Stability of vitamin C derivatives in solution and topical formulations.
The stability of ascorbic acid, ascorbyl palmitate and magnesium ascorbyl phosphate (VC-PMG) in both standard solutions and topical formulations was investigated by direct RP-HPLC analysis after sample dilution with a suitable aqueous-organic solvent mixture. The results showed that, whereas the two vitamin C derivatives were more stable than ascorbic acid, the ascorbyl esters showed significant differences. Esterification with palmitic acid in 6 position did not prevent hydrolysis of the molecule, either in solution or in emulsion; only the special preparation of products with high viscoelastic properties was able to reduce the typical behaviour of this compound. Conversely, the introduction of the phosphoric group in 2 position protected the molecule from break-up of the enediol system, confirming VC-PMG as a very stable derivative of vitamin C that may be easily used in various types of cosmetic products.
Austria
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Università di Padova, Dipartimento di Scienze Farmaceutiche, Italy.
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Bettero
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D001205:Ascorbic Acid / Q000031:analogs & derivatives* / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D003358:Cosmetics / Q000737:chemistry*; D004355:Drug Stability; D004655:Emulsions; D015394:Molecular Structure; D012015:Reference Standards; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet
D003358:Cosmetics; D004655:Emulsions; D012996:Solutions; C011669:ascorbate-2-phosphate; D001205:Ascorbic Acid; C031226:6-O-palmitoylascorbic acid