Comparative chemical composition,antioxidant and hypoglycaemic activities of Juniperus oxycedrus ssp. oxycedrus L. berry and wood oils from Lebanon

Juniper (Juniperus oxycedrus) is used in European cuisine for its distinguishing flavour. J. oxycedrus ssp. oxycedrus berry and wood essential oils were tentatively identified by GC and GC/MS. Fifty compounds were identified in the berry oil and 23 compounds were identified in the wood oil. The J. oxycedrus ssp. oxycedrus berry oil was characterised by high contents of α-pinene (27.4%) and β-myrcene (18.9%). Other important compounds were α-phellandrene (7.1%), limonene (6.7%), epi-bicyclosesquiphellandrene (2.3%) and δ-cadinene (2.2%) while, in the wood oil, δ-cadinene (14.5%) is a major main component, together with cis-thujopsene (9.2%) and α-muurolene (4.9%). In vitro evaluation of antioxidant activity by the DPPH method showed a significant activity for both oils with IC₅₀ values of 1.45 μl/ml for wood and 7.42 μl/ml for berries. Hypoglycaemic activity was investigated through the inhibition of α-amylase. The results revealed that oil obtained by hydrodistillation from J. oxycedrus ssp. oxycedrus wood exhibits an interesting activity with IC₅₀ of 3.49 μl/ml.     

Chemical composition and antioxidant activity of the essential oil of Clinopodium vulgare L.

This study was designed to examine the chemical composition and in vitro antioxidant activity of the essential oil of Clinopodium vulgare. GC–MS analysis of the oil resulted in the identification of 40 compounds, representing 99.4% of the oil; thymol (38.9%), γ-terpinene (29.6%) and p-cymene (9.1%) were the main components. The samples were subjected to a screening for their possible antioxidant activity by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene-linoleic acid assays. In the first case, IC₅₀ value of the C. vulgare essential oil was determined as 63.0 ± 2.71 μg/ml. IC₅₀ value of thymol and γ-terpinene, the major compounds of the oil, was determined as 161 ± 1.3 μg/ml and 122 ± 2.5 μg/ml, respectively, whereas p-cymene did not show antioxidant activity. In β-carotene-linoleic acid system, C. vulgare essential oil exhibited 52.3 ± 1.19% inhibition against linoleic acid oxidation. In both systems, antioxidant capacities of BHT, curcumine and ascorbic acid were also determined in parallel experiments.     

Composition,antimicrobial, antiradical and spasmolytic activity of Ferula heuffelii Griseb. ex Heuffel (Apiaceae) essential oil

The essential oil from underground parts of Ferula heuffelii from N.E. Serbia, was analysed using GC and GC–MS. The main compounds of the essential oil were elemicin (35.4%) and myristicin (20.6%). The essential oil exhibited the best antimicrobial activity against two strains of Candida albicans (MIC = 7.0 and 13.7 μg/ml), as well as against Micrococcus luteus (MIC = 13.7 μg/ml), Staphylococcus epidermidis (MIC = 17.6 μg/ml), Bacillus subtilis (MIC = 21.1 μg/ml) and Micrococcus flavus (MIC = 28.2 μg/ml). In the DPPH radical scavenging assay, essential oil showed substantial activity with SC₅₀ = 22.43 μl/ml. The essential oil was also tested for antispasmodic activity. It inhibited spontaneous contraction of isolated rat ileum dose-dependently, and at the concentration of 86.64 μg/ml exhibited 50% of the maximum effect of atropine. After incubation with 75.00 μg/ml of essential oil, acetylcholine did not induce contractions of ileum, and at 250.00 μg/ml, the essential oil almost completely abolished the spasmodic effect of potassium chloride (80 mM).     

Composition of the essential oil of Daucus gingidium L. ssp. gingidium

The essential oils obtained from leaves and fruits of Daucus gingidium ssp. gingidium have been studied. The main constituents of the essential oil from the leaves were sabinene (26.8%), α-pinene (10.8%), germacrene D (6.9%) and limonene (5.7%). Sabinene (60.6%) was the main compound identified in the essential oil of the fruits, followed by α-pinene (12.2%) and 4-terpineol (5.4%). Furthermore, qualitative and quantitative considerations about differences with literature data on Daucus carota have been made in order to confirm the species status of D. gingidium.     

Major chemotypes and antioxidative activity of the leaf essential oils of Cinnamomum osmophloeum Kaneh. from a clonal orchard

Essential oils of 92 cutting clones from a clonal orchard of Cinnamomum osmophloeum Kaneh. were obtained by hydrodistillation and characterised by gas chromatography–mass spectrometry. Our results showed that the yields of essential oils ranged between 0.09% and 2.65% (vol/fresh wt). The constituents of essential oils varied among samples. The major chemotypes classified in the individual cutting clones were cinnamaldehyde (50 plants, representing 50–95% of the total volatiles), linalool (1 plant, 73.3%), β-cubebene (2 plants, 59.4% and 78.7%), and cinnamyl acetate (1 plant, 61.8%). The antioxidant activities of the four chemotypes were determined using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The antioxidant activities of the essential oil decreased in the order of cinnamyl acetate > cinnamaldehyde > β-cubebene > linalool. Indigenous cinnamon oil extract showed a good free radical-scavenging capacity at all concentrations studied, except at 2 μg/ml. The scavenging activity increased with increasing concentration of the extract. The capability of the four essential oil chemotypes to reduce the stable radical, DPPH, to DPPH-H was assayed by a decrease in the IC₅₀ values of 10.4 (cinnamyl acetate type) to 29.7 (linalool type) μg/ml. These results suggest that the leaf essential oil of C. osmophloeum possesses chemical compounds with antioxidant activity which can be used as natural preservatives in food and/or by the pharmaceutical industry. Trees in this plantation which can be used for further propagation for the production of chemotypes of interest were identified.     

Essential oil composition of Pistacia lentiscus L. and Myrtus communis L.: Evaluation of antioxidant capacity of methanolic extracts

The seasonal variation of the essential oil composition, the antioxidant activity (DPPH, FRAP assays) and the total phenolic content (Folin-Ciocalteu assay) of two aromatic wild plants, Pistacia lentiscus L. (Anacardiaceae) and Myrtus communis L. (Myrtaceae), grown in Zakynthos, a Greek island, was investigated. The essential oil was obtained by hydrodistillation and subsequently analysed by GC–MS.     

Evaluation of the antioxidant activity of Ruellia tuberosa

The antioxidant activity of Ruellia tuberosa L. (Acanthaceae) was investigated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging assay and the hydrogen peroxide-induced luminol chemiluminescence assay. The methanolic extract (ME) and its four fractions of water (WtF), ethyl acetate (EaF), chloroform (CfF), and n-hexane (HxF) were prepared and then subjected to antioxidant evaluation. The results of both methods revealed that R. tuberosa possesses potent antioxidant activity. The antioxidant activities of the different fractions tested decreased in the order of EaF > CfF > ME > WtF > HxF according to the hydrogen peroxide-induced luminol chemiluminescence assay, and results were the same with the exception of the rank order of HxF and WtF according to the DPPH free radical-scavenging assay. The results provide useful information on the pharmacological activities associated with free radicals of this traditional folk remedy.     

Radical scavenging and antibacterial properties of the extracts from different Thymus pulegioides L. chemotypes

Radical scavenging and antibacterial properties of large thyme extracts isolated from five chemotypes of Thymus pulegioides L. growing wild in Lithuania were studied. The chemotypes were defined according to the main essential oil components: linalool (L), geranial/geraniol/neral (G/G/N), thymol (T), carvacrol/γ-terpinene/p-cymene (C/γT/pC) and thymol/carvacrol/γ-terpinene/p-cymene (T/C/γT/pC). The contents of phenolic compounds, flavonoids and flavonols were determined. It was found that the extracts of phenolic chemotypes containing remarkable concentrations of thymol and/or carvacrol were stronger DPPH and ABTS free radical scavengers in the model systems. The antibacterial activity of the extracts depended on the plant chemotype, extract preparation, solvent used and finally the sensitivity of bacteria. Bacillus cereus, Micrococcus luteus, Staphylococcus epidermidis and Staphylococcus aureus were the most sensitive to the all extracts applied, whereas Escherichia coli, Salmonella typhimurium and Enterobacter aerogenes remained resistant.     

Application of artificial neural networks to the prediction of the antioxidant activity of essential oils in two experimental in vitro models

Introduction

The antioxidant properties of essential oils (EOs) have been on the centre of intensive research for their potential use as preservatives or nutraceuticals by the food industry. The enormous amount of information already generated on this subject provides a rich field for data-miners as it is conceivable, with suitable computational techniques, to predict the antioxidant capacity of any essential oil just by knowing its particular chemical composition. To accomplish this task we here report on the design, training and validation of an Artificial Neural Network (ANN) able to predict the antioxidant activity of EOs of known chemical composition.

Methods

A multilayer ANN with 30 input neurons, 42 in hidden layers (20 → 15 → 7) and one neuron in the output layer was developed and run using Fast Artificial Neural Network software. The chemical composition of 32 EOs and their antioxidant activity in the DPPH and linoleic acid models were extracted from the scientific literature and used as input values. From the initial set of around 80 compounds present in these EOs, only 30 compounds with relevant antioxidant capacity were selected to avoid excessive complexity of the neural network and minimise the associated structural problems.

Results and discussion

The ANN could predict the antioxidant capacities of essential oils of known chemical composition in both the DPPH and linoleic acid assays with an average error of only 3.16% and 1.46%, respectively. We also discuss on the contribution of different compounds to these chemical activities.

Conclusions

These results confirm that artificial neural networks are reliable, fast and cheap tools for predicting antioxidant activity of essential oils from some of its components and can be used to model biochemical properties of complex natural products including the prediction of parameters associated with nutraceutical properties of food ingredients.     

Chemical composition and antioxidant and antimicrobial activity of two Satureja essential oils

Hydro-distilled volatile oils from the aerial parts of Satureja montana L., and Satureja subspicata Bartl. ex Vis., growing wild in Bosnia and Herzegovina, were analyzed by GC/MS. More than one hundred compounds were identified in both plant oils, representing 92.4–98.1% of the total oil. The major constituents of essential oils obtained from the plant material of S. montana, collected from two different localities, were thymol (31.7%), and geraniol (22.3%), respectively. The most abundant compounds in essential oils of S. subspicata, collected at two different stages of development, were thymol (28.6%), and spathulenol (37.6%), respectively. The screening of antimicrobial activity of essential oil samples was individually evaluated against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis using a paper disc diffusion method. All tested microorganisms were inhibited by essential oil samples. Antioxidant activity was tested using the DPPH radical-scavenging method. All samples showed activity comparable to thymol, which was used as a positive probe.     

Antimicrobial and antioxidant properties of the essential oils and methanol extract from Mentha longifolia L. ssp. longifolia

This study was designed to evaluate antimicrobial and antioxidant activities of the essential oil and methanol extract from Mentha longifolia ssp. longifolia. The essential oil showed strong antimicrobial activity against all 30 microorganisms tested whereas the methanol extract almost remained inactive. In contrast, the extract showed much better activity than the essential oil in antioxidant activity assays employed, e.g. in the inhibition of free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene/linoleic acid systems. In the former, the extract was able to reduce the stable free radical DPPH with an IC₅₀ of 57.4 μg/ml while that of the oils was 10 700 μg/ml. When compared to BHT, a synthetic antioxidant, both showed weaker antioxidative potential. Similarly, in β-carotene/linoleic acid assay, these samples were not effectively able to inhibit the linoleic acid oxidation; exhibiting only 24% and 36% inhibitions at 2 mg/ml, respectively; both were far below than that of BHT. Total phenolic constituent of the extract was 4.5 g/100 g as gallic acid equivalent. GC–MS analysis of the oil resulted in the identification of 45 constituents, cis-piperitone epoxide, pulegone and piperitenone oxide being the main components.     

Enzyme-enhanced extraction of antioxidant ingredients from red algae Palmaria palmata

The effect of various protease and carbohydrase treatments on the extraction of polyphenols and other antioxidant ingredients from the red algae Palmaria palmata (dulse) was investigated. In addition, the relative contribution of different fractions to the overall antioxidant capacity of the hydrolysate was evaluated. Considerable differences were observed both in total phenolic content (TPC) and antioxidant activities of the hydrolysates evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, oxygen radical absorbance capacity (ORAC) and ferrous ion-chelating ability assays. All the proteases tested had significant enhancing effect on the extraction of polyphenols and other active components compared to carbohydrases and cold water extraction (control). The Umamizyme extract had the highest TPC and consequently exhibited the strongest scavenging capacity against DPPH and peroxyl radicals. Further fractionation of the Umamizyme extract revealed that the crude polyphenol fraction possessed the highest peroxyl radical scavenging activity, whereas the crude polysaccharide fraction was more effective for chelating ferrous ions. The data from this study suggest the potential of protease treatment to improve value-added utilization of dulse extracts as antioxidants in functional foods and nutraceuticals.     

Solvent-free microwave extraction of essential oil from Dryopteris fragrans and evaluation of antioxidant activity

Solvent-free microwave extraction (SFME) of the essential oil from Dryopteris fragrans and its antioxidant activity were investigated. A central composite design combined with response surface methodology was applied to study the influences of extraction time, irradiation power and humidity (proportion of water pretreatment). A maximal extraction yield of 0.33% was achieved under optimal conditions of extraction time 34 min, irradiation power 520 W and humidity 51%. Sixteen compounds, representing 89.65% of the oil, were identified, of which the major ones, (1R,4S,11R)-4,6,6,11-tetramethyltricyclo[5.4.0.0(4,8)]undecan-1-ol (30.49%), 1R,4S,7S,11R-2,2,4,8-tetramethyltricyclo[5.3.1.0(4,11)]undec-8-ene (22.91%) and, 1,4,4a,5,6,7,8,8a-octahydro-2,5,5,8a-tetramethyl-1-naphthalenemethanol (15.11%), accounted for 68.51% of the oil. The antioxidant activity of the essential oil was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH), β-carotene/linoleic acid, and reducing power assay, the IC₅₀ values were 0.19, 0.09 and 0.18 mg/mL, respectively. All these results suggest that SFME represents an excellent alternative protocol for production of essential oils from plant materials.     

Determination of antioxidant activities of various extracts and essential oil compositions of Thymus praecox subsp. skorpilii var. skorpilii

The aim of this work is to examine the chemical composition and antioxidant activity of separated essential oils and different solvent extracts of Thymus praecox subsp. skorpilii var. skorpilii (TPS). The ethanol, acetone, methanol, hexane, aqueous extracts and separated essential oils of TPS were assessed for their antioxidant activities. Antioxidant activities were evaluated by reduction of Mo(VI) to Mo(V), reducing power, superoxide scavenging activity, free radical-scavenging activity, metal chelating activity, linoleic acid peroxidation, hydrogen peroxide scavenging activity and peroxide scavenging activity. Essential oils were characterized in total to be 41 components, whereas 9 components were isolated by column chromatography for antioxidant activity. TPS essential oil was found to contain thymol (40.31%) and o-cymene (13.66%) as the major components. The ethanol, methanol and water extracts exerted significant free radical-scavenging activity. The methanol and water extracts displayed highest superoxide scavenging activity. The water extract has the highest total phenolics (6.211 mg gallic acid (GAE)/g DW) and flavonoids (0.809 mg quercetin/g DW).     

Screening of the antioxidant potentials of six Salvia species from Turkey

This study was designed to examine the in vitro antioxidant activities of the methanol extracts of six Salvia species [Salvia caespitosa Montbret & Aucher ex Bentham (ENDEMIC), Salvia hypargeia Fisch. & Mey. (ENDEMIC), Salvia euphratica subsp. euphratica Montbret & Aucher ex Bentham (ENDEMIC), Salvia sclarea L., Salvia candidissima subsp. candidissima Montbret & Aucher ex Bentham and Salvia aethiopis L.] from Turkey. The extracts were screened for their possible antioxidant activities by two complementary test systems, namely DPPH free radical-scavenging and β-carotene/linoleic acid systems. Non-polar subfractions of the methanol extracts of Salvia species studied did not show any antioxidant activity in both test systems. In the first case, the most active plant was S. euphratica subsp. euphratica, an endemic species, with an IC₅₀ value of 20.7 ± 1.22 μg/ml, followed by S. sclarea (IC₅₀ = 23.4 ± 0.97 μg/ml) among the polar subfractions. In the β-carotene/linoleic acid test system, polar extract of S. hypargeia was superior to the polar extracts of other Salvia species studied (69.2% ± 1.90%). This activity was followed by S. sclarea with 63.5% ± 4.24% inhibition rate. The inhibition rate of the synthetic antioxidant, buthylated hydroxytoluene (BHT), was also determined to be 96%. Since the polar extracts of Salvia species dealt with here exhibited excellent antioxidant activities when compared to BHT, it seems possible to keep perishable fat-containing food longer by direct addition of an extract of sage.     

The in vitro and in vivo antioxidant properties of seabuckthorn (Hippophae rhamnoides L.) seed oil

The antioxidant capacity of seabuckthorn (Hippophae rhamnoides L.) seed oil was investigated with a number of established in vitro assays and in an in vivo study of carbon tetrachloride (CCl₄)-induced oxidative stress in mice. The results showed that DPPH radical scavenging activity, ferrous ion chelating activity, reducing power and inhibition of lipid peroxidation activity all increased with increasing concentrations of seabuckthorn seed oil. Moreover, the EC₅₀ values of seabuckthorn seed oil from the hydrogen peroxide, superoxide radical, hydroxyl radical scavenging assays were 2.63, 2.16 and 0.77 mg/ml, respectively. In the in vivo study, seabuckthorn seed oil inhibited the toxicity of CCl₄, as seen from the significantly increased activities of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase. The GSH content in the liver was also increased, whereas hepatic malondialdehyde was reduced. Taken together, these results clearly indicate that seabuckthorn seed oil has significant potential as a natural antioxidant agent.     

Major flavonoids with antioxidant activity from Teucrium polium L.

Teucrium polium L. (Lamiaceae) aerial parts are used widely in the daily diet and for medicinal purposes. This plant is used also as a spice and refreshing beverage. Phytochemical and bioactivity studies of this plant have been carried out. Aerial parts of the plant were extracted with petroleum ether, chloroform, methanol and water successively. Fractionation of the methanol extract yielded four major flavonoids. The crude extracts and isolated compounds were screened for their antioxidant and free radical scavenging activities using DPPH radical-scavenging, beta-carotene/linoleic acid and ammonium thiocyanate methods. Methanol extract, rutin and apigenin were found to be the most active fractions as radical-scavengers with IC₅₀ values of 20.1 ± 1.7, 23.7 ± 1.9 and 30.3 ± 2.1 μg/ml, respectively. The samples with the highest inhibition of oxidation of beta-carotene and lipid peroxidation in ammonium thiocyanate methods were also found to be methanol extract, rutin and apigenin. Methoxylated flavonoids exhibited a lesser antioxidant activity.     

Liposomal incorporation of carvacrol and thymol isolated from the essential oil of Origanum dictamnus L. and in vitro antimicrobial activity

The chemical composition of the essential oils from Origanum dictamnus L. (wild and organic cultivated plant) was analysed by GC–MS. Carvacrol, thymol, p-cymene, and γ-terpinene were identified as major constituents and isolated from both samples. The above components were successfully encapsulated in phosphatidyl choline-based liposomes and the possible improvement of their antioxidant and antimicrobial activities was tested against selected microbia. The antimicrobial properties of the oils were tested by a diffusion technique against four Gram positive and four Gram negative bacteria and three human pathogenic fungi, as well as the food-borne pathogen, Listeria monocytogenes. The percentage of the encapsulated carvacrol, the major component of the oil, was determined by GC–FID. In order to investigate any possible synergistic or antagonistic effect between carvacrol/thymol and carvacrol/γ-terpinene, the antimicrobial activities of the mixtures, were also determined before and after encapsulation in liposomes. All tested compounds presented enhanced antimicrobial activities after the encapsulation. Finally, in all cases, their antioxidant activity using differential scanning calorimetry was studied, in order to gain knowledge about their oxidation stability.