Use of haguro-so or an organic solvent extract thereof, or a compound represented by the following formula (I) or a salt thereof, for inhibiting a dopa oxidase activity, for inhibiting melanin production, or for whitening the skin； in the formula (I), R1 and R2, being the same or different, each represent a hydroxyl group, or a C1-4 linear or branched alkoxy group, or R1 and R2 together form a methylenedioxy group； R3 and R4, being the same or different, each represent a hydroxyl group, or a C1-4 linear or branched alkoxy group, or R3 and R4 together form a methylenedioxy group； R5 represents a hydrogen atom, a hydroxyl group, a C1-5 linear or branched alkoxy group, a C1-4 acyl group, or a sugar residue selected from the group consisting of (D-apio-β-D-furanosyl)oxy, (β-D-glucopyranosyl)oxy, (3-O,4-O-dimethyl-D-xylopyranosyl)oxy, (2-O,3-O,4-O-trimethyl-β-D-xylopyranosyl)oxy, and (3-O-methyl-β-D-glucopyranosyl)oxy； R6 and R7 are each a hydrogen atom and R8 and R9 together represent an oxygen atom, or R8 and R9 are each a hydrogen atom and R6 and R7 together represent an oxygen atom.
