Phenylpropanoid acid esters from Korean propolis and their antioxidant activities

Ten phenylpropanoic acid esters were isolated from an ethanolic extract of Korean propolis. Their structures were elucidated by spectroscopic methods including NMR and ESI-MS. Caffeic acid esters with catechol moiety exhibited significant ABTS and DPPH radical scavenging activity and protective effect against DNA damage by a Fenton reaction.     

Inhibition of fucosyltransferase VII by gallic acid and its derivatives

Gallic acid (GA) and several gallate derivatives were identified as inhibitors of fucosyltransferase VII (FucT VII). The inhibition by GA and (-)-epigallocatechin gallate (EGCG) is time-dependent and irreversible. GA and EGCG showed inhibition with IC(50) of 60 and 700 nM, respectively, after pre-incubation with FucT VII in the presence of MnCl(2). Absence of MnCl(2) results in significantly weaker inhibition. Complexation of Mn(2+) with GA, EGCG, and gallate esters was observed. Such complexation, however, is not rate-limiting for the inhibition of FucT VII. Therefore, time-dependent inhibition of fucosyltransferases by GA and EGCG is likely due to the slow inactivation by the inhibitors or Mn-inhibitor complex. Although Mg(2+) or Ca(2+) can replace Mn(2+) for FucT VII activation, none forms a complex with GA or EGCG and hence results in weaker inhibition of FucT VII. GA and EGCG also inhibit FucT IV and alpha2,3-(N)-sialyltransferase in the low micromolar range. The structure-function divergence could be observed, as EGCG, but not GA or gallate esters, inhibits Zn(2+) containing metalloproteases such as TNFalpha convertase, matrix metalloproteases 2 and 7.     

外源水杨酸对辣椒倍半萜环化酶基因表达及抗氧化酶系的作用

分析了外源水杨酸对辣椒叶片倍半萜环化酶基因表达及抗氧化酶系的作用 .结果表明 ,在 0 .5～4mmol·L-1的浓度范围内 ,SA处理均能不同程度地诱导辣椒叶片中倍半萜环化酶基因转录并表达酶活性 ,但是酶活性较低且在SA处理 36h后才出现 ;SA处理后 ,辣椒叶片SOD和POD酶活性较对照增高 ,CAT酶活性较对照降低 ,相应地 ,H2 O2 浓度升高 .H2 O2 含量的升高与SA对辣椒叶片抗氧化酶活性的综合影响有关     

Protection of DNA and membrane from gamma radiation induced damage by gallic acid

Gallic acid (3,4,5-trihydroxybenzoic acid, GA) is a naturally occurring plant phenol. In vitro and in vivo studies have shown that this phytochemical protected DNA and membranes against ionizing radiation. Rat liver microsomes and plasmid pBR322 DNA were exposed to various doses of gamma radiation in presence and absence of GA. Exposure of the microsomes to gamma radiation resulted in the formation of peroxides of membrane lipids measured as thiobarbituric acid reactive substances and presence of GA during irradiation prevented the formation of lipid peroxidation. Gamma irradiation of plasmid DNA resulted in induction of strand breaks in DNA resulting in disappearance of the supercoiled (ccc) form. Presence of GA during irradiation protected the DNA from undergoing the strand breaks. In in vivo studies it was found that whole body exposure of mice to gamma radiation (4 Gy) increased the formation of lipid peroxides in various tissues and damage to cellular DNA (as measured by alkaline comet assay) in peripheral blood leucocytes. Administration of GA to mice prior to whole body radiation exposure reduced the peroxidation of lipids and the damage to the cellular DNA indicating in vivo radiation protection of membranes and DNA by GA. (Mol Cell Biochem 278: 111–117, 2005)     

Monitoring of methyl jasmonate-responsive genes in Arabidopsis by cDNA macroarray: self-activation of jasmonic acid biosynthesis and crosstalk with other phytohormone signaling pathways.

Jasmonates mediate various physiological events in plant cells such as defense responses, flowering, and senescence through intracellular and intercellular signaling pathways, and the expression of a large number of genes appears to be regulated by jasmonates. In order to obtain information on the regulatory network of jasmonate-responsive genes (JRGs) in Arabidopsis thaliana (Arabidopsis), we screened 2880 cDNA clones for jasmonate responsiveness by a cDNA macroarray procedure. Since many of the JRGs reported so far have been identified in leaf tissues, the cDNA clones used were chosen from a non-redundant EST library that was prepared from above-ground organs. Hybridization to the filters was achieved using alpha-33P-labeled single-strand DNAs synthesized from mRNAs obtained from methyl jasmonate (MeJA)-treated and untreated Arabidopsis seedlings. Data analysis identified 41 JRGs whose mRNA levels were changed by more than three fold in response to MeJA. This was confirmed by Northern blot analysis by using eight representatives. Among the 41 JRGs identified, 5 genes were JA biosynthesis genes and 3 genes were involved in other signaling pathways (ethylene, auxin, and salicylic acid). These results suggest the existence of a positive feedback regulatory system for JA biosynthesis and the possibility of crosstalk between JA signaling and other signaling pathways.     

GC-MS analysis and in vitro antioxidant and enzyme inhibitory activities of essential oil from aerial parts of endemic Thymus spathulifolius Hausskn. et Velen

We investigated the antioxidant and enzyme inhibitory activities and chemical composition of the hydro-distilled essential oil (0.35% yield) from aerial parts of Thymus spathulifolius. Antioxidant capacity of the oil was assessed by different methods including free radical scavenging (DPPH and ABTS), reducing power (FRAP and CUPRAC) and phosphomolybdenum assay. Inhibitory activities were analyzed against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), α-amylase, α-glucosidase, and tyrosinase. Twenty-one constituents were identified representing 97.2% of the total oil with thymol (50.5%), borneol (16.7%) and carvacrol (7.7%) as the major components. The essential oil exhibited good antioxidant activity with IC₅₀ values of 3.82 and 0.22?mg/mL determined by free radical scavenging DPPH and ABTS, respectively. EC₅₀ values of FRAP and CUPRAC were found to be 0.12 and 0.34?mg/mL, respectively. The results of the present study support the uses of T. spathulifolius essential oil as a source of natural antioxidants and bioactivities for functional foods and phytomedicines.     

Screening of lactic acid bacteria from fermented vegetables by carbohydrate profiling and PCR-ELISA

AIMS: The aim of this study was to identify potential souring agents, isolated from fermented plant material, by API 50 CHL assay and a molecular method based on polymerase chain reaction and colorimetric hybridization (PCR-ELISA). METHODS AND RESULTS: Forty-two strains of lactic acid bacteria derived from plant material were screened by taking advantage of API 50 CHL and PCR-ELISA. Oligonucleotide probes used for hybridization in PCR-ELISA were specific for lactobacilli, the Leuconostoc family, Lactobacillus pentosus/plantarum and Lactobacillus brevis. The hybrides were detected by a colour-developing reaction. Bacteria isolated from fermented cucumbers were identified as Lact. plantarum-related (Lact. plantarum and Lact. pentosus) and Leuconostoc species. Most of the strains isolated from sauerkraut were identified as Lact. pentosus/plantarum. CONCLUSIONS: Complementary results were obtained in the identification of bacterial strains, isolated from fermented cucumbers and sauerkraut, by API 50 CHL and PCR-ELISA. SIGNIFICANCE AND IMPACT OF THE STUDY: PCR-ELISA proved to be suitable for the screening of large numbers of bacterial isolates from fermented vegetables. This will be useful for the identification of strains suitable for the design of starter cultures for the fermentation of plant material.     

Physico-chemical characterization, antioxidant and anticancer activities in vitro of a novel polysaccharide from Melia toosendan Sieb. Et Zucc fruit

A novel water-soluble polysaccharide pMTPS-3, obtained from Melia toosendan Sieb. Et Zucc fruit by hot-water extraction and ethanol precipitation, was fractionated by DEAE-52 cellulose anion-exchange and Sephadex G-100 gel filtration chromatography. Its primary structural features and molecular weight were characterized by Fourier infrared spectrometry (FTIR), gel permeation chromatography (GPC) and gas chromatography (GC). And the antioxidant activities of pMTPS-3 in vitro were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay, superoxide radical scavenging assay and hydroxyl radical scavenging assay. The results suggested that pMTPS-3 was a heteropolysaccharide, composed of arabinose, glucose, mannose, and galactose in the molar ratio of 17.3:28.3:41.6:12.6 with molecular weight 26 100 Da. The purified pMTPS-3 was revealed to have notable scavenging activity against DPPH radical in a concentration-dependent manner and present a moderate inhibition of superoxide radicals with an IC₅₀ (5.6 mg/ml), and potent inhibiting power for hydroxyl radical compared with crude polysaccharide. Further, it exhibited strong inhibition effect in vitro on the growth of human gastric cancer BGC-823 cells. It is strongly evidenced that pMTPS-3 purified from the crude polysaccharides of Melia toosendan Sieb. Et Zucc could be explored as a potential antioxidant and therapeutics.     

Combined effect of salicylic acid and salinity on some antioxidant activities,oxidative stress and metabolite accumulation in <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis>

It has been shown that salicylic acid (SA) acts as an endogenous signal molecule responsible for inducing abiotic stress tolerance in plants. The effect of SA and sodium chloride (NaCl) on growth, metabolite accumulation, oxidative stress and enzymatic and non-enzymatic antioxidant responses on common bean plants (Phaseolus vulgaris, cv. F-15) was studied. Results revealed that either SA or NaCl decrease, shoot, root and total plant dry weights. SA treatments decreased the contents of proline, and reduced forms of ascorbate and glutathione, however, the content of soluble sugars (TSS), thiobarbituric acid-reactive substances (TBARs) and oxidized ascorbate remained unaffected. On the other hand, salinity significantly reduced the levels of endogenous SA but increased the content of proline, soluble sugars, TBARs, ascorbate and glutathione, as well as all increasing the levels of antioxidant enzyme activities assayed, except CAT. The application of SA improved the response of common bean plants to salinity by increasing plant dry weight and decreasing the content of organic solutes (proline and TSS) and damage to the membrane (TBARs). Moreover, SA application under saline conditions decreased the levels of antioxidant enzyme activities POX, APX and MDHAR which could indicate successful acclimatization of these plants to saline conditions.     

Antibacterial and antioxidant activities of four kaempferol methyl ethers isolated from Dodonaea viscosa Jacq. var. angustifolia leaf extracts

Fractionation of dichloromethane and acetone fractions obtained by serial extraction from the leaf powder of Dodonaea viscosa Jacq. var. angustifolia (Sapindaceae) resulted in the isolation of four kaempferol methyl ethers. The compounds were identified by spectral data (¹H NMR, ¹³C NMR and MS) as: 3, 5, 7-trihydroxy-4'-methoxyflavone (1); 5, 7, 4'-trihydroxy-3, 6-dimethoxyflavone (2); 5, 7-dihydroxy-3, 6, 4'-trimethoxyflavone (santin) (3); and 5-hydroxy -3, 7, 4'-trimethoxyflavone (4) together with 3,4',5,7-tetrahydroxy flavone (kaempferol) (5). Antioxidant potential of the compounds was evaluated using a DPPH spectrophotometric assay, while antibacterial activity was determined using a serial dilution microplate technique. The isolates demonstrated varying degrees of antioxidant and antibacterial activities. Of all the compounds investigated, compounds 1 and 5 demonstrated some antioxidant activity (EC₅₀ = 75.49 ± 1.76 µM and 35.06 ± 0.85 respectively) but lower than l-ascorbic acid (EC₅₀ = 13.55 ± 0.28 µM) used as a standard antioxidant agent. The minimum inhibitory concentration (MIC) of isolated compounds against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa varied from 16 µg/ml to more than 250 µg/ml. Some structure activity relationships could be established for these compounds.     

Free radical scavenging and antioxidant activities of EPS2, an exopolysaccharide produced by a marine filamentous fungus Keissleriella sp. YS 4108

The reactive oxygen species (ROS) and free radical-initiated reactions are ascertained to play multiple roles in degenerative or pathological events such as aging, cancer, heart dysfunction and Alzheimer's disease. EPS2 with a mean molecular weight of 1.3 x 10(5) was characterized as an antioxidant exopolysaccharide from the broth of a marine filamentous fungus Keissleriella sp. YS 4108. Compositionally, it is composed of galactose, glucose, rhamnose, mannose and glucuronic acid in an approximate proportion of 50:8:1:1:0.4. The radical eliminating and antioxidant actions of the glycan was assessed in different in vitro systems showing that EPS2 exhibited profound scavenging activities in superoxide radical. As a reinforcement of the action, similar radical scavenging effects of EPS2 were also discerned with both site-specific and non site-specific hydroxyl radical using the deoxyribose assay method. Moreover, EPS2 effectively blocked as well the non site-specific strand-breaking of DNA induced by the Fenton reaction at concentrations of 0.1 and 1 mg/mL. Further investigation of the effect of EPS2 on human low density lipoprotein (LDL) system demonstrated that it significantly inhibited copper-mediated oxidation of LDL in a dose-dependent manner. These results suggest that EPS2, possessing pronounced free radical scavenging and antioxidant activities, could be of considerable preventive and therapeutic significance to some life-threatening health problems such as cancer, atherogenesis and Alzheimer's disease which pathologically initiated by the presence of free radicals leading to the inevitable peroxidation of important biomolecules.     

The reduction of nitroblue tetrazolium by red blood cells: a measure of red cell membrane antioxidant capacity and hemoglobin-membrane binding sites

The reduction of nitroblue tetrazolium (NBT) with intact Red Blood Cells (RBCs) is biphasic with an initial rapid reduction followed by a slower second phase. This biphasic kinetics has been explained with the initial rapid phase attributed to antioxidants in the red cell which reduce membrane bound NBT and the slower phase associated with the reaction of NBT with membrane bound hemoglobin. This model has been confirmed by a utilization of a number of red cell modifications which either increase the red cell antioxidants (vitamin C and vitamin E) or damage the red cell membrane (cumene hydroperoxide and N-ethylmaleimide). The utilization of this assay for human blood samples was investigated by studying a series of 20 human subjects ranging between 34 and 87 years of age. It was possible to fit all of these samples with two adjustable parameters which reflect the red cell membrane antioxidant capacity (x) and the hemoglobin membrane interactions (m). The antioxidant capacity shows a significant (p < 002; R = -.67) decrease with age. This finding is consistent with a decrease in the level of antioxidants in aged subjects. In addition, the number of hemoglobin membrane sites are negatively correlated with the antioxidant capacity (p < .02; R = -.52) suggesting that the oxidative stress associated with reduced antioxidants results in increased hemoglobin-membrane interactions.     

Synthesis of 2-keto-L-gulonic acid from gluconic acid by co-immobilized Gluconobacter oxydans and Corynebacterium sp.

2-Keto-L-gulonic acid was produced from gluconic acid using co-immobilized cells of Gluconobacter oxydans and Corynebacterium sp. with 2,5-diketo-D-gluconic acid. Gluconobacter oxydans and Corynebacterium sp. were entrapped together with polyvinylalcohol and alginate. 50 g/l glucose, 50 g/l gluconic acid, and the mixture of equal volume of 50 g/l glucose and 50 g/l gluconic acid were used as substrates. When the ratio of two cells was 1 to 1 with 100 mg cells/ml, the conversion of 2-KLG from gluconic acid was 38% (g/g). © Rapid Science Ltd. 1998