A novel melanin-like pigment derived from black tea leaves with immune-stimulating activity

Melanin-like pigment (MLP) was isolated From black tea leaves by alkaline e xtraction, acid hydrolysis, and repeated precipitation, and a yield of 2% ( dry weight basis) was obtained. The isolated MLP possessed physical and che mical properties comparable to melanins extracted from other sources. The i mmune-modulating activity of MLP was measured using plaque-forming cells as say. Oral administration of MLP significantly stimulated the spleen lymphoi d tissue in mice at doses ranging from 50 to 200 mg/ kg body weight, with a maximal antibody response at 75 mg/kg. The immune-stimulating activity of tea MLP may serve as a platform for drug discovery, and the abundance of ML P From tea suggests an economical sourer for health food application. (C) 2 001 Elsevier Science Ltd. All rights reserved.