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.     

Antioxidative activity of Rosmarinus officinalis L. essential oil compared to its main components

This study was designed to examine the in vitro antioxidant activities of Rosmarinus officinalis L. essential oil compared to three of its main components (1,8-cineole, α-pinene, β-pinene). GC–MS analysis of the essential oil resulted in the identification of 19 compounds, representing 97.97% of the oil, the major constituents of the oil were described as 1,8-cineole (27.23%), α-pinene (19.43%), camphor (14.26%), camphene (11.52%) and β-pinene (6.71%). The oil and the components were subjected to screening for their possible antioxidant activity by means of 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and β-carotene bleaching test. In the DPPH test system, free radical-scavenging activity of R. officinalis L. essential oil, 1,8-cineole, α-pinene and β-pinene were determined to be 62.45% ± 3.42%, 42.7% ± 2.5%, 45.61% ± 4.23% and 46.21% ± 2.24% (v/v), respectively. In the β-carotene bleaching test system, we tested series concentration of samples to show the antioxidant activities of the oil and its main components, whereas the concentrations providing 50% inhibition (IC₅₀) values of R. officinalis L. essential oil, 1,8-cineole, α-pinene and β-pinene were 2.04% ± 0.42%, 4.05% ± 0.65%, 2.28% ± 0.23% and 2.56% ± 0.16% (v/v), respectively. In general, R. officinalis L. essential oil showed greater activity than its components in both systems, and the antioxidant activities of all the tested samples were mostly related to their concentrations. Antioxidant activities of the synthetic antioxidant, ascorbic acid and BHT, were also determined in parallel experiments as positive control.     

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.     

Antioxidant potentials of buntan pumelo (Citrus grandis Osbeck) and its ethanolic and acetified fermentation products

The antioxidant potentials of buntan pumelo (Citrus grandis Osbeck) and its fermented products were determined. The essential oil from peel had higher total phenolic (214 mM) and flavonoid (134 mg QE/g of dried material) contents than those of different solvent extracts from fruit pulp. In addition, DPPH free radical-scavenging activity and ferric-reducing antioxidant power values determined for the essential oil were 26.1 ± 1.2% and 2.3 ± 0.3 mM, respectively, which were significantly higher than those of various fruit pulp extracts. The ethanol-fermented products of pumelo juice had higher total phenolic and flavonoid contents than those of fresh juice. For maintenance of the substantial antioxidant properties of pumelo products, ethanol-fermented juice rather than fresh or acetate-fermented juice is recommended. Through correlation analysis, the phenolic compounds in the fermented pumelo products were found to be the major contributors to the free radical-scavenging activity and ferric-reducing power.     

Chemical Composition and Antioxidant Activity of Essential Oil and Methanolic Extracts of Ferula microcolea (Boiss.) Boiss (Apiaceae)

The essential oils of Ferula microcolea, collected from west Iran were obtained by hydrodistillation during the flowering stage and analyzed by gas chromatography and gas chromatography/mass spectrometry. Under the optimum conditions of analysis, 22 constituents (mainly monoterpen compounds) were identified in Ferula microcolea, representing 93.6% of the oil. The main constituents were α-pinene (27.3%), β-pinene (16.4%), nonanal (8.7%), β-caryophyllene (8.5%), and thymol (6.7%). The samples were also subjected to screening for their possible antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl and β-carotene-linoleic acid assays. In the first case, the free radical-scavenging activity of polar sub-fraction of methanol extract showed to be superior as compared to other extracts (IC₅₀ = 34.3 ± 0.3 μg/ml). Nonpolar sub-fraction of methanol extract exhibited stronger activity than the essential oil. In the case of the linoleic acid system, oxidation of the linoleic acid was effectively inhibited by the polar sub-fraction of methanol extract (86.5 ± 0.9%), while the oil and nonpolar sub-fraction of methanol extract were less effective (55.2 ± 0.4% and 81.5 ± 0.8%, respectively).     

Essential oil composition,antimicrobial and antioxidant properties of Mosla chinensis Maxim

The essential oil of Mosla chinensis Maxim was analysed by gas chromatography/mass spectrometry, and its main components are carvacrol (57.08%), p-cymene (13.61%), thymol acetate (12.68%), thymol (6.67%), and γ-terpinene (2.46%). The essential oil exhibited great potential antimicrobial activity against all eight bacterial and nine fungal strains. Antioxidant activity was also tested, the essential oil showing significantly higher antioxidant activity than that of the methanol extract. In addition, the amounts of total phenol components in the plant methanol extract (47.3 ± 0.4 μg/mg) and the oil (80.7 ± 0.5 μg/mg) were determined. The results presented here indicate that the essential oil of M. chinensis has antimicrobial and antioxidant properties, and is therefore a potential source of antimicrobial and antioxidant agents for the food and pharmaceutical industries.     

Antioxidant,anticholinesterase and antimicrobial constituents from the essential oil and ethanol extract of Salvia potentillifolia

The essential oil of Salvia potentillifolia was analysed by GC and GC–MS. Totally, 123 components were detected in both hydrodistilled and steam-distilled oils, α- and β-pinenes being major compounds. The antioxidant activities were determined by using complementary tests, namely, DPPH radical-scavenging, β-carotene-linoleic acid and reducing power assays. The ethanol extract also showed better activity (IC₅₀ = 69.4 ± 0.99 μg/ml) than that of BHT in the DPPH system, and showed great lipid peroxidation inhibition in the β-carotene-linoleic acid system (IC₅₀ = 30.4 ± 0.50 μg/ml). The essential oil showed meaningful butyrylcholinesterase activity (65.7 ± 0.21%), and α-pinene showed high acetylcholinesterase inhibitory activity (IC₅₀ = 86.2 ± 0.96 μM) while β-pinene was inactive. Antimicrobial activity was also investigated on several microorganisms, and the essential oil showed high activity against Bacillus subtilis and B. cereus. It also exhibited remarkable anticandidal activity against Candida albicans and C. tropicalis with MIC values of 18.5 and 15.5 μg/ml, respectively, while α- and β-pinenes showed moderate activity.     

Phenolic composition,antioxidant and acetylcholinesterase inhibitory activities of Sclerocarya birrea and Harpephyllum caffrum (Anacardiaceae) extracts

Total phenolic content, proanthocyanidins, gallotannins, flavonoids, and antioxidant activities of Sclerocarya birrea and Harpephyllum caffrum methanolic extracts were evaluated using in vitro assays. S. birrea young stem extract contained the highest levels of total phenolic content (14.15 ± 0.03 mg GAE/g), flavonoids (1.21 ± 0.01 mg CE/g) and gallotannins (0.24 ± 0.00 mg GAE/g). H. caffrum stem bark extract had the highest content of proanthocyanidins (1.47%). The EC₅₀ values of the extracts in the DPPH free radical scavenging assay ranged from 4.26 to 6.92 μg/ml, compared to 6.86 μg/ml for ascorbic acid. A dose-dependent linear curve was obtained for all extracts in the ferric-reducing power assay. Dichloromethane and methanol extracts exhibited dose-dependent acetylcholinesterase inhibitory activity. Similarly, all extracts exhibited high antioxidant activity comparable to butylated hydroxytoluene based on the rate of β-carotene bleaching (84.1–93.9%). The two Anacardiaceae species provide a source of natural antioxidants and acetylcholinesterase inhibitors, and may be beneficial to the health of consumers.     

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 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.     

Composition and antioxidant and antimicrobial activity of the essential oil and extracts of Stachys inflata Benth from Iran

Composition and antioxidant and antimicrobial activities of essential oil and methanol extract polar and nonpolar subfractions of Stachys inflata were determined. GC and GC/MS analyse of the essential oil showed 45 constituents representing 95.46% of the oil, the major components linalool (28.55%), α-terpineol (9.45%), spathulenol (8.37%) and (2E)-hexenal (4.62%) constituted 50.99% of it. Essential oil and extracts were also tested for their antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene/linoleic acid assays. In the DPPH test, IC₅₀ value for the polar subfraction was 89.50 μg/ml, indicating an antioxidant potency of about 22% of that of butylated hydroxytoluene (IC₅₀ = 19.72 μg/ml) for this extract. In β-carotene/linoleic acid assay, the best inhibition belonged to the nonpolar subfraction (77.08%). Total phenolic content of the polar and nonpolar extract subfractions was 5.4 and 2.8% (w/w), respectively. The plant also showed a week antimicrobial activity against three strains of tested microorganisms. Linalool and α-terpineol were also tested as major components of the oil and showed no antioxidant but considerable antimicrobial activities.     

Antioxidant effect of oregano (Lippia berlandieri v. Shauer) essential oil and mother liquors

The conventional steam distillation process for oregano (Lippia berlandieri v. Shauer) essential oil extraction produces large volumes of mother liquor. This residual liquid represents a potential value because the soluble antioxidants it contains. Essential oil and ethyl acetate mother liquor extracts (MLEs) were evaluated for antioxidant activity. Total phenolic content and antioxidant activities by the 2-2′-diphenyl-1-picrylhydrazyl (DPPH) method, by the deoxyribose degradation assay, and by oxidation of low density lipoproteins (LDL) with CuSO₄ were evaluated. Oil yield was 4.34%. Total phenolic content was 151 ± 2.00 and 150.5 ± 0.98 mg of GAE (gallic acid equivalents)/mL for the essential oil and MLEs, respectively. DPPH assay showed a low radical scavenging activity (RSA) for oregano essential oil. Meanwhile MLEs exhibited no significant RSA at low concentrations, but at higher concentrations (100 μg/mL), it was superior to those exhibited by the controls ascorbic acid and butylated hydroxytoluene (BHT). Deoxy-d-ribose assay results for both essential oil and MLEs showed a good hydroxyl radical RSA at the concentrations tested. Essential oil and MLEs delayed induction time effectively. Solubility problems, chemical constituents, and their hydrophilic–lipophilic distribution are key factors that explain samples behavior for an eventual use of these natural products.     

Salinity impact on fruit yield,essential oil composition and antioxidant activities of Coriandrum sativum fruit extracts

This study is designed to examine the fruit essential oil composition, the total phenolic amounts and the antioxidant activities in methanolic extracts of Coriandrum sativum under saline conditions. Increasing NaCl levels to 75 mM reduced significantly the fruit yield by 36%. The essential oil yield was 0.30%, based on the dry weight; it increased by 77% and 84% at 50 and 75 mM NaCl, respectively, in comparison to the control. The major constituents were linalool and camphor, whose amounts increased with increasing NaCl concentrations. Antioxidant activities of the methanol extracts were determined by three different test systems, namely DPPH, β-carotene/linoleic acid and reducing power assays. In these three test systems, the highest activity was exhibited in control plants and was reduced significantly with increasing NaCl levels. In control plants, the total phenolic amount was 1.04 mg GAE/g DW which decreased by 43% and 66% at 50 and 75 mM NaCl, respectively.     

Profiling of in vitro neurobiological effects and phenolic acids of selected endemic Salvia species

The ethyl acetate and methanol extracts from 16 Salvia L. species were screened for their inhibitory activity against acetylcholinesterase, butyrylcholinesterase, lipoxygenase, and tyrosinase; the enzymes linked to neurodegeneration. Their antioxidant activity was also tested using DPPH radical scavenging, metal-chelation, and ferric-reducing antioxidant power (FRAP) assays. Total flavonoid content of the extracts was determined by AlCl₃ reagent, while HPLC technique was applied for analysis of various phenolic acids in the extracts. The extracts exerted weak cholinesterase and tyrosinase inhibition, and remarkable inhibition against lipoxygenase (13.07 ± 2.73-74.21 ± 5.61%) at 100 μg ml⁻¹. The methanol extracts showed higher antioxidant activity in DPPH radical scavenging and FRAP assays. The extracts were analyzed for their gallic, protocateuchic, p-hydroxy-benzoic, vanillic, caffeic, chlorogenic, syringic, o- and p-coumaric, ferulic, rosmarinic, and tr-cinnamic acid contents and the methanol extract of Salvia ekimiana (153.50 mg 100 g⁻¹) was revealed to be the richest in terms of rosmarinic acid.     

Antioxidant properties and quantitative UPLC-MS analysis of phenolic compounds from extracts of fenugreek (Trigonella foenum-graecum) seeds and bitter melon (Momordica charantia) fruit

Freeze-dried fenugreek (Trigonella foenum-graecum) seeds and bitter melon (Momordica charantia) fruit were extracted sequentially using non-polar to polar solvents, with further separation carried out on polar extracts by molecular weight cut off dialysis. The fenugreek ethyl acetate crude extract (FGE3) demonstrated the highest antioxidant activity, in terms of Trolox Equivalents (TE), for both the DPPH (35.338 ± 0.908 mg TE/g) and FRAP (77.352 ± 0.627 mg TE/g) assays. This extract also contained the highest phenolic content, in terms of Gallic Acid Equivalents (GAE) (106.316 ± 0.377 mg GAE/g). Despite having considerably lower antioxidant activity than fenugreek, the highest antioxidant activities for bitter fruit were observed in the hexane (BME1) and methanol hydrophilic < 3.5 kDa dialysed (BME4 < 3.5 kDa) extracts, while the highest phenolic content was found in the methanol hydrophilic > 3.5 kDa (BME4 > 3.5 kDa) dialysed extract. UPLC-MS was used to quantify 18 phenolic compounds from fenugreek and 13 from bitter melon in active crude extracts. The flavonoids apigenin-7-O-glycoside (1955.55 ng/mg) and luteolin-7-O-glycoside (725.50 ng/mg) were the most abundant compounds in FGE3, while bitter melon extracts contained only small amounts of mainly phenolic acids. A further 5 fenugreek and 1 bitter melon compounds were identified in trace amounts from the same extracts, respectively.     

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.     

Changes occurring in phenolic content,tocopherol composition and oxidative stability of Camelina sativa oil during storage

Changes occurring during storage in the content of polar phenolic compounds, the composition of tocopherols (T), the presence of primary and secondary oxidative products and titratable acidity in oil obtained from the seeds of Camelina sativa were studied. In fresh oil the content of polar phenolic compounds amounted to 128 mg/kg (expressed as chlorogenic acid), the content of α-T was (41 ± 8) mg/kg, of γ-T (710 ± 19) mg/kg and of δ-T (12 ± 3) mg/kg. β-T and tocotrienols were not detected. In oil stored at 50 °C the concentration of total tocopherols decreased to a value of (440 ± 13) mg/kg in 15 days. In that time the content of polar phenolic compounds in the oil stored at 50 °C was reduced to 72% of its initial value. The content of polar phenolic compounds in oil stored at 65 °C for 15 days was reduced to 21% of its initial value. The content of polar phenolic compounds in the C. sativa oil investigated decreased linearly with peroxide value and with p-anisidine value. The antioxidative activity of polar phenolic compounds extracted from camelina oil was also elucidated. Analysis revealed that the phenolic extract obtained from camelina oil added to a model lipid system for a certain time significantly retarded the process of autooxidation.     

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).     

Antioxidant activity and phenolics of an endophytic Xylaria sp. from Ginkgo biloba

The objective of this study was to evaluate the antioxidant activity of cultivated fruiting bodies of an endophytic Xylaria sp. (strain number YX-28), from Ginkgo biloba. The results indicated that the methanol extract exhibited strong antioxidant capacity in both 2,2-diphenyl-1-picrylhydrazyl (DPPH) analysis and β-carotene–linoleic acid model system. Total phenolic and flavonoid contents extracted by different solvents were determined using Folin–Ciocalteu procedure and the flavonoid–aluminium method. The results showed that total phenolic and flavonoid contents were the highest in methanol extract (54.51 ± 1.05 mg gallic acid equivalent/g dry weight and 86.76 ± 0.58 mg rutin equivalent/g dry weight), while the hexane extract was the lowest (9.71 ± 0.57 mg GAE/g dw and 10.14 ± 0.76 mg RE/g dw, respectively). The correlation coefficients from regression analysis showed a positive relationship between total phenolic content in the extracts and DPPH activity (R² = 0.7336), as well as between total flavonoid content and DPPH activity (R² = 0.9392). Furthermore, GC/MS method was used to confirm the presence of phenolics with antioxidant activity in the methanol extract and resulted in the identification of 41 compounds, esters, phenolics, alkanes, carboxylates and alcohols being the main components. In conclusion, cultivated fruiting bodies of Xylaria sp.YX-28 may have potential as natural antioxidant.     

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.