Catechin-7-O-β-d-glucopyranoside scavenges free radicals and protects human B lymphoma BJAB cells on H2O2-mediated oxidative stress

Catechin-7-O-β-d-glucopyranoside (CA-G) was previously isolated from red bean (the seed of Phaseolus calcaratus cv. Roxburgh). This study examined the ability of CA-G to scavenge reactive oxygen species generated by cell-free systems and to protect cells from oxidative stress caused by hydrogen peroxide (H₂O₂). The mechanism by which CA-G exerts its antioxidant and anti-apoptotic action on H₂O₂-exposed cells was also investigated. CA-G treatment prevented H₂O₂-mediated apoptosis and inhibited the formation of single stand breaks in DNA in H₂O₂-exposed BJAB cells. CA-G suppressed mitochondrial stress and caspase activation caused by H₂O₂. Mechanistic experiments revealed that the antioxidant mechanism of CA-G on H₂O₂-mediated oxidative damage was due to the direct scavenging of hydroxyl radicals and/or to the chelation of metal ions that were used to produce hydroxyl radicals from H₂O₂ via the Fenton reaction. Collectively, these findings suggest beneficial roles of CA-G or CA-G-rich red bean on the protection from oxidative damage.     

Biocatalytic resolution of glycidyl phenyl ether using a novel epoxide hydrolase from a marine bacterium,Rhodobacterales bacterium HTCC2654

As a continuous effort of developing highly enantioselective epoxide hydrolase from marine microorganisms, it was found that Rhodobacterales bacterium HTCC2654 was highly enantioselective toward racemic glycidyl phenyl ether (GPE). An open reading frame (ORF) encoding a putative epoxide hydrolase (EHase) was cloned from the genome of R. bacterium HTCC2654, followed by expression and purification in Escherichia coli. The purified EHase (REH) hydrolyzed (S)-GPE preferentially over (R)-GPE. Enantiopure (R)-GPE from kinetic resolution of 29.2 mM racemic GPE using the purified REH could be obtained with enantiopurity of more than 99.9% enantiomeric excess (ee) and 38.4% yield (theoretical, 50%) within 20 min (enantiomeric ratio (E-value): 38.4). The enantioselective activity of REH toward GPE was also confirmed by the analysis of the vicinal diol, 3-phenoxy-1,2-propanediol. To our knowledge, this study demonstrates the highest enantioselective resolution of racemic GPE using a purified biocatalyst among the known native EHases.     

A study on the characteristics of improvement in filtration performance by dust precharging

A hybrid dust-collector combining electrostatic charging with fabric filtration was developed and its performance characteristics were evaluated. Charged particles build porous dendritic structure on the filter surface by electrostatic attraction, increasing the collection efficiency of dust particles and reducing the pressure drop through the deposited dust layer and filter media. The cleaning performance of the dust layer is improved because the dendritic structured dust layer may be removed more easily by pulse jet cleaning flow. The results of the experiment showed a reduction of fine particle emission by 37% and 13% energy saving by precharging dust particles before filtration.     

Enantioselective hydrolysis of racemic epichlorohydrin using an epoxide hydrolase from Novosphingobium aromaticivorans

Previously we reported that an epoxide hydrolase (EHase) from Novosphingobium aromaticivorans could preferentially hydrolyze (R)-styrene oxide. In this study, we demonstrate that the purified NEH could be also effective in chiral resolution of racemic epichlorohydrin (ECH). Particularly, the purified NEH showed excellent hydrolyzing activity toward ECH to complete the reaction at a short period of incubation time. Enantiopure (S)-ECH could be obtained with a high enantiopurity of more than 99.99% enantiomeric excess (ee) and yield of 20.7% (theoretical, 50%). The chiral resolution of the purified NEH toward ECH was not susceptible to substrate inhibition by 500 mM racemic ECH.     

Anti-oxidant and anti-inflammatory properties of methanol extracts from various crops

Corn, sorghum, barley, Italian ryegrass (IRG), and alfalfa have long been used in human and/or animal diets. While their nutritional information is widely available, their potentials for anti-oxidation, anti-inflammation, and anti-tumor are barely explored. In the present study, several serial extracts were prepared from 70% methanol extracts of these forage crops and their bioactive potentials were investigated using cell-free and cell-mediated experimental systems. Chloroform extracts in this study generally showed stronger activity to scavenge hydroxyl radicals and superoxide anions than butanol or water extracts. IRG and sorghum chloroform extracts especially almost completely suppressed the lipopolysaccharide-mediated production of nitric oxide, tumor-necrosis factor-α, and interleukin-6. These extracts also inhibited dramatically the viability and DNA synthesis of human skin dermatofibrosarcoma cells without a toxic effect on primary cultured control cells. These beneficial effects appeared to be associated with the amount of flavonoids contained in the extracts.

     

The effect of particle shape on the pressure drop across the dust cake

In order to observe the effect of particle shape of poly-dispersed dusts on filter performance, the pressure drop across the dust cakes of fly ashes from a conventional power plant (PC), fluidized bed combustion (FBC), and paint incinerator (FI) was measured over a metal filter element in the accurate conditions. A fluidized bed column was used to prepare the dust feed stream of uniform particle distribution. The fine particles of FI ash have a tendency to be agglomerated at low transport velocity. The aggregates were broken at high velocity of more than 21 cm/sec. FBC ash composed of jagged type particles and containing high concentration of unburned-carbon showed higher pressure drop than that of PC ash composed mostly of spherical particles. FI ash composed of aggregates of very fine carbon particles presented the highest pressure drop among the fly ashes tested. The shape factors of PC, FBC, and FI ash were estimated as 0.91, 0.76, and 0.65, respectively, by the Ergun equation. The results implied that the irregular particle tends to form a higher pressure drop and to be more compressible than spherical one. This paper is dedicated to Professor Wha Young Lee on the occasion of his retirement from Seoul National University.