A Theoretical Study of 8-Chloro-9-Hydroxy-Aflatoxin B1, the Conversion Product of Aflatoxin B1 by Neutral Electrolyzed Water.

Theoretical studies of 8-chloro-9-hydroxy-aflatoxin B1 (2) were carried out by Density Functional Theory (DFT). This molecule is the reaction product of the treatment of aflatoxin B1 (1) with hypochlorous acid, from neutral electrolyzed water. Determination of the structural, electronic and spectroscopic properties of the reaction product allowed its theoretical characterization. In order to elucidate the formation process of 2, two reaction pathways were evaluated-the first one considering only ionic species (Cl⁺ and OH(-)) and the second one taking into account the entire hypochlorous acid molecule (HOCl). Both pathways were studied theoretically in gas and solution phases. In the first suggested pathway, the reaction involves the addition of chlorenium ion to 1 forming a non-classic carbocation assisted by anchimeric effect of the nearest aromatic system, and then a nucleophilic attack to the intermediate by the hydroxide ion. In the second studied pathway, as a first step, the attack of the double bond from the furanic moiety of 1 to the hypochlorous acid is considered, accomplishing the same non-classical carbocation, and again in the second step, a nucleophilic attack by the hydroxide ion. In order to validate both reaction pathways, the atomic charges, the highest occupied molecular orbital and the lowest unoccupied molecular orbital were obtained for both substrate and product. The corresponding data imply that the C9 atom is the more suitable site of the substrate to interact with the hydroxide ion. It was demonstrated by theoretical calculations that a vicinal and anti chlorohydrin is produced in the terminal furan ring. Data of the studied compound indicate an important reduction in the cytotoxic and genotoxic potential of the target molecule, as demonstrated previously by our research group using different in vitro assays.

Molecular mechanisms involved in the cytotoxicity induced by coumarins from Calophyllum brasiliense in K562 leukaemia cells.

OBJECTIVES: The aim of this study was to determine the cellular and molecular mechanisms of cell death induced by mammea A/BA and A/BB (3 : 1) on K562 cells. METHODS: These compounds were isolated from Calophyllum brasiliense and its cytotoxicity was tested using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell death was evaluated by Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and immunocytofluorescence of active caspase-3. Genotoxicity was tested using comet assay. Lastly, a chemoinformatic analysis was performed with Osiris-Molinspiration software. KEY FINDINGS: The mixture of mammea A/BA and A/BB (3 : 1) showed cytotoxic activity against K562 cells (IC50 = 43.5 µm). TUNEL positive cells and active caspase-3 were detected after treatment. Genotoxicity of mammea A/BA and A/BB on K562 was detected since first hour of treatment. Additionally, mammea A/BA and A/BB were found to be in compliance with Lipinski 'rule of 5' suggesting that they possess strong potential of druglikeness. CONCLUSIONS: The overall results confirm and extend the knowledge about coumarins as an important resource of antitumor drugs, and indicate that these compounds could be used in further preclinical studies against leukaemia.