PURPOSE: To provide new liquiritin derivatives excellent in melanogenesis- inhibitory effect and water solubility, capable of, therefore, ready preparation and capable of effectively showing a whitening effect by blending it with a base of an external-use medicine for the skin.

CONSTITUTION: Compounds of formula I (n is 1 or 2), e.g. in the case of n=1, liquiritin-α-glucoside showing the following properties; Molecular weight: 580.54; Melting point: 161.3-166.9°C; Solubility: readily soluble in water, soluble in methanol and insoluble in ethanol; Elemental analysis (theoretical value) : C 55.86%, H 5.56%; Anthrone color reaction: positive, etc. The above-mentioned compound can be obtained, e.g. by dissolving liquiritin in 0.1 M acetate buffer solution (pH 5.5) containing 10% ethanol, subsequently acting an enzyme derived from Bacillus macerans IFO-3490 strain thereon in the presence of dextrin and calcium chloride, then deactivating the enzyme, subsequently acting α-amylase thereon and purifying the reaction mixture.