ABTS Radical Cation Scavenging Activity Research Articles

여러 가지 특수미의 항산화 활성 및 항산화 성분

Dept. of Food Science and Technology, Chungbuk National University, Cheongju 361-763, KoreaAbstractThe objectives of this study were to determine antioxidant activity of the methanolic extracts from some specialty rices and to investigate relationships between antioxidant activities and antioxidant contents in the extracts. ABTS (2,2-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid)) radical cation scavenging activity, inhibitory effect on lipid peroxidation, chelating activity, reducing power and inhibitory effect on xanthine oxidase have been used to investigate the relative antioxidant activity of the extracts from specialty rices. The concentrations of total polyphenolics, phytic acid, and anthocyanin in the extracts were measured by spectrophotometric methods and vitamin E analysis was carried out by HPLC. The methanolic extracts prepared from black and red rices showed higher antioxidant activities and contained higher antioxidant compounds compared with other rices, apparently due to their intense red-purple color. The correlation coefficient between total polyphenolic content of methanolic extracts and ABTS radical cation scavenging activity, reducing power, and inhibitory effect of xanthine oxidase were 0.9921, 0.9856, and 0.8032, respectively.Key words: rice, antioxidant activity, antioxidant compound, correlation

Evolution of Phenolic Compounds and Antioxidant Activity during Malting

Two barley varieties, Gan4 and Hamelin, were malted to investigate the evolution of phenolic compounds and antioxidant activity during malting. The antioxidant activity was evaluated with DPPH radical scavenging activity, ABTS radical cation scavenging activity, reducing power, and metal chelating activity. Results showed that malting had significant influences on individual and total phenolic contents as well as antioxidant activities of two barley varieties. The contents of some phenolic compounds and the antioxidant activities decreased significantly during steeping and the early stages of germination and then increased remarkably during the later stages of germination and subsequent kilning. The most phenolic compounds identified in barley were (+)-catechin and ferulic acid, which both changed significantly during malting. Moreover, results from the Pearson correlation analysis showed that there were good correlations among DPPH radical scavenging activity, ABTS radical cation scavenging activity, reducing power, total phenolic content and sum of individual phenolic contents during malting.

Antioxidant activity of compounds isolated from the pyroligneous acid, Rhizophora apiculata

The polyphenols (CPAE II) was isolated from the dichloromethane extract of the pyroligneous acid, Rhizophora apiculata by simultaneous acid base and solvent extraction method. Its qualitative and quantitative composition was studied by gas chromatography mass spectroscopy (GC/MS) and out of 57 peaks, 52 compounds were identified, representing 95.47% of the total polyphenols. The CPAE II was then fractionated to four fractions (F1–F4) by means of thin layer chromatography and silica gel column chromatography with dichloromethane, dichloromethane/chloroform/ethyl acetate mixture (8:1:1; 4:3:3, v/v/v), and ethyl acetate, respectively. The antioxidant properties of the CPAE II and the fractions were evaluated. Among the four fractions, fraction 1 (F1) was the most potent in DPPH radical scavenging activity and molybdenum (VI) reducing power. It was subjected to further purification by means of silica gel column chromatography with hexane, hexane/diethyl ether mixture (9:1, 6:1, 3:1, v/v), and diethyl ether, respectively. 2,6-Dimethoxyphenol (syringol) and dihydroxybenzenes (catechol and 3-methoxycatechol) were isolated and identified by GC/MS, 1H NMR, 13C NMR spectral analyses, and confirmed by GC co-injection with authentic standards. Syringol, catechol and 3-methoxycatechol constitute 39.08, 4.21 and 1.10% of F1, respectively. Their antioxidant activities were evaluated by DPPH radical scavenging activity, ABTS radical cation scavenging activity, phosphomolybdenum and ferric reducing antioxidant power (FRAP). The trend in antioxidant capacity was similar in all the four assays, with dihydroxybenzenes > 2,6-dimethoxyphenols, although discrepancies in the ranking within the dihydroxybenzenes were present. These three compounds which showed significant antioxidant activities were isolated for the first time from the pyroligneous acid, R. apiculata.

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.

Physico-chemical characterization of starch ferulates of different degrees of substitution

Starch ferulates were prepared by reacting potato starch with ferulic acid chloride, using pyridine as a catalyst in dimethyl sulfoxide. Starch ferulates of different degrees of substitution (DS) were prepared and their formation was confirmed by the presence of the carbonyl signal around 1726 cm −1 in the FT-IR spectra. The thermal characteristics of the native starch and starch ferulates of different degrees of substitution were studied using TGA, DTG and DSC and the studies revealed the starch ferulates to be thermally more stable than the native starch. The starch esters exhibited 50% weight loss at temperatures from 332 to 375 °C while the native starch underwent 50% weight loss at 321 °C. The 1H and 13C NMR studies confirmed the structure of the modified starch. X-ray diffraction studies revealed the loss of the ordered B-type crystalline structure, characteristic of potato starch. The microstructural imaging of the starch esters exhibited a networking which was enhanced with increasing degree of substitution. The starch ferulates also exhibited DPPH radical and ABTS radical cation-scavenging activity.

The antioxidant activity and free radical-scavenging capacity of dietary phenolic extracts from horse gram ( Macrotyloma uniflorum (Lam.) Verdc.) seeds

Total phenolics and the antioxidative properties of two varieties of horse gram ( Macrotyloma uniflorum) were studied. The raw and dry-heated seed samples were extracted successively with methanol and 70% acetone separately. After removing the solvents, the extracts were freeze-dried. The black seeds contained relatively high levels of total phenolics and tannins than the brown seeds with respect to the treatments and solvents extraction. The extracts were subjected to assess their potential antioxidant activities using systems such as α,α-diphenyl-β-picrylhydrazyl (DPPH ), ABTS + , FRAP, linoleic acid emulsion, O 2 - and OH . The superoxide anion radical-scavenging activity was found to be higher in 70% acetone extract of the both raw and dry heated seeds of the respective varieties at the concentration of 600 μg in the reaction mixture. The DPPH radical and ABTS cation radical-scavenging activities were well proved and related with the ferric-reducing/antioxidant capacity of the extracts. Interestingly, among the various extracts, 70% acetone extracts of dry-heated samples of brown variety, and raw and dry-heated samples of black variety showed significantly ( P < 0.05) higher hydroxyl radical-scavenging activity. In general, all extracts exhibited good antioxidant activity (53.3–73.1%) against the linoleic acid emulsion system but were significantly ( P < 0.05) lower than the synthetic antioxidant, BHA (93.3%).

Antioxidant activity of methanolic extracts from some grains consumed in Korea

The objectives of this study were to determine antioxidant activity of the methanolic extracts from some grains and to investigate relationships between antioxidant activities and antioxidant contents in the extracts. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities, 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical cation scavenging activities, inhibitory effect on lipid peroxidation, chelating activity and reducing power have been used to investigate the relative antioxidant activities of the extracts from grains. The concentrations of total polyphenolics and carotenoids in the extracts were measured by spectrophotometric methods and vitamin E analysis was carried out by HPLC. The methanolic extracts prepared from red sorghum and black rice showed significantly higher antioxidant activities and contained higher polyphenolic contents than other grains such as white rice, brown rice, mungbean, foxtail millet, prosomillet, barley, and adlay. Polyphenolic compounds were the major naturally occurring antioxidants in grains. The correlation coefficient between total polyphenolic content and ABTS radical cation scavenging activity in the extracts was >0.99. However, no relationship was found between antioxidant activities and carotenoids and vitamin E derivatives.

Antioxidant activity of polyphenolic compounds extracted from defatted raw and dry heated Tamarindus indica seed coat

The antioxidative properties and total phenolic contents of raw and dry heated seed coat of Tamarindus indica were examined. The raw and dry heated samples were extracted with methanol followed by 70% acetone, after treating with petroleum ether, solvents were removed using rotary vacuum evaporator and the extracts which contain residual moisture were freeze-dried, respectively. Methanol extracts for both raw and dry heated seed coat samples contained higher level of total phenolics and tannins than the aqueous acetone extracts. The extracts were screened for their potential antioxidant activities using such as O 2 − , OH , α, α-diphenyl- β-picrylhydrazyl (DPPH ), ABTS + , FRAP and linoleic acid emulsion model systems. At different concentration of respective solvent extracts, the maximum level of superoxide anion radical scavenging activity (79–85%) was observed at 200 μg of both the raw and dry heated seed coat extracts in the reaction mixture. The DPPH radical and ABTS cation radical scavenging activities were well proved with the ferric reducing antioxidant capacity of the extracts. Interestingly, among the extracts, methanol and aqueous acetone extracts of dry heated sample showed the highest hydroxyl radical scavenging activity of 56.6 and 45.7%, respectively. All extracts, exhibited good antioxidant activity (64.5–71.7%) against the linoleic acid emulsion system and the values were lower and higher than the synthetic antioxdiant, BHA and ascorbic acid, respectively.

The antioxidant and free radical scavenging activities of processed cowpea ( Vigna unguiculata (L.) Walp.) seed extracts

The antioxidative properties and total phenolic contents of two varieties of cowpea ( Vigna unguiculata) were examined. The raw, dry heated and hydrothermal treated samples were extracted with 70% acetone and the extracts were freeze-dried. The unprocessed light brown seeds (LB) contained significantly higher level of total phenolics and tannins than the dark brown seeds (DB). The extracts were screened for their potential antioxidant activities using tests such as O 2 - , OH , α,α-diphenyl-β-picrylhydrazyl (DPPH ), ABTS + , FRAP, linoleic acid emulsion and β-carotene–linoleic acid in vitro model systems. At 800 μg of extract in the reaction mixture, the superoxide anion radical scavenging activity was found to be significantly higher in the raw and dry heated seed extracts than the hydrothermally processed seed samples of the respective varieties. The DPPH radical and ABTS cation radical scavenging activities were well proved and correlated with the ferric reducing antioxidant capacity of the extracts. Interestingly, among the various extracts, dry heated samples of LB and DB showed the highest hydroxyl radical scavenging activity of 83.6% and 68.2%, respectively. All extracts exhibited good antioxidant activity (74.3–84.6%) against the linoleic acid emulsion system. Using the β-carotene method, the values were significantly lower than BHT, BHA and Trolox. Owing to this property, the studies can be further extended to exploit not only the phenolic extracts but also the residual phenolic constituents associated with processed seed samples as health supplements and nutraceuticals.

The antioxidant activity and free radical-scavenging capacity of phenolics of raw and dry heated moth bean ( Vigna aconitifolia) (Jacq.) Marechal seed extracts

The antioxidative properties and total phenolic contents of Vigna aconitifolia were examined. The raw and dry heated samples were extracted with 70% acetone and the extracts were freeze-dried. The raw seeds contained higher levels of total phenolics (6.54%) and tannins (1.91%) than the dry heated seeds. The extracts were screened for their potential antioxidant activities using O 2 - , OH , α,α-diphenyl-β-picrylhydrazyl (DPPH ), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS + ), Ferric reducing/antioxidant power (FRAP), linoleic acid emulsion and Fe 2+ chelating systems. At 1 mg of extract in the reaction mixture, the superoxide anion radical-scavenging activity was found to be similar in raw and dry heated seed extracts. The DPPH radical and ABTS cation radical scavenging activities were well proved and correlated with the ferric reducing antioxidant capacity of the extracts. Interestingly, both raw and dry heated seed extracts showed the highest hydroxyl radical scavenging activity of 67.3% and 68.5%, respectively, at concentration of 1 mg/g extract. In addition, both extracts exhibited good peroxidation inhibiting activity (54.2% and 58.2%, respectively) against the linoleic acid emulsion system and the values were lower than BHA and Trolox. Fe 2+ chelating activity was also detected in both raw and dry heated seed with EDTA equivalent of 0.61 mg and 0.45 mg/g extracts, respectively.

Antioxidant properties and components of bran extracts from selected wheat varieties commercially available in Pakistan

Antioxidant activity of bran extracts from five wheat varieties indigenous to Pakistan, i.e. Punjab-96, Bhakkar-2002, Uqab-2000, SH-2002, and Pasban-90, has been evaluated. All the bran extracts exhibited appreciable total phenolic content (2.12–3.37 mg gallic acid equivalent/g bran), total flavonoid content (epicatechin equivalent 262–304 μg/g bran), chelating activity (ethylenediaminetetracetate equivalent 597–716 μg/g bran), 2,2′-diphenyl-1-picrylhydrazyl radical scavenging activity (51–79%), ABTS radical cation scavenging activity (Trolox equivalent 27–36 μmol/g), oxygen radical absorbance capacity (97–123 μmol/g), and total anthocyanin content (30–38 mg/kg bran). Tocopherol (22–26 ppm) and tocotrienol content (59–74 ppm) were determined by RP-HPLC. For confirmation of tocopherol content, polarographic study was conducted, which further authenticated the results (21–25 ppm). All the varieties exhibited appreciable antioxidant potential and significant differences were observed among the varieties in different systems of antioxidant activity evaluation.