Tabebuia avellanedae extract has been used in folk medicine in the treatment of some clinical disorders. Lapachol is an active compound from this medicinal plant. The procedure of labeling of blood constituents with technetium-99m (99mTc) could be used as an in vitro assay to evaluate some properties of natural and synthetic drugs. The aim of this work was to evaluate the effect of a T. avellanedae extract and lapachol solutions on the labeling of blood constituents with 99mTc. Whole blood (Wistar rats) was incubated with an aqueous T. avellanedae extract or lapachol. After, stannous chloride (reducing agent) and 99mTc (sodium pertechnetate) were added. Blood cells (BC) and plasma (P) were isolated by centrifugation. Samples of BC and P were precipitated with trichloroacetic acid to separation of soluble (FS) and insoluble (IF) fractions. The radioactivity in each fraction was counted and the percentage of incorporated radioactivity (%ATI) was determined. The data obtained showed that T. avellanedae extract significantly (p<0.05) altered the %ATI on blood constituents while no effects were observed with lapachol. As the labeling of blood constituents with 99mTc depends on the presence of a reducing, the extract of T. avellanedae seems to have substances with redox properties. In addition, these findings would be not associated with the lapachol.
Key words: Tabebuia avellanedae, lapachol, blood, stannous ion, technetium-99m.