Cylindrospermopsin (CYN) is a cyanotoxin that is cytotoxic to a wide variety of cells, particularly to the hepatocytes. In this study, the toxic effects of purified CYN were investigated in primary cultured hepatocytes of Neotropical fish Hoplias malabaricus. After isolation, attachment, and recovery for 72 h, the cells were exposed for 72 h to 0, 0.1, 1.0, 10, and 100 μg l of CYN. Then, cell viability and a set of oxidative stress biomarker responses were determined. Catalase, superoxide dismutase, glucose-6-phosphate dehydrogenase, and glutathione S-transferase activities were not affected by exposure to CYN. Concentration-dependent decrease of glutathione reductase activity occurred for most CYN-exposed groups, whereas non-protein thiol content increased only for the highest CYN concentration. Lipid peroxidation, protein carbonylation, and DNA damage levels were not altered, but reactive oxygen species levels increased in the cells exposed to the highest concentration of CYN. Cell viability decreased in all the groups exposed to CYN. Thus, CYN may cause a slight change in redox balance, but it is not the main cause of cell death in H. malabaricus hepatocytes.

Asphaltenes represent a solubility class of petroleum constituents that has been associated with a number of problems that arise from the use of heavier crude oils. As they are defined by their solubility and not their chemical structure, there are often certain difficulties in distinguishing them from other solubility fractions. In a widely adopted separation procedure, saturates generally consist of naphthenes and paraffins while aromatics, resins, and asphaltenes are often quite similar polynuclear aromatic species which may vary in the number of heteroatoms and sizes of ring systems and side-chains that are present. In our attempts to characterize asphaltenes extracted from vacuum residues, we found that the procedures employed for separating asphaltenes in a certain sample have a significant effect on the analytical data that is generated from it. We have thus investigated the influence of different variables on vacuum residues obtained from two Brazilian and one Venezuelan crude and suggest that the most important factors are: the proportion of heptane to sample, treatment by ultra-sound and recovery of asphaltenes in residues by toluene. Combinations of these variables can be employed to hinder aggregation and afford a better separation of asphaltenes and resins. The analytical techniques that were used to confirm this are: NMR ( 1 H and 13 C), gel permeation chromatography (GPC), infrared spectroscopy (IR), and elemental analysis. Information on the types of aromatic ring substitution patterns and terminal methyl groups may be obtained from spectroscopic techniques particularly from NMR.