Patent ID: 8563552

Claim:
A method for inhibiting melanin production comprising topically applying to skin of a human in need of such inhibition a preparation comprising an effective amount of a heterocyclic compound represented by formula (1) or a pharmacologically acceptable salt thereof: wherein X 1 ═X 2 ═N and X 3 ═CR 2 , or X 1 ═CR 2 and X 2 ═X 3 ═N; R 1 , R 2 , and R 3 are each independently H, C 1-6 alkyl, C 1-6 alkoxy, SH, OH, or NR b R c , wherein R b and R c are each independently H, C 1-6 alkyl, or hydroxy-C 1-6 alkyl, or wherein NR b R c forms a saturated or unsaturated 5- or 6-membered hetero ring; B is a group represented by formula (B1): wherein Y 1 is N, and Y 2 is CR 5 ; R 4 , R 5 , and R 6 are each independently H, C 1-6 alkyl, C 1-6 alkoxy, C 2-7 acyloxy, OH, amino, —NH-A, —NHCO-A, or —NHCOCH 2 -A, wherein A is C 1-6 alkyl, phenyl, or a 5- or 6-membered heterocyclic group, or R 4 and R 5 , or R 5 and R 6 together form a 5- or 6-membered hydrocarbon ring condensed with the hetero ring to which R 4 , R 5 , and R 6 are bound; with the proviso that at least one of R 1 , R 3 , R 4 , and R 6 is a group other than C 1-3 alkyl in the case where X 1 ═X 2 ═Y 1 ═N and X 3 ═CR 2 .