External dermal composition for anti-ageing and method for producing the same
The present invention has an object to provide an external dermal composition for anti-ageing, which prevents or improves apparent skin problems such as wrinkles, fine wrinkles, blemishes, and saggings caused by increasing age or ageing; and maintains or improves the barrier function and the hyaluronic acid production in the skin. The object is solved by providing an external dermal composition for anti-ageing, which contains an aqueous medium as a base material and one or more ingredients selected from L-ascorbic acid, derivatives thereof, and their salts as an effective ingredient(s).
1. A composition which comprises 2-O-α-D-glucosyl-L-ascorbic acid and sodium salt thereof that are in a crystalline form.
2. The composition of claim 1 , wherein the ratio of said 2-O-α-D-glucosyl-L-ascorbic acid and said sodium salt thereof is in the range of 60:40 to 45:55 by mass, on a dry solid basis.
3. The composition of claim 1 , wherein said sodium salt of 2-O-α-D-glucosyl-L-ascorbic acid in a crystalline form is a hydrous crystalline sodium salt of 2-O-α-D-glucosyl-L-ascorbic acid having diffraction angles (2θ) of 6.8°, 8.2°, 14.3°, 17.8°, and 18.4°; or an anhydrous crystalline sodium salt of 2-O-α-D-glucosyl-L-ascorbic acid having diffraction angles (2θ) of 8.0°, 9.0°, 16.4°, 17.9°, and 20.8°, when determined on powder X-ray diffraction analysis.
4. A crystal of sodium salt of 2-O-α-D-glucosyl-L-ascorbic acid.
5. The crystal of claim 4 , which is in a hydrous crystalline form having diffraction peaks at diffraction angles (2θ) of 6.8°, 8.2°, 14.3°, 17.8°, and 18.4°, or in an anhydrous crystalline form having diffraction peaks at diffraction angles (2θ) of 8.0°, 9.0°, 16.4°, 17.9°, and 20.8°.
6. The crystal of claim 5 , wherein said hydrous crystal belongs to an orthorhombic system and exhibits a space group of Pbca (#61) and a lattice constant of a=6.9733 Å, b=14.4839 Å, c=19.3221 Å, and V=1951.54 Å 3 .
7. A method for producing said crystal of sodium salt of 2-O-α-D-glucosyl-L-ascorbic acid of claim 4 , which comprises the steps of:
(a) dissolving 2-O-α-D-glucosyl-L-ascorbic acid in an aqueous sodium hydroxide solution;
(b) adding an organic solvent to the resulting solution;
(c) allowing the resulting mixture to stand to precipitate a crystal of sodium salt of 2-O-α-D-glucosyl-L-ascorbic acid; and
(d) collecting the precipitated crystal.
8. A composition comprising the crystal of sodium salt of 2-O-α-D-glucosyl-L-ascorbic acid of claim 4 .
9. The composition of claim 8 , which further comprises L-ascorbic acid or its derivative including a glycosyl-, acyl-, or phosphoryl-derivative of L-ascorbic acid.
10. The composition of claim 9 , wherein said glycosyl-derivative of L-ascorbic acid is 2-O-α-D-glucosyl-L-ascorbic acid.