Submerged culture medium composition for the antioxidant activity by Grifola frondosa TFRI1073

Effects of nutritional requirements for superoxide anion scavenging activity and reducing power by a newly screened Grifola frondosa TFRI1073 were studied in submerged cultures. The results clearly showed that the culture medium significantly affected superoxide anion scavenging activity and reducing power. In addition, both superoxide anion scavenging capability and reducing power were found to be greatly affected by varying the carbon source, the nitrogen source, the growth factor, and the mineral elements. The best superoxide anion scavenging activity could be obtained when the medium compositions (carbon source, nitrogen source, growth factor, and the mineral elements) were sucrose, ammonium chloride, nicotinic acid, K₃PO₄, and CuSO₄; while a maximal reducing power could be achieved when the medium composition setting as: xylose, arginine, ascorbic acid, K₂HPO₄, and MgSO₄. From a series experiments, the maximal superoxide anion scavenging activity and reducing power were 98.36±0.59% and 0.947±0.06 at 100 μg/mL, respectively. This study proved that modifying the composition of the medium can dramatically enhance the superoxide anion scavenging ability and reducing power by a newly screened G. frondosa TFRI1073.     

Evaluation of free radical‐scavenging activities of sweet potato protein and its hydrolysates as affected by single and combination of enzyme systems

To evaluate the free radical‐scavenging activities of sweet potato protein (SPP) and its hydrolysates, single enzymes alone (alcalase, neutrase, protamex) or in combination with flavourzyme were employed. Compared with SPP, free radical‐scavenging activities of the resulting hydrolysates were all significantly increased (P < 0.05). Alcalase (ALC) hydrolysates exhibited the highest superoxide, hydroxyl and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical‐scavenging activities (P < 0.05), which was 18.71 ± 0.22, 27.13 ± 0.24 and 90.10 ± 0.15% respectively. Compared with SPP hydrolysates by single enzymes, the hydrolysates obtained by combination of enzyme systems exhibited higher degree of hydrolysis, but lower free radicals scavenging activities. In addition, the content of several antioxidant amino acid residues, such as His, Met, Tyr and Phe, in ALC hydrolysates was much higher compared with SPP and other hydrolysates using amino acids composition assay. The results suggested that peptides with free radical‐scavenging activity could be released from entire SPP chain via moderate enzymatic hydrolysis.     

Antioxidant activities of red pepper (Capsicum annuum) pericarp and seed extracts

In this study, we examined the antioxidant activities of red pepper (Capsicum annuum, L.) pericarp and red pepper seed extracts. The extracts were evaluated by various antioxidant assays, including 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging, superoxide anion radical scavenging, hydroxyl radical scavenging, [2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulphonic acid)] (ABTS) radical scavenging, ferrous chelating activity, superoxide dismutase (SOD) activity and reducing power, along with the determination of total phenolic and flavonoid contents. All the extracts showed strong antioxidant activity by the testing methods. The red pepper pericarp extract exhibited strong ferrous chelating activity and high scavenging activity against free radicals, including both the hydroxyl and DPPH radicals, but it exhibited weaker scavenging activity for the superoxide anion radical and for SOD. In contrast, the red pepper seed extract exhibited strong SOD activity and high scavenging activity against the superoxide anion radical, but showed weaker ferrous chelating activity, hydroxyl radical scavenging, and DPPH radical scavenging. We observed that the reducing power level and ABTS radical scavenging activity of the red pepper seed were higher than those of the red pepper pericarp at the highest tested concentration. Most of the test results for the red pepper seed and red pepper pericarp extracts increased markedly with increasing concentration; however, the metal chelating, SOD and ABTS radical scavenging activities did not increase with the concentration. Highest total phenolic and flavonoid contents were obtained from the red pepper pericarp extracts. Overall, the red pepper seed and red pepper pericarp extracts were highly effective for the antioxidant properties assayed, with the exceptions of ferrous chelating activity, hydroxyl radical scavenging and SOD activity.     

Effects of Various Heat Treatments on Phenolic Profiles and Antioxidant Activities of Pleurotus eryngii Extracts

Free (FP) and bound phenolics (BP) were extracted from freeze dried (FD), oven dried (OD), as well as boiling treated (BT) Pleurotus eryngii samples. Free, bound, total phenolics were quantified using Folin–Ciocalteau assay. Qualitative and quantitative analysis of phenolic compounds were carried out using high‐performance liquid chromatography (HPLC) coupled with diode array detector (DAD), and a total of 8 phenolic compounds were detected. Free phenolic contents followed the order: Freeze‐dried free phenolics (FDFP) > Oven‐dried free phenolics (ODFP) > Boiling‐treated free phenolics (BTFP), and ranged from 95.42 (BTFP) to 442.50 (ODPF) μg gallic acid equivalents (GAE)/g dry weight (DW). Bound and total phenolic contents followed the order: FD > OD > BT, and ranged from 218.33 (BTBP) to 774.17 (FDBP) and 313.75 (BT total phenolics) to 1090.42 (FD total phenolics) μg GAE/g DW. Bound phenolics contributed 49.76% (OD), 69.59% (BT), and 71% (FD) of the total phenolic contents. All free and bound phenolic extracts were investigated for their antioxidant activities by 3 different assays, 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging activity, reducing power, and superoxide anion radical scavenging activity. FDFP showed strongest DPPH radical scavenging activity (IC₅₀ at 32.61 μg/mL), ODFP showed strongest reducing power (IC₅₀ at 26.31 μg/mL), and BTBP showed strongest superoxide anion radical scavenging activity (IC₅₀ at 14.07 μg/mL).     

Proximate composition and free radical scavenging activity of edible fruits from the Argentinian Yungas

The proximate composition and free radical scavenging effect of native food plants gathered in the Argentinian Yungas have been assessed. Some 25 samples were collected for proximate analysis and free radical scavenging effect of their MeOH‐soluble extracts. Total acidity, phenolics and solid content of 16 preserves prepared from native fruits have been determined. The samples belong to 13 different species corresponding to eight plant families, mainly Myrtaceae, Solanaceae and Ulmaceae. The highest organic acid contents (as citric acid) were found in the preserves of Psidium guineense and Cyphomandra betaceae with the lowest in Sideroxylon obtusifolium and Myrciantes pungens. Total phenolics in the preserves ranged from 0.34 g kg^?1 DM in Rhipsalis flocosa to 7.30 g kg^?1 DM in Celtis iguanae. The MeOH‐solubles of the fruits/petioles as well as the preserves were assessed for inhibition of the enzyme xanthine oxidase (XO), decoloration of the free radical 2,2‐diphenyl‐1‐picryl‐hydrazyl (DPPH) and scavenging of the superoxide anion. The highest effect of the solubles towards the DPPH assay was observed for M pungens and Rubus imperialis before processing. None of the samples was effective as a XO inhibitor or superoxide anion scavenger. The best protein sources in our study were the fruits of Carica quercifolia, Celtis iguanae and Sambucus nigra. Copyright © 2005 Society of Chemical Industry     

The phenolic constituents and free radical scavenging activities of Gynura formosana Kiamnra

Gynura formosana Kiamnra (Compositae) is a herbal folk medicine that is a popular vegetable in Taiwan. The free‐radical scavenging activities of a 70% aqueous acetone extract from the herb G formosana were evaluated. Bioassay‐guided fractionation, column separation on Diaion, Toyopearl HW 40(C), Sephadex LH‐20 and MCI CHP20P, and high‐performance liquid chromatography (HPLC) were used to isolate for the first time in G formosana four potent phenolics [caffeic acid ( I ), quercetin 3‐O‐rutinoside ( II ), kaempferol 3‐O‐rutinoside ( III ) and kaempferol 3‐O‐robinobioside ( IV )]. The IC₅₀ values of 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging activity for compounds I – IV were 6.7, 7.7, 300.3 and 286.7 µM , respectively, and, for superoxide radical scavenging activity, they were 187.3, 25.8, 55.3 and 87.4 µM , respectively. Using a spin trapping electron spin resonance (ESR) method, caffeic acid ( I ) and quercetin 3‐O‐rutinoside ( II ) exhibited good hydroxyl radical activity. The free radical scavenging activity of G formosana phenolics may improve the economic value of this herb and assist in its development as a health food. Copyright © 2004 Society of Chemical Industry     

Antioxidant and free radical scavenging activities of pigments extracted from molasses alcohol wastewater

The pigments from molasses alcohol wastewater were extracted by the macroporous resin adsorption method. The antioxidant and free radical scavenging activities of these pigments were also investigated. The adsorptive characteristics of five macroporous resins including HPD-600, HPD-500, D301-R, NKA-II and D296-R were studied and the results showed that the macroporous resin HPD-600 was most appropriate for extracting the pigments from molasses alcohol wastewater. The antioxidant and free radical scavenging activities of pigments extracted from alcohol wastewater were evaluated using nitrate, hydroxyl radical, superoxide anion radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) in vitro model systems. The pigment extract exhibited a concentration-dependent radical scavenging activity in all the systems. Meanwhile, scavenging activity of pigment extract in the DPPH system was found to be significantly (P < 0.05) higher than that in other systems and the 50% inhibitory concentration (IC₅₀ value) was about 0.07 mg/ml. The scavenging effect of pigment extract on superoxide anion radical was very weak with IC₅₀ value greater than 10 mg/ml.     

Antioxidant and antibacterial activities of polyphenolic compounds from bitter cumin (Cuminum nigrum L.)

Cumin is one of the commonly used spices in food preparations. It is also used in traditional ayurvedic medicine as a stimulant, carminative and astringent. Earlier we have reported that bitter cumin (Cuminum nigrum L.) possess the most potent antioxidant activity among cumin varieties—cumin, black cumin and bitter cumin. In this study, we have further characterized the polyphenolic compounds of bitter cumin and also their antioxidant and antibacterial activity using different model systems. The major polyphenolic compounds of cumin seeds were extracted with 70% methanol, 70% acetone, water, separated by HPLC and their structures were elucidated by LC-MS. The profile of phenolic acids/flavonols in bitter cumin were found to be gallic acid, protocatechuic acid, caffeic acid, ellagic acid, ferulic acid, quercetin and kaempferol. The antioxidant activity of the cumin extract was tested on 1,1-diphenyl-2-picryl hydrazyl (DPPH) free radical scavenging, soybean lipoxygenase-dependent lipid peroxidation, rat liver microsomal lipid peroxidation and superoxide anion (O²⁻) scavenging. The bitter cumin extract exhibited high antioxidant activity with IC₅₀ values of 14.0±0.5 μg, 28.0±3.0 μg, 110±14.0 μg and 125.4±8.7 μg of the extract, respectively for DPPH free radical scavenging, soybean lipoxygenase-dependent lipid peroxidation, rat liver microsomal lipid peroxidation and superoxide anion scavenging. Further, the extract offered a significant protection against DNA damage induced by hydroxyl radicals. Among a spectrum of food-borne pathogenic and spoilage bacteria tested, the cumin extract significantly inhibited the growth of Bacillus subtilis, Bacillus cereus and Staphylococcus aureus. Thus, bitter cumin with an array of polyphenolic compounds possesses potent antioxidant and antibacterial activities.An erratum to this article can be found at     

Natural volatile treatments increase free‐radical scavenging capacity of strawberries and blackberries

Free‐radical scavenging capacities of strawberries and blackberries treated with methyl jasmonate (MJ), allyl isothiocyanate (AITC), essential oil of Melaleuca alternifolia (tea‐tree oil or TTO), and ethanol (EtOH) were investigated. All of these natural volatiles tested reduced the severity of decay in both strawberries and blackberries during storage at 10 °C as compared to the control. Most of these compounds enhanced antioxidant capacity and free‐radical scavenging capacity, except the AITC treatment. The MJ treatment for strawberries and blackberries had the highest antioxidant capacity, expressed as oxygen radical absorbance capacity (ORAC) values, after 7 days of storage. Moreover, the MJ treatment promoted the antioxidant capacity in strawberries and blackberries as measured by the radical 2,2‐di (4‐tert‐octylphenyl) ‐1‐picrylhydrazyl (DPPH) and the radical cation 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt (ABTS^?+) scavenging activity in both 7 and 14 days after storage. The MJ treatment also increased scavenging capacities on the superoxide radical (O₂^??), hydrogen peroxide (H₂O₂), hydroxyl radical (^?OH), and singlet oxygen (¹O₂) in strawberries and blackberries. Treatment with TTO or EtOH enhanced most of these free‐radical scavenging capacities, except for H₂O₂ in strawberries, and for O₂^?? and ¹O₂ in blackberries. These results indicated that all of the natural volatile compounds tested in this study, except AITC, promoted the antioxidant capacity and scavenging capacity of most major free radicals and, thus, helped to improve the physiology of berry fruits and enhanced their resistance to decay. While AITC was also very effective in reducing decay, its effect on free‐radical scavenging capacity was inconsistent, suggesting that additional mechanisms may be involved in its inhibition of fungal growth. Copyright © 2007 Society of Chemical Industry     

不同处理条件对猴头菇抗氧化活性的影响

研究不同加工、烹制条件对猴头菇抗氧化活性的影响。在不同处理条件下处理猴头菇子实体,然后从清除羟自由基的能力、还原力、清除超氧阴离子自由基和清除DPPH自由基的能力4个方面测定不同处理条件对猴头菇抗氧化活性的影响。结果显示,随烘烤温度升高,清除羟自由基的能力与还原力显著升高,清除超氧阴离子自由基的能力和清除DPPH自由基的能力显著降低。微波处理对清除羟自由基基本没有影响,但能显著升高还原力、清除超氧阴离子自由基和清除DPPH自由基的能力。煮处理中,清除超氧阴离子自由基的能力、还原力和清除DPPH自由基的能力显著高于炒处理;而对于清除羟自由基,炒处理则显著高于煮处理。研究结果为猴头菇加工、烹制条件的改善提供理论依据。     

葡萄籽低聚原花青素体外抗氧化活性研究

以实验室分离纯化得到的葡萄籽低聚原花青素为研究对象,水溶性维生素E和维生素C为对照,分别考察葡萄籽低聚原花青素对DPPH自由基、ABTS自由基、超氧阴离子自由基（O2-·）的清除能力以及铁离子还原能力（FRAP）。结果表明,葡萄籽低聚原花青素对DPPH自由基、ABTS自由基以及超氧阴离子自由基具有较高的清除能力,IC50值分别为23.52 μg/mL、51.38 μg/mL和684.46 μg/mL,具有较高的还原能力,且均优于对照水溶性维生素E。与维生素C相比,原花青素对ABTS自由基的清除能力以及还原能力均优于维生素C,两者DPPH自由基的清除能力相当,原花青素和水溶性维生素E在极低质量浓度（0.05～1.00 μg/mL）范围内,对超氧自由基具有清除能力,清除率为30%～40%,随着质量浓度的增加,维生素C的超氧阴离子自由基清除能力优于葡萄籽低聚原花青素。     

Antioxidant Effects of Herbal Tea Leaves from Yacon (Smallanthus sonchifolius) on Multiple Free Radical and Reducing Power Assays,Especially on Different Superoxide Anion Radical Generation Systems

Yacon (Smallanthus sonchifolius), a native Andean plant, has been cultivated as a crop and locally used as a traditional folk medicine for the people suffering from diabetes and digestive/renal disorders. However, the medicinal properties of this plant and its processed foods have not been completely established. This study investigates the potent antioxidative effects of herbal tea leaves from yacon in different free radical models and a ferric reducing model. A hot‐water extract exhibited the highest yield of total polyphenol and scavenging effect on 1,1‐diphenyl‐2‐picryl hydrazyl (DPPH) radical among four extracts prepared with hot water, methanol, ethanol, and ethylacetate. In addition, a higher reducing power of the hot‐water extract was similarly demonstrated among these extracts. Varying concentrations of the hot‐water extract resulted in different scavenging activities in four synthetic free radical models: DPPH radical (EC₅₀ 28.1 μg/mL), 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) cation radical (EC₅₀ 23.7 μg/mL), galvinoxyl radical (EC₅₀ 3.06 μg/mL), and chlorpromazine cation radical (EC₅₀ 475 μg/mL). The yacon tea‐leaf extract further demonstrated superoxide anion (O₂^?) radical scavenging effects in the phenazine methosulfate‐NADH‐nitroblue tetrazolium (EC₅₀ 64.5 μg/mL) and xanthine oxidase assay systems (EC₅₀ 20.7 μg/mL). Subsequently, incubating human neutrophilic cells in the presence of the tea‐leaf extract could suppress the cellular O₂^? radical generation (IC₅₀ 65.7 μg/mL) in a phorbol 12‐myristate 13‐acetate‐activated cell model. These results support yacon tea leaves may be a good source of natural antioxidants for preventing O₂^? radical‐mediated disorders.     

In vitro antioxidant activity of different cultivars of banana flower (Musa paradicicus L.) extracts available in India

Abstract: Six different cultivars of banana flowers (Musa paradicicus) (Kathali, Bichi, Shingapuri, Kacha, Champa, and Kalabou) were analyzed for the content of polyphenol expressed as gallic acid equivalent and flavonoid expressed as quercetein equivalent, and the in vitro total antioxidative activities of the flower extracts were compared with standard and expressed as trolox equivalent. The reducing power, 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and 2,2‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) radical cation (ABTS?⁺) scavenging activities, inhibition of lipid peroxidation in a linoleic acid emulsion system, and liposome peroxidation system were measured and compared with respective standard antioxidants. Iron‐mediated Fenton reaction was carried out to evaluate the protective effect of the extract of banana flower (Kacha cultivar) against H₂O₂‐induced DNA damage. The Kacha variety contains the maximum amount of polyphenol (11.94 ± 0.03 mg of gallic acid equivalent/g of dry weight) and flavonoid (0.174 ± 0.001 g of quercetin equivalent/g of polyphenol). It also has the highest total antioxidant capacity, DPPH radical scavenging activity, and ABTS?⁺ radical scavenging activity with a least EC₅₀ value of 0.051 mg/mL. Hepatic cell damage in iron‐mediated Fenton reaction caused by free radicals is reduced by the banana flower extract. On the basis of the results obtained, the banana flowers are found to be a potential source of natural antioxidants. This is the first report on the antioxidant properties of the extracts from banana flowers. The study suggests that the flowers of M. paradicicus that are found in India and consumed as vegetable can provide valuable functional ingredients that help in the prevention of oxidative stress.     

Optimization of Conditions for the Extraction of Antioxidants from Leaves of <Emphasis Type="Italic">Syzygium cumini</Emphasis> L. Using Different Solvents

The aim of the present study was to find out the best method for extracting antioxidants from Syzygium cumini L. leaves. The extraction was done by three different methods: sequential cold percolation extraction method, decoction extraction method, and maceration extraction method. Antioxidant activity, total phenol, and flavonoid content were determined in all different extracts of various extraction methods of S. cumini L. leaves. Antioxidant activity was tested by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical, superoxide anion radical and hydroxyl radical scavenging activities, and reducing capacity assessment. Sequential cold percolation extraction method proved to be the best extraction method. The acetone extract had maximum phenol and flavonoid content and showed best DPPH free radical scavenging activity and reducing capacity assessment. Ethyl acetate extract showed best superoxide radical scavenging activity, while aqueous extract showed best hydroxyl radical scavenging activity. It can be concluded that sequential cold percolation extraction method is the best method of extracting leaf antioxidants for this plant at least.     

Identification of phenolic compound in manuka honey as specific superoxide anion radical scavenger using electron spin resonance (ESR) and liquid chromatography with coulometric array detection

Apitherapy has become the focus of attention as a form of folk and preventive medicine for treating certain conditions and diseases as well as promoting overall health and well‐being. In apitherapy, honey is the therapeutic agent used for dressing surgical wounds, burns or skin ulcers, as well as for dyspepsia, peptic ulcer, etc., because of its antioxidant activity. Therefore, it is important to determine the antioxidants in honey by analytical techniques. In the present study, the antioxidant activities of honeys from different floral sources were investigated by electron spin resonance (1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and H₂O₂/NaOH/DMSO scavenging systems), liquid chromatography with coulometric array detection (LC‐ED), and liquid chromatography with electrospray mass spectrometry (LC‐MS). The antioxidant activities of some unifloral honeys (acacia, Chinese milk vetch, buckwheat and manuka) were evaluated using the radical scavenging systems. It was shown that DPPH radical scavenging activity was significantly different among the honeys, with buckwheat and manuka honeys having significantly higher scavenging activity than acacia honey. In addition, only manuka honey had specific scavenging activity for superoxide anion radicals. The compound responsible for this activity in manuka honey was identified by LC‐ED and LC‐MS. Careful examination of the LC‐ED chromatographic patterns of manuka and other honey samples revealed a distinct peak in the chromatogram of manuka honey to be methyl syringate (MSYR). The radical scavenging activity of MSYR was specific for superoxide anion radicals, similar to the case of manuka honey. Copyright © 2005 Society of Chemical Industry     

3 种食用菌多糖自由基清除作用研究

研究金顶侧耳、姬菇和毛头鬼伞3 种食用菌粗多糖和精多糖对超氧阴离子自由基(O2·)、羟自由基(·OH)、DPPH 自由基的清除作用。结果表明,金顶侧耳、姬菇和毛头鬼伞精多糖与粗多糖相比,对O2·清除率分别提高62.5%、58.3% 和51.5%;对·OH 清除率分别提高33.1%、42.3% 和33.2%;对DPPH 自由基清除率分别提高56.0%、63.5% 和60.3%。粗多糖经精制后,自由基清除能力明显提高,表明多糖是清除自由基的主要功效成分。     

Evaluation of antioxidant activities and total phenolic contents of typical malting barley varieties

Fourteen typical malting barley varieties from China were evaluated for their DPPH radical, ABTS radical cation and superoxide anion radical scavenging activities, reducing power, metal chelating activities, and total phenolic contents (TPC). All barley samples exhibited significant antioxidant activities determined by different assays, and contained significant levels of phenolic compounds. Gan4 and Wupi1 barley exhibited the highest DPPH radical scavenging activity, ABTS radical cation scavenging activity and reducing power. Gan4 and Humai16 barley showed the highest TPC, whereas the highest superoxide anion radical scavenging activity and metal chelating activity were found in Huaimai19 and Ken3 barley, respectively. The Pearson correlation analysis revealed that the TPC showed strong correlations with DPPH radical scavenging activity, ABTS radical cation scavenging activity, and reducing power (P < 0.01), whereas its correlations with superoxide anion radical scavenging activity and metal chelating activity were poor (P > 0.05). Moreover, DPPH radical scavenging activity, ABTS radical cation scavenging activity and reducing power were well positively correlated with each other (P < 0.01). Principal component analysis (PCA) was applied to understand the interrelationships among the measured antioxidant activity evaluation indices, and to gain an overview of the similarities and differences among the 14 barley varieties.     

Phenolic acid composition and antioxidant properties of Malaysian honeys

Abstract: The phenolic acid and flavonoid contents of Malaysian Tualang, Gelam, and Borneo tropical honeys were compared to those of Manuka honey. Ferric reducing/antioxidant power assay (FRAP) and the 1,1‐diphenyl‐2‐picryl‐hydrazyl (DPPH) radical‐scavenging activities were also quantified. All honey extracts exhibited high phenolic contents (15.21 ± 0.51– 42.23 ± 0.64 mg/kg), flavonoid contents (11.52 ± 0.27– 25.31 ± 0.37 mg/kg), FRAP values (892.15 ± 4.97– 363.38 ± 10.57 μM Fe[II]/kg), and high IC₅₀ of DPPH radical‐scavenging activities (5.24 ± 0.40– 17.51 ± 0.51 mg/mL). Total of 6 phenolic acids (gallic, syringic, benzoic, trans‐cinnamic, p‐coumaric, and caffeic acids) and 5 flavonoids (catechin, kaempferol, naringenin, luteolin, and apigenin) were identified. Among the Malaysian honey samples, Tualang honey had the highest contents of phenolics, and flavonoids, and DPPH radical‐scavenging activities. We conclude that among Malaysian honey samples, Tualang honey is the richest in phenolic acids, and flavonoid compounds, which have strong free radical‐scavenging activities.     

Composition and radical‐scavenging activity of Thymus glabrescens Willd. (Lamiaceae) essential oil

BACKGROUND: Knowledge about the chemical and therapeutic properties of Thymus glabrescens Willd. (Lamiaceae) is scarce and inconsistent. Therefore the main objectives of this study were to determine the yield and chemical composition of essential oils from wild‐growing T. glabrescens populations, to assess their radical scavenging activity and to correlate the results with published data in order to deduce which components are responsible for the activity. RESULTS: The plant material yielded between 4.0 and 8.0 mL kg^?1 of essential oil. All samples contained considerable but variable concentrations of thymol (22.3–55.1%), depending on the source. Radical‐scavenging activities of the oils were estimated by 1,1‐diphenyl‐2‐picrylhydrazyl free radical (DPPH) assay against butylated hydroxytoluene (BHT) and thymol as positive controls. The observed activities (IC₅₀ values ranged from 94 to 230 µg mL^?1) were strongly influenced by thymol concentration, as verified by rapid screening for DPPH radical‐scavenging activity on thin layer chromatography (TLC) plates and regression analysis. CONCLUSION: These results represent the first report on the free radical‐scavenging activity of T. glabrescens essential oil and one of the first comprehensive reports on its composition. Thymus glabrescens could be used in the food industry for seasoning purposes or for preserving processed foods from oxidative degradation. Copyright © 2008 Society of Chemical Industry     

不同乳酸菌胞外分泌物抗氧化活性的研究

以1,1-二苯基-2-三硝基苯肼（DPPH）自由基、羟自由基、超氧阴离子自由基清除能力和还原能力为评价指标,以维生素C作阳性对照,分析不同来源的28株乳酸菌的胞外分泌物体外抗氧化活性,并研究不同抗氧化活性测定方法间的相关性。结果表明,菌株GB8、WC5和GC2抗氧化能力较强,其中菌株GB8对超氧阴离子自由基清除率（98.26%）和还原能力最高（0.964）,菌株WC5对DPPH自由基的清除率最高,为74.90%;菌株GC2对羟自由基、DPPH自由基及超氧阴离子自由清除率分别为58.67%、73.09%、87.50%,还原能力为0.806,表现出最强的综合抗氧化能力。4种体外抗氧化活性分析方法的相关性结果表明,羟自由基与DPPH自由基（R2=0.633）、超氧阴离子与还原能力（R2=0.488）方法间达到了极显著相关（P＜0.01）;羟自由基与还原能力（R2=0.295）方法间达到了显著相关（P＜0.05）。