RESUMEN
Plants have been used for the human beings as food, as additives and/or as medicines. There are controversies about the biological effects of several natural products and, it is worthwhile to try to develop experimental assays to evaluate properties of extracts of plants. Pfaffia sp. is utilized in popular medicine and various properties have been attributed to its extract. Red blood cells (RBC) and plasma proteins are labeled with technetium-99m (Tc-99m) and this labeling procedure depends on a reducing agent and stannous ion is usually used. There are reports that drugs can alter the labeling of blood elements with Tc-99m. We have evaluated the influence of a Pfaffia sp. extract on the labeling of blood constituents with Tc-99m and on the morphology of RBC. Blood was incubated with an aqueous extract of Pfaffia sp., stannous chloride and Tc-99m. Samples were centrifuged and plasma and blood cells were separated and also precipitated with trichloroacetic acid. Soluble and insoluble fractions were separated. The results did not show alteration in the uptake of radioactivity and no modifications on the shape of the RBC in presence of Pfaffia sp. Once this labeling process depends on a reducing agent, probably, this extract has compounds with anti-oxidant properties as already described elsewhere, that could protect the stannous ions against the oxidation process. This fact would aid the labeling process of blood elements with Tc-99m.