title: Influence of sodium metabisulfite and glutathione on the stability of vitamin C in O/W emulsion and extemporaneous aqueous gel.
abstract: Vitamin C exerts several functions on skin as collagen synthesis, depigmentant and antioxidant activity. Vitamin C is unstable in the presence of oxygen, luminosity, humidity, high temperatures and heavy metals, which presents a significant challenge to the development of cosmetic formulations. Therefore, the utilization of an effective antioxidant system is required to maintain the vitamin C stability. The purpose of this research work was to develop prototypes of cosmetic formulations, as O/W emulsion and extemporaneous aqueous gel, containing vitamin C and to evaluate the influence of sodium metabisulfite (SMB) and glutathione (GLT), as antioxidants, on the stability of the active substance. A HPLC stability-indicating method was developed and validated for this study and stability assays were performed in 90 and 26 days and storage conditions were 5.0+/-0.5, 24+/-2 and 40.0+/-0.5 degrees C. The HPLC stability-indicating method showed linearity (r(2)>0.99), specificity, R.S.D.<1.22% and accuracy/recovery ranging from 95.46 to 101.54%. Preparations with SMB or GLT and the antioxidant-free presented results statistically distinct, demonstrating the necessity of the antioxidant system addition. O/W emulsions with SMB or GLT retained the vitamin C content >90.38% stored at 5.0+/-0.5 and 24+/-2 degrees C. For the aqueous gel with SMB or GLT, the active substance concentration was maintained >94.03%. Considering the vitamin C stability, the SMB and the GLT showed to be statistically adequate, as antioxidants, for the cosmetic formulations.
authors.affiliation: Laboratory of Cosmetology, Department of Pharmacy, School of Pharmaceutical Sciences, University of São Paulo, 580 Prof. Lineu Prestes Av., bl. 13, Conjunto das Químicas, Cidade Universitária, 05508-900 São Paulo, SP, Brazil.
authors.forename: Adriana M
authors.initials: AM
authors.lastname: Maia
authors.forename: André Rolim
authors.initials: AR
authors.lastname: Baby
authors.forename: Claudinéia A S O
authors.initials: CA
authors.lastname: Pinto
authors.forename: Wilson J
authors.initials: WJ
authors.lastname: Yasaka
authors.forename: Eunice
authors.initials: E
authors.lastname: Suenaga
authors.forename: Telma M
authors.initials: TM
authors.lastname: Kaneko
authors.forename: Maria Valéria Robles
authors.initials: MV
authors.lastname: Velasco
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D001205:Ascorbic Acid / Q000032:analysis / Q000737:chemistry*; D004355:Drug Stability; D004655:Emulsions; D005782:Gels; D005978:Glutathione / Q000737:chemistry*; D009821:Oils / Q000737:chemistry; D013447:Sulfites / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D000975:Antioxidants; D004655:Emulsions; D005782:Gels; D009821:Oils; D013447:Sulfites; D014867:Water; C005200:sodium metabisulfite; D005978:Glutathione; D001205:Ascorbic Acid