RESUMO
HPLC stability-indicating method was validated for Vitamin C (ascorbic acid) in semisolid pharmaceutical/cosmetic formulations containing glutathione and sodium metabisulfite, as antioxidants. The described procedure included a reliable, precise, accurate and specific method determination employing a 250mm x 4.6mm C(18) column, 0.2% metaphosphoric acid/methanol/acetonitrile (90:8:2, v/v/v) as the mobile phase and detection at 254nm. Nicotinic and ascorbic acids were employed as standards, both presenting purity of 99.0%. Linearity was established for the ascorbic acid concentrations ranging form 1.0 to 12microg mL(-1), accuracy/recovery percentage was 95.46-101.54%, precision values were 0.38 (intra-day) and 1.22% (inter-days), and LOD and LOQ were found to be 0.05 and 0.17microg mL(-1), respectively. The working mobile phase elevated the ascorbic acid retention time to approximately 3.5min at a flow rate of 1.0mL min(-1) and provided resolution of the active from the nicotinic acid (internal standard), degradation product (oxalic acid) and other excipients from the pharmaceutical/cosmetic preparations.
RESUMO
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.
Assuntos
Antioxidantes/química , Ácido Ascórbico/química , Glutationa/química , Sulfitos/química , Ácido Ascórbico/análise , Estabilidade de Medicamentos , Emulsões , Géis , Óleos/química , Água/químicaRESUMO
Determinaram-se os teores de cálcio , fósforo e ferro nas cinco espécies de água doce: Prochilodus scrofa (corimbatá) , Leporinus copelandi (piaba), Salminus maxillosus (dourado), Pimelodus clarias (mandiúva), e Lepiorinus piara(piapara). A variação da concentração de cálcio entre as espécies foi significativa, tendo se constatado maiores valores na piapara, corimbatá e dourado e menores na piava e mandiúva. O teor de fósforo igualmente variou conforme as espécies, tendo o dourado apresentado a maior concentração e a piava a menor. O teor de ferro foi relativamente constante, com exceção da piapara, que apresentou valor significativamente elevado. Nas espécies analisadas, as proporções entre os elementos cálcio e fósforo (Ca:P) foram ligeiramente inferiores em relação àquelas normalmente aceitas como padrão. Os dados obtidos, em confronto com os da literatura, sugerem que os peixes de água doce são, de modo geral, mais ricos em minerais do que os peixes marinhos (AU).