Heuy-Ling Chu

Protective effects of sweet orange (Citrus sinensis) peel and their bioactive compounds on oxidative stress

Protective effects of sweet orange (Citrus sinensis) peel and their bioactive compounds on oxidative stress were investigated. According to HPLC-DAD and HPLC-MS/MS analysis, hesperidin (HD), hesperetin (HT), nobiletin (NT), and tangeretin (TT) were present in water extracts of sweet orange peel (WESP). The cytotoxic effect in 0.2mM t-BHP-induced HepG2 cells was inhibited by WESP and their bioactive compounds. The protective effect of WESP and their bioactive compounds in 0.2mM t-BHP-induced HepG2 cells may be associated with positive regulation of GSH levels and antioxidant enzymes, decrease in ROS formation and TBARS generation, increase in the mitochondria membrane potential and Bcl-2/Bax ratio, as well as decrease in caspase-3 activation. Overall, WESP displayed a significant cytoprotective effect against oxidative stress, which may be most likely because of the phenolics-related bioactive compounds in WESP, leading to maintenance of the normal redox status of cells.

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.

Protective effect of Cordyceps militaris against high glucose-induced oxidative stress in human umbilical vein endothelial cells.

The protective effect of Cordyceps militaris against high glucose-induced oxidative stress in human umbilical vein endothelial cells (HUVECs), as compared with Cordyceps sinensis, was examined. The cytotoxicity of HUVECs induced by 40mM glucose was ameliorated by water extracts of C. militaris (CME) and water extracts of C. sinensis (CSE). CME and CSE inhibited the increase in ROS and NO in HUVECs induced by 40mM high glucose. Moreover, CME increased the Bcl-2/Bax ratio, modulated the mitochondrial membrane potential and reduced the caspase-3 activity in high glucose-induced HUVECs. In addition, cordycepin, a component of CME and CSE, displayed protective effects against oxidative stress, which was partly responsible for the cytoprotective effects of CME and CSE against high glucose-induced oxidative stress in HUVECs. Overall, the obtained results show C. militaris helps preventing diabetic endothelial dysfunction and related complications.

Effects of selected organo-sulfur compounds on melanin formation.

The effect of organo-sulfur compounds, including 1-propylmercaptan (PM), dimethyl disulfide (DMDS), diallyl disulfide (DADS), propyl disulfide (PDS), and 2,5-dimethylthiophene (DMT), on melanin formation was investigated. Among the selected five organo-sulfur compounds, PM displayed a significant inhibitory effect on tyrosinase activity (IC(50) = 0.5 mM) and the highest inhibitory action on o-quinone formation. In the B16 intracellular model system, the inhibitory action of selected five organo-sulfur compounds on tyrosinase activity and melanin formation may be, in part, attributed to the reduction of the reactive oxygen species (ROS) formation and positive modulation of the GSH/GSSG ratio in B16 cells. Among the five organo-sulfur compounds, PM appeared to be the most potent inhibitor of melanin formation. The analysis of inhibitory kinetics revealed that PM is a mixed-type inhibitor. This is the first study indicating that organo-sulfur compounds tested may play an important role in the regulation of melanin formation, making them the potent candidates for skin-whitening agents.

The Anti-Inflammatory and Vasodilating Effects of Three Selected Dietary Organic Sulfur Compounds from Allium Species

The anti-inflammatory and vasodilating effects of three selected dietary organic sulfur compounds (OSC), including diallyl disulfide (DADS), dimethyl disulfide (DMDS), and propyl disulfide (PDS), from Allium species were investigated. In the anti-inflammatory activity assay, the three OSC demonstrated significant inhibition of nitric oxide (NO) and prostaglandin E2 (PGE2) production in LPS-induced RAW 264.7 cells. The expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX-2) in activated RAW 264.7 cells was inhibited by the three OSC, indicating that the three OSC prevented the LPS-induced inflammatory response in RAW 264.7 cells. For the vasodilative assay, the three OSC were ineffective in producing NO in SVEC4-10 cells, but they did enhance prostacyclin (PGI2) production. The expression of COX-2 in SVEC4-10 cells was activated by DADS and DMDS. Pretreatment of SVEC4-10 cells with the three OSC decreased ROS generation in H2O2-induced SVEC4-10 cells. In addition, the three OSC significantly inhibited angiotensin-I converting enzyme (ACE). The up-regulation of PGI2 production and COX-2 expression by DADS and DMDS and the reduction of ROS generation by DADS, DMDS, and PDS in SVEC4-10 cells contributed to the vasodilative effect of the three OSC. Collectively, these findings suggest that DADS, DMDS, and PDS are potential anti-inflammatory and vasodilative mediators.