Cytoprotective effect of white tea against H2O2-induced oxidative stress in vitro.

The protective effect of water extracts of white tea (WEWT) on oxidative stress in vitro is investigated. WEWT, like water extracts of green tea (WEGT) and water extracts of Pu-erh tea (WEPT), demonstrates a marked inhibition of the oxidation of liposome, albumin and LDLmodel systems. WEWT protects against H2O2-induced cytotoxicity, in a dose-dependent manner. The inhibition of ROS generation and MDA formation by WEWT in H2O2-induced Clone 9 cells parallels the effects on cell viability. Moreover, GSH and antioxidant enzymes may play an important role in the protective effect that is associated with H2O2-induced oxidative stress. The HPLC-DAD and HPLC-MS/MS analysis, shows that sixteen bioactive compounds are present in WEWT, which may partially account for its protective effect against oxidative insult. These results suggest that the mechanism of the protective actions of WEWT is related to its antioxidant potential and the maintenance of the normal redox status of the cell.

Antiproliferative activity and apoptosis induction of Eucalyptus Citriodora resin and its major bioactive compound in melanoma B16F10 cells.

Antiproliferative activity and apoptosis induction of ethyl acetate of Eucalyptus citriodora resin (EAEER), and its major bioactive compound in melanoma B16F10 cells were investigated. 6-[1-(p-Hydroxy-phenyl)ethyl]-7-O-methyl aromadendrin (HEMA), a flavanol derivative, was isolated from EAEER and identified on the basis of its mass and NMR spectra. The results from MTT assay showed high antiproliferative effects of EAEER and HEMA on B16F10 cells. Moreover, EAEER- and HEMA-induced cell apoptosis was association with the decrease in the mitochondrial transmembrane potentials (Δψ(m)), increase in Bax/Bcl-2 ratio, and activation of caspase-3. Cells treated with EAEER and HEMA generated intracellular reactive oxygen species (ROS) and nitric oxide (NO), indicating that ROS and RNS play important roles in the induction of apoptosis in B16F10 cells. Taken together, EAEER and its major bioactive compound, HEMA, inhibited the proliferation of B16F10 cells via apoptosis and may be a potential antimelanoma agent.

Antioxidant properties of roasted coffee residues.

The antioxidant activity of roasted coffee residues was evaluated. Extraction with four solvents (water, methanol, ethanol, and n-hexane) showed that water extracts of roasted coffee residues (WERCR) produced higher yields and gave better protection for lipid peroxidation. WERCR showed a remarkable protective effect on oxidative damage of protein. In addition, WERCR showed scavenging of free radicals as well as the reducing ability and to bind ferrous ions, indicating that WERCR acts as both primary and secondary antioxidants. The HPLC analyses showed that phenolic acids (chlorogenic acid and caffeic acid) and nonphenolic compounds [caffeine, trigonelline, nicotinic acid, and 5-(hydroxymethyl)furfuraldehyde] remained in roasted coffee residues. These compounds showed a protective effect on a liposome model system. The concentrations of flavonoids and polyphenolic compounds in roasted coffee residues were 8,400 and 20,400 ppm, respectively. In addition, the Maillard reaction products (MRPs) remaining in roasted coffee residues were believed to show antioxidant activity. These data indicate that roasted coffee residues have excellent potential for use as a natural antioxidant source because the antioxidant compounds remained in roasted coffee residues.

Effects of pu-erh tea on oxidative damage and nitric oxide scavenging.

The effects of pu-erh tea, which is prepared by fermentation of tea, on oxidative damage and nitric oxide scavenging, compared with various other brands of tea were investigated. The total antioxidant activity was determined using the Trolox equivalent antioxidant capacity (TEAC) assay. The results showed that TEAC values of the 200 microg/mL water extracts of pu-erh tea (WEPT), green tea, oolong tea, and black tea were 86.3, 85.3, 87.4, and 80.3 (microg/mL), respectively, indicating that WEPT showed a significant antioxidant activity. WEPT, like green tea extract, oolong tea extract, and black tea extract, exhibited a remarkable protective effect in lipid (liposome) and nonlipid (protein and deoxyribose) model systems, implying that it is an inhibitor of lipid and nonlipid oxidative damage. It also exhibited metal-binding ability, reducing power, and scavenging effect for free radicals. Moreover, WEPT showed a decreasing effect on nitric oxide production of lipopolysaccharide-induced RAW 264.7 macrophages. In addition, the results revealed that epicatechin (EC), flavonoid, ascorbic acid, and polyphenolic compounds are present in WEPT, which may partially account for the protective effect on oxidative damage. Thus, WEPT may have potential as an antioxidant and as a nitric oxide scavenging agent.

Identification of an antioxidant, ethyl protocatechuate, in peanut seed testa.

The antioxidant activity and identification of the antioxidant component of peanut seed testa were investigated. The antioxidant activity of peanut seed testa was studied in the linoleic acid model system by using the ferric thiocyanate method. Among the five organic solvent extracts, the ethanolic extracts of peanut seed testa (EEPST) produced higher yields and stronger antioxidant activity than other organic solvent extracts. EEPST was separated into 17 fractions on silica gel column chromatography. Fraction 17, which showed the largest yield and significant antioxidant activity, was separated by thin-layer chromatography. Four major antioxidative subfractions were present. Subfraction 17-2 was found to be effective in preventing oxidation of linoleic acid. This subfraction was further fractionated and isolated and characterized by UV, MS, IR, and (1)H NMR techniques. The active compound was identified as ethyl protocatechuate (3,4-dihydroxybenzoic acid ethyl ester).