The in vitro antioxidative properties of the essential oils and methanol extracts of Satureja spicigera (K. Koch.) Boiss. and Satureja cuneifolia ten

This study was designed to examine the in vitro antioxidant activities of the essential oil and methanol extracts of Satureja spicigera and S. cuneifolia from Turkish flora. GC and GC/MS analysis of the essential oils resulted in the identification of 40 and 29 compounds, representing the 99.4% and 99.5% of the oils, respectively. Major constituents of the oils were carvacrol (42.5% and 67.1%), γ-terpinene (21.5% and 15.2%) and p-cymene (20.9% and 6.7%), respectively. Methanol extracts were also obtained from the aerial parts of the plants. The samples were subjected to a screening for their possible antioxidant activities by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene–linoleic acid assays. In general, samples obtained from S. cuneifolia exerted greater antioxidant activities than did those obtained from S. spicigera. In the DPPH test system, free radical-scavenging activity of S. spicigera oil was determined to be 127 ± 1.63 μg/ml, whereas IC₅₀ value of S. cuneifolia was 89.1 ± 2.29 μg/ml. In the β-carotene–linoleic acid test system, antioxidant activities of the oil were 81.7 ± 1.14% and 93.7 ± 1.83%, respectively. Antioxidant activities of the synthetic antioxidant, BHT, ascorbic acid, curcumin and α-tocopherol were also determined in parallel experiments.     

Chemical composition,antioxidant and antibacterial activities of the essential oils isolated from Tunisian Thymus capitatus Hoff. et Link.

The chemical composition, antioxidant and antibacterial activities of essential oils isolated by hydrodistillation from the aerial parts of Tunisian Thymus capitatus Hoff. et Link. during the different phases of the plant development, and from different locations, were evaluated. The chemical composition was analyzed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The main components of the essential oils were carvacrol (62–83%), p-cymene (5–17%), γ-terpinene (2–14%) and β-caryophyllene (1–4%). The antioxidant activity of the oils (100–1000 mg l⁻¹) was assessed by measurement of metal chelating activity, the reductive potential, the free radical scavenging (DPPH) and by the TBARS assay. The antioxidant activity was compared with that of synthetic antioxidants: butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). Both the essential oils and BHA and BHT showed no metal chelating activity. Although with the other methodologies, there was a general increase in the antioxidant activity, with increasing oil concentration, maxima being obtained in the range of 500 and 1000 mg l⁻¹ for flowering and post-flowering phase oils. Major differences were obtained according to the methodology of antioxidant capacity evaluation. Antibacterial ability of Th. capitatus essential oils was tested by disc agar diffusion against Bacillus cereus, Salmonella sp., Listeria innocua, four different strains of Staphylococus aureus (C15, ATCC25923, CFSA-2) and a multi-resistant form of S. aureus (MRSA-2). Antibacterial properties were compared to synthetic antibiotics. Higher antibacterial activity was observed with the flowering and the post-flowering phase essential oils.     

Evaluation of the antioxidant activity of three microalgal species for use as dietary supplements and in the preservation of foods

The antioxidant activity of the microalgal ethanolic extracts of Porphyridium cruentum, Phaeodactylum tricornutum and Chlorella vulgaris was determined by means of the β-carotene–linoleate model system. The results show that the activity of C. vulgaris extract was higher than those obtained for the other microalgal extracts tested and for the synthetics BHA (butylated hydroxyanisole), and BHT (butylated hydroxytoluene). In addition, the major constituents present in the ethanolic extracts of the three microalgae species were analyzed by means of GC and GC–mass spectrometry. The results showed that the tested microalgae may be an important source of natural antioxidants, as an alternative to higher plants or the production by chemical synthesis.     

Chemical composition and biological activities of Algerian Thymus oils

The compositions of essential oils isolated from nine samples of three Thymus species (Thymus algeriensis, Thymus pallescens and Thymus dréatensis) were analysed by GC and GC–MS, and a total of 114 components were identified. T. pallescens collected from various regions showed a great similarity in their compositions and were characterised by carvacrol (44.4–57.7%), p-cymene (10.3–17.3%) and γ-terpinene (10.8–14.2%) as the major components for four samples; only one sample was thymol-rich (49.3%) with a small amount of carvacrol (9.0%). On the other hand, T. algeriensis showed a chemical polymorphism, even for samples from the same location, and two new chemotypes for this species were proposed. Oxygen-containing monoterpenes were the predominant class (76.3%) in T. dreatensis oil, with linalool (30.4%), thymol (20.2%) and geraniol (19.6%) as the principal constituents. The oils were screened for their possible antioxidant activities by four complementary assays, namely DPPH free radical scavenging, hydroxyl radical scavenging, inhibition of lipid peroxidation and reducing power. The two new chemotypes of T. algeriensis exhibited strong hydroxyl radical scavenging (IC₅₀ = 2.2–3.3 μg/ml), but were not or only slightly active against the other radicals and exhibited a weak reducing power. Despite their chemical similarity, T. pallescens oils sometimes produced significant differences in their antioxidant activities. The essential oils were also screened for their antimicrobial activity against five bacteria (three Gram-positive and two Gram-negative) and one yeast (Candida albicans). The tested essential oils showed antimicrobial activity against the microorganisms used, in particular against two important pathogens, C. albicans and Helicobacter pylori.     

Antioxidant, antiacetylcholinesterase and antimicrobial activities of Cymbopogon schoenanthus L. Spreng (lemon grass) from Tunisia

Aqueous extract, proanthocyanidin rich extract, and organic extracts of Cymbopogon schoenanthus L. Spreng (lemon grass) shoots from three different locations in South Tunisia were screened for their antioxidant, acetylcholinesterase and antimicrobial activities. In addition to the evaluation of these activities, the contents of flavonoids and total phenolic compounds were determined.Antioxidant activity measured by DPPH assay showed that the proanthocyanidin extract exhibited higher antioxidant activity than the aqueous extract. Extract concentration providing 50% inhibition (IC₅₀) ranged from 16.4 ± 6.8 μg/mL to 26.4 ± 6.8 μg/mL. The antioxidant activity was also determined using the β-carotene/linoleic acid bleaching test. The best results (IC₅₀ = 0.11 ± 0.10 mg/mL) were obtained with the proanthocyanidin extract of the plants collected from the desert region (Dhibat).The greatest acetylcholinesterase inhibitory activity (IC₅₀ = 0.23 ± 0.04 mg/mL) was exhibited by the ethyl acetate and methanol extracts of the plants collected from the mountainous region. It seems that extracts obtained with more polar solvents gave better results.The proanthocyanidin extracts showed a good antimicrobial activity against Streptococcus sobrinus at low concentration (MIC = 4 mg/mL). Therefore, these extracts could be used to prevent carious lesions by inhibiting S. sobrinus growth.     

Free radical scavenging properties and phenolic characterization of some edible plants

Antioxidant activity of the ethanolic extracts of the fruits of Fritillaria pontica Wahlenb. (Liliaceae), Euonymus latifolius (L.) Mill. ssp. latifolius (Celastraceae), and Vicia sativa L. ssp. nigra (L.) Ehrh. var. nigra L. (Fabaceae), the aerial parts of Turritis laxa (Sibth & Sm.) Hayek (Brassicaceae), Vicia cracca L. (Fabaceae), and Oxyria digyna (L.) Hill. (Polygonaceae) was screened by 2,2-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and ferric-reducing antioxidant power (FRAP) assays at 0.5, 1.0, and 2.0 mg ml⁻¹ concentrations. Total phenolic contents of the extracts were determined using Folin-Ciocalteau reagent. T. laxa was also tested for its anti-acetylcholinesterase activity. The extracts were analyzed by LC–DAD–MS for their flavonoid content and the ethanolic extract of T. laxa has been found to contain rutin in appreciable amounts (7.63 ± 0.2%). Rutin and hyperoside were detected qualitatively in F. pontica, where vitexin was identified in O. digyna. It was also the most active in the antioxidant tests.     

Antioxidant and antibacterial activities of Nephelium lappaceum L. extracts

Ether, methanolic and aqueous extracts of lyophilized rambutan (Nephelium lappaceum L.) peels and seeds were evaluated for phenolic contents, antioxidant and antibacterial activities. High amounts of phenolic compounds were found in the peel extracts and the highest content was in the methanolic fraction (542.2 mg/g dry extract). Several potential antioxidant activities, including reducing power, β-carotene bleaching, linoleic peroxidation and free radical scavenging activity, were evaluated. The peel extracts exhibited higher antioxidant activity than the seed extracts in all methods determined (P < 0.05). The methanolic fraction was found to be the most active antioxidant as shown by their 50% DPPH inhibition concentration, 4.94 μg/mL. The results indicated this fraction exhibited greater DPPH radical scavenging activity than BHT and ascorbic acid (0.32 g dry extract/g BHT or ascorbic acid). Antibacterial activity against eight bacterial strains was assessed by disc diffusion and broth macrodilution methods. All peel extracts exhibited antibacterial activity against five pathogenic bacteria. The most sensitive strain, Staphylococcus epidermidis, was inhibited by the methanolic extract (MIC 2.0 mg/mL).     

Chemical,biochemical and electrochemical assays to evaluate phytochemicals and antioxidant activity of wild plants

Plants are a source of compounds that may be used as pharmacologically active products. Cytisus multiflorus, Filipendula ulmaria and Sambucus nigra have been used as important medicinal plants in the Iberian Peninsula for many years, and are claimed to have various health benefits. Herein, the phytochemical composition and antioxidant activity of the mentioned wild medicinal plants were evaluated in vitro, based on chemical, biochemical and electrochemical methods. F. ulmaria was found to be richest in antioxidant phytochemicals, such as phenolics (228 mg GAE/g DW), flavonoids (62 mg CE/g DW), ascorbic acid (2700 μg/g DW) and tocopherols (497 μg/g DW). The antioxidant activity was found to vary in the order: F. ulmaria > S. nigra > C. multiflorus, irrespective of the analysis method. Electrochemical methods have proven to be rapid and inexpensive techniques to characterise the antioxidant activity of plant extracts.     

Chlorogenic acids and related compounds in medicinal plants and infusions

The consumption of plant infusions for prevention and treatment of health disorders is a worldwide practise. Various pharmacological activities inherent to medicinal plants have been attributed to their phenolic composition, including chlorogenic acids (CGA). Studies have shown potential beneficial properties of CGA to humans such as antioxidant, hepatoprotective, hypoglycaemic. In the present study, the CGA composition of 14 dried medicinal plants was determined by HPLC-UV and LC-DAD–ESI-MS. The plants with the highest CGA contents were Ilex paraguariensis, Bacharis genistelloides, Pimpinella anisum, Achyrochine satureioides, Camellia sinensis, Melissa officinalis and Cymbopogon citratus, with 84.7 mg/100 g–9.7 g/100 g, dry weight. Plant infusions were prepared (at 0.5%) in order to evaluate the actual consumption of CGA through these beverages. Total CGA contents in the infusions were similar to those in the methanolic extracts and indicated that a satisfactory extraction occurs during the preparation of infusions. These CGA-rich plants deserve attention regarding the pharmacological properties attributed to CGA.     

Antioxidant activities of Sideritis congesta Davis et Huber-Morath and Sideritis arguta Boiss et Heldr: Identification of free flavonoids and cinnamic acid derivatives

Different solvent extracts of endemic Sideritis (Labiatae) species, Sideritis congesta Davis et Huber-Morath and Sideritis arguta Boiss et Heldr, were analyzed for free flavonoids (quercetin, apigenin, myricetin and kaempferol) and cinnamic acid derivatives (rosmarinic acid, ferulic acid, caffeic acid, p-coumaric acid and chlorogenic acid) using HPLC-DAD. All the phenolics were quantified in acid-hydrolyzed extracts, except rosmarinic acid, chlorogenic acid and myricetin which were quantified in raw samples. Antioxidant activities of extracts of these two plants and many of their components in pure form were evaluated based on DPPH^. and ABTS^.+ assays. In general, S. arguta extracts displayed higher antioxidant activity than S. congesta extracts possibly due to their richness in antioxidant components of strong activity. Acetone extract of S. arguta, with its strikingly high TEAC value of 3.2 mM trolox and low IC₅₀ value of 38.3 ??g/mL showed the highest antioxidant potency among all extracts. ??-tocopherol, the positive control, displayed IC₅₀ and TEAC values of 33.8 ??g/mL and 2.9 mM trolox, respectively. No direct correlation was found between antioxidant activities and total phenolic contents of the plant extracts studied.     

Antimicrobial activity of essential oil extracts of various onions (Allium cepa) and garlic (Allium sativum)

Antimicrobial activity of different concentrations (50, 100, 200, 300 and 500 ml/l) of essential oil extracts of three type of onions (green, yellow and red) and garlic against two bacteria, Staphylococcus aureus, Salmomella Enteritidis, and three fungi, Aspergillus niger, Penicillium cyclopium and Fusarium oxysporum, was investigated. The essential oil (EO) extracts of these Allium plants (garlic and onions) exhibited marked antibacterial activity, with garlic showing the highest inhibition and green onion the lowest. Comparatively, 50 and 100 ml/l concentrations of onions extracts were less inhibitory than 200, 300 and 500 ml/l concentrations. However, with garlic extract, high inhibitory activity was observed for all tested concentrations. S. aureus showed less sensitivity towards EO extracts inhibition, however S. Enteritidis was strongly inhibited by red onion and garlic extracts. The fungus F. oxysporum showed the lowest sensitivity towards EO extracts, whereas A. niger and P. cyclopium were significantly inhibited particularly at low concentrations. Conclusively, where seasoning is desired, essential oil extracts of onions and garlic can be used as natural antimicrobial additives for incorporating in various food products.     

Antioxidant properties of Agaricus blazei, Agrocybe cylindracea, and Boletus edulis

Three mushrooms are currently available in Taiwan, including Agaricus blazei, Agrocybe cylindracea, and Boletus edulis. Their ethanolic and hot water extracts were prepared and antioxidant properties studied. Ethanolic extracts from three mushrooms were more effective than hot water extracts in antioxidant activity using the conjugated diene method and scavenging ability on 1,1-diphenyl-2-picrylhydrazyl radicals whereas hot water extracts were more effective in reducing power, scavenging ability on hydroxyl radials and chelating ability on ferrous ions as evidenced by their lower EC₅₀ values. Overall, for both extracts, B. edulis was more effective among antioxidant properties assayed. Naturally occurring antioxidant components including total tocopherols (3.18-6.18 mg/g) and total phenols (5.67-5.81 mg/g) were found in the extracts and their contents were associated (r=0.636-0.907) with EC₅₀ value of antioxidant properties. Based on the results obtained, both extracts from these three mushrooms were effective in antioxidant properties.     

The relationship between the content of Maillard reaction-like products and bioactivity of Canadian honeys

Honey possesses antioxidant and antibacterial activities; however the compounds that are responsible for these activities are still under investigation. To determine whether there are common features/compounds that underlie the antioxidant and antibacterial activities, 20 Canadian honeys were analysed using the oxygen radical absorbance capacity (ORAC) and the broth micro-dilutions assay, respectively. Principal component analysis revealed the highest correlation between ORAC and Maillard reaction-like products (MRLP) (R = 0.938, p < 0.0001). In addition, the extremely significant correlations between ORAC, MRLPs, phenolic content and honey colour may suggest that these compounds represent the same chemical entity and exert their antioxidant activity while being part of a higher molecular weight structure. Moreover, the antioxidant activity and MRLPs were also the dominant variables contributing to the antibacterial activity against Escherichia coli (R = 0.737, p < 0.0001 and R = 0.65, p < 0.002, respectively) however no such correlation against Bacillus subtilis. In conclusion, MRLPs in honey appear to underlie the antioxidant and partially the antibacterial activity against E. coli.     

Antioxidant activity of the essential oil and various extracts of Nepeta flavida Hub.-Mor. from Turkey

This study was designed to examine the chemical composition and in vitro antioxidant activity of the essential oil and various extracts (hexane, dichloromethane and methanol sub-fractions) of Nepeta flavida. GC and GC–MS analyses of the essential oil resulted in the identification of 68 compounds, representing 96.4% of the oil; 1,8-cineole (38.9%) and linalool (25.1%) were the main components, comprising 64.0% of the total oil. The samples were subjected to a screening for their possible antioxidant activities by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene-linoleic acid assays. In the first case, the IC₅₀ value of the N. flavida essential oil was determined to be 42.8 ± 2.19 μg/ml. Among the extracts, the strongest activity was exhibited by the polar sub-fraction of the methanol extract with an IC₅₀ value of 63.2 ± 1.75 μg/ml. In the β-carotene-linoleic acid system, N. flavida essential oil exhibited 86.3% ± 1.69 inhibition against linoleic acid oxidation. Among the extracts prepared with various solvents, a correlation was observed between the polarity and antioxidant activity. The extracts exhibited the same activity pattern in this system the most active one is the polar sub-fraction, 79.7% ± 0.89. On the other hand, 1,8-cineole, a major compound of the essential oil, exhibited marked antioxidant activity in both systems, whereas the other compound, linalool, did not show any activity. The amount of total phenolics was highest in the polar and non-polar sub-fractions. Particularly, a positive correlation was observed between the total phenolic content and the antioxidant activity of the extracts. As estimated from the results, amounts of phenolic compounds were less in hexane and dichloromethane extracts than in the others. In conclusion, antioxidant potentials of polar and non-polar methanol sub-fractions could be attributed to their high phenolic contents. In both systems, antioxidant capacities of BHT, ascorbic acid, curcumin and α-tocopherol were also determined in parallel experiments.     

GC/MS analysis and in vitro antioxidant activity of essential oil and methanol extracts of Thymus caramanicus Jalas and its main constituent carvacrol

Chemical composition of the essential oil, antioxidant activity (DPPH and β-carotene/linoleic acid assays), and total phenolic content (Folin–Ciocalteu assay) of aerial parts of Thymus caramanicus were determined. The highest radical-scavenging activity (DPPH test) was shown by the polar subfraction of the methanol extract (IC₅₀ = 43.0 μg/ml) which was also higher than that of butylated hydroxytoluene (BHT, IC₅₀ = 19.7 μg/ml). However, it was the nonpolar subfraction of the methanol extract that showed the highest inhibition (84.4%), as assessed by the β-carotene/linoleic acid assay, which was only slightly lower than that shown by BHT (93.3%). The antioxidant activities of the essential oil main component (carvacrol) were also evaluated for comparison. Total phenolic content of the polar subfraction, as gallic acid equivalents, was 124.3 μg/mg. Essential oil extracted from the aerial parts by hydrodistillation was analysed by GC and GC/MS. Fifteen constituents, representing 99.3% of the oil, were identified, of which the major ones, carvacrol (85.9%), thymol (3.3%), p-cymene (3.2%), γ-terpinene (1.8%) and borneol (1.3%), accounted for 95.6% of the oil.     

Antioxidant and antimicrobial activities of Laetiporus sulphureus (Bull.) Murrill

Antioxidant capacity and antimicrobial activities of Laetiporus sulphureus (Bull.) Murrill. extracts obtained with ethanol were investigated in this study. The study was aimed at determining the antioxidant activity (DPPH free radical-scavenging, β-carotene/linoleic acid systems), total phenolic content and total flavonoid concentration of L. sulphureus. Inhibition values both of L. sulphureus ethanol and the standards increased parallel with the elevation of concentration in the linoleic acid system. Inhibition values of L. sulphureus (LS) extract, BHA and α-tocopherol standards were found to be 82.2%, 96.4% and 98.6%, respectively, at a concentration of 160 μg/ml. DPPH free radical-scavenging activity was found to exhibit 14%, 26%, 55% and 86% inhibition, respectively, at concentrations of 100, 200, 400 and 800 μg/ml. Total flavanoids were 14.2 ± 0.12 μg mg⁻¹ (quercetin equivalent) while the phenolics were 63.8 ± 0.25 μg mg⁻¹ (pyrocatechol equivalent) in the extract. Positive correlations were found between total phenolic content in the mushroom extracts and their antioxidant activities. Edible mushrooms may have potential as natural antioxidants. L. sulphureus showed narrow antibacterial activity against Gram-negative bacteria and strongly inhibited the growth of the Gram-positive bacteria tested. The crude extract exhibited high anticandidal activity on Candida albicans. Therefore, the extracts could be suitable as antimicrobial and antioxidative agents in the food industry.     

Evaluation of antioxidant,antibacterial and anti-tyrosinase activities of four Macaranga species

The methanolic fresh leaf extracts of Macaranga gigantea, Macaranga pruinosa, Macaranga tanarius and Macaranga triloba were screened for their antioxidant properties (AOP), tyrosinase inhibition and antibacterial activities. Total phenolic content (TPC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging, ferric-ion reducing power (FRAP), ferrous-ion chelating (FIC) and lipid peroxidation inhibition (LPI) activities were used to evaluate the AOP. Modified 3,4-dihydroxy-L-phenylalanine (L-DOPA) method was used to determine tyrosinase inhibition activity, whereas antibacterial activity was determined using the disc-diffusion technique. TPC screening of the same species from different collection sites showed no significant difference between sites. M.triloba showed the highest ascorbic acid equivalent antioxidant activity (AEAC), FRAP and LPI values. M. tanarius, which showed the lowest TPC, AEAC, FRAP and LPI activities, exhibited the best FIC activity. M. pruinosa showed the best tyrosinase inhibition activity, whereas M. triloba showed the best antibacterial activity against Gram-positive bacteria species, with minimal inhibition dosage (MID) values as low as 10 μg/disc.     

Antioxidant activity and proline content of leaf extracts from Dorystoechas hastata

Dorystoechas hastata (D. hastata) is a monotypic plant endemic to Antalya province of Turkey. D. hastata leaves are used to make a tea locally called “çalba tea”. Diethyl ether (E), ethanol (A), and water (W) were used for the sequential preparation of extracts from dried D. hastata leaves. A hot water extract (S) was also prepared by directly boiling the powdered plant in water. The antioxidant activities of the extracts were tested by ferric thiocyanate (FTC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging methods. E extract exhibited the greatest antioxidant activity with FTC method, whereas S extract exhibited the lowest IC₅₀ value (6.17 ± 0.53 μg/ml) for DPPH radical scavenging activity. Total phenolic contents of the extracts were estimated by Folin–Ciocalteu method and S extract was found to contain the highest amount (554.17 ± 20.83 mg GAE/g extract) of phenolics. Extract A contained highest flavonoid content and there was a inverse linear correlation (R² = 0.926) between IC₅₀ values for DPPH radical scavenging activity and flavonoid contents of all extracts. Reducing power of extracts increased in a concentration-dependent manner. S extract was found to possess higher reducing power than equivalent amount of ascorbic acid at 20 and 25 μg/ml concentrations. Linear correlation between reducing power and concentration of E, A, and W extracts (R² > 0.95) was observed. A, W, and S extracts contained relatively high levels of proline. The results presented suggest that D. hastata may provide a natural source of antioxidants and proline.     

Chemical composition,antimicrobial potential against cariogenic bacteria and cytotoxic activity of Tunisian Nigella sativa essential oil and thymoquinone

We investigate in this work the chemical composition by GC–EIMS, the antibacterial and the cytotoxic activities of Tunisian Nigella sativa essential oil and its bioactive compound, thymoquinone, were tested against various clinical cariogenic bacteria (n = 30). Eighty-four compounds were identified in the essential oil. The major one was p-cymene (49.48%) whereas thymoquinone represented only 0.79%. The essential oil (2.43 mg/disc) containing only 3.35 μg of thymoquinone showed pronounced dose dependant antibacterial activity against Streptococcus mitis, Streptococcus mutans, Streptococcus constellatus and Gemella haemolysans (15.5 ± 0.707 mm). However, pure thymoquinone compound (150 μg/disk) was active against all the studied strains especially S. mutans and S. mitis (24.5 ± 0.71 and 22 ± 1.41 mm inhibition zones, respectively).