Chemical composition and cytotoxic activities of Rhodomyrtus tomentosa (Aiton) Hassk. essential oil extracted by microwave-assisted hydrodistillation.

Since ancient times, the three Salvia L. species: Salvia aegyptiaca L., Salvia lanigera Poir., and Salvia multicaulis Vahl, have been utilised in traditional medicine all across the world. These species are now subjected to in-depth chemical and pharmacological investigations in order to find physiologically active chemicals. In the present study, the essential oil composition and biological activity of these Salvia L. species were studied. Using various extraction methods: hydrodistillation (HD) and microwave-assisted hydrodistillation (MAHD) to compare extraction efficiency, volatile metabolites were analysed and characterised by Gas chromatography/mass spectroscopy (GC/MS), while the antimicrobial efficiency for both the HD and MAHD essential oils was examined against four pathogens: Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Candida albicans using microdilution assay. S. aegyptiaca, 12 and 14 compounds, were characterised by HD and MAHD extraction, respectively. Sesquiterpene hydrocarbons (85.87% HD & 72.74% MAHD) repidentified by HD and MAHD extraction, respectively. Monoterpenes (36.58% HD and 49.63% MAHD) and their oxygenated derivatives (31.4% HD and 28.63% MAHD) were the predominant compound classes. From S. lanigera, 12 and 8 compounds were identified by HD and MAHD extraction, respectively. Sesquiterpene hydrocarbons were present in S. lanigera essential oils with 8.3% HD and 2.4% MAHD. Moreover, the most potent antimicrobial activity was observed with the S. multicaulis essential oil collection employing either HD or MAHD extraction, while S. lanigera essential oils extracted by MAHD exhibited almost as high antimicrobial activity. The approach of MAHD saves time with all the improvements in product yield. Essential oils extracted using MAHD might be used to treat bacterial infections instead of standard antibacterial medications.

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

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.

Essential oils (EOs) from the seed of Michelia tonkinensis were extracted in four ways hydrodistillation (HD), microwave‐assisted hydrodistillation (MHD), ultrasound‐assisted hydrodistillation (UHD) and enzyme‐assisted hydrodistillation (EHD). The chemical constituents of these EOs were analysed by gas chromatography (GC‐FID) and gas chromatography/mass spectrometry (GC/MS). Phenylpropanoids were the main components in which safrole is the dominant constituent (82.98‐91.53%), followed by monoterpene hydrocarbons (5.26‐11.94%). In comparison with traditional hydrodistillation method (HD only), the EOs obtained from the MHD, UHD and EHD methods have the higher safrole contents (91.32%, 90.96% and 90.25%, respectively). The essential oils were also tested for their antioxidant, anti‐imflammatory, antimicrobial and cytotoxic activities. The HD essential oil sample showed inhibitory activity against 6/8 tested microorganisms, i.e., Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Bacillus subtillis, Candida albicans, and Saccharomyces cerevisiae. The MHD and EHD exhibited the inhibitory activity against three strains E. coli, A. niger and F. oxysporum. The UHD inhibited E. coli and F. oxysporum.

Microwave assisted hydrodistillation (MAHD) and conventional hydrodistillation techniques were compared in the extraction of essential oils from Amomum subulatum seeds. The time required for MAHD method (70 min) is lesser than that for HD method (4 hr). There is a slight increase in the yield of extracted oil in MAHD method (3.35%) compared to HD (3%). GC-MS results show that MAHD extracted essential oil was wealthier in oxygenated compounds. 1, 8-Cineole was found to be a major compound in case of both the essential oil, followed by α-pinene. In MAHD the percentage of the major oxygenated monoterpene (1, 8- cineol) slightly increases from 88% to 89% as compared to hydrodistillation. Contrarily to this, the percentage of monoterpene hydrocarbon were decreased in MAHD than HD extracted oil. MAHD and HD extracted oils show good antibacterial activities against gram-negative and gram-positive bacteria. MAHD extracted oil shows better antibacterial activity than HD extracted against both gram positive and gram-negative bacteria. 2, 2-diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging antioxidant activities show that MAHD extract has better inhibition percentage than HD extract, and the IC50 value of MAHD was less than HD extracted oil.

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.

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

The essential oils from Marchantia paleacea obtained by microwave-assisted hydro-distillation (MAHD) and conventional hydrodistillation (HD) methods were compared. For MAHD method, the effects of different parameters, such as extraction time, the moisture of the matrix and the irradiation power, on the yield of essential oils were investigated. Maximum global yields were obtained using the following conditions: extraction time, 40 min; the irradiation power, 450 V and the moisture of the matrix, 80 %. MAHD was superior in terms of saving energy and extraction time (40 min, compared with 3 h for HD). The yield of essential oils by MAHD method was ten-fold higher than that of HD method. The extracts of essential oils were analyzed by GC-MS. The obtained results were compared with references. The result also indicated that the using microwave irradiation did not change the composition of essential oils.

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.

Yield, chemical composition, and antioxidant activity of essential oil obtained from Ferula persica oleo-gum-resin: Effect of the originated region, type of oleo-gum-resin, and extraction method

The essential oils from peels and leaves of Citrus clementine Hort. ex Tan. were extracted via two methods: conventional hydrodistillation (CHD) and microwave-assisted hydrodistillation (MAHD). Their physicochemical properties were investigated. Their chemical compositions of the oils were determined by GC/FID and GC/MS. A total of forty-one and seventy-seven compounds of the total essential oil composition of the peels and leaves respectively were identified. The peel oils were dominated by monoterpene hydrocarbons in which limonene was the main component (95.48% [CHD], and 95.03% [MAHD]). The leaf oils were also dominated by sesquiterpene hydrocarbons with sabinene (26.02% [CHD], and 19.52% [MAHD]), β-elemene (10.50% [CHD], and 18.04% [MAHD]), linalool (9.88% [CHD], and 7.51% [MAHD]), (E)-β-ocimene (5.87% [CHD], and 5.00% [MAHD]), β-caryophyllene (4.04% [CHD], and 7.49% [MAHD]), and δ-selinene (4.76% [CHD], and 8.02% [MAHD]) as major components. The oil contents of peels were obtained with 5.31% and 5.67% by CHD method and MAHD method, respectively. The oil contents of the leaves were obtained with 0.33% and 0.20% by CHD method and MAHD method, respectively. The antimicrobial activity (disc diffusion antibiotic sensitivity assay) of the oils was investigated against six reference test organisms including two Gram (+) bacteria (Bacillus subtilis, Staphylococcus aureus), three Gram (-) bacteria (Escherichia coli, Pseudomonas aeruginosa, Shigella flexneri), and one fungus (Candida albicans).

In this study, the essential oils from lemon (Citrus aurantifolia) peels were extracted using hydrodistillation and microwave-assisted hydrodistillation and their volatile compositions were compared via gas chromatography-mass spectrometry (GC-MS) analysis. Microwave-assisted hydrodistillation (MHD) achieved the oil yield of 2.48% at microwave power of 470W and extraction time of 60 min. The yield obtained using conventional hydrodistillation (HD) was 2.2% at 90 min at 120 °C. GC-MS analysis revealed a total of 17 and 8 components existing in the oil samples produced by MHD and HD methods respectively. The main components shared by both samples were limonene, α-pinene, β-pinene, β-cymene, ocimene, and sabinene. Overall, these results suggest that MHD could produce lemon (Citrus aurantifolia) peels essential oil at a higher yield within a shortened period of time as compared to the traditional HD, thus it could be used as an alternative for HD to reduce costs of the extraction process.

Kinetics of mace (Myristicae arillus) essential oil extraction using microwave assisted hydrodistillation: Effect of microwave power

Pinus eldarica (Pinaceae), an evergreen plant, is distributed across the warm and dry climates of western Asia, including Asia Minor, the Middle East, and land surrounding the Caspian Sea. Essential oils (EOs) from different aerial parts of this tree have been used in traditional medicine. We aimed to investigate the chemical profile and antimicrobial activity of the EO from P. eldarica grown in northwestern Iran. EO from the needles, bark, and pollen were extracted with boiling water using a Clevenger apparatus at yield of 0.7–1.2 cm3/100 g of dry plant material. The main chemical components of the EO from the needles were D-germacrene (18.17%), caryophyllene (15.42%), γ-terpinene (12.96%), and β-pinene (10.62%); those from the bark were limonene (16.99%), caryophyllene oxide (13.22%), and drimenol (13.2%); and those from the pollen were α-pinene (25.64%) and limonene (19.94%). In total, 83 constituents were characterized in the EOs, using gas chromatography mass spectrometry analysis; mainly, sesquiterpene hydrocarbons in needle EO and monoterpene hydrocarbons in pollen and bark EOs. β-Pinene, β-myrcene, limonene, and caryophyllene were identified in the EOs from all three plant parts. The antibacterial and antifungal properties of the EOs were examined: pollen EO exhibited antibacterial activity against Escherichia coli; bark EO inhibited the growth of Candida albicans and Staphylococcus aureus; and the needle EO inhibited the growth of S. aureus. Thus, the EOs from aerial parts of P. eldarica can benefit the EO industry and antibiotic development.

In the present study, we determined the chemical composition of Clinopodium macrostemum essential oil obtained by microwave-assisted hydrodistillation and its effect on the growth and development of Culex quinquefasciatus mosquito larvae. The essential oil compounds were identified by gas chromatography-mass spectrometry analysis, and bioassays were conducted to evaluate the influence on the developmental stages of early second instar larvae of Cx. quinquefasciatus until the emergence of adults, using essential oil concentrations of 50, 100, 200, 400, and 800mg/L. The gas chromatography-mass spectrometry analyses revealed that the leaf essential oil of C. macrostemum contained 32 compounds and the major chemical compounds identified were linalool (55.4%), nerol (6.4%), caryophyllene (6.25%), menthone (5.8%), geraniol acetate (4.1%), terpineol (3.7%), and pulegone (2.8%). The essential oil yield obtained by microwave-assisted hydrodistillation was 0.8% at 20 min. The treatments showed lethal concentrations (LC50 and LC90) of 22.49 and 833.35mg/L, respectively, after the final measurement of the total number of dead larvae (second, third, and fourth instars), and LC50 and LC90 of 6.62 and 693.35mg/L, respectively, at the end of the experimental period. The essential oil inhibited the growth and development of the mosquito larvae by 32% (relative growth index = 0.68) at 50mg/L, and up to 47% (relative growth index = 0.53) at 800mg/L. The present study demonstrated the larvicidal effect of C. macrostemum essential oil on Cx. quinquefasciatus, which can be attributed to the oxygenate compounds obtained by the extraction method.