Anacardium occidentale Bark Lectin: Purification, Immobilization as an Affinity Model and Influence in the Uptake of Technetium-99M by Rat Adipocytes

Lectins, proteins that recognize carbohydrates, have been immobilized on inert supports and used in the screening or purification of glycoproteins. Anacardium occidentale bark infusion has been used as a hypoglycemic agent in Brazil. The toxicity of natural products may be evaluated determining their capability to alter the biodistribution of technetium-99M (99mTc). This work reports the isolation and characterization of a lectin from A. occidentale bark (AnocBL), its evaluation as an affinity support for glycoprotein isolation and lectin effect on the uptake of 99mTc by rat adipocytes. AnocBL was isolated from 80 % ammonium sulphate supernatant by affinity chromatography on fetuin–agarose. SDS–PAGE showed a single protein band of 47 kDa. The monossacharide l-arabinose and the glycoproteins fetuin, asialofetuin, ovomucoid, casein, thyroglobulin, peroxidase, fetal bovine serum and IgG inhibited the activity. The lectin activity was stable until 70 °C and at a pH range of 3.0–7.5. AnocBL–Sepharose column bound fetuin indicating that the lectin matrix may be used to obtain glycoconjugates of biotechnological interest. In vitro assay revealed that glucose and insulin increase 99mTc uptake by rat adipocytes. AnocBL decreases 99mTc uptake, and this effect was not detected in the presence of glucose. Fetuin inhibited AnocBL effect in all insulin concentrations.