Effects of brazilin and haematoxylin on the lipidperoxidation in the rat liver mitochondria

Brazilin protects cultured rat hepatocytes from BrCCl3-induced toxicity

Brazilin, the main constituent of Caesalpinia sappan, is an antioxidative substance that has catechol moiety in its chemical structure. Considering the antioxidant-activity of brazilin, it was expected to have protective effects on the toxicities of radical generating chemicals. The incubation of rat hepatocytes with BrCCl3 resulted in significant increase in lipid peroxidation, leakage of cytoplasmic enzymes and cytoplasmic glutathione depletion. The BrCCl3-induced toxicities on hepatocytes were reduced by the treatment of brazilin. Brazilin has been also proved to have a protective effect on the BrCCl3-induced depression of microsomal calcium sequestration activity. These results indicate that brazilin plays a protective role in BrCCl3-induced hepatocyte injury of the rat.

Application of current chemical concepts to metal-hematein and -brazilein stains

Current chemical concepts were applied to Weigert's, M. Heidenhain's and Verhoeff's iron hemateins, Mayer's acid hemalum stain and the corresponding brazilein compounds. Fe bonds tightly to oxygen in preference to nitrogen and is unlikely to react with lysyl and arginyl groups of proteins. Binding of unoxidized hematoxylin by various substrates has long been known to professional dyers and was ascribed to hydrogen bonding. Chemical data on the uptake of phenols support this theory. Molecular models indicate a nonplanar configuration of hematoxylin and brazilin. The traditional quinonoid formula of hematein and brazilein was revised. During chelate formation each of the two oxy- groups of the dye shares an electron pair with the metal and contributes a negative charge to the chelate. Consequently, the blue or black 2:1 (dye:metal) complexes are anionic. Olation of such chelates affects the staining properties of iron hematein solutions. The color changes upon oxidation of hematoxylin, reaction of hematein with metals, and during exposure of chelates to acids can be explained by molecular orbital theory. Without differentiation or acid in dye chelate solutions, staining patterns are a function of the metal. Reactions of acidified solutions are determined by the affinities of the dye ligands. Brazilein is much more acid-sensitive than hematein. This difference can be ascribed to the lack of a second free phenolic -OH group in brazilein, i.e. one hydrogen bond is insufficient to anchor the dye to tissues. Since hematein and brazilein are identical in all other respects, their differences in affinity cannot be explained by van der Waals, electrostatic, hydrophobic or other forces.