• Natural Product Sciences
• /
• 제8권4호
• /
• pp.162-164
• /
• 2002

The methanol extracts of 42 Korean indigenous plants were evaluated for the DNA strand-scission activity. As a result, the 17 extracts were found to be active in the criteria of $IC_{50}$}<$25\;{\mu}g/ml$. Among others, the MeOH extracts of Caesalpinia sappan and Mucuna birdwoodiana showed the most potent DNA strand-scission activity with $IC_{50}$ values of 5.9 and $4.9\;{\mu}g/ml$, respectively. Therefore, the partition and fractionation for C. sappan were performed and tested in the DNA strand-scission assay system for further bioassay-guided fractionation.

• Environmental Engineering Research
• /
• 제12권5호
• /
• pp.211-217
• /
• 2007

Polycyclic aromatic hydrocarbon growth from cyclopentadiene (CPD) pyrolysis was investigated using a laminar flow reactor operating in a temperature range of 600 to $950^{\circ}c$. Major products from CPD pyrolysis are benzene, indene and naphthalene. Formation of observed products from CPD is explained as follows. Addition of the cyclopentadienyl radical to a CPD $\pi$-bond produces a resonance-stabilized radical, which further reacts by one of three unimolecular channels: intramolecular addition, C-H bond $\beta$-scission, or C-C bond $\beta$-scission. The intramolecular addition pathway produces a 7-norbornenyl radical, which then decomposes to indene. Decomposition by C-H bond $\beta$-scission produces a biaryl intermediate, which then undergoes a ring fusion sequence that has been proposed for dihydrofulvalene-to-naphthalene conversion. In this study, we propose C-C bond $\beta$-scission pathway as an alternative reaction channel to naphthalene from CPD. As preliminary computational analysis, Parametric Method 3 (PM3) molecular calculation suggests that intramolecular addition to form indene is favored at low temperatures and C-C bond $\beta$-scission leading to naphthalene is predominant at high temperatures.

• Bulletin of the Korean Chemical Society
• /
• 제20권8호
• /
• pp.921-924
• /
• 1999

Hydrogels were prepared from poly( Υ-glutamic acid) (PGA) solution by g-irradiation of 90 kGy and 170 kGy. The hydrogels were more cross-linked with a higher dosage g-irradiation and completely hydrolyzed at 85℃ within 4 hours resulting in homogeneous solution. NMR techniques were employed to clarify chemical bond formation and scission involved during γ-irradiation and hydrolysis. Characterization of these samples was carried out by taking both liquid state and solid state NMR spectra of PGA and hydrolyzed hydrogels and comparison of these spectra with the solid state NMR spectra of hydrogels. Our results indicate that complicated chemical bond formation and scission have occurred during hydrolysis and γ-irradiation. The samples prepared with higher dosage of γ-irradiation showed more diverse chemical bond formation and scission.

• Applied Biological Chemistry
• /
• 제40권4호
• /
• pp.307-312
• /
• 1997

유색미의 항암활성을 in vitro에서 조사하기 위한 기초실험으로서, 유색미 겨의 유기용매 추출물에 의한 DNA strand scission 및 발암 promotion의 억제효과를 조사하였다. 실험에는 유색미로 상해향혈나와 수원415호의 두 품종과 함께 대조구로 추청을 사용하였다. 품종별 변이원 억제활성은 70% 에탄올추출물 및 모든 유기용매 분획물에서 추청<상해향혈나<수원415호의 순서로 증가하였다. 그러나 DNA strand scission에 대한 억제활성은 70% 에탄올 추출물에서 상해향혈나<추청<수원415호의 순서로 증가하였다. 클로로포름 분획물에 대하여 조사한 결과, 상해향혈나에는 거의 DNA strand scission을 억제하는 활성이 없었으며, 예상과는 달리 추청은 오히려 상해향혈나보다 약간 활성이 높았다. 그리고 수원415호의 클로로포름분획물은 70%에탄올 추출물의 경우와 비슷한 수준의 강한 억제활성을 보였다(약 50% 억제). 발암 promotor에 의하여 유도된 Epstein-Barr 바이러스의 early diffusible antigen의 발현수준을 지표로 하여 70% 에탄올 추출물의 발암 promotion의 억제효과를 측정한 결과, 추청<상해향혈나< 수원415호의 순서로 억제활성이 높아짐을 알 수 있었다. 세 품종 모두의 클로로포름분획물에서 발암 promotion을 완전히 차단하는 효과가 발견되었지만, 세포독성이 동반되지 않은 promotion에 대한 억제효과는 수원415호에서만 유일하게 관찰되었다.

• 공업화학
• /
• 제10권3호
• /
• pp.432-437
• /
• 1999

폴리에틸렌 열분해실험을 반응기 크기가 $10cm^3$인 스테인레스 스틸 반응기에서 수행하였으며 이때 반응온도는 $390{\sim}450^{\circ}C$이었다. 열분해생성물인 반응생성물과 기체생성물을 분리하여 채취하였고 각 생성물의 분자량분포는 HPLC-GPC와 GC분석을 통해 얻었다. 열분해반응의 개시-종료, 전파-비전파반응, 즉 수소탈취반응, 사슬절단, 고분자물질과 라디칼과의 결합반응 등을 설명할 수 있는 random, specific 생성물의 분자랑분포에 대한 distribution balance식을 제안하였다. 말단절단 과정에 의해 저분자량의 비응축성 기체생성물 (C1~C5)이 생성되었으며 이 기체생성물의 평균분자량은 38이었다. 무작위절단과 말단절단의 속도매개변수 중의 하나인 활성화에너지는 각각 35, 17 kcal/mole 이었다.

• Natural Product Sciences
• /
• 제9권2호
• /
• pp.105-108
• /
• 2003

During our research program to find DNA strand-scission agents from higher plants, the MeOH extracts of the stems of Mucuna birdwoodiana Tutcher. (Leguminosae) exhibited the most potent activity with an $IC_{50}$ value of $4.9\;{\mu}g/ml$. Thus, detailed laboratory investigation was performed, and led to the isolation of known compounds, $({\pm})$-catechin (1) and (-)-epicatechin(2) as active principles. Compounds 1 and 2 showed significant activity of DNA strand-scission with $IC_{50}$ values of 10.8 and $7.5\;{\mu}g/ml$, respectively (positive control, bleomycin: $IC_{50}\;3.3\;{\mu}g/ml$.

• Archives of Pharmacal Research
• /
• 제26권2호
• /
• pp.147-150
• /
• 2003

To find anticancer agents from higher plants, DNA strand-scission assay method was employed for bioassay-guided fractionation as well as for screening the crude extracts. During the screening, an ethyl acetate extracts of the heartwood of Caesalpinia sappan L. (Leguminosae) exhibited potent DNA strand-scission activity. Therefore, the ethyl acetate extracts of the dried heartwood of C. sappan was subjected to the bioassay-guided fractionation, which led to the isolation of a known compound, brazilin (1) as the active constituent. In addition, caesalpine J (2) was also isolated as an inactive constituent.

• Archives of Pharmacal Research
• /
• 제23권5호
• /
• pp.501-506
• /
• 2000

We examined the antifibrotic effect of a methanol extract from Stephania tetrandra (ST) on experimental liver fibrosis. liver fibrosis was induced by bile duct ligation and scission (BDL/S) in rats. In BDL/S rats, activity levels of aspartate transaminase (AST), alanine transaminse (ALT), alkaline phosphatase (ALP), concentration of total bilirubin in serum, and hydroxyproline content of the liver were significantly increased. The ST treatment (either 100 ${m}g/kg/day$ or 200 ${m}g/kg/day$, p.o. for 4 weeks) in BDL/S rats reduced the serum AST, ALT and ALP activity levels significantly (p<0.01). Similarly, when compared to the control group, the concentration of hydroxyproline in the livers of the BDL/S rats treated with 100${m}g$ or 200${m}g$ ST treated rats decreased by 40% and 33% respectively, when compared to the BDL/S control group (p<0.01). The morphological characteristics of fibrotic liver that were observed in the BDL/S control group, improved in the ST treated BDL/S group. In the fibrotic liver of BDL/S rats treated with ST, a marked reduction in the numbers of alpha smooth muscle cell actin positive stellate cells was observed. These results indicate that doses of either 100 or 200 ${m}g/kg/day$ of methanol extract from S. tetrandra, had an antifibrotic effect in rats with liver fibrosis induced by bile duct ligation and scission.

• Journal of Applied Biological Chemistry
• /
• 제43권3호
• /
• pp.156-160
• /
• 2000

The possible mechanism of the DNA strand breaking activity of the hot-water extract of Fructus Chaenomelis (dried fruit of Chaenomeles sinensis) in a closed circular duplex replica form DNA (RFI DNA) was studied through agarose gel electrophresis under various conditions. Induction of DNA strand scission by the hot-water extract of C. sinensis occurred in dose and time-dependent manners. $Cu^{2+}$ was indispensable for the induction of DNA strand breakage. Exogeneous chelating agents inhibited the DNA breaking activity, conforming the catalytic action of $Cu^{2+}$ on generation of free radicals responsible for oxidative damage. Antioxidant enzymes and some radical scavengers were used to investigate the major radical species triggering the DNA strand scission, demonstrating that a highest inhibitory activity was found in the presence of catalase, while less in the presence of tiron (a scavenger for superoxide radical), 2-aminoethyl-isothiuroniumbromide-HBr, cysteamine (scavengers for hydroxyl radical), and 1,4-diazabicyclo [2,2,2] octane (a scavenger for singlet oxygen) in decreasing order. The findings implied that oxygen radical species generated in presence of transition divalent cation during the oxidation of some compounds contained in the hot-water extract of C. sinensis is mainly responsible for inducing genotoxicity.

• Bulletin of the Korean Chemical Society
• /
• 제30권12호
• /
• pp.2973-2978
• /
• 2009

The decomposition reaction mechanism of $CH_3CF_2O$ radical formed from hydroflurocarbon, $CH_3CHF_2$ (HFC-152a) in the atmosphere has been investigated using ab-initio quantum mechanical methods. The geometries of the reactant, products and transition states involved in the decomposition pathways have been optimized and characterized at DFT-B3LYP and MP2 levels of theories using 6-311++G(d,p) basis set. Calculations have been carried out to observe the effect of basis sets on the optimized geometries of species involved. Single point energy calculations have been performed at QCISD(T) and CCSD(T) level of theories. Out of the two prominent decomposition channels considered viz., C-C bond scission and F-elimination, C-C bond scission is found to be the dominant path involving a barrier height of 12.3 kcal/mol whereas the F-elimination path involves that of a 28.0 kcal/mol. Using transition-state theory, rate constant for the most dominant decomposition pathway viz., C-C bond scission is calculated at 298 K and found to be 1.3 ${\times}$ 10$^4s{-1}$. Transition states are searched on the potential energy surfaces involving both decomposition channels and each of the transition states are characterized. The existence of transition states on the corresponding potential energy surface are ascertained by performing Intrinsic Reaction Coordinate (IRC) calculation.