveol were noticeably higher in microwave methods than those present in HD method. In aqueous medium, linear oxygenated monoterpenes may be converted to a monocyclic terpinyl cation, which it could lose a proton to give limonene. The main biosynthetic pathway of these compounds, as well as a possible route of their conversion into limonene, due to prolonged heating in the HD method, was proposed. The antimicrobial activity of D. kotschyi essential oils against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria was evaluated by broth micro-dilution susceptibility manner. The most sensitive bacteria to these oils was found to be S. aureus with the lowest minimum inhibitory concentration value of 2 mg mL−1 for MAHD and SFME specimens. The results indicated that oils obtained by microwave methods were more active against S. aureus.

This study investigated the potential use of microwave energy as an effective technique for the extraction of essential oil (EO) from some plant species belonging to Lamiaceae family growing in Egypt, involving Origanum majorana L., Mentha pipereta L., Mentha longifolia L., Origanum syriacum L., Lavandula angustifolia L., Rosmarinus officinalis L., and Thymus vulgaris L., in comparison with conventional extraction using hydrodistillation (HD) approach, in terms of extraction time, oil yields, and chemical composition. The results showed that the use of microwave in a relevant technique, namely microwave‐assisted hydrodistillation (MAHD) required an extraction of 60 minutes, while HD required 180 minutes. In general, EO yield being extracted by MAHD was higher than those extracted by HD. Gas chromatography in combination with mass spectrometry (GC/MS) analysis indicated noticeable quantitative changes in EOs composition extracted by MAHD and HD extraction methods. Except for O majorana L., GC/MS analysis of extracted oils using MAHD showed higher amounts of oxygenated constituents compared to HD extraction. The results of this study introduced MAHD as rapid, economical and environmental friendly extraction method. A comparative analysis was stated here between the EOs of all plant species under study on chemometric tools such as principal components analysis (PCA) and agglomerative hierarchical clustering (AHC). In general, the PCA results showed that there is significant variation between species in the quality and quantity of EO composition. However, no significant difference is observed based on the extraction method used (HD and MAHD).

Background: The processing of kinnow (Citrus reticulata) juice generates 30–34% peel waste, which is loaded in bioactive compounds like phenolics, limonin, and pectin. This study examined the antibacterial efficacy and storage stability of essential oil (EO) derived from kinnow peel, emphasizing its prospective use in the food, pharmaceutical, and cosmetic sectors. Methods: Kinnow peels were collected from juice venders of Hisar and Sirsa between December 2022 and January 2023. EO was extracted using four methods: Hydrodistillation (HD), Microwave Assisted Hydrodistillation (MAHD), Ultrasonic Assisted Hydrodistillation (UAHD), and Ohmic Heating Assisted Hydrodistillation (OHHD). The antimicrobial activity was assessed by the well diffusion technique against established bacterial and fungus strains. For the storage study, oils were kept in amber-colored bottles at refrigerator and freezer temperatures for 12 months. Fresh and stored oils were characterized using FTIR and GC-MS analysis. Data were evaluated utilizing ANOVA in SPSS 25.0, with statistical significance established at p<0.05. Results: The EO extracted from kinnow peel exhibited the strongest antimicrobial activity against Staphylococcus aureus, followed by Pseudomonas aeruginosa. It also exhibits antifungal effects against Aspergillus niger and Candida albicans. FTIR and GC-MS analyses confirmed limonene as the dominant compound. The highest concentrations were found in freshly extracted samples: HD (92.04%), MAHD (85.19%), UAHD (86.09%), and OHHD (85.12%). After 12 months of storage, the limonene content decreased slightly but remained more stable at –10°C: HD (88.11%), MAHD (84.23%), UAHD (85.24%), and OHHD (84.48%), compared to storage at 4°C: HD (87.06%), MAHD (85.61%), UAHD (84.90%), and OHHD (84.12%). Conclusion: The EO shown greater efficacy against gram-positive bacteria compared to gram-negative pathogens. Prolonged storage led to a reduction in low-molecular-weight compounds, with better retention observed at lower temperatures. These findings suggest that kinnow peel EO holds promise for applications in food preservation and natural antimicrobial formulations.

This study investigated the effectiveness of microwave-assisted hydrodistillation (MAHD) and solvent-less microwave extraction (SLME) for extracting essential oil (EO) from lemon peels in comparison with conventional hydrodistillation (HD) in terms of extraction time, extraction yield, physical properties, chemical composition, operation cost, and antioxidant activity. The results showed that MAHD and SLME methods required an extraction time of 15 minutes while the required extraction time in HD was 120 minutes. There were no significant differences among physical properties (refractive index, specific gravity, and color) of extracted EOs by the three methods. Gas chromatography analysis did not indicate any noticeable change in the composition of EOs extracted by microwave-assisted extraction methods (MAHD and SLME) and HD method. DPPHº analysis of the extracted EOs indicated that microwave irradiation did not adversely influence antioxidant activity of the extracted EOs. The results of this study introduced MAHD and SLME as rapid, economical, and environmentally friendly extraction methods.

The present study was carried out to determine, for the first time, the chemical composition, antioxidant and antimicrobial activities of essential oils from leaves of Salvia officinalis L. cultivated in Algeria. The essential oils (EOs) obtained by different extraction techniques: the microwave-assisted hydrodistillation (MAHD), the conventional hydrodistillation (HD) technique and the steam distillation (SD). The volatile compounds were analyzed by gas chromatography flame ionization detector (GC-FID) and by gas chromatography-mass spectrometry (GC-MS). The results were compared in terms of extraction time, yield extraction and chemical composition. The effect of drying method on the chemical composition of the essential oil generated by air or by oven drying. The results obtained showed that dried plant material yielded more essential oils than the fresh one. The highest EO yields were obtained for the oven-dried at 60°C (2.5 %) for one day, followed by the air-dried plant material for twenty one days (2.25 %). The chemical analysis of EO led to the identification of 28, 30 and 25 compounds in HD, MAHD and SD oils, respectively. The main components of EO resulting from the different extraction techniques were 1,8-cineole (11.00-12.16 %), α-thujone (15.80-17.92 %), camphor (10.70-23.95 %), α-humulene (4.50-9.61 %) and viridiflorol (9.49-13.10 %). The method of drying induced very significant variations for some compounds, especially for main compounds such as camphor (21.78-25.36 %), α-thujone (16.84-17.40 %) 1,8-cineole (15.15-17.92 %), caryopyllene oxide (5.46-8.42 %). The antioxidant activity evaluated by DPPH (1,1 diphenyl-2picryl-hydrazyl) radical scavenging assay showed an appreciable efficiency. The antimicrobial activity tested on seven microorganisms showed that the EO obtained by SD was remarkably more active, and that Pseudomonas aeruginosa and Candida albicans were resistant to all tested oils.

BackgroundAchillea fragrantissima (F. Asteraceae) is traditionally used to treat skin infections and inflammation. The present work intended to prepare essential oils (EOs) from A. fragrantissima aerial parts growing widely in Egypt and investigate its antibacterial activity against skin-related pathogens and in vitro cell-based anti-inflammatory activity.MethodsEOs of the fresh aerial parts were extracted by hydrodistillation (HD), microwave-assisted hydrodistillation (MAHD), and head-space (HS), while those of the dried ones were prepared by supercritical fluid (SF). The result EOs were analyzed using GC/MS. The antibacterial activity was evaluated alongside Pseudomonas aeruginosa ATCC 9027, Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 25923, Streptococcus pyogenes ATCC 12344, Clostridium perfringens ATCC 13124 by agar diffusion, microwell dilution, and biofilm formation tests. The anti-inflammatory activity was evaluated by measuring tumor necrosis factor-alpha (TNF-α), interleukin 2 (IL-2), and 6 (IL-6) in lipopolysaccharides (LPS)- stimulated RAW 264.7 cells using ELISA assays in addition, expression of nitric oxide synthase (iNOS) was measured via western blot.ResultsThe SF method gave the highest EO yield (1.50 mL v/w). Oxygenated components constituted the highest percentage in the four methods, 84.14, 79.21, 73.29 and 33.57% in the HS, HD, MAHD, and SF, respectively. Moreover, variation in the amount of identified compounds was apparent; in HS EO α-thujone (29.37%), artemisia ketone (19.59%), and santolina alcohol (14.66%) are major components, while α-thujone (20.38%) and piperatone (12.09%) were significant in HD. Moreover, ( +)-spathulenol (12.22%) and piperatone (10.48%) were significant in MAHD, while piperatone (14.83%) and β-sitosterol (11.07%) were significant in SF EO. HD, MAHD, and SF EOs exhibited susceptibility against P. aeruginosa (IZ = 9–14 mm), E. coli (11–13 mm), and C. perfringens (IZ = 10–14 mm) in agar diffusion assay. MAHD EOs demonstrated potent growth inhibition (MICs = 0.25–2 mg/mL), followed by HD EOs (MICs = 13–52 mg/mL) to all tested microorganisms in well microdilution assay. Also, they exert MBC values equal to or higher than the MICs. Furthermore, SF EOs inhibited the biofilm formation of all tested microorganisms by 65.12—80.84%. Specifically, MAHD and HD EOs efficiently suppress the biofilm of S. pyogenes (77.87%) and P. aeruginosa (60. 29%), respectively. Ultimately, HD and SF EOs showed anti-inflammatory activity by suppressing the TNF-α, IL-2, and IL-6 release and iNOS expression in LPS-stimulated RAW 264.7 macrophages.ConclusionA. fragrantissima EO is rich in oxygenated volatile compounds with antibacterial and anti-inflammatory activities. It is encouraged as a bioactive agent for adjusting skin infections, though additional studies are essential for their safety in clinical settings.

Comparative seasonal variation and chemical composition of essential oils from the leaves and stems of Schefflera heptaphylla using microwave-assisted and conventional hydrodistillation

Evaluating the Effects of Microwave-Assisted Hydrodistillation on Antifungal and Radical Scavenging Activities of Oliveria decumbens and Chaerophyllum macropodum Essential Oils

Extraction of essential oils of Ferulago angulata with microwave-assisted hydrodistillation

Essential oil from Cinnamomum cassia bark through hydrodistillation and advanced microwave assisted hydrodistillation