Variation in major antioxidants and total antioxidant activity of Yuzu (Citrus junos Sieb ex Tanaka) during maturation and between cultivars     

Yoo KM  Lee KW  Park JB  Lee HJ  Hwang IK 《Journal of agricultural and food chemistry》2004,52(19):5907-5913

Epidemiological studies suggest that a high consumption of fruits can reduce the risk of some cancers and cardiovascular disease, and this may be attributable to the antioxidant activity of vitamins and phenolic compounds. The present study investigated the variations in vitamin C, total phenolic, hesperidin, and naringin contents, and total antioxidant activity of yuzu (Citrus junos Sieb ex Tanaka)-which is a popular citrus fruit in Korea and Japan-between cultivars and during maturity. The amounts of phenolics and vitamin C and the antioxidant activity in all tested yuzu cultivars were higher in peel than in flesh. Ripening increased the total antioxidant activity and vitamin C content in both peel and flesh of yuzu. However, the amounts of all total phenolics, hesperidin, and naringin in peel increased with ripening, whereas they decreased slightly in flesh. There was a highly linear relationship between the vitamin C content and the total antioxidant activity in both peel (r(2) = 1.000) and flesh (r(2) =0.998), suggesting that vitamin C plays a key role in the antioxidant activity of yuzu. In addition, the contribution of each antioxidant to the total antioxidant activity of yuzu was determined using a 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging assay and is expressed here in terms of the vitamin C equivalent antioxidant capacity (VCEAC). The means of vitamin C, naringin, and hesperidin in yuzu were 90.4, 63.8, and 65.7 mg/100 g fresh yuzu, respectively. The relative VCEAC values of these compounds were in the following order: vitamin C (1.00) > naringin (0.195) > hesperidin (0.162). Therefore, the estimated contribution of each antioxidant to the total antioxidant capacity of 100 g of fresh yuzus is as follows (in mg of VCEAC): vitamin C (90.36 mg) > naringin (12.44 mg) > hesperidin (10.64 mg). Our results indicate that mature yuzu contains higher amounts of vitamin C and phenolics than other citrus fruits and could therefore be used as a significant dietary source of antioxidants.  相似文献   

Humic acid effects on 2-hydroxypyridine metabolism by starving Arthrobacter crystallopoietes cells     

S. Hwang  R. L. Tate III. 《Biology and Fertility of Soils》1997,25(1):36-40

Bacterial strains amended to soil to facilitate bioremediation of sites contaminated with organic substances must be capable of surviving and functioning in the presence of a variety of soil organic and mineral components. Thus, the influence of humic acid on 2-hydroxypyridine catabolism, retention of 2-hydroxypyridine catabolic activity by whole cells, and hydrophobicity of the Arthrobacter crystallopoietes cells was examined. Humic acid, added to the starvation medium of the arthrobacter cells, which had been acclimated to catabolize 2-hydroxypyridine, resulted in increased stability of this metabolic activity compared to that of comparable cells starved in the absence of humic acid. For example, after 7 days starvation, cells incubated in the presence of 0.1% (wt/vol) humic acid oxidized 2-hydroxypyridine at a rate of 54.9μmolh^–1 compared to 14.6μmolh^–1 in the absence of humic acid. Although after 1 day starvation 2.5-fold more 2-hydroxypyridine-catabolizing activity was detected in the presence of humic acid than in its absence, this enzymatic activity declined to undetectable levels after 3 days starvation both with and without humic acid in the starvation medium. No effect of humic acid was noted on protein content of the cells. Hydrophobicity of the cells was not affected by humic acid during the first 4 days of starvation but after 7 days humic acid lessened the reduction in this property. Thus, changes in cell protein content and hydrophobicity did not explain the effect of humic acid on 2-hydroxypyridine catabolism of starving A. crystallopoietes cells. Received: 21 March 1996  相似文献   

Concentration and Sources of PM10 and its Constituents in Alsasua, Spain     

Jon Zabalza  David Ogulei  Philip K. Hopke  Jong Hoon Lee  Injo Hwang  Xavier Querol  Andrés Alastuey  Jesús M. Santamaría 《Water, air, and soil pollution》2006,174(1-4):385-404

Ambient concentrations of PM₁₀ were measured every fifteen minutes from November 2002 to October 2003 at Alsasua (Northern Spain) using a laser particle counter. A high volume sampler was also used to collect 24-h integrated PM₁₀ samples at a frequency of three running days per week (i.e. three consecutive PM₁₀ samples followed by five days without sampling) for gravimetric determination of PM₁₀ mass concentrations followed by chemical analysis of its chemical components. The annual mean PM₁₀ concentration obtained using the laser particle counter with gravimetric correction was 22.7 μg m^?3 (365 days), while the mean for the gravimetric samples was 29.5 μg m^?3 (134 days). A total of 94 integrated PM₁₀ samples were analyzed for 60 chemical species using a combination of inductively coupled plasma spectrometry (ICP) and ion chromatography (IC). The concentrations of the main PM₁₀ components were found to be generally in agreement with the values reported for other Spanish cities. Bilinear Positive Matrix Factorization (PMF2) was used to study the sources of PM₁₀ and its constituents. Six main sources of PM₁₀ were identified (average contribution to total PM₁₀ mass in parentheses): crustal material (35%), secondary sulfate (21%), secondary nitrate (14%), motor vehicles (12%), sea-salt aerosol (12%) and metallurgical industries (3%).  相似文献   

Liquid chromatographic determination of vitamin K1 trans- and cis-isomers in infant formula     

S M Hwang 《Journal of the Association of Official Analytical Chemists》1985,68(4):684-689

The normal phase liquid chromatographic (LC) method for determination of trans- and cis-isomers of vitamin K1 (phylloquinone) in infant formula described here uses an Apex silica column, isocratic elution, and UV absorption detection at 254 nm. Vitamin K1 is extracted quantitatively from the product matrix by pretreating the as-fed liquid with concentrated ammonium hydroxide and methanol, and then extracting it with a 2:1 mixture of dichloromethane and isooctane. The extract is cleaned up by silica open-column chromatography and concentrated for LC analysis. For trans-vitamin K1, the method precision is less than or equal to 3.3% RSD (relative standard deviation), and the spike recovery is 98 +/- 4%. For cis-vitamin K1, the precision is less than or equal to 12% RSD, determined at levels near the detection limit, and the spike recovery is 95 +/- 9%. The detection limit is 0.3 ng for both isomers at signal/noise = 3.  相似文献   

Ultrastructure of individual and compound starch granules in isolation preparation from a high-quality, low-amylose rice, ilpumbyeo, and its mutant, G2, a high-dietary fiber, high-amylose rice     

Kim KS  Hwang HG  Kang HJ  Hwang IK  Lee YT  Choi HC 《Journal of agricultural and food chemistry》2005,53(22):8745-8751

The ultrastructures of isolated starch granules from Ilpumbyeo (IP), a low-amylose japonica rice, and its mutant, Goami2 (G2), a high-amylose rice, which have extreme contrasts in physicochemical properties, cooking qualities (Kang, H. J.; Hwang, I. K.; Kim, K. S.; Choi, H. C. Comparative structure and physicochemical properties of Ilpumbyeo, a high-quality japonica rice, and its mutant, Suweon 464. J. Agric. Food Chem. 2003, 51, 6598-6603. Kim, K. S.; Kang, H. J.; Hwang, I. K.; Hwang, H. G.; Kim, T. Y.; Choi, H. C. Comparative ultrastructure of Ilpumbyeo, a high-quality japonica rice, and its mutant, Suweon 464: Scanning and transmission electron microscopy studies. J. Agric. Food Chem. 2004, 52, 3876-3883), and susceptibility to amylolytic enzymes (Kim, K. S.; Kang, H. J.; Hwang, I. K.; Hwang, H. G.; Kim, T. Y.; Choi, H. C. Fibrillar microfilaments associated with a high-amylose rice, Goami2, a mutant of Ilpumbyeo, a high-quality japonica rice. J. Agric. Food Chem. 2005, 53, 2600-2608), were compared. In isolated preparation, IP consisted entirely of well-separated individual starch granules (ISG), whereas G2 consisted of two populations, the large voluminous bodies and the smaller forms, the ISGs. High-voltage electron microscopy revealed that each of the voluminous bodies consisted of tightly packed smaller subunits, the ISGs, indicating that they represent the compound starch granules (CSGs) of G2. This suggests that the structural as well as functional unit of G2 involved in food processing is, unlike IP and other ordinary rices, not ISG but is primarily CSG. ISGs located at the periphery of CSGs were fused to each other with adjacent ones forming a thick band or wall encircling the entire circumference. The periphery of ISGs separated from CSGs of G2 consisted of thin radially oriented filaments arranged side by side along the entire granule surface, whereas no such filaments occurred in ISG of IP. It appears that the thick band and the peripheral filaments surrounding CSGs and ISGs, respectively, function as a structural barrier that limits the entrance of water into the granules and subsequent absorption, causing the low swelling power, incomplete gelatinization, and finally poor quality of cooked rice in G2.  相似文献   

Isolation and antifungal activity of 4-phenyl-3-butenoic acid from Streptomyces koyangensis strain VK-A60     

Lee JY  Lee JY  Moon SS  Hwang BK 《Journal of agricultural and food chemistry》2005,53(20):7696-7700

An antifungal compound was isolated from the culture broth of Streptomyces koyangensis strain VK-A60 using various chromatographic procedures. On the basis of the high-resolution EI-mass and 1H and 13C NMR data, the compound was identified as 4-phenyl-3-butenoic acid. Colletotrichum orbiculare, Magnaporthe grisea, and Pythium ultimum were most sensitive to 4-phenyl-3-butenoic acid. Strong inhibitory effects of 4-phenyl-3-butenoic acid also were found against Pectobacterium carotovorum subsp. carotovorum and Ralstonia solanacearum. 4-Phenyl-3-butenoic acid effectively suppressed the development of M. grisea on rice leaves at the concentration of more than 10 microg/mL, and the protective activity was in general similar to that of the commercial fungicide tricyclazole. Treatment with 100 microg/mL of 4-phenyl-3-butenoic acid also effectively inhibited the anthracnose development on cucumber plants, although its in vivo efficacy was somewhat less effective than that of the commercial fungicide chlorothalonil.  相似文献   

Role of the Arabidopsis glucose sensor HXK1 in nutrient,light, and hormonal signaling     

Moore B  Zhou L  Rolland F  Hall Q  Cheng WH  Liu YX  Hwang I  Jones T  Sheen J 《Science (New York, N.Y.)》2003,300(5617):332-336

Glucose modulates many vital processes in photosynthetic plants. Analyses of Arabidopsis glucose insensitive2 (gin2) mutants define the physiological functions of a specific hexokinase (HXK1) in the plant glucose-signaling network. HXK1 coordinates intrinsic signals with extrinsic light intensity. HXK1 mutants lacking catalytic activity still support various signaling functions in gene expression, cell proliferation, root and inflorescence growth, and leaf expansion and senescence, thus demonstrating the uncoupling of glucose signaling from glucose metabolism. The gin2 mutants are also insensitive to auxin and hypersensitive to cytokinin. Plants use HXK as a glucose sensor to interrelate nutrient, light, and hormone signaling networks for controlling growth and development in response to the changing environment.  相似文献   

A short Fe-Fe distance in peroxodiferric ferritin: control of Fe substrate versus cofactor decay?     

Hwang J  Krebs C  Huynh BH  Edmondson DE  Theil EC  Penner-Hahn JE 《Science (New York, N.Y.)》2000,287(5450):122-125

The reaction of oxygen with protein diiron sites is important in bioorganic syntheses and biomineralization. An unusually short Fe-Fe distance of 2.53 angstroms was found in the diiron (mu-1,2 peroxodiferric) intermediate that forms in the early steps of ferritin biomineralization. This distance suggests the presence of a unique triply bridged structure. The Fe-Fe distances in the mu-1, 2 peroxodiferric complexes that were characterized previously are much longer (3.1 to 4.0 angstroms). The 2.53 angstrom Fe-Fe distance requires a small Fe-O-O angle (approximately 106 degrees to 107 degrees). This geometry should favor decay of the peroxodiferric complex by the release of H2O2 and mu-oxo or mu-hydroxo diferric biomineral precursors rather than by oxidation of the organic substrate. Geometrical differences may thus explain how diiron sites can function either as a substrate (in ferritin biomineralization) or as a cofactor (in O2 activation).  相似文献   

Reversing the inactivation of peroxiredoxins caused by cysteine sulfinic acid formation     

Woo HA  Chae HZ  Hwang SC  Yang KS  Kang SW  Kim K  Rhee SG 《Science (New York, N.Y.)》2003,300(5619):653-656

The active-site cysteine of peroxiredoxins is selectively oxidized to cysteine sulfinic acid during catalysis, which leads to inactivation of peroxidase activity. This oxidation was thought to be irreversible. However, by metabolic labeling of mammalian cells with 35S, we show that the sulfinic form of peroxiredoxin I, produced during the exposure of cells to H2O2, is rapidly reduced to the catalytically active thiol form. The mammalian cells' ability to reduce protein sulfinic acid might serve as a mechanism to repair oxidatively damaged proteins or represent a new type of cyclic modification by which the function of various proteins is regulated.  相似文献   

TAZ, a transcriptional modulator of mesenchymal stem cell differentiation     

Hong JH  Hwang ES  McManus MT  Amsterdam A  Tian Y  Kalmukova R  Mueller E  Benjamin T  Spiegelman BM  Sharp PA  Hopkins N  Yaffe MB 《Science (New York, N.Y.)》2005,309(5737):1074-1078

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