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

Abstract Melanin-like pigment (MLP) was isolated from black tea leaves by alkaline extraction, acid hydrolysis, and repeated precipitation, and a yield of 2% (dry weight basis) was obtained. The isolated MLP possessed physical and chemical properties comparable to melanins extracted from other sources. The immuno-modulating activity of MLP was measured using plaque-forming cells assay. Oral administration of MLP significantly stimulated the spleen lymphoid tissue in mice at doses ranging from 50 to 200 mg/kg body weight, with a maximal antibody response at 75 mg/kg. The immuno-stimulating activity of tea MLP may serve as a platform for drug discovery, and the abundance of MLP from tea suggests an economical source for health food application.