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The exposure of mammalian cells to UV light induces various deleterious responses. Some of the major harmful effects are DNA damage, cell membrane peroxidation, systemic immune suppression, and aging acceleration. Reactive oxygen species and free radicals are believed to be largely responsible for some of the deleterious effects of UV upon cells. Typical administration of antioxidants has recently proved to represent a successful strategy for protecting the cells against UV-mediated oxidative damage. The objective of this study was to investigate the inhibitory effect of phenolic acids (caffeic acid, ferulic acid, gallic acid, and protocatechuic acid) on oxidative damage in human erythrocytes and low-density lipoprotein (LDL) induced by UVB radiation. The results revealed that the thiobarbituric acids reactive substances induced by UVB were decreased from 2.78 to 0.12-0.89 nmol MDA/mg protein in erythrocyte ghost and from 0.72 to 0.14-0.43 nmol MDA/mg protein in LDL by the addition of phenolic acids (100 muM). Caffeic acid, ferulic acid, and gallic acid exhibited over 85 and 60% inhibitory effect toward UVB-induced oxidation in erythrocytes and LDL, respectively. Phenolic acids, especially gallic acid, could maintain the normal glutathione levels and glutathione peroxidase activity in hemolysate from erythrocytes that were exposed to UVB radiation in comparison with untreated control. The results indicate that the antioxidant activities of caffeic acid and ferulic acid play a potential role in protection against UVB oxidative damage to human erythrocytes and LDL.

An innovative retort cooking method was developed for firm tofu sterilization to replace the traditional hydrogen peroxide treatment. The caramelized firm tofu was sterilized by autoclaving at 105 degrees C for 20 min, which led to a 3 log cycle reduction of total plate count. Shelf life of the processed firm tofu was extended at least 3 months. As compared with chemical treatment, thermal treatment degraded total and individual isoflavones to a lesser extent, and only minor changes were observed. The percent DPPH free radical scavenging capacity of autoclaved firm tofu was significantly higher than that of the hydrogen peroxide treated samples. Even after prolonged heat treatment, the three-dimensional network structure of the autoclaved firm tofu did not change significantly. Texture profile analysis and sensory evaluation confirmed autoclaved firm tofu to be acceptable.

Volatile compounds formed from the reaction of 3-hydroxy-2-butanone/ammonium acetate at 25, 55 and 85 °C were investigated. Six compounds were characterized by gas chromatography-mass spectrometry (EI and CI). Among the volatile compounds identified, an interesting intermediate compound, 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline, was found. 15 N-Labeled ammonium acetate was used to confirm the structure of 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline. The formation pathway of these volatile compounds was proposed. In these model systems, 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline was formed at the reaction temperature below 25 °C. On the other hand, tetramethylpyrazine was the major component when the reaction temperature was higher than 85 °C. The amounts of 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline and tetramethylpyrazine increased linearly with the increasing heating time at 55 °C. Protic solvents did not promote 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline formation but did favor the formation of tetramethylpyrazine. A kinetic study of 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline formation was also performed, and the activation energy was found to be 16.5 kcal/mol.

The antioxidant and pro-oxidant effects of various tea extracts were investigated. The tea extracts, especially the green, pouchong, and oolong tea extracts, markedly stimulated the oxidation of deoxyribose in the presence of Fe3+ and H2O2. The rate of DNA degradation, induced by bleomycin-Fe3+, was also accelerated by tea extracts (green tea, pouchong tea, and oolong tea) up to 65-fold at the dosage of 0.125 mg, and then decreased at higher dosages. Black tea exhibited greater stimulatory effects than the other three teas at higher dosage. The systems that contained only tea extracts and 2‘-deoxyguanosine (2‘-dG) do not induce the oxidation of 2‘-dG to 8-hydroxy-2‘-deoxyguanosine. Addition of ascorbic acid to the reaction system accelerated the oxidation of deoxyribose, DNA, and DNA bases, however, the oxidation was decreased by a high dosage of tea extracts. Tea extracts showed dual effects in the model system that was dependent on the ability of both reducing iron and scavenging oxy-radicals. Keywords:...

A significant enhancement of the tetramethylpyrazine (TMP) formation at high pressure was observed in the 3-hydroxy-2-butanone/ammonium acetate model system. In a water system, the activation volume of TMP formation under high pressure was found to be −6.82 mL/mol. A mechanism was proposed to elucidate the formation of TMP under a weak acidic condition and high hydrostatic pressure. Solvents such as propylene glycol (PG), glycerol, methanol, ethanol, propanol, and butanol were found to enhance TMP formation. Kinetic analyses indicated that TMP formation in aqueous, 80% PG, and ethanol systems followed pseudo-zero-order reaction kinetics. The activation energies were found to be 18.84 ± 1.3, 14.19 ± 7.1, and 13.09 ± 4.7 kcal/mol, respectively. The intermediate of TMP formation was characterized as tetramethyldihdyropyrazine using gas chromatography−mass spectrometry. A 15N-labeled ammonium acetate/3-hydroxy-2-butanone model system was used to confirm the incorporation of a nitrogen atom in the molecule of ...

The relationship between antioxidant activity and antimutagenicity of various tea extracts (green tea, pouchong tea, oolong tea, and black tea) was investigated. All tea extracts exhibited markedly antioxidant activity and reducing power, especially oolong tea, which inhibited 73.6% peroxidation of linoleic acid. Tea extracts exhibited a 65-75% scavenging effect on superoxide at a dose of 1 mg and 30 - 60% scavenging effect on hydrogen peroxide at a dose of 400 microgram. They scavenged 100% hydroxyl radical at a dosage of 4 mg except the black tea. Tea extracts also showed 50 - 70% scavenging effect on alpha, alpha-diphenyl-beta-picrylhydrazyl radical. The antioxidant activity and the scavenging effects on active oxygen decreased in the order semifermented tea > nonfermented tea > fermented tea. Tea extracts showed strong antimutagenic action against five indirect mutagens, i.e., AFB1, Trp-P-1, Glu-P-1, B[a]P, and IQ, especially oolong and pouchong teas. The antioxidant effect of tea extracts was well correlated to their antimutagenicity in some cases but varied with the mutagen and antioxidative properties.

Lactuca indica L. (Compositae family) is used as a folk medicine in anti-inflammatory, antibacterial, antidiabetic, and other medications in Asia. The objectives of this study were to evaluate the antiproliferative effect of ethanol extracts of Lactuca indica L. (EEL) on human leukemic HL-60 cell lines and its active components. The results showed that EEL exhibited strong cytotoxic effects against HL-60 cells; the IC50 value was 313 microg/mL. Flow cytometric analysis of the externalization of phosphatidylserine (PS) using the annexin V/PI method on EEL-treated HL-60 cells showed a concentration-dependent increase of apoptosis. Moreover, EEL could induce typical DNA fragmentation in a concentration- and time-dependent manner as determined by electrophoresis and TUNEL assays. The treatment of HL-60 cells with EEL induced significant accumulation of cells in the G0/G1 phase, indicating that EEL is a cell-cycle-dependent anticancer agent. Our results also indicate that EEL-induced apoptosis in HL-60 cells is associated with the loss of mitochondrial membrane potential (delta psi m). EEL contains 5% phenolic compounds, such as quercetin, caffeic acid, rutin, and chlorogenic acid. Among the four active phenolic compounds, quercetin was found to be the most effective in inhibition against cell viability and in alteration of mitochondrial function. Our results suggest that the induction of apoptosis by EEL might offer a pivotal mechanism for its chemopreventive action.

The objectives of this study were to study the antioxidant activities and nitric oxide (NO) scavenging effects of vegetables in vitro systems and to study the inhibitory effects of vegetables on the NO production and NO-induced DNA damage in RAW 264.7 macrophage. The results indicated that water extracts from Indian lotus, Jew's ear, shiitake, eggplant, and winter mushroom showed stronger antioxidant activity and free-radical-scavenging ability than that of other vegetable extracts. The scavenging effects of vegetable extracts on NO derived from sodium nitroprusside (SNP) were in decreasing order of water spinach > Indian lotus > eggplant and garland chrysanthemum. In the macrophage model system, the water extracts from fresh daylily flower, sponge gourd, pea sprout, and eggplant exhibited over 80% inhibition on NO generation stimulated by lipopolysaccharide. The extract from fresh daylily flower that expressed the strongest inhibition on NO production was attributed to the ability to reduce the inducible nitric oxide synthase (iNOS) induction. However, the extracts from pea sprout and eggplant suppressed the NO production by scavenging on NO and inactivating toward iNOS enzyme. In addition, the water extracts from fresh daylily flower, sponge gourd, pea sprout, and eggplant also showed over 40% inhibitory effect on DNA damage induced by SNP in RAW 264.7 macrophage. The data also indicated that eggplant and pea sprout extracts contained higher total phenolic compounds, anthocyanins, and ascorbic acids and appeared to be responsible for their antioxidant activities and scavenging effects on NO derived from SNP.

The effect of superheated steam treatment on the oxidative stability of lipids in packaged Zousoon (pork bundles) was investigated. The aroma quality of Zousoon samples was evaluated by sensory analysis and chromatographic analysis of volatiles. Results of this study indicated that oxidation of lipids occurred in pan-fried Zousoon after prolonged storage. Significant amounts of highly volatile compounds such as formaldehyde, acetaldehyde, acetone, and hexanal in Zousoon were identified by a modified method of cysteamine derivatization followed by gas chromatography-mass spectrometry (GC-MS) analysis. Superheated steam was found to be effective in suppressing lipid oxidation in canned Zousoon as compared with Zousoon fried by the conventional method in a frying pan. The superheated steam-fried samples had relatively low thiobarbituric acid reactive substance (TBARS) and peroxide (POV) values before and after storage, whereas samples prepared by pan frying had relatively high TBARS and POV values before and after storage. Superheated steam-fried Zousoon had superior lipid stability to that prepared by the conventional pan-frying method.