In recent years, interest in studying the beneficial properties of resveratrol on human health has greatly increased because it exhibits a number of therapeutic effects. Due to poor water solubility and extensive first-pass metabolism, resveratrol has low bioavailability after oral administration. Buccal films are one of the approaches to improve the bioavailability, since the active ingredient bypasses the first-pass metabolism and variable environment in the gastrointestinal tract. In the master thesis, the stability of resveratrol in buccal films used as a dietary supplement was studied, which was evaluated by several analytical methods (HPLC, IR spectroscopy, LC/MS-MS, NMR, optical microscope and SEM). In a 3-month stability study (25 °C / 60 % relative humidity and 40 °C / 75 % relative humidity) and photostability study where the powder standard of trans-resveratrol and buccal films with incorporated trans-resveratrol were exposed to UV light, with HPLC, IR and 1H NMR analytical methods it was found that trans-resveratrol is stable in both cases. Cis-resveratrol was detected and identified only with LC/MS-MS analysis, where the content was very low compared to trans-resveratrol (<1%). In HPLC analysis it was found that the content of trans-resveratrol in the methanol solution after 5 days of exposure to UV light is reduced to 10%, and in LC/MS-MS analysis it was found that isomerization to cis-resveratrol also occurs. Since we also wanted to simulate the real conditions as much as possible, we carried out a 1-month stability study, where buccal films were exposed to the sunlight and room conditions. In this study, we found that the storage of buccal films on the sunlight is not recommended, as the content of trans-resveratrol in films is reduced. By evaluating the stability of resveratrol in buccal films, we also found that the storage of films in the primary packaging is very important since it protects them from environmental factors. Humidity and UV light are two critical environmental factors that can affect the stability of resveratrol in buccal films, as they affect the physical stability of films; due to low or high humidity, buccal films become more rigid or softer, and due to UV light, color of the buccal film turns into orange-brown and cracks on the surface occurs. Buccal films represent an adequate pharmaceutical form for incorporating trans-resveratrol, as these, if films are stored in the primary packaging, are stable under different storage conditions.
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