Young Soo Keum

Utilization of quercetin and quercetin glycosides from onion (Allium cepa L.) solid waste as an antioxidant, urease and xanthine oxidase inhibitors

This study aimed to determine the flavonol glycosides from onion solid waste (OSW) using HPLC analysis, with antioxidant and enzyme inhibitory activities. We found considerable amount of quercetin-4-O-monoglucoside (QMG: 254.85), quercetin-3,4-O-diglucoside (QDG: 162.34), quercetin (Q: 60.44), and isorhamnetin-3-glucoside (IMG: 23.92) (mg/100g) dry weight (DW) of OSW. For OSW, the methanol and ethanol showed the strongest antioxidant activities, followed by ethyl acetate, chloroform, and n-hexane extracts. Among the flavonols, Q and QDG possessed higher antioxidant activities. OSW and flavonol glycosides displayed significant enzyme inhibitory activity, with IC50 values ranging from 12.5±0.11 to 32.5±0.28 for OSW, 8.2±0.07 to 16.8±0.02 for flavonol glycosides, and 4.2±0.05μg/mL for thiourea (positive control) towards urease; while 15.2±0.8 to 35.8±0.2 (μg/mL) for OSW, 10.5±0.06 to 20.8±0.05 (μg/mL) for flavonol glycosides, and 6.5±0.05μg/mL for allopurinol (positive control) towards xanthine oxidase, respectively. The OSW and flavonol glycosides may thus be considered as potential antioxidant and antigout agents.

Metabolism of methoxychlor by Cunninghamella elegans ATCC36112.

Methoxychlor is considered as pro-estrogen, while some of its metabolites are more potent endocrine disruptors than the parent insecticide. Major activation of methoxychlor is through cytochrome P450-catalyzed demethylation to bisphenol A-like metabolites. Cunninghamella elegans is a well-known fungal species with its strong resemblance of the xenobiotic metabolism of the mammalian system. In this study, the metabolism of methoxychlor was investigated with the corresponding organism. Methoxychlor was rapidly transformed to approximately 11 metabolites in phase I metabolism, including oxidation, hydroxylation, and dechlorination. Concentrations of phase I metabolites reached a maximum at 4-6 days and gradually decreased until the end of the experiments. Most metabolites from the phase I reaction were further transformed to sugar conjugates. Approximately 11 or more glucose conjugates were found in culture supernatants and gradually increased, while no glucuronides were observed throughout the experiments. Piperonyl butoxide and chlorpyrifos strongly inhibit the degradation of methoxychlor and concomitant accumulation of metabolites, indicating cytochrome P450 mediated metabolism. Little or no glycosides were detected in chlorpyrifos- and piperonyl butoxide-treated cultures. From the results, Cunninghamella elegans has shown strong similarities of the phase I metabolism of methoxychlor, while the conjugation reaction is different from those of animal metabolism.

Metabolism of Nitrodiphenyl Ether Herbicides by Dioxin-Degrading Bacterium Sphingomonas wittichii RW1

Nitrodiphenyl ether herbicides, including chlomethoxyfen, nitrofen, and oxyfluorfen are potent herbicides. Some metabolites and parent compounds are considered as possible mutagens and endocrine disruptors. Both properties pose serious hygienic and environmental risks. Sphingomonas wittichii RW1 is a well-known degrader of polychlorinated dibenzo- p-dioxins, dibenzofurans, and diphenyl ethers. However, no detailed research of its metabolic activity has been performed against pesticides with a diphenyl ether scaffold. In this study, we report S. wittichii RW1 as a very potent diphenyl ether herbicide-metabolizing bacterium with broad substrate specificity. The structures of metabolites were determined by instrumental analysis and synthetic standards. Most pesticides were rapidly removed from the culture medium in the order of nitrofen > oxyfluorfen > chlomethoxyfen. In general, herbicides were degraded through the initial reduction and N-acetylation of nitro groups, followed by ether bond cleavage. Relatively low concentrations of phenolic and catecholic metabolites throughout the study suggested that these metabolites were rapidly metabolized and incorporated into primary metabolism. These results indicate that strain RW1 has very versatile metabolic activities over a wide range of environmental contaminants.

Extraction of antioxidants and flavonoids from yuzu (Citrus junos Sieb ex Tanaka) peels: a response surface methodology study

In the present investigation, extraction of antioxidants and flavonoids from the peels of yuzu fruit using a single factor experiment and a response surface methodology (RSM) based on central composite design was studied. Four independent variables were evaluated at five levels with total 29 experimental runs, including ethanol concentration (EtOH), ratio of liquid to material (L/S), extraction temperature (T), and extraction time (t). The total phenolic content (TPC), total flavonoids content (TFC), two indicators of antioxidant capacity (FRAP and DPPH), and three individual major flavonoids in yuzu (hesperidin, naringin, and phloretin) served as the response functions. Quadratic polynomial equations were obtained by multiple regression analysis to predict the optimal extraction conditions. The regression analysis showed that >95u2009% of variations were explained by the models of different responses considered. The responses were significantly influenced by all studied factors. The Multiresponse optimized conditions targeted at maximizing all the responses were found to be EtOHu2009=u200965.550u2009%; Tu2009=u200943.864u2009°C; tu2009=u2009119.673xa0min; and L/Su2009=u200937.168xa0ml/g, with a desirability of 0.950. At the optimized conditions, the experimental values of FRAP (964.9u2009±u200923.1xa0mgTE/g DW), DPPH (453.0u2009±u20095.2xa0mgTE/g DW), TPC (1161.2u2009±u200925.2xa0mgGAE/g DW), (TFC393.4u2009±u2009mgQE/g DW), hesperidin (337.2u2009±u20094.0xa0mg/g DW), naringin (244.9u2009±u20091.1xa0mg/g DW), and phloretin (43.9xa0mg/g DW) were in a reasonable agreement with the predicted values. The extraction method was applied successfully to extract antioxidants and flavonoids from yuzu peels. It also allows a fast and cost-saving process for extraction of the studied phytochemicals, in addition to improvement of the quantity of the targeted extract.

Metabolism of a fungicide mepanipyrim by soil fungus Cunninghamella elegans ATCC36112.

Mepanipyrim is a fungicide against several plant pathogens. However, no metabolic details have been established in fungi, which is the most important biomass in the natural environment. Cunninghamella elegans is a well-known fungal species with its strong resemblance to the mammalian xenobiotic metabolism. In this study, the detailed metabolic pathways of mepanipyrim were investigated with C. elegans. Approximately 87% of mepanipyrim was removed within 12 h with concomitant accumulation of nine metabolites. Structures of the metabolites were fully or tentatively identified with GC-MS and (1)H NMR. To determine the possible role of representative oxidative enzymes, piperonyl butoxide and methimazole were treated, and the kinetic responses of mepanipyrim and its metabolites were measured. Dose-dependent inhibition of metabolism was observed with piperonyl butoxide, while methimazole also inhibited the metabolism less effectively. The results indicate the possible involvement of cytochrome P450 and flavin-dependent monooxygenase in mepanipyrim metabolism. Comprehensive metabolic pathways can be deduced from the detailed analysis of metabolite profiles in control and inhibitor assays.

Antioxidant, anti-inflammatory, and enzyme inhibitory activity of natural plant flavonoids and their synthesized derivatives

The synthesized flavonoid derivatives were examined for their antioxidant, anti‐inflammatory, xanthine oxidase (XO), urease inhibitory activity, and cytotoxicity. Except few, all the flavonoids under this study showed significant antioxidant activity (45.6%–85.5%, 32.6%–70.6%, and 24.9%–65.5% inhibition by DPPH, ferric reducing/antioxidant power, and oxygen radical absorption capacity assays) with promising TNF‐α inhibitory activity (42%–73% at 10 μM) and IL‐6 inhibitory activity (54%–81% at 10 μM) compared with that of control dexamethasone. The flavonoids luteolin, apigenin, diosmetin, chrysin, O3Ꞌ, O7‐dihexyl diosmetin, O4Ꞌ, O7‐dihexyl apigenin, and O7‐hexyl chrysin, showed an inhibition with IC50 values (4.5‐8.1 μg/mL), more than allopurinol (8.5 μg/mL) at 5 μM against XO and showing more than 50% inhibition at a final concentration (5 mM) with an IC50 value of ranging from 4.8 to 7.2 (μg/mL) in comparison with the positive control thiourea (5.8 μg/mL) for urease inhibition. Thus, the flavonoid derivatives may be considered as potential antioxidant and antigout agents.

Metabolism of a New Herbicide, [14C]Pyribenzoxim, in Rice

The in vivo metabolism of a new herbicide pyribenzoxim (benzophenone Ο-[2,6-bis(4,6-dimethoxypyrimidin-2-yloxy)benzoyl]oxime) in rice was carried out using container trials. Two radiolabeled forms of [carbonyl-(14)C]pyribenzoxim (P1) and [ring-(14)C(U)]pyribenzoxim (P2) were treated separately as formulations for foliar treatment by single applications of 50 g of active ingredient (ai)/ha at the 4-6 leaves stage. At 0, 7, 30, and 60 days after treatment (DAT), samples of panicle, foliage/rest of plant, and roots were taken for analysis. Upon harvest (120 DAT), rice plants were separated into grain, husk, straw, and root parts. Total radioactive residues (TRRs) at each sampling date were determined to show that the final radioactive residues at harvest were low in grain, husk, straw, and roots, accounting for <17 ppb. The concentration of final residues in the rice plant decreased rapidly, and less than 0.1% of initial TRRs remained at harvest. At 7 DAT, metabolite 1 [M1, 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy)benzoic acid] and two unknown compounds (other-1 and other-2) were detected in foliage extract, accounting for 3.5% TRRs (21.0 ppb), 3.1% TRRs (19.0 ppb), and 9.0% TRRs (54.3 ppb), respectively, while 26.1% of M1 was observed in solvent wash. Any other metabolites were not detected in the plant, including expected metabolite M3 (benzophenone oxime). On the basis of the results obtained, a metabolic pathway of pyribenzoxim in a rice plant was proposed.

An agile, simplified and sonication mediated one-pot aqueous extraction and antibacterial assessment of predominant Korean mushrooms

Solvent-based extractions have always held the upper hand when it comes to mushrooms. Assimilating the fact that mushrooms are a part of culinary components cooked in water and not in solvents; solvent-based extraction becomes a priority. Effective water based extraction stretches 24 h, leaving space for prospective improvising through analytical interference. We have demonstrated the effective downsizing of the extraction time from 24 h to 2 min via sonication based extraction strategies. A water bath-based method could achieve effective extraction at 30 min, whereas further enhancement was seen through the use of a probe sonication approach to 2 min. The extraction efficiency was tested based on the antibacterial activity of mushroom extracts against two pathogens, Streptococcus mutans and Pseudomonas aeruginosa. The systematic optimization of the sonication approach and a comparison of their effectiveness versus conventional approaches are demonstrated. The bioactive components in the extracts obtained via the different extractions have been characterized using biochemical characterization as well as GC-MS analysis. The enhanced extraction and potent role of butanoic acid, hexadecanoic acid, octadecanoic acid and 1,2-benzenedicarboxylic acid were confirmed to be behind the success behind the sonication mediated extraction.

Structure-inhibitory activity relationships of pyrrolnitrin analogues on its biosynthesis

Pyrrolnitrin is a bacterial metabolite, served as a natural lead of agricultural fungicides. In a previous study, fenpiclonil was proven to inhibit the oxidative transformation of aminopyrrolnitrin to pyrrolnitrin, catalyzed by aminopyrrolnitrin oxidase (PrnD). This monooxygenase has an interesting catalytic activity of selective oxidation of aromatic amines, rather than aliphatic amines. However, its structural details are not well understood. In this study, various analogues of pyrrolnitrin were prepared to elucidate the structures of active site of PrnD through structure-activity relationships. In vivo pyrrolnitrin biosynthesis inhibition was determined with Burkholderia sp. O33 and Pseudomonas fluorescens Pf-5. Quantitative analysis of pyrrolnitrin and precursors indicates that 2,3-disubstituted phenyl at 3rd carbon and small substituents at 4th carbon of pyrrole are strictly required to give strong inhibitory effects. In addition, dissociable proton of pyrrole is also critical for inhibitory activity. Molecular simulation with homology-based PrnD model suggests a highly restricted conformational space in active site. The results may help more detailed understanding of this unusual enzyme. In addition, the information will be useful for the development of novel fungicide, compatible with pyrrolnitrin-producing bacterium.

Effects of pesticides on the bacterial production of pyrrolnitrin.

Pyrrolnitrin is a halogenated bacterial metabolite with antifungal and antibacterial activities which served as a lead structure of synthetic fungicides. Several pyrrolnitrin-producing bacteria are considered to be promising biopesticides. However, the application of these microorganisms is not straightforward since many synthetic pesticides usually coexist in agricultural fields and inevitably affect the efficacy of biocontrol agents. In this regard, effects of 25 xenobiotics, including 18 pesticides, were investigated for pyrrolnitrin biosynthesis by Burkholderia sp. O33 and Pseudomonas fluorescens Pf-5. Strong inhibition of pyrrolnitrin synthesis was observed in 9 chemicals, including 6 pesticides, while glyphosate and validamycin enhance biosynthesis. Fenpiclonil and fludioxonil strongly inhibit the oxidative transformation of aminopyrrolnitrin to pyrrolnitrin. Halogenation reaction to aminopyrrolnitrin was reduced by methimazole, a well-known flavin-dependent monooxygenase inhibitor. Most pesticides gave moderate growth inhibitory effects. The results suggested that synthetic chemicals can modulate the efficacy of pyrrolnitrin producing bacteria, through the inhibition of cell growth or pyrrolnitrin biosynthesis. Pathway specific inhibition by fenpiclonil, fludioxonil, and methimazole will give structural insights of corresponding enzymes.