共查询到20条相似文献,搜索用时 15 毫秒
1.
A. Sharma C. L. S. N. Rao B. K. Ball S. K. Hasija 《World journal of microbiology & biotechnology》1996,12(6):615-617
Forty bacterial isolates from the effluents of a gelatin factory (Jabalpur, India) were screened for protease activity and the two most potent producers were identified as Bacillus laterosporus and a Flavobacterium sp. The enzymes of both isolates were optimal at pH 8 and 60°C, with maximum activity after 90 min. The enzyme activity of B. laterosporus was suppressed by Fe2+, Mg2+, Mn2+ and Zn2+ ions but was enhanced by Ba2+ and Ca2+. That of Flavobacterium sp. was suppressed by Mg2+ and Mn2+ ions but enhanced by Ba2+, Ca2+ and Fe2+. The enzyme activity of the former was strongly inhibited by KCN, whereas that of the latter was only slightly inhibited by 8-hydroxyquinoline. 相似文献
2.
Beata Jasiewicz Arleta Sierakowska Wojciech Jankowski Marcin Hoffmann Weronika Piorońska Agnieszka Górnicka 《Free radical research》2018,52(6):724-736
A series of new di- and polyamine-caffeine analogues were synthesised and characterised by NMR, FT-IR, and MS spectroscopic methods. To access the stability of the investigated caffeine analogues, molecular dynamic simulations were performed in NAMD 2.9 assuming CHARMM36 force field. To evaluate the antioxidant capacity of new compounds, three different antioxidant assays were used, namely 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH?) scavenging activity, ferrous ions (Fe2+) chelating activity, and Fe3+→Fe2+reducing ability. In vitro, the ability of new derivatives to protect human erythrocytes against oxidative haemolysis induced by free radical from 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH) was estimated. The cytotoxic activity was tested using MCF-7 breast cancer cells and human erythrocytes. All compounds showed the antioxidant capacity depending mostly on their ferrous ions chelating activity. In the presence of AAPH, some derivatives were able to effectively inhibit the oxidative haemolysis. Two derivatives, namely 8-(methyl(2-(methylamino)ethyl)-amino)caffeine and 8-(methyl(3-(methylamino)propyl)amino)caffeine, showed cytotoxic activity against MCF-7 breast cancer cells but not against human erythrocytes. Therefore, it is concluded that the selected di- and polyamine caffeine analogues, depending on their chemical structure, were able to minimise the oxidative stress and to inhibit the tumour cell growth. The confirmed antioxidant and cytotoxic properties of some caffeine derivatives make them attractive for potential applications in food or pharmaceutical industries. 相似文献
3.
Ekrem KÖksal Sevim Beyza ÖztÜrk Sarikaya Ercan Bursal 《Journal of enzyme inhibition and medicinal chemistry》2013,28(2):395-405
Silymarin, a known standardized extract obtained from seeds of Silybum marianum is widely used in treatment of several diseases of varying origin. In the present paper, we clarified the antioxidant activity of silymarin by employing various in vitro antioxidant assay such as 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH·) scavenging, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, total antioxidant activity determination by ferric thiocyanate, total reducing ability determination by Fe3+ ? Fe2+ transformation method and Cuprac assay, superoxide anion radical scavenging by riboflavin/methionine/illuminate system, hydrogen peroxide scavenging and ferrous ions (Fe2+) chelating activities. Silymarin inhibited 82.7% lipid peroxidation of linoleic acid emulsion at 30 μg/mL concentration; butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol and trolox indicated inhibition of 83.3, 82.1, 68.1 and 81.3% on peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, silymarin had an effective DPPH· scavenging, ABTS√+ scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe3+) reducing power by Fe3+ ? Fe2+ transformation, cupric ions (Cu2+) reducing ability by Cuprac method, and ferrous ions (Fe2+) chelating activities. Also, BHA, BHT, α-tocopherol and trolox, were used as the reference antioxidant and radical scavenger compounds. Moreover, this study, which clarifies antioxidant mechanism of silymarin, brings new information on the antioxidant properties of silymarin. According to the present study, silymarin had effective in vitro antioxidant and radical scavenging activity. It could be used in the pharmacological and food industry because of its antioxidant properties. 相似文献
4.
Ken Yamaguchi Yoh Tokoro Kazuo Oshima Katsunobu Tanaka Takeo Suzuki 《Bioscience, biotechnology, and biochemistry》2013,77(9):2189-2190
Four mannanases (Mannanases I, II, III, and IV) were isolated from the culture filtrate of a Streptomyces sp. by ion exchange chromatography. Mannanase IV was the main component and accounted for 64.4% of the total activity of the four mannanases. Mannanase IV was further purified by gel filtration, and the purified Mannanase IV was homogeneous on disc-gel electrophoretic analysis.Optimum pH and temperature for the activity of Mannanase IV were 6.8 and 57°C, respectively. It was stable at temperatures up to 45°C when examined at pH 6.8 for 30min, and lost only 15% of its activity at 70°C for 30min at pH 6.8. The isoelectric point and molecular weight were pH 3.65 and 42,900, respectively. The enzyme was strongly inactivated by Al3+, Hg2+, Fe2+, Fe3+, Cd2+, Ag+, Sn2+, and Cu2+, and completely inhibited by iodoacetic acid and N-bromosuccinimide. The enzyme hydrolyzed mannotriose to mannose and mannobiose, but did not hydrolyze mannobiose. 相似文献
5.
The widespread use of Deverra scoparia Coss. & Durieu in Algerian folk‐medicine as a remedy can be relatively attributed to its total phenolic compounds. The current study aimed to provide a scientific basis for optimal collection and usage of Deverra scoparia Coss. & Durieu plant. Hence, 37 samples were gathered from nine sites in Algeria during two seasons 2016 and 2017, then exposed to a green extraction. Total phenolic (TPC), flavonoid (FC) and condensed tannins (CTC) content were estimated spectrophotometrically. The antioxidant activity was measured using five different methods, DPPH., ABTS.+, FRAP, CUPRAC and Fe2+‐chelating. The results have revealed considerable amounts of TPC varied from 804 to 1544 mg GAE/100 g dry matter, FC started from 187 up to 410 mg QE/100 g dry matter and CTC varied from 111 to 394 mg CE/100 g dry matter. The best IC50 values (μg/mL) of DPPH., ABTS?+, FRAP, CUPRAC and Fe2+‐chelating tests were 56.62, 5.41, 21.26, 52.93 and 78.10, respectively. Moreover, high correlations were found between CTC and most of the antioxidant tests. Hence, CTC are suggested to be the principal group of antioxidant activity in Deverra scoparia Coss. & Durieu extracts. 相似文献
6.
Jelena Živković Tatjana Ćebović Zoran Maksimović 《Central European Journal of Biology》2012,7(3):559-568
The aim of the present study was to examine the antioxidant activity of three Veronica species (Plantaginaceae). The antioxidant potential of various extracts obtained from aerial flowering parts was evaluated
by DPPH-free (1,1-diphenyl-2-picrylhydrazyl-free) radical scavenging activity and ferric-reducing antioxidant power assays.
Considerable antioxidant activity was observed in the plant samples (FRAP values ranged from 0.97 to 4.85 mmol Fe2+/g, and DPPH IC50 values from 12.58 to 66.34 μg/ml); however, these levels were lower than the activity of the control compound butylated hydroxytoluene
(BHT) (FRAP: 10.58 mmol Fe2+/g; DPPH IC50: 9.57 μg/ml). Also, the in vivo antioxidant effects were evaluated in several hepatic antioxidant systems in rats (activities of glutathione peroxidase,
glutathione reductase, peroxidase, catalase, xanthine oxidase, glutathione content and level of thiobarbituric acid reactive
substances) after treatment with different Veronica extracts, or in combination with carbon tetrachloride (CCl4). Pretreatment with 100 mg/kg b.w. of Veronica extracts inhibited CCl4-induced liver injury by decreasing TBA-RS level, increasing GSH content, and bringing the activities of CAT and Px to control
levels. The present study suggests that the extracts analyzed could protect the liver cells from CCl4-induced liver damage by their antioxidative effect on hepatocytes. 相似文献
7.
Summary
Pseudomonas sp. strain TB-135 produces D-lactic acid from 1,2-propanediol (1,2-PD) and requires Ca2+, Mg2+ and Fe2+ for growth but does not require thiamine. The strain produced pyruvic acid only under Fe2+-deficient conditions and the addition of Cu2+ increased pyruvic acid production. Under optimal conditions (0.03 ppm of FeSO4 and 0.5ppm of CuSO4), the strain accumulated 14 mg pyruvic acid par ml after 3 days of cultivation. The thiamine concentration in the cells grown on Fe2+-deficient medium was about 6% of that in the cells grown on Fe2+-sufficient medium, though pyruvate dehydrogenase (EC 1.2.4.1) activities of both types of cells were the same. We conclude that the low thiamine content of the cells is responsible for the acid production. 相似文献
8.
The extracellular alkaline protease in the supernatant of cell culture of the marine yeast Aureobasidium pullulans 10 was purified to homogeneity with a 2.1-fold increase in specific protease activity as compared to that in the supernatant
by ammonium sulfate fractionation, gel filtration chromatography (Sephadex™ G-75), and anion-exchange chromatography (DEAE
Sepharose Fast Flow). According to the sodium dodecyl sulfate-polyacrylamide gel electrophoresis data, the molecular mass
of the purified enzyme was estimated to be 32.0 kDa. The optimal pH and temperature of the purified enzyme were 9.0 and 45°C,
respectively. The enzyme was activated by Cu2+ (at a concentration of 1.0 mM) and Mn2+ and inhibited by Hg2+, Fe2+, Fe3+, Zn2+, and Co2+. The enzyme was strongly inhibited by phenylmethylsulfonyl fluoride, but weakly inhibited by EDTA, 1–10-phenanthroline, and
iodoacetic acid. The K
m and V
max values of the purified enzyme for casein were 0.25 mg/ml and 0.0286 μmol/min/mg of protein, respectively. After digestion
of shrimp protein, spirulina (Arthospira platensis) protein, proteins of marine yeast strains N3C (Yarrowia lipolytica) and YA03a (Hanseniaspora uvarum), milk protein, and casein with the purified alkaline protease, angiotensin I converting enzyme (ACE) inhibitory activities
of the resulting peptides reached 85.3%, 12.1%, 29.8%, 22.8%, 14.1%, and 15.5%, respectively, while the antioxidant activities
of these were 52.1%. 54.6%, 25.1%, 35%, 12.5%, and 24.2%, respectively, indicating that ACE inhibitory activity of the resulting
peptides from the shrimp protein and antioxidant activity of those produced from the spirulina protein were the highest, respectively.
These results suggest that the bioactive peptides produced by digestion of the shrimp protein with the purified alkaline protease
have potential applications in the food and pharmaceutical industries. 相似文献
9.
Chayakorn Pumas Panmuk Vacharapiyasophon Yuwadee Peerapornpisal Pimporn Leelapornpisid Walailuck Boonchum Masaharu Ishii Chartchai Khanongnuch 《Phycological Research》2011,59(3):166-174
Four cyanobacterial strains including Cyanosarcina sp. SK40, Phormidium sp. PD40‐1, Scytonema sp. TP40 and Leptolyngbya sp. KC45 were selected and investigated for the phycobiliprotein (PBP) content and thermostable antioxidant activity of their cell‐free extracts. The highest content of 181.63 mg/g dry weight phycobiliprotein was found in Leptolyngbya sp. KC45 with phycoerythrin (PE) as the main phycobiliprotein. Among the PBPs of four thermotolerant cyanobacteria, PE from Leptolyngbya sp. KC45 exhibited the highest thermal stability as 80% of the original level remained after being heated at 60°C for 30 min. Antioxidant activities were detected in the cell‐free extracts of all cyanobacteria and that of Leptolyngbya sp. KC45 was also found in the highest value of 7.44 ± 0.14 and 3.89 ± 0.08 mg gallic acid equivalent (GAE) g?1 dry weights determined by 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH) and reducing power assay, respectively. This also corresponded to the phenolic compound content. Based on DPPH and reducing power assay, antioxidant activities of all cyanobacterial extracts showed the high thermostability as approximately 80% remained after being heated at 80°C for 30 min. However, it clearly indicated that the thermostability of antioxidant activity from the hot spring cyanobacterial cell‐free extract was not contributed only by the PE, but also came from phenolic compounds and other oxidative substances. 相似文献
10.
《Bioscience, biotechnology, and biochemistry》2013,77(4):608-613
A levanase from Bacillus sp. was purified to a homogeneous state. The enzyme had a molecular weight of 135,000 and an isoelectric point of pH 4.7. The enzyme was most active at pH 6.0 and 40°C, stable from pH 6.0 to 10.0 for 20 hr of incubation at 4°C and up to 30°C for 30 min of incubation at pH 6.0. The enzyme activity was inhibited by Ag +, Hg2 +, Cu2 +, Fe3 +, Pb2+, and p-chloromercuribenzoic acid. The enzyme hydrolyzed levan and phlein endowise to produce levanheptaose as a main product. The limit of hydrolysis of levan and phlein were 71% and 96%, respectively. 相似文献
11.
Phytase from Nocardia sp. MB 36 was purified (9.65-fold) to homogeneity by acetone precipitation, ion exchange, and molecular sieve chromatography. Native polyacrylamide gel electrophoresis (PAGE) and zymogram analysis showed a single active protein in the purified enzyme preparation. Sodium dodecyl sulfate (SDS)-PAGE analysis showed that phytase was a monomeric protein with a molecular weight of approximately 43 kDa. Phytase exhibited activity and stability over a broad pH range (2–8) and elevated temperatures (50–80°C), and utilized several phosphate compounds as substrates. Phytase was extremely resistant to pepsin and trypsin. Various metal ions viz. Fe2+, Co2+, and Mn2+, and NH4+, ethylenediaminetetraacetic acid or EDTA and phenylmethylsulfonyl fluoride or PMSF had no influence on activity, while Ca2+ and Zn2+ enhanced activity by 15 % and 3.58 %, respectively. SDS caused significant reduction in enzyme activity (41.8 %), while 2,3-butanedione did so moderately (15.9 %). Features of Nocardia sp. MB 36 phytase suggest a potential for animal feed applications. 相似文献
12.
为充分开发黄花倒水莲(Polygala fallax)的内生真菌资源,获得具有抗植物病原真菌、抗氧化活性的内生真菌,该文以黄花倒水莲内生真菌为研究对象,使用平板对峙法检测内生真菌对6种植物病原真菌的抑菌活性,测定内生真菌发酵液的DPPH清除自由基能力和总还原能力,评价内生真菌的抗氧化活性,并对具有强抑菌活性和抗氧化活性的菌株进行形态和ITS鉴定。结果表明:(1)黄花倒水莲内生真菌中有2株内生真菌对香蕉专化尖孢镰刀菌、柑橘树脂病菌、叶点霉菌、香蕉具条叶斑病菌、茄病镰刀菌、三七根腐病菌具有明显的抑菌活性,抑菌率在50.3%~91.4%之间,其中HNLF-5对柑橘树脂病菌的抑菌率为73.2%,HNLF-44对香蕉专化尖孢镰刀菌抑菌率为91.4%。(2)内生真菌发酵液具有良好的抗氧化活性,DPPH清除率均在80%以上,总还原能力吸光值范围为0.279 2~0.748 8。(3)HNLF-44菌株为链格孢属真菌。该研究表明,药用植物黄花倒水莲内生真菌具有较好的生物活性,为后续从黄花倒水莲内生真菌中挖掘潜在新型抑菌活性和抗氧化活性物质奠定了基础。 相似文献
13.
The xynA gene encoding a xylanase from the recently isolated Bacillus sp. strain BP-7 has been cloned and expressed in Escherichia coli. Recombinant xylanase A showed high activity on xylans from hardwoods and cereals, and exhibited maximum activity at pH 6 and 60°C. The enzyme remained stable after incubation at 50°C and pH 7 for 3 h, and it was strongly inhibited by Mn2+, Fe3+, Pb2+, and Hg2+. Analysis of xylanase A in zymograms showed an apparent molecular size of 24 kDa and a pI of above 9. The amino acid sequence of xylanase A, as deduced from xynA gene, shows homology to alkaline pI-low molecular weight xylanases of family 11 such as XynA from Bacillus subtilis. Analysis of codon usage in xynA from Bacillus sp. BP-7 shows that the G+C content at the first and second codon positions is notably different from the mean values found for glycosyl hydrolase genes from Bacillus subtilis. 相似文献
14.
Rare unifloral willow (Salix spp.) honeys obtained from nectar or honeydew were investigated by direct RP‐HPLC‐DAD method in order to identify and quantify compounds that can be used as possible markers of their origin. Antioxidant and antiradical activities of willow honeys were evaluated using FRAP (=ferric reducing antioxidant assay) and DPPH (=1,1‐diphenyl‐2‐picrylhydrazyl radical) tests, respectively. Also HMF (=5‐(hydroxymethyl)furfural), diastase activity, and CIE L*a*b*C*h* chromatic coordinates were evaluated. Abscisic acids (ABA) are typical of willow nectar honey, with a predominance of (Z,E)‐ABA on (E,E)‐ABA (98.2 and 31.7 mg/kg, resp.). Kinurenic acid and salicylic acid are useful to mark willow honeydew honey. The proposed HPLC‐DAD method proved to be easy and reliable to identify the two different Salix spp. honeys, being not affected from any sample preparation artifact. Total antioxidant activity measured with the FRAP assay ranged from 3.2 to 12.6 mmol Fe2+/kg, and the antiradical activity measured with the DPPH assay ranged from 0.6 to 3.0 mmol TEAC (=Trolox equivalent antioxidant capacity)/kg in nectar and honeydew honeys, respectively. Salix spp. nectar and honeydew honeys proved to be two completely different honeys, because, besides color attributes, they show different antioxidant properties and specific compounds. 相似文献
15.
An epoxide hydrolase gene of about 0.8 kb was cloned from Rhodococcus opacus ML-0004, and the open reading frame (ORF) sequence predicted a protein of 253 amino acids with a molecular mass of about
28 kDa. An expression plasmid carrying the gene under the control of the tac promotor was introduced into Escherichia coli, and the epoxide hydrolase gene was successfully expressed in the recombinant strains. Some characteristics of purified recombinant
epoxide hydrolase were also studied. Epoxide hydrolase showed a high stereospecificity for l(+)-tartaric acid, but not for d(+)-tartaric acid. The epoxide hydrolase activity could be assayed at the pH ranging from 3.5 to 10.0, and its maximum activity
was obtained between pH 7.0 and 7.5. The enzyme was sensitive to heat, decreasing slowly between 30°C and 40°C, and significantly
at 45°C. The enzyme activity was activated by Ca2+ and Fe2+, while strongly inhibited by Ag+ and Hg+, and slightly inhibited by Cu2+, Zn2+, Ba2+, Ni+, EDTA–Na2 and fumarate. 相似文献
16.
Lei Kai Xiao-Hang Ma Xue-Lai Zhou Xiao-Ming Jia Xia Li Kang-Ping Guo 《World journal of microbiology & biotechnology》2008,24(3):401-406
In order to study the properties of a thermostable uricase produced by Microbacterium sp. strain ZZJ4-1, the enzyme was purified by ammonium sulfate precipitation and DEAE-cellulose ion exchange, hydrophobic
and molecular sieve chromatography. The molecular mass of the purified enzyme was estimated to be 34 kDa by SDS-PAGE. The
enzyme was stable between pH 7.0 and 10.00. The optimal reaction temperature of the enzyme was 30 °C at pH 8.5. The K
m
and K
cat
of the enzyme were 0.31 mM and 3.01 s−1, respectively. Fe3+ could enhance the enzyme activity, whereas Ag+, Hg2+, o-phenanthroline and SDS inhibited the activity of the enzyme considerably. After purification, the enzyme was purified 19.7-fold
with 31% yield. As compared with uricases from other microbial sources, the purified enzyme showed excellent thermostability
and other unique characteristics. The results of this work showed that strains of Microbacterium could be candidates for the production of a thermostable uricase, which has the potential clinical application in measurement
of uric acid. 相似文献
17.
Red cabbage is a source of health beneficial substances with antioxidant and antigenotoxic properties. HPLC analysis specifying
the content of the investigated extract indicated that mainly anthocyanins (ATH) were responsible for its abilities. Cytological
research was conducted with two experimental models: plant tissues—meristematic cells of Vicia faba, and animal tissue elements—human lymphocytes. Positive influence of ATH extract on mitotic activity of Vicia cells exposed to Cu2+ stress, and inhibitory effect of ATH on cytotoxic actions of Cu2+ on lymphocytes were demonstrated. In all experimental series with ATH application in combinations with Cu2+, mitotic index (MI) were higher than those obtained for only Cu2+ stressed tissues. Preincubation in ATH before Cu2+ stress had the best effect. Similarly, after ATH applications in all tested series decrease in frequency of micronuclei (MN)
appearance was noticed in comparison with only Cu2+ stressed material. In the case of Vicia cells ATH acted effectively even applied after Cu2+ stress. It suggests that this ATH mixture not only prevents and limits but also heals the cytological injury caused by Cu2+ stress. 相似文献
18.
Free metal activity and total metal concentrations as indices of micronutrient availability to barley [Hordeum vulgare (L.) ‘Klages’] 总被引:1,自引:0,他引:1
The form in which a micronutrient is found in the rhizosphere affects its availability to plants. We compared the availability to barley of the free hydrated cation form of Fe3+, Cu2+, Zn2+, and Mn2+ versus their total metal concentrations (free ion plus complexes) in chelator-buffered solutions. Free metal ion activities were estimated using the chemical equilibrium program GEOCHEM-PC with the corrected database. In experiment 1, barley was grown in nutrient solutions with different Fe3+ activities using chelators to control Fe levels. Chlorosis occurred at Fe3+ activities of 10–18 and 10–19
M for barley grown in HEDTA and EDTA solutions, respectively. In experiment 2, barley was grown in nutrient solutions with the same calculated Fe3+ activity and the same chelator, but different total Fe concentrations. Leaf, root and shoot Fe concentrations were higher from CDTA buffered solutions which had the higher total Fe concentration indicating the importance of the total Fe concentration on Fe uptake. Results from treatments using EDTA or HEDTA, with one exception, were similar to the results from the CDTA treatment. This suggests differences in critical Fe3+ activities found in experiment 1 were due to differences in the total Fe concentration and not errors in chelate formation constants used to estimate the critical activities. Results for Cu, Zn, and Mn were similar to Fe; despite solutions with equal free Cu2+, Zn2+ and Mn2+ activities, plant concentrations of these metals were generally greater when grown in the solutions with the greater total amount of Cu, Zn, or Mn. When the free Zn2+ activity was kept constant while the total amount of Zn was increased from 4.4 to 49 M, leaf Zn concentration increased from 77 to 146 g g-1. In order to predict metal availability to barley and other species in chelator-buffered nutrient solutions, both free and total metal concentrations in solution must be considered. The critical Fe3+ activities required by barley in this study are much higher than those from tomato and soybean, 10-28
M, which strongly supports the Strategy 2 model of Fe uptake for Poaceae. This is related to the importance of the Fe3+ (barley) and the Fe2+ (tomato and soybean) ions in Fe uptake. Fe-stressed barley is known to release phytosiderophores which compete for Fe3+ in the nutrient solution, while tomato and soybean reduce Fe3+ to Fe2+ at the epidermal cell membranes to allow uptake of Fe2+ from Fe3+ chelates in solution.Abbreviations CDTA
trans-1,2-diaminocyclohexane-N,N,N,N-tetracetic acid
- DTPA
diethylenetriaminepentacetic acid
- EDTA
ethylenediaminetetracetic acid
- EDDHA
ethylenediamine-di(o-hydroxyphenylacetic acid)
- HBED-N,N
di(2-hydroxybenzoyl)-ethylenediamine-N,N-diacetic acid
- HEDTA-N
hydroxyethylenediaminetriacetic acid
- MES-2
(N-morpholino)ethanesulfonic acid
- NTA
nitrilotriacetic acid 相似文献
19.
Midori Okabayashi Nobutaka Takahashi Teiichi Fukami 《Bioscience, biotechnology, and biochemistry》2013,77(5):877-879
Dehydrodicaffeic acid dilactone (DDACD) was found in a cultured mushroom by screening for catechol-O-methyltransferase inhibitors. The enzyme which converts two molecules of caffeic acid to DDCAD has been extracted from the mushroom and purified and the enzyme reaction has been studied. It was markedly inhibited by reducing agents, such as NADPH, NADH, glutathione and ascorbic acid but stimulated by Fe3+, Fe2+, Co2+, Ni2+, Cu2+, Cu+ and Zn2+ ions. Sodium diethyldithiocarbamate and sodium cyanide known to be copper chelating agents inactivated the enzyme, but activity was restored by addition of Cu2+ or Cu+. Although the enzymic reaction did not occur under anaerobic conditions, 18O-oxygen was not incorporated into DDCAD. o-Diphenol oxidase catalyzed DDCAD formation from caffeic acid and the DDCAD-forming enzyme catalyzed the formation of DOPAchrome from DOPA. Thus, the DDCAD-forming enzyme is a type of o-diphenol oxidase. Peroxidase and hydrogen peroxide produced DDCAD from caffeic acid.On the other hand, DDCAD was non-enzymatically synthesized from caffeic acid in the presence of CuCl2 in 64% yield. In both enzymic and non-enzymic syntheses, both (+)- DDCAD and (?)-DDCAD were produced. 相似文献
20.
《Journal of enzyme inhibition and medicinal chemistry》2013,28(1):44-53
In the present study, we determined the antioxidant activity of cepharanthine and fangchinoline from Stephania rotunda by performing different in vitro antioxidant assays, including 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging, N,N- dimethyl-p-phenylenediamine dihydrochloride (DMPD) radical scavenging, superoxide anion (O2?–) radical scavenging, hydrogen peroxide scavenging, total antioxidant activity, reducing power, and ferrous ion (Fe2+) chelating activities. Cepharanthine and fangchinoline showed 94.6 and 93.3% inhibition on lipid peroxidation of linoleic acid emulsion at 30 μg/mL concentration, respectively. On the other hand, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol, and trolox indicated inhibitions of 83.3, 92.2, 72.4, and 81.3% on peroxidation of linoleic acid emulsion at the same concentration (30 μg/mL), respectively. According to the results, cepharanthine and fangchinoline have effective antioxidant and radical scavenging activity. 相似文献