The invention relates to an application for extracting natural compound (I) from black mulberry, the compound (I) has strong inhibition effect for tyrosinase and is applied for preventing skin mottle, freckle, senile plaque or the like skin chromatosis and whitening, and the compound (I) is a food additive. The activity of the compound (I) is strong proved by the mensuration of the inhibition activity, the compound (I) has good stability and obvious growth inhibition action for the melanoma cell, can reduce the activity of the tyrosinase in the melanoma cell and biological synthesis level of the melanin in the cell.