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

Microwave assisted hydro-distillation (MAHD) and conventional hydro-distillation (HD) 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 ​h). There is a slight increase in the yield of extracted oil in MAHD method (3.35%) compared to HD (3%). Gas chromatography–mass spectrometry 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 was 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 half-maximal inhibitory concentration IC50 value of MAHD was less than HD extracted oil.     

Comparison of MAHD with UAE and Hydrodistillation for the Analysis of Volatile Oil From Four Parts of Perilla frutescens Cultivated in Southern China

Three different isolation techniques, specifically microwave-assisted hydrodistillation (MAHD), ultrasound-assisted extraction (UAE), and conventional hydrodistillation (HD) were employed to obtain essential oils from whole plants, leaves, roots, and stems of Perilla frutescens. The essential oils were analyzed using gas chromatography with flame ionization detection and gas chromatography with mass spectrometry. Variations in chemical composition were observed; these were attributed to differences in plant organs. Variations in the percentages of the main constituents of the oils extracted based on plant organ were irregular and affected the quantity and composition of the oils. Oil yields were affected by the method of extraction and extraction organ variation. The maximum volume of oil was extracted from leaves via MAHD and the minimum was extracted from roots via UAE. Oil yields ranged from 0.05% to 0.53%. The contents of essential oil varied significantly with the plant organ. In the essential oils of the plant parts studied were showed a predominance of oxygenated monoterpenes. Variation of extraction methods and organs may influence the oil components either qualitatively or quantitatively.     

A study on the essential oil of Ferulago campestris: How much does extraction method influence the oil composition?

The essential oil of different parts of Ferulago campestris (Bess.) collected in Sicily has been extracted by microwave-assisted hydrodistillation (MAHD) and by classic hydrodistillation (HD). A comparative qualitative-quantitative study on the composition of the oils was carried out. A total of 100 compounds were identified in the oils obtained by MAHD, whereas 88 compounds characterized the HD oils. The most prominent components were, in all different parts of F. campestris and in both extraction methods, 2,4,5-trimethylbenzaldehyde and 2,4,6-trimethylbenzaldehyde isomers; the latter was not previously found. The attempt to evaluate where the oil components are located in all parts of the plant was carried out by means of a kinetic study. Then, electron microscopy observation on the different parts before and after MAHD and HD was performed.     

Phytochemical Investigation by Microwave‐Assisted Extraction of Essential Oil of the Leaves of Walnut Cultivated in Algeria

Walnut (Juglans regia L.) leaves are used traditionally as an herbal tea indicated for non‐insulin‐dependent diabetics. In recent years, the type‐II diabetes is occurring worldwide with increasing frequency. Thus, there is an urgent need to explore the new beneficial biomolecules on the human health. Our objective was to investigate, for the first time, the volatiles profile of Juglans regia L. leaves from Algiers region. The extraction of essential oil of fresh plant material was performed by microwave‐assisted hydrodistillation (MAHD), for the first time, a relatively recent method, then by the conventional hydrodistillation technique (HD) for comparison. The collected extracts were analyzed by GC‐FID and GC/MS using two capillary columns with different polarity. Extraction time of 1 h by MAHD provided higher yields (0.050±0.001% (w/w)) than by HD (0.030±0.006% (w/w)) after 3 h. A total of 38 compounds were identified using both techniques. Essential oils had similar qualitative but different quantitative composition in terms of chemical compounds. The MAHD method improved yield while reducing the extraction time. The sesquiterpenes were the dominant family in both MAHD and HD essential oils with β‐caryophyllene being the major constituent. Monoterpenes, including hydrocarbon and oxygenated, prevail in HD volatile fraction with β‐pinene and eucalyptol, respectively, as major components.     

Comparison of microwave-assisted and conventional hydrodistillation in the extraction of essential oils from mango (Mangifera indica L.) flowers

Microwave-assisted hydrodistillation (MAHD) is an advanced hydrodistillation (HD) technique, in which a microwave oven is used in the extraction process. MAHD and HD methods have been compared and evaluated for their effectiveness in the isolation of essential oils from fresh mango (Mangifera indica L.) flowers. MAHD offers important advantages over HD in terms of energy savings and extraction time (75 min against 4 h). The composition of the extracted essential oils was investigated by GC-FID and GC-MS. Results indicate that the use of microwave irradiation did not adversely influence the composition of the essential oils. MAHD was also found to be a green technology.     

Rapid analysis of the essential oils from dried Illicium verum Hook. f. and Zingiber officinale Rosc. by improved solvent-free microwave extraction with three types of microwave-absorption medium

A new method of extracting essential oils from dried plant materials has been studied. By adding a microwave-absorption medium (MAM) to a reactor, solvent-free microwave extraction (SFME) was improved and can be used to extract essential oils from dried plant material without pretreatment. With a microwave irradiation power of 85 W it took only approximately 30 min to extract the essential oils completely. The whole extraction process is simple, rapid, and economical. Three types of MAM, iron carbonyl powder (ICP), graphite powder (GP), and activated carbon powder (ACP), and two types of dried plant material, Illicium verum Hook. f. and Zingiber officinale Rosc., were studied. The results were compared with those obtained by use of conventional SFME, microwave-assisted hydrodistillation (MAHD), and conventional hydrodistillation (HD), and the conclusion drawn was that improved SFME was a feasible means of extracting essential oils from dried plant materials, because there were few differences between the composition of the essential oils extracted by improved SFME and by the other methods.     

Chemical Composition and Antimicrobial Activity of the Essential Oils Extracted by Microwave-Assisted Hydrodistillation from the Flowers of Two Plumeria Species

Microwave-assisted hydrodistillation (MAHD) was applied to obtain essential oils from the fresh flowers of Plumeria rubra Linn (PRL) and Plumeria rubra Linn var. acutifolia (PRLA) cultivated in China, which were subsequently analyzed via gas chromatography with flame ionization detection and gas chromatography with mass spectrometry. The essential oils were assessed for their antimicrobial activity. A variation of the chemical composition attributed to varieties was revealed. The essential oil of PRLA was found to have a high content of carboxylic acids (59.7%) with n-hexadecanoic acid (35.8%) and n-tetradecanoic acid (11.2%) as main components. Whereas, the PRL oil was characterized by high hydrocarbon content (38.6%), in which 9-hexacosene (14.6%) was found to be the major constituent. All essential oils possessed antimicrobial activity especially against five bacteria with diameter of inhibition zone (DD) and minimum inhibitory concentrations (MIC) values in the range of 6.8 to 21.3 mm and 2.8 to 46.5 mg/mL, respectively.     

Improved solvent-free microwave extraction of essential oil from dried Cuminum cyminum L. and Zanthoxylum bungeanum Maxim

Solvent-free microwave extraction (SFME) is a recently developed green technique which is performed in atmospheric conditions without adding any solvent or water. SFME has already been applied to extraction of essential oil from fresh plant materials or dried materials prior moistened. The essential oil is evaporated by the in situ water in the plant materials. In this paper, it was observed that an improved SFME, in which a kind of microwave absorption solid medium, such as carbonyl iron powders (CIP), was added and mixed with the sample, can be applied to extraction of essential oil from the dried plant materials without any pretreatment. Because the microwave absorption capacity of CIP is much better than that of water, the extraction time while using the improved SFME is no more than 30 min using a microwave power of 85 W. Compared to the conventional SFME, the advantages of improved SFME were to speed up the extraction rate and need no pretreatment. Improved SFME has been compared with conventional SFME, microwave-assisted hydrodistillation (MAHD) and conventional hydrodistillation (HD) for the extraction of essential oil from dried Cuminum cyminum L. and Zanthoxylum bungeanum Maxim. By using GC-MS system the compositions of essential oil extracted by applying four kinds of extraction methods were identified. There was no obvious difference in the quality of essential oils obtained by the four kinds of extraction methods.     

Chemical Constituents,Antioxidant, Anti-Tyrosinase,Cytotoxicity, and Anti-Melanogenesis Activities of Etlingera elatior (Jack) Leaf Essential Oils

Essential oils of plants have been used widely in cosmetic preparations. Being both perfuming and active ingredients, the functions of essential oils mean they are high-value ingredients. In this study, the leaf of Etlingera elatior (Jack) or Torch ginger was used. The essential oils (EO) were prepared by conventional hydrodistillation (HD) and microwave-assisted hydrodistillation (MAHD). The volatile compounds of EOs were analyzed by gas chromatography spectroscopy (GC-MS). The antioxidant activities by means of DPPH radical scavenging and ferric-reducing antioxidant power (FRAP) were determined. The inhibition of tyrosinase activity was investigated. The cytotoxicity was performed against human fibroblast cell lines (NIH/3T3) and melanoma cell lines (A375 and B16F10). The decreasing melanin content was measured in melanoma cell lines. The resulting essential oils were detected for 41 compounds from HD extraction dominants by terpenes, namely sesquiterpenes (48.499%) and monoterpenes (19.419%), while 26 compounds were detected from MAHD with the fatty alcohols as the major group. The higher antioxidant activities were found in HD EO (IC50 of 16.25 ± 0.09 mg/mL from DPPH assay and 0.91 ± 0.01 mg TEAC/g extract from FRAP assay). The survival of normal fibroblast cell lines remained at 90% at 500 µg/mL HD EO, where the EO possessed the half-maximal toxicity dose (TD50) of 214.85 ± 4.647 and 241.128 ± 2.134 μg/mL on B16F10 and A375 cell lines, respectively. This could suggest that the EO is highly selective against the melanoma cell lines. The melanin content was decreased at the half-maximum efficacy (IC50) at 252.12 ± 3.02 and 253.56 ± 3.65 in the A375 and B1610 cell lines, respectively, which were approximately 2.8-fold lower than kojic acid, the standard compound. The results of this study evidence the use of Etlingera elatior (Jack) leaf as a source of essential oil as an active agent in cosmetics.     

Antioxidant activity of crude extracts and essential oils from flower buds and leaves of Cistus creticus and Cistus salviifolius

Volatile oils from flowers and leaves of C. creticus L. and C. salviifolius L. were extracted by two extraction methods; namely, hydrodistillation and solid-phase micro-extraction (SPME). The chemical composition of essential oils was analyzed by GC and GC–MS. The volatile extracted from leaves and flowers of C. criticus using SPME was dominated by monoterpenes and sesquiterpenes hydrocarbon with α-pinene, camphene and α-cubebene as major components. In hydrodistillation, the oil extracted from leaves was dominated by oxygenated diterpenes and diterpenes hydrocarbon with manoyl oxide and sclarene as major components, whereas, the oil extracted from flowers was dominated by oxygenated diterpenes and diterpenes hydrocarbon with manoyl oxide and abietatriene as major components. The volatile from flowers and leaves of C. salviifolius obtained by SPME were dominated by monoterpenes and sesquiterpenes with δ-3-carene, α-pinene, β-pinene, and E-caryophyllene as major constituents. On the other hand, the oils from flowers and leaves of C. salviifolius obtained by hydrodistillation were dominated by oxygenated diterpenes, diterpenes hydrocarbon and esters with dehydro abietol, abietol, manoyl oxide and methyl octadecenoate as major components. In the leaves, the major components of the oil were manoyl oxide, E-ethyl cinnamate, and Z-ethyl cinnamate. These oils showed weak antioxidant activity when compared to the positive controls α-tocopherol, ascorbic acid, and EDTA, while the crude extracts aq. MeOH, butanol, and water showed good antioxidant activity. Discriminating between the studied plants based on the extraction method was also possible upon applying Principle component analysis (PCA) to the obtained GC–MS data.     

Inhibitory Effect of GRAS Essential Oils and Plant Extracts on the Growth of Aspergillus westerdijkiae and Aspergillus carbonarius Strains

The effect of essential oils (obtained using hydrodistillation) and plant extracts (ethanolic, aqueous, and hexanic extractions) of 10 different plants cultivated in Brazil were tested using the diffusion agar method, with the objective of evaluating the inhibitory effect of the oils and extracts on the mycelial growth of Aspergillus westerdijkiae NRRL 3174 and A. carbonarius RC 2054 (UNRC). Of the 40 essential oils and plant extracts analyzed, oregano essential oil and plant extract, rosemary essential oil, and the clove ethanolic extract were the best choice to obtain the growth parameters (radial growth rates (mm day⁻¹) and lag phase (h)) due the good results presented and the volume of oil/extract obtained. Comparing all the essential oils and plant extracts that were tested for growth parameters, the best results were obtained for the clove ethanolic extract for both strains assayed. These results demonstrated an outstanding potential use of some of these products in prevention of fungal contamination in food. However, further studies need to be conducted to determine the ability of these oils and extracts to inhibit or reduce ochratoxin A production.     

Chemical composition of the Brazilian native Cinnamomum stenophyllum (Meisn.) Vattimo-Gil essential oil by GC-qMS and GC × GC-TOFMS,and its cytotoxic activity

Cinnamomum stenophyllum (Meisn.) Vattimo-Gil (Lauraceae) is a native and vulnerable Brazilian species restricted to the Atlantic Forest. The leaf essential oil obtained by hydrodistillation was characterized for the first time by two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC-TOFMS). This analysis resulted in the tentatively identification of 80 compounds, showing the superior performance of this method in comparison to the seven compounds identified by GC–MS. The identified compounds included 8 ketones, 7 monoterpene hydrocarbons, 30 oxygenated monoterpenes, 4 sesquiterpene hydrocarbons and 23 oxygenated sesquiterpenes, showing that the C. stenophyllum oil contained mostly oxygenated mono and sesquiterpenes. The oil cytotoxicity was tested against two human cancer cell lines, colon adenocarcinoma (HCT-116) and breast cancer carcinoma (MCF-7), and the non-tumor retinal pigment epithelial cells (RPE) using the colorimetric MTT assay. Both cancer cell lines were sensible to leaf essential oil, with IC₅₀ < 20 μg/mL (HCT, IC₅₀ = 9.95 μg/mL and MCF-7, IC₅₀ = 16.65 μg/mL), while there was no cytotoxicity against the non-tumor cells at tested concentrations (IC₅₀ > 50 μg/mL), suggesting selectivity to cancer cells. The results showed that the C. stenophyllum leaf essential oil has a cytotoxic potential, presenting several compounds already known as biologically active against tumor cells.     

A comparison between different techniques for the isolation of rosemary essential oil

Traditional hydrodistillation (HD), supercritical fluid extraction (SFE), organic solvent extraction (SE), and water microwave assisted hydrodistillation (MAHD) techniques were compared and evaluated for their effectiveness in the isolation of rosemary essential oil. The microwave assisted hydrodistillation technique was optimized in terms of both delivered power and time duration. The extracts/distillates were analyzed by GC and GC-MS. Microwave distillation, which exploits the physical action of microwaves on plants, showed a series of advantages over the other approaches: low cost, use of water in sample pre-treatment step, greatly reduced isolation time, and attainment of high quality essential oil distillate. Moreover, the absence of environmental impact of this innovative technique was also emphasized.     

Characterization of volatile compounds of <Emphasis Type="Italic">Daucus crinitus</Emphasis>Desf. Headspace Solid Phase Microextraction as alternative technique to Hydrodistillation

Background  

Traditionally, the essential oil of aromatic herbs is obtained using hydrodistillation (HD). Because the emitted volatile fraction plays a fundamental role in a plant's life, various novel techniques have been developed for its extraction from plants. Among these, headspace solid phase microextraction (HS-SPME) can be used to obtain a rapid fingerprint of a plant's headspace. Daucus crinitus Desf. is a wild plant that grows along the west coast of Algeria. Only a single study has dealt with the chemical composition of the aerial part oils of Algerian D. crinitus, in which isochavicol isobutyrate (39.0%), octyl acetate (12.3%), and β-caryophyllene (5.4%) were identified. Using GC-RI and GC-MS analysis, the essential oils and the volatiles extracted from separated organs of D. crinitus Desf. were studied using HS-SPME.     

The Chemical Profiling of Essential Oils from Different Tissues of Cinnamomum camphora L. and Their Antimicrobial Activities

Cinnamomum camphora L. is grown as an ornamental plant, used as raw material for furniture, as a source of camphor, and its essential oil can be used as an important source for perfume as well as alternative medicine. A comparative investigation of essential oil compositions and antimicrobial activities of different tissues of C. camphora was carried out. The essential oils were extracted by hydrodistillation with a Clevenger apparatus and their compositions were evaluated through gas chromatography-mass spectrometry (GC-MS), enantiomeric composition by chiral GC-MS, and antimicrobial properties were assayed by measuring minimum inhibitory concentrations (MICs). Different plant tissues had different extraction yields, with the leaf having the highest yield. GC-MS analysis revealed the presence of 18, 75, 87, 67, 67, and 74 compounds in leaf, branch, wood, root, leaf/branch, and leaf/branch/wood, respectively. The significance of combining tissues is to enable extraction of commercial quality essential oils without the need to separate them. The oxygenated monoterpene camphor was the major component in all tissues of C. camphora except for safrole in the root. With chiral GC-MS, the enantiomeric distributions of 12, 12, 13, 14, and 14 chiral compounds in branch, wood, root, leaf/branch, and leaf/branch/wood, respectively, were determined. The variation in composition and enantiomeric distribution in the different tissues of C. camphora may be attributed to the different defense requirements of these tissues. The wood essential oil showed effective antibacterial activity against Serratia marcescens with an MIC of 39.1 μg/mL. Similarly, the mixture of leaf/branch/wood essential oils displayed good antifungal activity against Aspergillus niger and Aspergillus fumigatus while the leaf essential oil was notably active against Trichophyton rubrum. C. camphora essential oils showed variable antimicrobial activities against dermal and pulmonary-borne microbes.     

Essential oil composition, cytotoxic and antibacterial activities of five Etlingera species from Borneo

Essential oils obtained by hydrodistillation from the rhizomes of Etlingera pyramidosphaera (K. Schum.) R. M. Sm, E. megalocheilos (Griff.) A.D. Poulsen, comb. nov., E. coccinea (Blume) S. Sakai & Nagam, E. elatior (Jack) R. M. Sm, and E. brevilabrum (Valeton) R. M. Sm were analyzed by GCMS. The highest oil yield was obtained from E. pyramidosphaera (0.45%), followed by E. elatior (0.38%), E. coccinea (0.30%), E. brevilabrum (0.28%) and E. megalocheilos (0.25%). The major constituents of the essential oils were oxygenated monoterpenes, followed by sesquiterpenes, oxygenated sesquiterpenes, oxygenated diterpenes and diterpenes. The essential oils from E. pyramidosphaera and E. brevilabrum exhibited the best cytotoxicity against MCF 7 (LC50: 7.5 +/- 0.5 mg mL(-1)) and HL 60 (LC50: 5.0 mg mL(-1)), respectively. Strong inhibition was also observed for the essential oils of E. coccinea and E. megalocheilos against Staphylococcus aureus (MIC: 8.0 +/- 0.5 mg mL(-1), and 5.0 +/- 0.5 mg mL(-1)) and Streptococcus pyrogenes (MIC: 6.0 +/- 0.5 mg mL(-1) and 8.0 +/- 0.5 mg mL(-1)).     

Chemical composition and antimicrobial activity of essential oils from Centaurea pannonica and C. jacea

The chemical composition and antimicrobial activity of the essential oils obtained by hydrodistillation from Centaurea pannonica (Heufel) Simonkai and C. jacea L. (Asteraceae), were investigated. The essential oils were analyzed by GC and GC-MS. Forty five and twenty nine compounds were identified in the two oils, respectively. C. pannonica oil was rich in fatty acids (43.7%), with 9-octadecanoic acid (34.0%) and (Z,Z)-9,12-octadecadienoic acid (8.6%) as the major compounds. In contrast, the essential oil of C. jacea was dominated by oxygenated sesquiterpenes (43.2%), among which caryophyllene oxide (23.5%) and spathulenol (8.9%) were the major constituents. However, the oil was also characterized by an important fatty acid fraction (15.5%), with 9-octadecanoic acid (8.9%) and hexadecanoic acid (6.6%) being the main components. The antimicrobial activities of the essential oils were evaluated by the microdilution method against three Gram-positive and three Gram-negative bacteria, and one yeast. Both oils exhibited significant antimicrobial activity, especially against Gram-positive bacteria.     

Effects of solvent-free microwave extraction on the chemical composition of essential oil of Calamintha nepeta (L.) Savi compared with the conventional production method

The essential oil of Calamintha nepeta has been obtained by solvent-free microwave extraction (SFME) and by classical hydrodistillation (HD). A comparative qualitative-quantitative study on the composition of the oils was carried out. A total of 38 compounds, constituting 97.6% of the oil, were identified in the oil obtained by SFME, whereas 46 compounds, representing 95.4% of the oil, were characterized in the HD oil. SFME-distilled oil is richer in lightly oxygenated monoterpenes (LOM) than HD oil. It also has a higher amount of sesquiterpenes and a lower quantity of hydrocarbon monoterpenes. HD oil seems to be affected by chemical changes more than SFME oil.     

Chemical Composition and Evaluation of Insecticidal Activity of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum Essential Oils against Stored Products Pests

The problems of the environment and human health related to the use of synthetic and broad-spectrum insecticides have increasingly motivated scientific research on different alternatives and among these, the use of green systems, such as essential oils, have been explored. Several species of the Apiaceae and Asteraceae families, aromatic herbs rich in secondary bioactive metabolites, are used in the industrial field for pharmaceutical, cosmetic, and food purposes. Different essential oils extracted from some species of these families have shown acute toxicity and attractive and/or repellent effects towards different insects. In our work, we investigated the toxic potential of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum essential oils against four insect species, Sitophilus oryzae, Lasioderma serricorne, Necrobia rufipes, and Rhyzoperta dominica, which are common pests of stored products. The composition of both oils, extracted by hydrodistillation from the aerial parts of the two plants, was evaluated by GC×GC-MS. Calendula incana subsp. maritima essential oil was rich in oxygenated sesquiterpenoids, such as cubebol (35.39%), 4-epi-cubebol (22.99%), and cubenol (12.77%), while the Laserpitium siler subsp. siculum essential oil was composed mainly of monoterpene hydrocarbons, such as β-phellandrene (42.16%), limonene (23.87%), and β-terpinene (11.80%). The toxicity Petri dish bioassays indicated that C. maritima oil killed a mean of 65.50% of S. oryzae and 44.00% of R. dominica adults, indicating a higher biocidal activity in comparison with L. siculum oil, while toward the other species, no significant differences in mortality were recorded. Calendula maritima oil could be, then, considered a promising candidate for further tests as an alternative biocide toward S. oryzae and R. dominica. The possibility that the relatively high content of oxygenated sesquiterpenoids in C. maritima essential oil determines its higher biocidal activity is discussed.     

Effect of microwaves on the in situ hydrodistillation of four different Lamiaceae

The development of alternative techniques to classic hydrodistillation (HD) has been prompted because of the drawbacks of the more traditional technique. These drawbacks include: partial thermal degradation, high energy consumption and the fact that it is a time-consuming process. In situ microwave-generated hydrodistillation (MGH) and microwave hydrodiffusion and gravity (MHG) are suitable methods which may improve the preparation of essential oils. In this work, we report a comparison study of HD, MGH and MHG used in the extraction of four plant species cultivated in Piedmont (Italy): lavender, oregano, basil and sage. Both microwave-assisted procedures gave excellent results; in particular the essential oils obtained under MHG were very similar to those obtained with HD. In MGH, the polarity and the physico-chemical properties of the extracted compounds caused bigger differences in essential oil composition.