Whitening cosmetic

1. A cosmetic agent, comprising:

(A) at least one cysteine compound represented by formula (I) or a salt thereof:

wherein

X and Y are each independently OR 1 or NHR 2 wherein R 1 and R 2 are each independently a hydrogen atom or a C 1-22 alkyl group;

Z is a hydrogen atom or a C 1-22 alkyl group; and

W is a C 1-22 alkyl group, a C 1-22 alkoxy group or a C 1-22 alkylamino group; and

(B) at least one whitening agent,

wherein:

(A) said at least one cysteine compound or a salt thereof is one or more members selected from the group consisting of N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid, a salt of N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid, N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid 2-ethyl ester, and a salt of N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid 2-ethyl ester; and

(B) said at least one whitening agent is one or more members selected from the group consisting of arbutin, cetyl ascorbyl ether, kojic acid, 4-methoxy salicylic acid, chamomilla recutita extract, ellagic acid, linoleic acid, glutathione, tranexamic acid, 4-n-butylresorcinol, and 4-hexylresorcinol.

2. The cosmetic agent according to claim 1 , wherein (B) said at least one whitening agent is one or more members selected from the group consisting of arbutin, kojic acid, 4-methoxy salicylic acid, chamomilla recutita extract, glutathione, and tranexamic acid.

3. The cosmetic agent according to claim 1 , wherein (B) said at least one whitening agent is one or more members selected from the group consisting of arbutin, kojic acid, chamomilla recutita extract, tranexamic acid.

4. The cosmetic agent according to claim 1 , wherein (A) said at least one cysteine compound or a salt thereof is N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid 2-ethyl ester or a salt thereof, and (B) said at least one whitening agent is kojic acid.

5. The cosmetic agent according to claim 1 , wherein (A) said at least one cysteine compound or a salt thereof is N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid 2-ethyl ester or a salt thereof, and (B) said at least one whitening agent is tranexamic acid.

6. The cosmetic agent according to claim 1 , wherein (A) said at least one cysteine compound or a salt thereof is N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid 2-ethyl ester or a salt thereof, and (B) said at least one whitening agent is a chamomilla recutita extract.

7. The cosmetic agent according to claim 1 , wherein (A) said at least one cysteine compound or a salt thereof is N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid 2-ethyl ester or a salt thereof, and (B) said at least one whitening agent is arbutin.

8. The cosmetic agent according to claim 1 , wherein (A) said at least one cysteine compound or a salt thereof and (B) said at least one whitening agent are present in a mass ratio of (A)/(B)=1/20-5000/1 (g/g).

9. The cosmetic agent according to claim 1 , wherein (A) said at least one cysteine compound represented by formula (I) is one or more members selected from the group consisting of a (2R,4S)-form, a (2S,4R)-form, and a mixture thereof.

10. The cosmetic agent according to claim 1 , wherein (A) said at least one cysteine compound represented by formula (I) is a (2S,4R)-form.

11. A melanin production suppressive agent, comprising:

(A) at least one cysteine compound represented by formula (I) or a salt thereof:

wherein

X and Y are each independently OR 1 or NHR 2 wherein R 1 and R 2 are each independently a hydrogen atom or a C 1-22 alkyl group;

Z is a hydrogen atom or a C 1-22 alkyl group; and

W is a C 1-22 alkyl group, a C 1-22 alkoxy group or a C 1-22 alkylamino group; and

(B) at least one whitening agent

wherein:

(A) said at least one cysteine compound or a salt thereof is one or more members selected from the group consisting of N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid, a salt of N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid, N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid 2-ethyl ester, and a salt of N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid 2-ethyl ester; and

(B) said at least one whitening agent is one or more members selected from the group consisting of arbutin, cetyl ascorbyl ether, kojic acid, 4-methoxy salicylic acid, chamomilla recutita extract, ellagic acid, linoleic acid, glutathione, tranexamic acid, 4-n-butylresorcinol, and 4-hexylresorcinol.

12. The melanin production suppressive agent according to claim 11 , wherein (B) said at least one whitening agent is one or more members selected from the group consisting of arbutin, kojic acid, 4-methoxy salicylic acid, chamomilla recutita extract, glutathione, and tranexamic acid.

13. The melanin production suppressive agent according to claim 11 , wherein (A) said at least one cysteine compound represented by formula (I) is one or more members selected from the group consisting of a (2R,4S)-form, a (2S,4R)-form, and a mixture thereof.

14. The melanin production suppressive agent according to claim 11 , wherein (A) said at least one cysteine derivative represented by formula (I) is a (2S,4R)-form.

15. A method of suppressing melanin production, comprising administering to a subject in need thereof an effective amount of a cosmetic agent according to claim 1 .

16. A method according to claim 15 , wherein said administering is topical administering.

17. A method of whitening skin, comprising administering to a subject in need thereof an effective amount of a cosmetic agent according to claim 1 .

18. A method according to claim 17 , wherein said administering is topical administering.

19. A method of suppressing melanin production, comprising administering to a subject in need thereof an effective amount of a cosmetic agent according to claim 2 .

20. A method according to claim 19 , wherein said administering is topical administering.

21. A method of whitening skin, comprising administering to a subject in need thereof an effective amount of a cosmetic agent according to claim 2 .

22. A method according to claim 21 , wherein said administering is topical administering.