Solvent-Free Microwave Extraction: Phytochemistry and Bioactivities of Essential Oil from Stachytarpheta jamaicensis, L. in Banyuwangi

‘Mato Peiyu’ pomelo (Citrus grandis (L.) Osbeck ‘Mato Peiyu’) leaves from pruning are currently an agricultural waste. The aim of this study was to isolate essential oils from these leaves through steam distillation (SD) and solvent-free microwave extraction (SFME) and to evaluate their applicability to skin care by analyzing their antimicrobial, antioxidant (diphenyl-1-picrylhydrazyl scavenging assay, β-carotene/linoleic acid assay, and nitric oxide scavenging assay), anti-inflammatory (5-lipoxygenase inhibition assay), and antityrosinase activities. The gas chromatography–mass spectrometry results indicated that the main components of ‘Mato Peiyu’ leaf essential oils were citronellal and citronellol, with a total percentage of 50.71% and 59.82% for SD and SFME, respectively. The highest bioactivity among all assays was obtained for 5-lipoxygenase inhibition, with an IC50 value of 0.034% (v/v). The MIC90 of the antimicrobial activity of essential oils against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans ranged from 0.086% to 0.121% (v/v). Citronellal and citronellol were the main contributors, accounting for at least 54.58% of the essential oil’s bioactivity. This paper is the first to report the compositions and bioactivities of ‘Mato Peiyu’ leaf essential oil, and the results imply that the pomelo leaf essential oil may be applied in skin care.

Essential oils (EOs) are widely used in cosmetic, pharmaceutical, fragrance and food industry. Solvent Free Microwave Extraction (SFME) is a green method for the extraction of essential oils from aromatic plants. The aim of the study is to compare SFME with conventional hydro-distillation (HD) technique, for the extraction of EO from four selected underutilised Citrus plant species in the essential oil industry; Citrus medica, C. reticulata, C. madurensis and C. limon in terms of chemical composition, antioxidant activity and energy consumption. The EOs were extracted using SFME (Microwave power: 700 W for 5 minutes and 400 W for 55 minutes) and HD (for 1 hour) and chemically analysed using Gas Chromatography (GC) and Gas Chromatography and Mass Spectrometry (GC-MS). The Antioxidant activity of the EOs were determined using Ferric Reducing Antioxidant Power (FRAP) and Total Polyphenolic Content (TPC) assays. The GC and GCMS identified 4(10)-Thujene (33.82%) as the major compound in C. medica oil, extracted by HD while that was L- terpinene-4-ol (18%) when extracted by SFME technique. The β-Linalool was the major component in C. reticulata (42.98%) and C. madurensis (37.95%) in SFME extracted EOs, however, it has been dropped down to 26.71% and 26.83% respectively during HD extraction. In C. limon, D-Limonene (43.069%) was abundant in HD- extracted EOs while it was (R)-(+)-Citronellal (39.08%) in SFME-extracted EO. SFME yielded EOs with higher amounts of more valuable oxygenated compounds with higher antioxidant capacities over HD. In comparison with HD, the SFME technique presented higher efficiency with reduced extraction times, costs and energy, yielding EOs with excellent chemical profiles and relatively high antioxidant activity. Keywords: Essential oils, Solvent free Microwave extraction, GC, GCMS, Antioxidant

Lippia alba cultivar ‘Kavach’ is an aromatic, multi-branched, trailing, deep-rooted shrub that can be planted on slopes to control soil erosion. Cuttings of this genotype were planted on the edges of field plots developed by depositing agricultural soil on the rocky terrain of Aravalli mountain range land on which the Institute is located in New Delhi. Shoots harvested several times a year in the third, fourth and fifth year from planting were sampled for leaves and flowers bearing Inflorescences to determine their biomass yield. The Inflorescences and leaves sampled from the harvests of third year were analyzed by GC and GC/MS for their oil quality. Altogether 55 compounds were identified in leaf and Inflorescence oils; a set of 47 compounds made up 96.3% of the leaf oil and 46 compounds made up 97.0% of Inflorescence oil. The concentrations of linalool and 1,8-cineole were 67.7% and 6.4% in the leaf oil, whereas these were 79.3% and 5.2%, respectively, in Inflorescence oil. The Inflorescence oil also contained cis- and trans-linalool oxides (2.8%). The importance of the flower oil of L. alba cultivar ‘Kavach’ as a linalool-rich oil resource is discussed in terms of traditional sources of such oil and unique features of the cultivar.

Hyptis brevipes Poit. leaf and inflorescence essential oils obtained by hydrodistillation, were analyzed by gas chromatography mass spectroscopy (GC-MS). Fifty seven components were identified in the leaf oil. The major componentsgermacrene D (13.54%), caryophyllene (12.31%), phthalamide doxime (9.47%) and caryophyllene oxide (8.57%). Thirty seven components were identified in inflorescence oil with the main components being in caryophyllene oxide (45.09%), 1,5,5,8-tetramethyl-12-Oxabicyclo [9.1.0] dodeca-3,7-diene (4.95%), caryophyllene (4.79%) and a-bourbonene (4.20%). The compositions of both oils varied qualitatively and quantitatively. Key words: Hyptis brevipes, essential oil, GC-MS analysis, germacrene D, caryophyllene oxide.

The orange tree (Citrus sinensis) is a species of fruit shrubs of the Rutaceae family. Essential oils from citrus peels are widely used in various agro-food and pharmaceutical preparations and hence they must be recovered using green extraction methods. In this study, we compare the efficiency of five extraction techniques (conventional hydro-distillation (HD), Salt-assisted extraction by HD (S-HD), Ultrasound-assisted extraction by HD (US-HD), Enzymes-assisted extraction by HD (E-HD), and Solvent-free microwave extraction (SFME)) for the extraction of essential oil from Citrus sinensis peels. The essential oils were compared with regard to their chemical compositions, light microscopy analysis, total energy consumption, and antioxidant activity. GC/MS analysis allowed the identification of 28 compounds in the different essential oils. The principal identified component was limonene (86.7 %, 87.9 %, 88.2 %, 88.3 %, 85.4 % for HD, S-HD, US-HD, E-HD, and SFME, respectively), followed by β-pinene, sabinene, linalool and α-terpineol. The obtained essential oils were analyzed for their antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl radical scavenging method. Results indicated that essential oil extracted by SFME showed the highest antioxidant activity (IC50 = 0.0175 mg/ml) and extraction yield (3.58 % ± 0.05) consuming lower energy (0.312 kW h-1) in a shorter extraction time (30 min) comparing with the other tested techniques. Hence, the SFME would be an interesting green method for the recovery of essential oil from C. sinensis peels useful in agro-food, cosmetic, and pharmaceutical preparations as an alternative for undesirable chemical additives.

In this study, laurel essential oils were obtained by using solvent-free microwave extraction (SFME) and hydrodistillation (HD) methods from Laurus nobilis leaves and determined their antioxidant and antimicrobial activity. Extraction time was reduced by about 43% in SFME at 622 W and 67% in SFME at 249 W compared to hydrodistillation. Essential oil of laurel was extracted by SFME at 622 W (100%) and 249 W (40%) power levels and HD inhibited oxidation generated by ABTS radical by 93.88%, 94.13% and 92.06%, respectively. Trolox equivalent antioxidant capacities (TEAC) of essential oils were 0.18 mM/mL oil for SFME at 622 W, 1.36 mM/mL oil for SFME at 249 W and 2.40 mM/mL oil for HD (p L. nobilis were extracted by SFME at 100% and 40% power levels and HD inhibited linoleic acid peroxidation by 70.57%, 63.53% and 89.18% respectively. Inhibition effects of laurel essential oils obtained by SFME at different power levels and HD on DPPH radical cation oxidation were not significantly different. The strongest antioxidant activity against DPPH radical was found in the essential oil obtained by SFME at 100% power level. Essential oils displayed antimicrobial activity against Staphylococcus aureus 6538P, Escherichia coli O157:H7 and Salmonella typhimurium NRRL E 4463 except for Listeria monocytogenes. The inhibitory effect on Staphylococcus aureus 6538P survival of laurel oil obtained from SFME by using lower power level was found to be lower than that obtained from SFME at 100% power level and HD (p

The essential oils of Thymbra spicata var. spicata were obtained by both hydrodistillation and solvent-free microwave extraction methods. Chemical composition and antibacterial activity of the essential oils were examined. The main constituents of both essential oils obtained by solvent-free microwave extraction and hydrodistillation from Thymbra spicata var. spicata were carvacrol (44.8–36.1%), γ-terpinene (23.8–26.1%), and p-cymene (7.3–9.6%), respectively. The essential oil obtained from solvent-free microwave extraction contained substantially higher amounts of oxygenated compounds and lower amounts of monoterpenes than hydrodistillation. The antibacterial activities of the essential oils from solvent-free microwave extraction and hydrodistillation were evaluated by the disc diffusion method against six bacterial strains. The essential oil extracted by solvent-free microwave extraction was more effective than the essential oil extracted by hydrodistillation against the tested bacteria except for E. coli ATCC 25922- and S. aureus ATCC 25923+. Especially, S. aureus ATCC 25923+ was more sensitive against the essential oils obtained from Thymbra spicata var. spicata. Scanning electron microscopy measurements show that glands (that are filled with essential oils) were subjected to more severe thermal stresses and localized high pressure by microwave heating, the pressure build up within the glands could have exceeded their capacity for expansion and break down of cell walls. Solvent-free microwave extraction resulted in more extract release more rapidly than in hydrodestillation.

Solvent-free microwave extraction of essential oils from Thymus vulgaris L. and Melissa officinalis L.

The volatile chemical composition and qualitative as well as quantitative variation of the leaf and peel essential oils of five species belonging to Citrus genus were studied. The investigated Citrus species were Citrus aurantifolia (Christm.) Swingle, Citrus limon L. (Osbeck), Citrus maxima (Burm.f.) Merr. R, Citrus medica L. and Citrus medica *Citrus limon. Essential oils were isolated by hydrodistillation and analysed using GC-MS/FID. In total 49 compounds comprising of 83.1-99.0% of the volatile compositions were identified in five leaf essential oils whereas 45 compounds comprising of 97-99.4% of the volatile compositions were identified in peel essential oils. Oxygenated monoterpenes were the predominant composition present in the leaf oils of all Citrus species whereas sesquiterpene hydrocarbons were the main composition found in C. maxima leaf oil (39.9%). Monoterpene hydrocarbons were predominating in the isolated peel oils. Principal component analysis of Citrus species was employed to provide a comprehensive evaluation of essential oil components. Both PCA and cluster analysis of both leaf and peel essential oils were classified into two clusters and then subsequent subclusters, characterized according to the major essential oil components. Monoterpene hydrocarbons, oxygenated hydrocarbons and diterpenes were identified as the significant category of compounds characterised for Citrus essential oils.

Dancy tangerine trees have been imported from abroad and successfully cultivated in some newly reclaimed areas in Egypt. Reclamation areas (arid desert areas that are converted into areas suitable for agriculture) in Egypt are located in different geographical regions that differ from each other in weather conditions and soil characteristics, which may cause changes in essential oils, and thus a diversity of their biological activity. So, the changes in Dancy tangerine essential oils and their components were investigated under the conditions of two reclaimed desert areas (west and south) of Egypt to find out the extent of opportunities for expanding its cultivation in new reclamation regions as a natural source of essential oils, because if it is successful in those areas, the production of essential oils from plants will increase. The essential oils of leaves, flowers, and peels were separated by hydrodistillation and analyzed by GC/MS. The statistical analysis was carried out using ANOVA-1. Different variations were found in leaf, flower, and peel essential oils under both locations. Linalool was the main component in leaf essential oil but the major component in flower and peel essential oils was limonene. Oxygenated monoterpenes was the major chemical group in leaf essential oil, while monoterpene hydrocarbons were the basic group in flower and peel essential oils. Leaf, flower, and peel essential oil contents (% or ml/kg), major components, and major groups were higher in western samples than those from southern samples. Oxygenated diterpenes group appeared in leaf essential oil and was completely absent in both flowers and peels essential oils. This research paper determined that occupation of cultivation regions in reclaimed zones leads to changes in Dancy tangerine essential oil and its components. Also, this attempt serves as a hint to know adequate cultivation region for essential oil production according to the ingredients of benefit.

The essential oils (EOs) obtained by solvent-free microwave extraction (SFME) and hydrodistillation (HD) from endemic Origanum husnucanbaseri H. Duman, Aytaç & A. Duran were investigated using the gas chromatography–mass spectrometry system. The main constituents of both oils obtained from SFME and HD from O. husnucanbaseri are borneol (15.2–12.8%), α-terpineol (12.3–10.8%) and trans-sabinene hydrate (11.8–9.92%). The EO obtained from SFME contained substantially higher amounts of oxygenated compounds and lower amounts of monoterpenes than that from HD. The antibacterial activities of the EOs from SFME and HD were evaluated by the disc diffusion method against six bacterial strains. The EO extracted by SFME was more effective than the EO extracted by HD against the tested bacteria, except for Klebsiella pneumoniae American type culture collection (ATCC) 13883. Streptococcus pyogenes ATCC 19615 and Staphylococcus aureus ATCC 25923 in particular were more sensitive against the EO extracted by SFME.

The purpose of this study is to determine the chemical profile of the essential oils extracted from South African grown Citrus sinensis (L.) osbeck leaf and peels (fresh and dried) using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) and evaluate the essential oils anti-inflammatory potential. The analysis gave forty and fifty-four compounds accounting for 91.5 % and 99.6 % respectively identified in fresh and dried leaf essential oils. The major compounds in fresh leaf essential oil were sabinene (20.4 %) and terpinen-4-ol (13.2 %) while β-elemene (16.3 %) and sabinene (10.7 %) were identified in dried leaf essential oil. In fresh and dried peel oils, twenty-four and twenty-five compounds accounting for 99.3 % and 99.4 % respectively were identified whereby limonene (80.5-73.6 %) was the most prevalent compound. Citrus sinensis dried leaf and peel bioactive essential oils compounds significantly (p< 0.01) suppressed oedema in rats hind paw mostly at 200 mg/kg dose level indicating good anti-inflammatory activity. The abundance of limonene in Peels essential oil and β-elemene and sabinene in leaf essential oil played a significant role in anti- inflammatory properties of Citrus sinensis. To the best of our knowledge, this is the first comprehensive chemical profile report on South African grown C. sinensis despite being a major citrus producing country.

Lime essential oil (EO) is rich in different biological properties as an antiseptic and antimicrobial. Agrarian locations (ALs) in Egypt are characterized by different environmental characteristics that affect the content and composition of lime EO and thus its biological properties. Leaves, flowers, and peels of lime were collected from trees cultivated in three ALs, namely, north, central, and Upper Egypt. EO was separated by a hydro-distillation (HD) method; then analyzed using a Gas chromatography (GC) and Gas chromatography/mass spectrometry (GC/MS) analysis. The maximum contents of leaf (0.5 % and 1.3 ml/ 250g), flower (0.2 % and 0.5 ml/ 250g) and peel (0.3 % and 1.3 ml/ 250g) EOs were obtained from the samples collected from Upper Egypt. The major component of leaf and peel EOs were limonene. Dimethyl anthranilate was the main compound of flower EO. Oxygenated monoterpenes (OM) was the main group in leaf and flower EOs, while a monoterpene hydrocarbon (MH) was the main group of peel EO. The maximum values of limonene from leaf EO (40.3 %) and limonene from peel EO (36.5 %), dimethyl anthranilate (22.3 %), OM from flower EO (66.1 %), and MH (59.8 %) were obtained from the samples collected from Upper Egypt AL. The greatest amount of OM from leaf EO (55.9 %) has resulted from the samples collected from the central AL. It may be concluded that this study avail as a reference for choosing the adequate AL to extract the EO according to the compositions of interest.

The chemical composition of leaf and flower essential oils of Origanum onites L. were analyzed using Thermo Scientific TSQ GC-MS/MS. Also, antioxidant activities of the leaf and flower essential oils were investigated by using DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical scavenging activity and β-carotene linoleic acid assays. BHA (Butylated hydroxyanisole) and BHT (Butylated hydroxytoluene) were used as standards. The essential oil yields of O. onites were 1.75 % for leaves, and 4.25 % for flowers. A total of twenty-three compounds representing 99.9 % of leaf oil and twenty-four compounds constituted 99.6 % of the flower oil were determined. Oxygenated monoterpenes were detected at a high percentage (69.2 %) in leaf essential oil and carvacrol (64.9 %) was determined as the main compound. Also, flower essential oil was dominated by sesquiterpene hydrocarbons (73.5 %) and α-cubebene (36.4 %) was determined as major compound. For leaf oil, a high antioxidant capacity was determined, primarily due to carvacrol and p-cymene.

This study reports the essential oil composition and headspace volatiles profile of Achillea coarctata Poir. from Serbia. The inflorescences, stems and leaves, and the aerial parts of A. coarctata were analyzed separately. Germacrene D, α-terpineol and 1,8-cineole were the main constituents of the aerial parts essential oil; 1,8-cineole, cis-cadin-4-en-7-ol and α-terpineol were the most dominant compounds in the inflorescence essential oil, while the most abundant components in the stem and leaf oil were germacrene D, cis-cadin-4-en-7-ol and ledol. The percentages of monoterpenoids and sesquiterpenoids in the aerial parts were the same, while there were differences in distribution of these compound classes in inflorescence and stem and leaf essential oils. The major components of the headspace volatiles were the same for aerial parts, inflorescence and stem and leaves: 1,8-cineole, β-pinene and α-pinene.