• Journal of the Korean Chemical Society
• /
• v.55 no.3
• /
• pp.346-353
• /
• 2011

Base hydrolysis of 7-hydroxy-2H-chromen-2-one (HC) and 7-hydroxy-2H-chromen-2-one-4-acetic acid (HCA) in aqueous-methanol and aqueous-acetone mixtures were studied kinetically at temperature range from 283 to 313 K. The activation parameters of the reactions were evaluated and discussed. Moreover, the change in the activation energy barrier of the investigated compounds from water to water-methanol and water-acetone mixtures was estimated from the kinetic data. It is observed that the change in activation barriers is more or less the same for the hydrolysis of HC and HCA. Base hydrolysis of HC and HCA follows a rate law with $k_{obs}=k_2[OH^-]$. The decrease in the rate constants of HC and HCA as the proportion of methanol or acetone increases is due to the destabilization of $OH^-$ ion. The high negative values of entropy of activation support the proposal mechanism, i.e. the investigated reaction takes place via the formation of an intermediate complex. Moreover, these values refer to the rigidity and stability of the intermediate complex. Thus, the ring opening of the intermediate complex would be the rate controlling step.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.8
• /
• pp.2683-2688
• /
• 2012

The position of the thermodynamic equilibrium for reverse thermochromic spiropyran 6-carboxylates (SP-COOHs) was easily determined in aqueous binary mixtures, such as water-methanol, water-acetonitrile and water-dimethyl sulfoxide. The existence of more than one type of interconvertible species of the ring-opened form of SP-COOH in aqueous binary solvents enables us to evaluate the molar extinction coefficients of the ring-opened species of SP-COOH and to obtain the thermodynamic parameters.

• Journal of Ginseng Research
• /
• v.22 no.3
• /
• pp.155-160
• /
• 1998

This stuffy was carried to establish a new efficient method for the preparation of edible crude ginseng saponin. The conventional butanol extraction and resin adsorption methods were compared for the contents of total crude ginseng saponin and major ginsenosides. Seventy- percent methanol extract was applied to Diaion HP-20 column and the resin was washed with Hn and eluted with absolute methanol. The methanol elute was dried in vivo and analyzed for its ginsenosides. Use of ethanol instead of methanol to make edible crude ginseng saponin gave a similar result. Butanol extraction was performed by the conventional method. The final aqueous layer from butanol extraction was passed through Diaion HP-20 column followed by elution with methanol and Diaion HP-20 passed fraction was extracted with butanol to recover remaining components, respectively, in order to determine saponin loss. TLC and HPLC qualitatively and quantitatively monitored Ginsenosides, respectively. Loss of ginsenosides was higher in butanol extraction method than in Diction HP-20 adsorption method. In addition, saponin fractions prepared by Diction HP-20 adsorption method showed higher content of each ginsenoside, showing 8.2% higher purity than that of butanol extracted fraction. From these results, we propose the resin adsorption method as a new efficient measure for the preparation of crude ginseng saponin, which is edible by using spirit instead of methanol.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.24 no.2
• /
• pp.305-312
• /
• 1995

Ixeris dentata was extracted with methanol and then the methanol extract was further fractionated to hexane, chloroform, ethyl acetate, butanol and aqueous fraction. The methanol extract of lxeris dentata had the strong antimutagenic effect on the aflatoxin B1(AFB1) and N-methyl-N'-nitro-N-nitrosoguanidine(MNNG) in Ames mutagenicity test and SOS chromotest. Among the solvent extracted fractions from the methanol extract, the chloroform fraction exhibited the greatest antimutagenic effect suppressing the mutagenicity of AFB1 with inhibition rate of 74 percent. The methanol extract of Ixeris dentata also revealed the inhibitory effect on the growth of MG-63 human osteosarcoma cells after 6 days of breeding at 37℃. The chloroform fraction and the ethyl acetate fraction from the methanol extract of lxeris dentata were most effective and inhibited the growth of MG-63 cells by 97 and 93 percent, respectively. It is suggested that the inhibitory effects of lxeris dentata on the mutagenicity and the growth of MG-63 human osteosarcoma cells are strong in the lipid soluble fractions.

• Journal of Marine Bioscience and Biotechnology
• /
• v.1 no.4
• /
• pp.260-267
• /
• 2006

The Liquid Culture Assay using a recombinant Agrobacterium tumefaciens strain has been developed as a means for quorum sensing autoinducer screening. However, the low aqueous solubility of marine natural product extracts used as potential autoinducers has been a hindrance in the screening process. Although the addition of organic solvents and/or surfactants could increase aqueous solubility, errors in data interpretation including false positive results could be a serious problem. Therefore, determining the best possible solvent and surfactant at the optimum concentration is crucial. Evaluating methanol, ethanol, 1-propanol, DMSO and DMF at concentration ranges of 0~10% revealed < 2% methanol to be most favorable when tested for ${\beta}$-gal activity and growth inhibition of the recombinant A. tumefaciens strain. On the other hand, among surfactants tested, Triton X-100 was similarly effective in increasing the delivery of autoinducers for activity at less than 0.05% concentration.

• Korean Journal of Plant Resources
• /
• v.19 no.3
• /
• pp.405-410
• /
• 2006

A series of aqueous or methanol extracts from four different Korean salad plants were assayed to determine their allelopathy and antioxidant activity. The extracts applied on filter paper in a Petri-dish bioassay significantly inhibited root growth of against alfalfa (Medicago sativa) seedlings. Leaf extracts from 40 g dry tissue $L^{-1}$ of Aster yomena was most phytotoxic to alfalfa root growth, and followed by that of Cirsium japonicum, Taraxacum officinale, and Ixeris dentate. Methanol extracts of plants dose-dependently increased DPPH free radical scavenging activity in vitro. Antioxidant activity of methanol extracts from the same plant species was investigated, and the result showed high DPPH free radical scavenging activity in Cirsium japonicum, Aster yomena, and Ixeris dentate, however, in Taraxacum officinale was least activity. By means of HPLC analysis, chlorogenic acid, p-coumaric acid, and total phenolics with 7.68, 17.47 and 18.64 mg, $100g^{-1}$, respectively, showed the highest amounts in methanol extracts from Cirsium japonicum leaves. These results suggest that Compositae salad plants contain water-soluble substances with allelopathic potential as well as antioxidant activity.

• Fire Science and Engineering
• /
• v.29 no.2
• /
• pp.39-43
• /
• 2015

The flash point is the major property to characterize fire and explosion hazard of liquid mixtures. The flash point is the lowest temperature at which a liquid gives off enough vapor to form a flammable air-vapor mixture. The flash points of two aqueous mixtures, water-methanol and water-ethanol, were measured using Seta flash closed cup tester. A prediction method based on activity coefficient models, Wilson and UNIQUAC equations, was used to calculate the flash point. The calculated flash points were compared to the results by the calculating method using Raoult's law. The calculated values based on activity coefficients models were found to be better than those based on the Raoult's law.

• Food Science and Preservation
• /
• v.4 no.3
• /
• pp.311-315
• /
• 1997

Proximate compositions of black rice and antioxidative effects of its methanol extract on refined perilla oil were investigated. Black rice seeds were composed of water 12.4%, crude protein 7.9%, crude fat 2.2%, crude fiber 1.0%, ash 1.4% and N-free extract 75.1%. The hexane and 80% methanol fractions in yields were higher than 80% ethanol and chloroform. In AOM(active oxygen method) test, antioxidative effects of black rice added to the refined perilla oil was increased with dose-dependent fashion in concentration of the black rice extracts. Among several extracts tested, 80% aqueous methanol extract showed the highest antioxidative activity, followed by hexane, chloroform, in that order. The peroxide value and TBA value for their antioxidation stability were also lower than that of control. This result was similar to that of AOM test.

• Korean Membrane Journal
• /
• v.5 no.1
• /
• pp.1-9
• /
• 2003

Due to the increasing intelligence, the increasing connectivity, and always-on characteristics energy needs for the portable electronics cannot be managed by the state-of-art battery technology. Micro fuel cell fuelled by aqueous methanol is gaining lots of interest from the new energy storage developers since it has the potential to offer the longer operation time to the portable electronic devices. Although the technical barriers to the commercialization exit, it is expected that the micro fuel cell technology bring huge benefits to the current energy storage market once it matures. In the article, benefits, challenges and market players of the direct methanol fuel cell arena is briefly reviewed.

• Journal of Microbiology and Biotechnology
• /
• v.2 no.1
• /
• pp.1-6
• /
• 1992

The aspartame, $\alpha$-L-aspartyl-L-phenylalanine methylester, is an artificial sweetener. Taking advantage of the fact that the aspartame is a derivative of dipeptide, synthesis of aspartame from the artificial polypeptide made by an artificial gene has been attempted. The artificial polypeptide (LAP32), a polymer of tripeptide (aspartyl-phenylalanyl-lysine), was purified from the E. coli cells harboring a recombinant plasmid containing the artificial gene. This polypeptide was then digested with trypsin and carboxypeptidase B to produce dipeptide (Asp-Phe). Using the esterase activity of $\alpha$-chymotrypsin, the dipeptide was directly converted into Asp-Phe methylester in a water-methanol system. When the methanol concentration in reaction mixture was 25%, 50% of dipeptide was converted to the dipeptide methylester without producing any by-products.