Senna occidentalis (So) seed proteins have been investigated for their in vivo and in vitro biological activities. This leguminous plant, which grows frequently as a weed in pastures, has been associated with reported cases of intoxication of animals by spontaneous ingestion. In previous work, protein fractions derived from aqueous extracts of So seeds showed the capacity of affecting humoral and cellular immune responses in toxicity assays using mice. In addition, proteins isolated by reverse phase HPLC from the toxic fractions which showed citotoxicity and antiviral activities in vitro, demonstrated the presence of hemagglutinin component(s) with properties similar to lectins in hemagglutination assays using 2% human ABO, sheep and mouse erythrocyte suspensions in PBS. In the present work, the fraction F75 precipitated with (NH₄)₂SO₄ at 75% saturation was assayed for its toxicity in vivo using one day old chickens. Histopathological analyses confirmed that the F75 protein fraction was hepatotoxic and also had toxicity to lymphoid organs (spleen and Fabricius bursa) of treated chickens. In addition, both F75, the HPLC isolated components and the So crude extract (CE) were shown to contain protein(s) component(s) capable of inhibiting trypsin. From the results obtained, two components of So seed extracts having apparent molecular masses of about 14 and 20 kDa appeared  to be the major compounds responsible for these in vivo and in vitro activities. The corresponding protein bands obtained by polyacrylamide gel electrophoresis followed by Western blotting to PVDF membranes had their 20 N-terminal amino acids sequenced.

Supported by FAPESP, CNPq and FAPEMIG – EDT 24000