Immunotropic Activity and Acute Toxicity of Melanin Isolated from Horse Chestnut (Aesculus hippocastanum L.) Seed Coats

Peroral administration to mice of melanin isolated from horse chestnut (Aesculus hippocastanum L.) seed shells as an aqueous solution (10%) at doses of 2000, 2500, 3000, 4000, and 5000 mg/kg produced no symptoms of acute toxicity in all experimental animals. The mortality corresponded to class VI relatively harmless compounds (LD₅₀ > 5000 mg/kg). Melanin administered intragastrically at doses of 0.5 and 5.0 mg/kg had an induced effect on humoral immunity. The maximum effectiveness was manifested at a dose of 5.0 mg/kg, where the content of antibody-forming cells in the spleen increased by 4.1 times and was 1.7 times greater than that induced by Immunal. Melanin at the studied doses reliably stimulated the formation of a clone of antigen-specific T-lymphocytes and had a stimulating effect on central and peripheral immunity organs, increasing the number of nucleated cells of the thymus by a maximum of 2.8 times; of the spleen, by 1.7 times; and of the lymph nodes, by 5.7 times, like Immunal.