Limonene Oxide Research Articles

Microdroplets Accelerate Ring Opening of Epoxides.

The nucleophilic opening of an epoxide is a classic organic reaction that has widespread utility in both academic and industrial applications. We have studied the reaction of limonene oxide with morpholine to form 1-methyl-2-morpholino-4-(prop-1-en-2-yl) cyclohexan-1-ol in bulk solution and in electrosprayed microdroplets with a 1:1 v/v water/methanol solvent system. We find that even after 90min at room temperature, there is no product detected by nuclear magnetic resonance spectroscopy in bulk solution whereas in room-temperature microdroplets (2-3μm in diameter), the yield is already 0.5% in a flight time of 1ms as observed by mass spectrometry. This constitutes a rate acceleration of ~ 105 in the microdroplet environment, if we assume that as much as 5% of product is formed in bulk after 90min of reaction time. We examine how the reaction rate depends on droplet size, solvent composition, sheath gas pressure, and applied voltage. These factors profoundly influence the extent of reaction. This dramatic acceleration is not limited to just one system. We have also found that the nucleophilic opening of cis-stilbene oxide by morpholine is similarly accelerated. Such large acceleration factors in reaction rates suggest the use of microdroplets for ring opening of epoxides in other systems, which may have practical significance if such a procedure could be scaled. Graphical Abstract This graphical image is distorted. It is too extended in the vertical direction. Please fix.ᅟ.

Limonene oxidation over Ti-MCM-41 and Ti-MWW catalysts with t-butyl hydroperoxide as the oxidant

This paper presents the method of limonene epoxidation over Ti-MCM-41 and Ti-MWW catalysts in the presence of t-butyl hydroperoxide as an oxidant. Natural limonene used in the epoxidation process was obtained via steam distillation (97% purity). The purpose of the research was to obtain the highest yield of 1,2-epoxylimonene, but the performed studies showed that the process of limonene epoxidation is more complex because in addition to epoxidation products (1,2-epoxylimonene and its diol which were formed usually in small amount) also the following oxygenated derivatives of limonene are formed: carvone, carveol, and perillyl alcohol (products of allylic oxidation (hydroxylation) at positions 6 and 7 in limonene molecule). Therefore, ultimately, the most favorable conditions for the limonene oxidation process were selected at the highest conversion of limonene and at high values of perillyl alcohol and carveol or one of these two products. Perillyl alcohol and carveol have found numerous applications in medicine, among others, therefore this direction seems to be the most beneficial. This also work presents the short characteristization of the titanium silicate Ti-MCM-41 and Ti-MWW catalysts used in the research, taking into account their structure, properties and applications are presented.

Whole-Genome Sequencing and Genetic Analysis Reveal Novel Stress Responses to Individual Constituents of Essential Oils in Escherichia coli.

Food preservation by the use of essential oils (EOs) is being extensively studied because of the antimicrobial properties of their individual constituents (ICs). Three resistant mutants (termed CAR, CIT, and LIM) of Escherichia coli MG1655 were selected by subculturing with the ICs carvacrol, citral, and (+)-limonene oxide, respectively. These derivative strains showed increased MIC values of ICs and concomitantly enhanced resistance to various antibiotics (ampicillin, trimethoprim, chloramphenicol, tetracycline, kanamycin, novobiocin, norfloxacin, cephalexin, and nalidixic acid) compared to those for the parental strain (wild type [WT]). Whole-genome sequencing (WGS) of these hyperresistant strains permitted the identification of single nucleotide polymorphisms (SNPs) and deletions in comparison to the WT. In order to analyze the contribution of these mutations to the increased antimicrobial resistance detected in hyperresistant strains, derivative strains were constructed by allelic reversion. A role of the SoxR D137Y missense mutation in CAR was confirmed by growth in the presence of some ICs and antibiotics and by its tolerance to ICs but not to lethal heat treatments. In CIT, increased resistance relied on contributions by several detected SNPs, resulting in a frameshift in MarR and an in-frame GyrB ΔG157 mutation. Finally, both the insertion resulting in an AcrR frameshift and large chromosomal deletions found in LIM were correlated with the hyperresistant phenotype of this strain. The nature of the obtained mutants suggests intriguing links to cellular defense mechanisms previously implicated in antibiotic resistance.IMPORTANCE The antimicrobial efficacy of ICs has been proven over the years, together with their potential to improve traditional heat treatments by reducing treatment intensity and, consequently, adverse effects on food quality. However, the mechanisms of bacterial inactivation by ICs are still not well understood, in contrast to antibiotics. We performed WGS of three E. coli strains that are hyperresistant to ICs. The information provided detailed insight into the mechanisms of bacterial resistance arising from exposure to carvacrol, citral, and (+)-limonene oxide. Future experiments will undoubtedly yield additional insights into genes and pathways contributing to the acquisition of endogenous resistance to ICs.

Life cycle assessments of bio-based sustainable polylimonene carbonate production processes

Biomass is a promising feedstock for the production of sustainable biopolymers, which could offer a significant reduction of the adverse environmental impacts associated with conventional petroleum-based polymers. To further evaluate their potential, this study investigated the environmental impacts associated with the production of the newly proposed biopolymer polylimonene carbonate. Different feedstocks (citrus waste and microalgae) were selected and a conceptual process design from limonene oxidation to polymer synthesis was completed. Using life cycle assessment, the potential for energy integration and the contributions of individual process sections on the overall process environmental impacts were thoroughly analysed. The results showed, that sustainable polylimonene carbonate synthesis was limited by the use of tert-butyl hydroperoxide as the limonene oxidation agent and consequently, a more environmentally-friendly and energy-efficient limonene oxidation method should be developed. Based on the economic analysis, the polymer cost was estimated to range from $1.36 to $1.51 kg−1, comparable to the costs of petrol-based polystyrene ($1.2 to $1.6 kg−1). Moreover, this study found that both feedstock selection and the biowaste treatment method have significant effects on the process environmental impacts, and a carbon negative process was achieved when applying the waste biomass for electricity generation. Therefore, it was concluded that future process designs should combine polymer production with the co-generation of energy from waste biomass.

GAS CHROMATOGRAPHY COMBINED TO MASS SPECTROMETRY ANALYSES OF SOME CITRUS PEELS BIOACTIVE COMPOUNDS AGAINST THE COTTON LEAFWORM, SPODOPTERA LITTORALIS (BOISD.)

Hexane (Hex) extracts of fresh navel orange (citrus sinensis) and lemon (citrus limon) peel were prepared to isolate and identify toxic bioactive secondary metabolites for potential use as natural ecofriendly biopesticides against the cotton leafworm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae). Hex extracts were fractionated by column chromatography. The fractions that showed activity against the larvae, were identified and quantified by gas chromatography combined to mass spectrometry(GC/MS), after checking component profile by thin layer chromatography (TLC). The results revealed that F2 and F3 fractions were the toxic active fractions of both lemon and orange peel Hex extracts, but lemon fractions were more toxic than orange ones. F2 and F3 fractions of orange extract causd 60 and 20% larval mortality, respectively. Both lemon extract fractions caused 100% morality. Orange fractions had approximately equal dlimonene content (≈86%) as illustrated by mass spectral fragmentation pattern. However, F2 fraction contained slightly higher amounts of linalool, α-terpinol and citral than F3 fraction. The active fraction of both lemon and orange peel extracts contained d-limonene, α-pinene, linalool, citronllal and citral. Limonene oxide, geranial and terpineol were only detected in orange peel extracts. The results indicated that secondary metabolites quality and quantity differ according to the citrus spp., and the quantity of d-limonene is much lower (≈15%) in lemon than orange extracts in spite of lemon peel was more toxic than the orange. However, d-limonene was a major compound in both extracts. The results suggest that citrus extract contains many toxic compounds, other than limonene, and /or they could potentiate each other to give the observed toxicity. It could be concluded that the quantity of d-limonene is not a determinant factor, but it is probable that other metabolites confer toxicity allover citrus extract depending on the species.

Epoxidation of natural limonene extracted from orange peels with hydrogen peroxide over Ti-MCM-41 catalyst

Abstract The paper presents the oxidation of natural limonene (extracted from waste orange peels) by 60 wt% hydrogen peroxide, in the presence of Ti-MCM-41 catalyst and in methanol as the solvent. The aim of the research was to develop the most favorable technological parameters for the process of limonene oxidation (temperature, molar ratio of limonene to hydrogen peroxide, methanol concentration, Ti-MCM-41 catalyst content and reaction time) by analyzing changes in the main functions describing this process: the conversion of limonene, selectivities of appropriate products, the conversion of hydrogen peroxide and the effective conversion of hydrogen peroxide. The process is environmentally friendly process and it uses renewable raw material - limonene and a safe oxidant -hydrogen peroxide. During the study, very valuable oxygenated derivatives of limonene were obtained: 1,2-epoxylimonene, its diol, carvone, carveol, and perillyl alcohol. These compounds are used in medicine, cosmetics, perfumery, food and polymers industries.

Functional characteristics of chemosensory proteins in the sawyer beetle Monochamus alternatus Hope.

The Japanese pine sawyer, Monochamus alternatus Hope (Coleoptera: Cerambycidae), is a major pest of pines and it is also the key vector of the exotic pinewood nematode in China. In the present study, we cloned, expressed, and purified a chemosensory protein (CSP) in M. alternatus. We surveyed its expression in various developmental stages of male and female adult tissues and determined its binding affinities for different pine volatiles using a competitive binding fluorescence assay. A CSP known as CSP5 in M. alternatus was obtained from an antennal cDNA library and expressed in Escherichia coli. Quantitative reverse transcription polymerase chain reaction results indicated that the CSP5 gene was mainly expressed in male and female antennae. Competitive binding assays were performed to test the binding affinity of recombinant CSP5 to 13 odour molecules of pine volatiles. The results showed that CSP5 showed very strong binding abilities to myrcene, (+)-β-pinene, and (-)-isolongifolene, whereas the volatiles 2-methoxy-4-vinylphenol, p-cymene, and (+)-limonene oxide have relatively weak binding affinity at pH 5.0. Three volatiles myrcene, (+)-β-pinene, and (-)-isolongifolene may play crucial roles in CSP5 binding with ligands but this needs further study for confirmation. The sensitivity of insect to host plant volatiles can effectively be used to control and monitor the population through mass trapping as part of integrated pest management programs.

Enhanced catalytic oxidation of monoterpenes by zeolite-Y entrapped iron complex: spectral studies and mechanistic vision

[Fe(L)2(H2O)2]–Y complex (where, L = (Z)-2-((4-hydroxybenzylidene)-amino)benzoic acid) has been synthesized by Flexible Ligand (FL) method and characterized by chemical analysis (CHN, ICP-OES, TGA, AAS), diffraction method (XRD), absorption spectroscopy (FTIR, UV–Vis), BET and SEM techniques. To investigate the catalytic performance (activity, stability, and reusability), [Fe(L)2(H2O)2]–Y was employed as heterogeneous catalyst in the liquid phase oxidation of α-pinene and limonene with H2O2 oxidant. [Fe(L)2(H2O)2]–Y catalyzed the oxidation of α-pinene via free radical formation as confirmed by in-situ IR and DR UV–Vis spectroscopy. [Fe(L)2(H2O)2]–Y showed conversion of α-pinene (67%) and limonene (79%) with better TONs, which is far better performance than neat iron complex.

Stability and release behavior of encapsulated flavor from spray-dried Saccharomyces cerevisiae and maltodextrin powder

Yeast cells (Saccharomyces cerevisiae), from which β-glucans have been partially extracted, were used to encapsulate flavor inside the lipid bilayer membrane as natural encapsulant. The focus of this study was to investigate the release and stability of flavors (d-limonene and ethyl hexanoate) encapsulated in yeast cells and maltodextrin (MD) (DE = 19) by spray drying. The release behavior of encapsulated flavors from yeast cells was measured at 40, 60, 80, and 105 °C with different moisture content (0, 50, 100, and 200% of powder). Water affected flavor release from the yeast cells. The release rate constants were correlated using Gaussian distribution of the activation energy of the release rate constants. The release of d-limonene from the spray-dried MD powder showed a different trend than that of yeast cells at various temperatures. The activation energies of the release rate constant for ethyl hexanoate and d-limonene from yeast were 55 and 49 kJ/mol, respectively, under a wet condition. The formation rates of limonene oxide and carvone were slower in yeast than that of MD powder at 30 °C after 2 months.

Senna occidentalis (L.) Link and Senna hirsuta (L.) H. S. Irwin & Barneby: constituents of fruit essential oils and antimicrobial activity

Senna occidentalis and S. hirsuta are mostly gathered from the wild for medicinal use and have a disagreeable odour when crushed. The volatile oils isolated from fresh fruits of S. occidentalis and S. hirsuta were subjected to gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS) and antimicrobial assays. GC and GC-MS analyses permitted the identification of 58 constituents. S. occidentalis oil was dominated by cyperene (10.8%), β-caryophyllene (10.4%), limonene (8.0%) and caryophyllene oxide (6.8%). The main components of S. hirsuta fruit oil were benzyl benzoate (24.7%), τ-cadinol (18.9%), 2,5-dimethoxy-p-cymene (14.6%) and β-caryophyllene (5.1%). S. occidentalis fruit oil exhibited better antimicrobial activity (MIC 78–312 μg/mL) against Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Aspergillus niger compared with S. hirsuta oil. The compositions and the activities of the fruit essential oils of S. occidentalis and S. hirsuta are reported for the first time.

Variation of Volatile Oil Contents and Constituents in Lesser Known Plant Species for Formulating Mosquito Repellents

Volatile oils also known as essential oils are found in aromatic plants and contain volatile compounds that contribute to particular fragrances and flavours. Main uses of these volatile oils range from aroma therapy, food additives, cosmetics, natural medicines to insect repellents. Although there are common plants that produce volatile oils capable as mosquito repellents, certain plants are not known for this ability or under-utilised. Therefore, this research aimed at identifying lesser known volatile oil producing species and to formulate the plant products into safe and low cost insect repellents. An expert survey was first conducted by interviewing 7 subject experts and 13 local ayurvedic practitioners to identify the existing and potential volatile oil producing plant species which can be used as mosquito repellents. This survey identified 60 species and out of those 16 species (Ocimum tenuiflorum, Azadirachta indica, Acorus calamus, Atalantia ceylanica, Ocimum sanctum, Plectranthus amboinicus, Plectranthus zatarhendi, Vetiveria zizanioides, Acronychia pendunculata, Osmium gratissium, Aegle marmelos, Limonia acidissima, Murraya koenigii, Ricinus communis, Cinnamomum verum and Tagetes erecta) was selected after a weighted ranking system for further study. Hydro-distillation for 5 hours was used with 100 g of leaves for oil extraction for each species with three replicates. Particle size was kept at 1.5 cm for this purpose with 1:12 water ratio. Oil constituents were identified using GC-MS analysis. According to the results C. verum yielded the highest mean oil content (0.0113±0.0024 ml/g) followed by A. marmelos (0.0095±0.0018 ml/g). 0.0018 ml/g). 0.0018 ml/g). 0.0018 ml/g). 0.0018 ml/g). A. ceylanica bears the highest number of constituents followed by M. koenigii and L. acidissima. However, the highest number of constituents which act as mosquito repellents showed by L. acidissima and C. verum as the present study. Those constituents are α-Pinene, 3-Carene, Terpinolene, Caryophyllene oxide in C. verum and α-Pinene, Limonene, Terpinolene and Caryophyllene oxide in L. acidissima. Keywords: Volatile oil, Lesser known plants, Oil content, Oil constituents, Mosquito repellent Acknowledgement: Centre for Forestry and Environment, University of Sri Jayewardenepura, Central Instrumentation facility of the Faculty of Applied Sciences, University of Sri Jayewardenepura and Sadaharitha Plantations Limited.

Effect of oxygen and heating on aromas of pummelo (Citrus maxima) essential oil

Objective: To investigate effects of oxygen and heating on aromas and volatile components of pummelo essential oil (PEO). Method: The PEOs were analyzed by sensory evaluation, gas chromatography coupled with mass spectrometry (GC-MS), GC-olfactometry (GC-O) and sensory reconstruction analysis. Results: The PEO co-treated by oxygen and heating exhibited significant differences in both aromas and volatile compositions from those of the fresh, the nitrogen-protected, the heated and the oxygen-exposed PEOs. The strong sweet and floral notes of the oxygen and heating co-treated PEO were attributed to high concentration of limonene oxides; the strong minty note was resulted from the increase of L-carvone. Conclusion: The results indicate that limonene oxides and L-carvone could significantly change the aroma of PEO co-treatment by oxygen and heating, providing valuable information for the production and storage of aromatic products of PEO.

Photocatalytic partial oxidation of limonene to 1,2 limonene oxide.

The silylation of crystalline TiO2 P25, commonly used for photocatalytic degradation of pollutants, results in an exceptionally selective catalyst for the aerobic limonene epoxidation to 1,2-limonene oxide under solar light irradiation. The hypothesized mechanism involves the singlet oxygen generated through energy transfer from the excited TiO2 to adsorbed O2 molecules. The reaction product is the valued precursor of bio-based poly(limonene carbonate), a thermoplastic polymer of superior thermal and optical properties whose industrial production is in need of an efficient green synthesis of limonene oxide.

Zeolite-Y entrapped metallo-pyrazolone complexes as heterogeneous catalysts: Synthesis, catalytic aptitude and computational investigation

Transition metal [M = VO(IV) and/or Co(II)] complexes with Schiff base ligand (Z)-3-methyl-1-phenyl-4-(2,2,2-trifluoro-1-(2-hydroxyphenyl)imino)ethyl)-1H-pyrazol-5-ol (H2L) have been entrapped in the super cages of zeolite-Y by Flexible Ligand Method. These nanohybrid materials have been characterized by preferential physico-chemical techniques such as ICP-OES, elemental analyses, (FT-IR, 1H and 13C-NMR and electronic) spectral studies, BET, scanning electron micrographs (SEMs), AAS, X-ray diffraction patterns (XRD) and thermogravimetric analysis. The density functional theory calculations are performed to find optimized structures together with the bond angles, bond lengths, dihedral angles and electronic properties of ligand and neat complexes. The catalytic competence of zeolite-Y entrapped metallo-pyrazole complexes was examined by the oxidation of olefins viz. limonene, cyclohexene, styrene, and α-pinene using H2O2 as an oxidant. So as to ensure the shielding effect of the nanohybrid over the active center on the catalytic properties, the performance of the entrapped complexes (heterogeneous system) was weighing up against the neat complexes (homogeneous system). The effect of experimental variables (such as solvents, mole ratio of substrate and oxidant, the amount of catalyst and reaction time) with their probable justification on the conversion of limonene was discussed. Under the optimized reaction conditions, [VO(L)·H2O]-Y was found to be potential candidate, achieving 87.44%, 90.01%, 82.01%, and 85.44% conversions of limonene, cyclohexene, styrene, and α-pinene oxidation reactions, respectively.

Thermodynamic Analysis of α‐Pinene and Limonene Allylic Oxidation over a FePcCl16‐NH2‐SiO2 Catalyst

AbstractFrom oxidation over a FePcCl16‐NH2‐SiO2 catalyst and tert‐butyl hydroperoxide (TBHP) as oxidant, verbenone, α‐pinene epoxide, and verbenol were obtained from α‐pinene while carvone, limonene 1,2‐epoxide and carveol were produced from limonene. TBHP decomposes into O2, tert‐butanol, and di‐tert‐butyl peroxide (DTBP). With the aim to perform a batch‐reactor conceptual design, α‐pinene and limonene oxidation was thermodynamically analyzed. Standard enthalpy and entropy of formation, liquid heat capacity, enthalpy of reaction and vaporization, and Gibbs free energy were determined by group contribution methods using Aspen Plus® simulation. Although the results depend on the method, it was found that α‐pinene and limonene oxidations were exothermic and spontaneous at the selected reaction temperature. However, TBHP decomposition into O2, tert‐butanol, and DTBP was an endothermic reaction.

Montmorillonite as the catalyst in oxidation of limonene with hydrogen peroxide and in isomerization of limonene

Abstract In our studies montmorillonite (MMT) was used as the heterogeneous, natural catalyst. This material was previously prepared by bentonite purification with help of the sedimentation method. The obtained catalyst was characterized by: XRD, SEM, BET and EDX. Catalytic tests with montmorillonite as the catalyst were performed with the natural terpene – R-(+)-limonene. This compound was oxidized with hydrogen peroxide and, moreover, in the separate process it was also isomerized. As the main products of limonene oxidation were detected: (1,2-8,9)-diepoxide, perillyl alcohol, carvone, carveol, 1,2-epoxylimonene and 1,2-epoxylimonene diol. In the isomerization of R-(+)-limonene were formed: terpinenes, terpinolene and p-cymene. Conversions of limonene in these processes reached 70–80%. The application of montmorillonite (the natural of origin) in the studied processes (oxidation and isomerization) is environmentally friendly, it allows to reduce the cost of the studied processes. The resulting products of the processes of oxidation and isomerization of R-(+)-limonene have many applications.

Kinetics of the Aqueous Phase Reactions of Atmospherically Relevant Monoterpene Epoxides.

Laboratory and field measurements have demonstrated that an isoprene-derived epoxide intermediate (IEPOX) is the origin of a wide range of chemical species found in ambient secondary organic aerosol (SOA). In order to explore the potential relevance of a similar mechanism for the formation of monoterpene-derived SOA, nuclear magnetic resonance techniques were used to study kinetics and reaction products of the aqueous-phase reactions of several monoterpene epoxides: β-pinene oxide, limonene oxide, and limonene dioxide. The present results, combined with a previous study of α-pinene oxide, indicate that all of these epoxides will react more quickly than IEPOX with aqueous atmospheric particles, even under low-acidity conditions. As for α-pinene oxide, the observed products can be mainly rationalized with a hydrolysis mechanism, and no long-lived organosulfate or nitrate species nor species that retain the β-pinene bicyclic carbon backbone are observed. As bicyclic ring-retaining organosulfate and nitrate species have been previously observed in monoterpene-derived SOA, it appears that monoterpene-derived epoxides may not be as versatile as IEPOX in producing a range of SOA species, and other mechanisms are needed to rationalize organosulfate and nitrate formation.

Pro-oxidative effects of spray drying orange oil in a bench top dryer

ABSTRACTThe influence of potential heat exposure during spray drying on the oxidative stability of spray dried orange oil was studied. The design of some of the table top spray driers expose dried product to dryer exit air temperatures in the powder collection chamber or on the walls of the dryer if there is an accumulation of material on the drying chamber walls. This heat exposure may accelerate oxidation of the product in subsequent storage. To determine the potential for heat damage to affect oxidation of the powders produced, an orange oil infeed emulsion (carrier material - modified starch) was prepared and spray dried using the sample collection chamber supplied by the manufacturer as standard equipment. The spray dryer was then modified to extend the collection chamber inlet such that the product remained cooler than in the standard collection chamber. In this study, the spray dryer was operated for 1 h (inlet air temperature; 180°C and an exit air temperature; 100°C). Thus, the spray dry product could have been exposed to as much as 1 h of heating in the collection chamber (potentially at temperatures as high as the exit air temperature). In the case of spray drying with a collection chamber extension, the collected product was maintained at ca. room temperature. This would approximately mimic the heat exposure powders receive in an industrial spray dryer. Powders produced using both equipment designs were taken from both the collection and drying chambers, adjusted in water activity (0.33) under a nitrogen environment, and then put into storage in an incubator maintained at 35°C for 4 weeks (exposed to air). The ratio of limonene oxide to limonene was used to monitor oxidation using gas chromatography. This study showed a substantial increase in rate of oxidation of the spray dried powder from the table top spray dryer with the standard commercial collection chamber and much less in case of an extended collection chamber. The powder from the respective drying chamber also showed a higher rate of oxidation in comparison to its collection chamber. Thus, we urge researchers studying heat damage (e.g., oxidation) of powders produced on the table top dryers to be conscious of overestimating heat damage during drying.

Chemical Composition, Antioxidant and Anti-bacterial Potential of Essential Oil of Medicinal plant Isodon rugosus

Isodon rugosus is a medicinally valuable herb containing a variety of important secondary metabolites and essential oil with important chemical constituents of pharmaceutical precursors. The active components of volatile oil of I. rugosus were analyzed using GC-MS. Anti-oxidant potential of the oil was assessed with 2, 2-diphenyl-1-picrylhydrazyl (DPPH). Anti-bacterial power of the essential oil accessed disc diffused method. A total of 19 constituents were quantified and identified with different concentrations in essential oil. Among which Caryophyllene oxide was 28.99%. Limonene oxide cis was 26.52%, (Z, E)-Farnesol was 17.34%, followed by 1-erpinen-4-ol 3.33%, o-Cymene 2.04 while the concentrations of rest of constituents were between 1.11 to 0.2%. The investigation showed that the essential oil of I. rugosus possessed significant antibacterial and antioxidant potential

Essential oil; lavender; antimicrobial activity; bioactive compound; GC-MS; Mycobacterium smegmatis.

<p>Tuberculosis (TB) is a great cause of morbidity and mortality around the world. The increasing incidence of multidrug-resistant (MDR) <em>Mycobacterium tuberculosis </em>and co-infection TB-AIDS led to the need to develop new TB drugs, and plants could be a source of them. The hexane extract of <em>Citrus sinensis </em>with anti-TB activity was analyzed by GC-MS. This analysis showed the presence of 40 volatile components, including monoterpenes (81.74%), sesquiterpenes (1.32%), fatty acids (1.15%), and some other oxygenated non-aromatic compounds (15.73%). Some identified compounds were tested against <em>M. tuberculosis </em>H37Rv, and one clinical isolated MDR <em>M. tuberculosis </em>strain. Results showed that palmitic acid, decanal, caryophyllene oxide, and <em>cis</em>-limonene oxide contributed to the anti-TB activity of hexane extract of <em>C. sinensis </em>peel.</p>