The present study evaluates the antioxidant activity of the flavonol quercetin, and its functional stability as a raw material and when added in formulations. The iron-chelating activity was determined using the bathophenanthroline assay, and the functional stability was evaluated with the antilipoperoxidative assay. Raw material presented concentrationdependent antilipoperoxidative and iron-chelating activities. The initial antilipoperoxidative activity of the raw material, cream and gel-cream were 63%, 78%, and 69%, respectively. There was no detectable loss of activity during 182 days (6 months) of storage at all tested temperatures (4°C, room temperature [RT], 37°C, and 45°C) for the raw material. Considering the method variability of 10%, activity loss greater than 10% for nonionic cream was detected after 126 days at 4°C (20.1%), decreasing thereafter to 22.2% after 182 days. At 45°C, the loss of activity started after 182 days (13.2%). For the anionic gel-cream, activity loss started after 84 days (28.4%, 45°C), decreasing after 182 days to 40.3% at 45°C. At 37°C, activity loss was detected after 182 days (12%). In conclusion, the results suggest that the activity of quercetin depends on iron chelation, and its possible usefulness as a topical antioxidant to prevent oxidative stress-induced skin damage depends on maintaining its antilipoperoxidative activity stored at RT, which avoids special storage conditions.
The aim of this investigation was to monitor metronidazole concentrations in the gingival crevicular fluid (GCF) collected from periodontal pockets of dogs after treatment with an experimental 15% metronidazole gel. Five dogs had periodontitis induced by cotton ligatures placed subgingivally and maintained for a 30-day period. After the induction period, only pockets with 4 mm or deeper received the gel. Each pocket was filled up to the gingival margin by means of a syringe with a blunt-end needle. GCF was collected in paper strips and quantified in an electronic device before and after 15 minutes, 1 h, 6 h, 24 h and 48 h of gel administration. The GCF samples were assayed for metronidazole content by means of a high performance liquid chromatography method. Concentrations of metronidazole in the GCF of the 5 dogs (mean ± SD, in µg/mL) were 0 ± 0 before gel application and 47,185.75 ± 24,874.35 after 15 minutes, 26,457.34 ± 25,516.91 after 1 h, 24.18 ± 23.11 after 6 h, 3.78 ± 3.45 after 24 h and 3.34 ± 5.54 after 48 h. A single administration of the 15% metronidazole gel released the drug in the GCF of dogs in levels several-fold higher than the minimum inhibitory concentration for some periodontopathogens grown in subgingival biofilms for up to one hour, but metronidazole could be detected in the GCF at least 48 hours after the gel application.
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