Effect of Imoniga ginger extract on tyrosinase, TRP-1, and TRP-2 protein levels. B16 melanoma cells were cultured for 3 days in the medium with (lane 2, 0.001%; lane 3, 0.003%) or without (lane 1) Imoniga ginger extract. A 20mg portion of cell extracts per lane was used for SDS polyacrylamide gel electrophoresis.