• Bulletin of the Korean Chemical Society
• /
• v.23 no.1
• /
• pp.103-106
• /
• 2002

A new reaction mechanism is proposed for the reaction of thianthrene cation radical perchlorate $(Th^{+{\cdot}}CIO_4^-}$ and tert-butyl peroxide in acetonitrile at room temperature on the basis of experimental and theoretical results. Rapid C-O bond rupture instead of O-O bond cleavage was observed by a good peroxy radical trapping agent, thianthrene cation radical. Products were N-tert-butyl acetamide, thianthrene 5-oxide (ThO), thianthrene 5,5-dioxide $(SSO_2)$, and thianthrene (Th). Thianthrene 5,10-dioxide (SOSO) was not obtained. A comparative computational study of the cation radical of tert-butyl peroxide is made by using B3LYP and CBS-4. The computational results are helpful to explain the reaction mechanism.

• Applied Biological Chemistry
• /
• v.47 no.2
• /
• pp.279-282
• /
• 2004

An antioxidant was isolated from Korean mistletoe (Viscum album var. coloratum) by consecutive purification using silica gel, Sephadex LH-20, and RP-HPLC. The active principle was identified as homo-flavoyadorinin-B (3',7-dimethoxyluteolin-4'-O-[apiosyl $(1{\rightarrow}2)$ glucoside]) by spectral analyses. It inhibited 74.6% of hydroxyl radical and 30.6% of superoxide anion radical at 0.01 mM; however, th~compound did not show any scavenging activity against hydrogen peroxide radical. At 0.1 mM, above compound scavenged superoxide anion radical about twice as effective as positive controls, BHT and ${\alpha}-tocopherol$. Radical scavenging activities of homo-flavoyadorinin-B on DPPH, hydroxyl, and hydrogen peroxide radicals were almost same with those of positive controls.

• Korean Journal of Pharmacognosy
• /
• v.33 no.3 s.130
• /
• pp.219-223
• /
• 2002

In order to screen new radical scavenging principle which is expected to be antiaging drug lead, we have isolated 160 strains of the marine-derived fungi and investigated 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity for their acetone extracts. The significant activities (>50% Inhibition) were observed in 8 strains of fungi (MFA006, MFA0l4, MFA040, MFA133, MFA139, MFA143, MFA148, MFA153), and among them, MFA153 (Aspergillus parasiticus) showed the most significant radical scavenging activity. The active components were purified by assay-guided isolation to yield two known benzyl alcohols, l53B3 (1) and l53B4 (2), and their structures were determined by physicochemical evidence. Two compounds (1,2) showed the significant radical scavenging activity with $IC_{50}$ values of 0.6 and $1.4{\mu}M$ against DPPH, respectively.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.4
• /
• pp.624-628
• /
• 2007

Synthesis of 4-substituted 3-exo-methylenechroman derivatives was carried out by the n-Bu3SnH-mediated vinyl radical cyclization as the key step starting from various salicylaldehydes.

• Archives of Pharmacal Research
• /
• v.25 no.1
• /
• pp.77-79
• /
• 2002

Farnesylhydroquinone (1) has been isolated from the mycelium of a marine-derived fungus of the genus Penicillium. The structure of the compound (1) has been elucidated by spectral method. The compound 1 exhibits potent radical scavenging activity ($IC_{50}{\;}12.5{\;}{\mu}M$) against the DPPH.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.12
• /
• pp.2501-2504
• /
• 2007

• Bulletin of the Korean Chemical Society
• /
• v.27 no.12
• /
• pp.2097-2100
• /
• 2006

• Bulletin of the Korean Chemical Society
• /
• v.31 no.6
• /
• pp.1467-1468
• /
• 2010

• Advances in Traditional Medicine
• /
• v.9 no.2
• /
• pp.128-134
• /
• 2009

The antioxidant potency of methanolic extract Clerodendrum infortunatum Linn. (MECI), which are widely used in the Indian indigenous system of medicine for different purposes, was studied. The antioxidant potential was evaluated using different established in vitro antioxidant tests viz. determination of total amount of polyphenolics compounds, DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging, nitric oxide scavenging, superoxide anion radical scavenging, hydroxyl radical scavenging and reductive power assay. It was found that MECI contain a high amount of polyphenolics and possesses significant free radical scavenging activity in all the assay. The higher activity was may be due to presence of richest amount of polyphenolics and flavonoids in it.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.12
• /
• pp.3565-3569
• /
• 2013

A home-made pinhole-type glass nozzle was employed to generate vibronically excited but jet-cooled benzyl-type radicals from precursor 2-fluoro-4-chlorotoluene with a large amount of carrier gas He, from which the visible vibronic emission spectrum was recorded with a long-path monochromator. From an analysis of the spectrum observed, it was found that two benzyl-type radicals, 2-fluorobenzyl and 2-fluoro-4-chlorobenzyl radicals, were formed from the precursor in corona discharge. The possible pathway for the production of benzyl-type radicals that can explain the spectroscopic observation is herein proposed. In addition, the electronic energy of the $D_1{\rightarrow}D_0$ transition and the vibrational mode frequencies in the $D_0$ state of the 2-fluoro-4-chlorobenzyl radical were determined for the first time.