Oxidative stress related effect of xenobiotics on eukaryotic model organism, Saccharomyces cerevisiae.

Ecotoxicological assays have traditionally focused on the effects of chemicals at the individual level by exploiting mortality and reproduction as endpoints. Although these two parameters are ecologically relevant, they rarely provide information regarding the elemental toxic mechanisms. Obviously, the number of xenobiotics used has been rapidly increased. Thus, any established measurement that shortens the actual outcome and, simultaneously provides information about toxic mechanisms is desirable. This research focused on the study of oxidative stress response as a biomarker in the eukaryotic model organism, Saccharomyces cerevisiae. For this, yeast cells were exposed to a set of selected environmentally relevant chemicals via different approaches, including cellular diagnostics, gene expression analysis and chemo-genetic screening. The results demonstrated that at the cellular level, model organisms reacted to different chemicals in distinct manner. For each xenobiotic, the correlation between toxic response of molecular and cellular levels are presented. Namely, the expression of target genes after chemical exposure affected the cellular alteration as evidenced by an elevated level of superoxide dismutase and a reduced amount of glutathione. Furthermore, the results derived from chemo-genetic screening, in which mutants lacking of gene of interest were employed, exhibited more susceptibility to test chemicals in comparison to the wildtype. The response of oxidative stress upon chemical exposure in budding yeast from this study is potentially useful for an establishment of a proper bio-test system which can eventually be linked to adverse effects at an individual level in higher eukaryotes.

Ecotoxicity testing of paraquat metabolites degraded by filamentous fungi in model organism.

Paraquat has been intensively used worldwide for several decades for the purpose of weed control in profit crop plantation. This leads to the accumulation of the herbicide and its metabolites in the environment. One promising method to reduce and/or eliminate the paraquat-contaminants is via microbial bioremediation. Filamentous fungi, Aspergillus tamarii PRPY-2, isolated from rubber tree plantation in the northern part of Thailand exhibited the ability to degrade paraquat in liquid media at laboratory scale. Thus, utilization of this species in paraquat-contaminated sites is potentially feasible. However, metabolites generated during biodegradation processes are possibly more toxic than the parent compound. Hence, before introducing this microbe into the environment, it is necessary to ensure that metabolites have no adverse effects on the ecosystem. The present work focuses on the study of the toxic effects of paraquat metabolites on the eukaryote model organism using Saccharomyces cerevisiae of wild type and five mutant strains. The relation between paraquat degradation and growth of fungi was firstly performed. Ecotoxicity testing was done via chemo-genetic screening method. Oxidative stress-related enzyme, superoxide dismutase of S. cerevisiae was also verified. The results illustrated that fungi could degrade 100% of paraquat in Czapeck Dox liquid medium within 21 days. Ecotoxicity data indicated that all yeast strains grew better in a medium containing paraquat metabolites than the one containing parent compound. Among them, mutant lacking superoxide dismutase (SOD1) gene was the most affected strain. Moreover, enzyme activity of yeast cells exposed to paraquat metabolites was found to be lower than that exposed to parent compound. In summary, metabolites degraded by A. tamarii are less toxic to model organism than paraquat. Therefore, the utilization of this species for remediation purpose was found to be safe for the environment.

Purified Gymnemic Acids from Gymnema inodorum Tea Inhibit 3T3-L1 Cell Differentiation into Adipocytes.

Gymnema inodorum (GI) is an indigenous medicinal plant and functional food in Thailand that has recently helped to reduce plasma glucose levels in healthy humans. It is renowned for the medicinal properties of gymnemic acid and its ability to suppress glucose absorption. However, the effects of gymnemic acids on adipogenesis that contribute to the accumulation of adipose tissues associated with obesity remain unknown. The present study aimed to determine the effects of gymnemic acids derived from GI tea on adipogenesis. We purified and identified GiA-7 and stephanosides C and B from GI tea that inhibited adipocyte differentiation in 3T3-L1 cells. These compounds also suppressed the expression of peroxisome proliferator-activated receptor gamma (Pparγ)-dependent genes, indicating that they inhibit lipid accumulation and the early stage of 3T3-L1 preadipocyte differentiation. Only GiA-7 induced the expression of uncoupling protein 1 (Ucp1) and pparγ coactivator 1 alpha (Pgc1α), suggesting that GiA-7 induces mitochondrial activity and beige-like adipocytes. This is the first finding of stephanosides C and B in Gymnema inodorum. Our results suggested that GiA-7 and stephanosides C and B from GI tea could help to prevent obesity.

Determination of Free Radical Scavenging, Antioxidative DNA Damage Activities and Phytochemical Components of Active Fractions from Lansium domesticum Corr. Fruit.

Lansium domesticum Corr. or "long-kong" is one of the most popular fruits in Thailand. Its peel (skin, SK) and seeds (SD) become waste unless recycled or applied for use. This study was undertaken to determine the bioactivity and phytochemical components of L. domesticum (LD) skin and seed extracts. Following various extraction and fractionation procedures, 12 fractions were obtained. All fractions were tested for antioxidant capacity against O2(-•) and OH(•). It was found that the peel of L. domesticum fruits exhibited higher O2(-•) and OH(•) scavenging activity than seeds. High potential antioxidant activity was found in two fractions of 50% ethanol extract of peel followed by ethyl acetate (EA) fractionation (LDSK50-EA) and its aqueous phase (LDSK50-H2O). Therefore, these two active fractions were selected for further studies on their antioxidative activity against DNA damage by hydrogen peroxide (H2O2) in human TK6 cells using comet assay. The comet results revealed DNA-protective activity of both LDSK50-EA and LDSK50-H2O fractions when TK6 human lymphoblast cells were pre-treated at 25, 50, 100, and 200 µg/mL for 24 h prior to H2O2 exposure. The phytochemical analysis illustrated the presence of phenolic substances, mainly scopoletin, rutin, and chlorogenic acid, in these two active fractions. This study generates new information on the biological activity of L. domesticum. It will promote and strengthen the utilization of L. domesticum by-products.

Antimutagenicity and antioxidative DNA damage properties of oligomeric proanthocyanidins from Thai grape seeds in TK6 cells.

Oligomeric proanthocyanidins (OPCs) are found mostly in red grape seeds. Many publications have reported that OPCs possess an excellent anti-oxidant effects. Since it could against cellular damage from reactive oxygen species (ROS) led to reduce the risk of chronic disease and cancers. We carried out this study on the Thai OPCs to evaluate the mutagenicity/ anti-mutagenicity and anti-oxidative DNA damage effects in TK6 cells by micronucleus (MN) and comet assays. In the MN assay, OPCs-treatment of TK6 cells at concentrations ranging from 10-200 ?g/ml (4 and 24 h) did not cause micronucleus induction over the negative control group but revealed a significant reduction the micronucleus frequencies against the known mutagen (mitomycin C). In the comet assay, OPCs-treated TK6 cells at concentrations of 100, 250, 500, and 1,000 ?g/ml could inhibit DNA damage induced by H(2)O(2) as indicated by 18.7, 36.4, 30.6, and 60.1%, respectively. Our results suggest that OPCs possess the anti-mutagenic and anti-oxidative DNA damage effects in TK6 cells under the conditions of this assay.