• Mass Spectrometry Letters
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• v.4 no.2
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• pp.38-40
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• 2013

Glycans released from ovalbumin by PNGase F were analyzed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry using three different dihydroxybenzoic acid (DHB) matrix systems: 2,5-DHB, 2,6-DHB, and a 2,5-DHB/2,6-DHB binary matrix. Relative to the results obtained with the single-component matrices (2,5-DHB or 2,6-DHB), the 2,5-DHB/2,6-DHB binary matrix boasted lower background noise and higher sensitivity. A total of 16 glycan peaks were observed using the 2,5-DHB/2,6-DHB binary matrix, while only 10 and 9 glycan peaks were observed using the 2,5-DHB and 2,6-DHB matrices, respectively.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.378.2-378.2
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• 2002

Phellinus linteus has been used as anti-tumor and immuno stimulating agents in folk remedies. From precipitate of MeOH ex. by activited guided fractionation. 5.8-epidioxy ergosta-6.22-dien-3ol. palmitic acid. linoleic acid, and methyl linolate. 3.4-dihydroxybenzoic acid methylester and 4-(3'4'-Dihydroxyphenyl)-3-butene-2one were isolated. DPPH method was used to examine of antioxidative activity of the isolated compounds. As the result, 3.4-dihydroxybenzoic acid methylester, and phenolic compound. 4-(3'4'-Dihydroxyphenyl) -3-butene-2one were found to be a scavenger of 1,1-diphenyl-2-picrylhydrzyl radical. (omitted)

• Journal of the Korean Electrochemical Society
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• v.6 no.2
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• pp.130-133
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• 2003

3,4-dihydroxybenzoic acid(3,4-DHBA) was electropolymerized on glassy carbon electrode to give the GC/p-3,4-DHBA type electrode which was modified with dopamine by the help of 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride(EDC) acting as a coupling agent. The carboxylic sites on the polymeric surface of p-3,4-DHBA and mine group at the dopamine gave a QCA(Au)/p-3,4-DHBA-dopamine type of modified electrodes. The o-quinone moieties at the electrode surface exhibited high selectivity to titanium ions in solution. The redox process of the electrode is hydroquinone : quinone +$2H^+2e^-$, which had two strong and two weak pairs of peaks at CV. The modified electrode can deposit Ti(IV) ions as much as $4.13\times10^{-5}gcm^{-2}$. The calibration curve of the electrodes, log of the surface coverage-normalized redox response vs log[Ti], exhibited an excellent correlation$(r{\geq}0.997)$ for titanium concentrations ranging from $5.25\times10^{-4}\;to\;5.25\tiems10^{-8}M.$.

• Bulletin of the Korean Chemical Society
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• v.30 no.5
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• pp.1127-1130
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• 2009

The effects of different dihydroxybenzoic acid (DHB) isomers, when used as matrix materials in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), were investigated in analyses of polyethylene glycol (PEG) polymers. PEG polymers ranging from 400 to 8,000 Da were prepared in different DHB isomer matrices using solvent-based and solvent-free methods. PEG samples were detected only in matrices of 2,3-DHB, 2,5-DHB, and 2,6-DHB while the most intense peaks were observed using 2,6-DHB in both solvent-free and solvent-based preparations.

• Journal of Life Science
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• v.27 no.3
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• pp.325-333
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• 2017

High level of plasma cholesterol is strongly associated with the development of atherosclerosis and coronary heart disease. Clinical trials designed to reduce plasma cholesterol level by diet or pharmacological intervention have resulted in marked reduction of disease incidence. The enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase which reduces cholesterol biosynthesis in the liver is the key enzyme of the mevalonate pathway that produces cholesterol. In this study, 71 naturally occurring phenolic compounds were tested for inhibitory activities against HMG-CoA reductase. Eleven compounds out of 71 showed inhibitory activities: three hydrolyzable tannin (geraniin, acetonyl geraniin and pentagalloyl ${\beta}-D-glucose$), four benzoic acid derivatives (benzoic acid, trans-cinnamic acid, 2,4-dihydroxybenzoic acid and 2,5-dihydroxybenzoic acid), and four naphthoquinone derivatives (1,2-naphthoquinone, 1,4-naphthoquinone, plumbagin and shikonin). At the concentration of $10{\mu}g/ml$, 1,4-naphthoquinone inhibited HMG-CoA reductase by 99.4%, and then plumbagin 91.4%, pentagalloyl ${\beta}-D-glucose$ 46.6%, 2,4-dihydroxybenzoic acid 40.9%, shikonin 37.7%, 1,2-naphthoquinone 36.6%, trans-cinnamic acid 32.0%, acetonyl geraniin 30.2%, benzoic acid 28.5%, geraniin 28.3% and 2,5-dihydroxybenzoic acid 22.3%, respectively. $IC_{50}$ values of 1,4-naphthoquinone and plumbagin was $2.1{\mu}g/ml$ and $5.8{\mu}g/ml$, respectively.

• Food Science and Preservation
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• v.19 no.2
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• pp.229-234
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• 2012

The antioxidant substance in black onion was identified. The assays that used 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzthiazo line-6-sulphonic acid) ($ABTS^+$) radicals showed that the ethyl acetate fraction of black onion methanol extract had a higher level of radical-scavenging activity than the other fractions. Two antioxidative compounds were purified and isolated from the ethyl acetate fraction via column chromatographies of silica gel and Sephadex LH-20 using the guided DPPH radical-scavenging assay. The isolated compounds were identified as 3,4-dihydroxybenzoic acid (1) and quercetin (2) based on mass spectrometry and nuclear magnetic resonance. The isolated compounds showed a high level of DPPH and ABTS+ radical-scavenging activity. Compound 2 had a higher level of radical-scavenging activity than 1.

• Journal of the Korean Wood Science and Technology
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• v.32 no.2
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• pp.58-64
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• 2004

For the utilization of chestnut inner bark as forest biomass, the diethyl ether solubles of hot water extract from chestnut inner bark was analyzed by HPLC. Each peak was identified by comparing with retention time of standard regents and their purity from obtained UV spectrum by RI detector. Identified 6 compounds were gallic acid, 3,5-dihydroxybenzoic acid, 2,4,6-trihydroxybenzoic acid and protocatecualdehyde as phenolic acids and aldehyde, and catechin and epicatechin as flavonoids.

• Food Science and Biotechnology
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• v.18 no.2
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• pp.463-470
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• 2009

Sixteen antioxidative active compounds isolated from the EtOAc layer of MeOH extracts of kochujang, Korean fermented red pepper paste, were structurally elucidated as fumaric acid, methyl succinate, succinic acid furan-2-yl ester methyl ester (gochujangate, a novel compound), 2-hydroxy-3-phenylpropanoic acid, 3,4-dihydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 6,7-dihydroxy-2H-chromen-2-one (esculetin), caffeic acid, cis-p-coumaric acid, trans-p-coumaric acid, daidzin, genistin, apigenin 7-O-$\beta$-D-apiofuranosyl($1{\rightarrow}2$)-$\beta$-D-glucopyranoside, apigenin 7-O-$\beta$-Dglucopyranoside, and quercetin 3-O-$\alpha$-L-rhamnopyranoside by mass spectrometry (MS) and nuclear magnetic resonance (NMR) experiments. These compounds were analyzed for the first time as antioxidants from kochujang.

• Mass Spectrometry Letters
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• v.11 no.1
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• pp.6-9
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• 2020

Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) analysis of ionic liquid matrices (ILMs) prepared using pyridine and dihydroxybenzoic acid (DHB), such as 2,3-DHB and 2,5-DHB, displayed an unconventional peak at m/z 232.0, which was regarded as [DHB+pyridine-H]⁺. The peak at m/z 232.0 was not observed from other ILMs prepared using other DHB isomers, such as 2,4-DHB, 2,6-DHB, 3,4-DHB, and 3,5-DHB. Two requirements to observe the peak at m/z 232.0 in a DHB/pyridine ILM are suggested. First, carboxyl and hydroxyl groups must be located ortho to each other. Second, the secondary hydroxyl group must be located at a carbon with a high electron density. Based on these two requirements, a potential mechanism for the generation of the peak at m/z 232.0 is suggested.

• Applied Biological Chemistry
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• v.50 no.4
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• pp.358-361
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• 2007

The heartwoods of Rhus verniciflua was extracted with $H_2O$ and the concentrated extract was partitioned with $CHCl_3$, EtOAc, n-BuOH and $H_2O$, successively. From the EtOAc and n-BuOH fractions, four compounds were isolated through the repeated silica gel, ODS and Sephadex LH-20 column chromatographies. They were determined as sinapyl aldehyde (1), 2,4-dihydroxybenzaldehyde (2), 2,4-dihydroxybenzoic acid (3) and 2,4-dihydroxyphenylglyoxylic acid (4) on the basis of spectroscopic data, respectively. Among the isolated compounds, sinapyl aldehyde $(34.7{\pm}0.6%)$ and 2,4-dihydroxyphenylglyoxylic acid $(43.8{\pm}0.9%)$ showed the strong antioxidative activity than artificial antioxidant BHT $(14.4{\pm}0.3%)$ in DPPH radical scavenging activity.