Evaluation of radical scavenging system in two microalgae in response to interactive stresses of UV-B radiation and nitrogen starvation

The effects of UV-B radiation and/or deprivation of nitrogen stresses on growth rate, some antioxidant compounds, and activities of some antioxidant enzymes, superoxide dismutase (SOD; EC1.15.1.1), ascorbate peroxidase (APx; EC1.11.1.11), guaiacol peroxidase (GUPx; EC1.11.1.7) and glutathione reductase (GR, EC 1.6.4.2), as well as the levels of total glutathione pool, UV-B absorbing pigments, malondialdehyde (MDA) and H2O2 concentrations were studied in Spirulina platensis and Dunaliella salina. Less damage was observed in response to the combined UV-B and nitrogen deprivation as shown by growth rate and photosynthetic pigments especially in Dunaliella salina. A significant increase in flavonoids and phenolics under dual stress was observed. Conversely, a great reduction in malondialdehyde (MDA) and H2O2 concentrations were recorded under the combined stress compared to the effect of each stress. Furthermore, a significant increase in GSH/GSSG ratio toward the control was recorded in response to combined stresses, whereas a significant reduction in this ratio was observed in both microalgae in response to each stress. Increased activities of antioxidant enzymes were recorded under UV-B and nitrogen deprivation stresses. Keywords: Abiotic stresses, Oxidative damage, Antioxidant enzymes, Dunaliella salina, Spirulina platensi

Potential Antitumor Activity and Apoptosis Induction of Glossostemon bruguieri

Glossostemon bruguieri (moghat) is used as a nutritive and demulcent drink. This study was performed to investigate the antiproliferative effects of moghat root extract (MRE) and its apoptotic mechanism in hepatocellular carcinoma (HCC) cells, HepG2 and Hep3B. MTT assay, morphological changes, apoptosis enzyme linked immunosorbent assay, caspase and apoptotic activation, flow cytometry, and immunoblot analysis were employed. The IC50 of MRE for HepG2 (910±6 μg/ml) and for Hep3B (1510±5 μg/ml) induced significant growth-inhibitory effects against HCC cells, with no cytotoxic effect on normal hepatocytes. MRE treatment induced apoptotic effects to HepG2 cells in a caspase-dependent manner and via upregulating p53/p21 and PCNA. The upregulation of p21 was controlled by p53 expression in HepG2 but not in Hep3B despite upregulation of Bax protein in both cell lines. Interestingly, p21 may be a remarkable switch to G1 arrest in HepG2 cells, but not in Hep3B cells. In addition, Fas- and mitochondria-mediated pathways were found to be involved in MRE-induced apoptosis in Hep3B cells. The GC-MS analysis of MRE revealed two major constituents of pharmaceutical importance: the flavonoid apigenin (17.04%) and the terpenoid squalene (11.32%). The data presented in this paper introduces G. bruguieri as a promising nontoxic herb with therapeutic potential for HCC. To the authors’ knowledge, the present study provides the first report on the anticancer activity of MRE on HCC cells

Ecotoxicity of Ag-nanoparticles on two microalgae, Chlorella vulgaris and Dunaliella tertiolecta

The increasing application of nanotechnology highlights the need to clarify and understand it. In this work, the subacute toxicity of Ag-NPs to the fresh water microalga Chlorella vulgaris and marine microalga Dunaliella tertiolecta were assessed. The effect of Ag-NPs was induced by exposing both algae to increasing concentrations of Ag-NPs (0, 10, 50, 100 and 200 mg/L). Cellular viability and reactive oxygen species (ROS) formation were determined to evaluate the toxic effect of Ag-NPs on algal growth. Superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities and lipid peroxidation (MDA) levels in the algal cells varied with the concentration of Ag-NPs suspensions and exposure times (up to 8 d). As a result, 100 and 200 mg/L Ag-NPs caused a statistically significant decrease in cell viability, as well as SOD, CAT and POD activities, and a significant increase in ROS formation and MDA levels in tissues (P <0.05), suggesting that the algal cells exposed to these two concentrations of Ag-NPs suffered from oxidative stress. The extent of depletion of antioxidant enzyme activities and the elevation of MDA in Dunaliella tertiolecta was the greatest, indicating that Dunaliella tertiolecta might be the most susceptible to Ag-NP exposure. These results indicated a potential risk from Ag-NPs released into the aqueous environment