Polysaccharide Microspheres as Delivery System of Antioxidant Agents Contained in the Blueberry

INTRODUCTION Free radicals are produced in biological systems and from external sources, and can be responsible for a series of degenerative disorders, including mutagenesis, cancer, ageing and cardiovascular disease. Antioxidants are the compounds, which combat the free radicals. Epidemiological studies indicated that a higher level of natural antioxidants (ascorbic acids, vitamin E, carotenoids and phenolics) especially from fruits and vegetables in human everyday diet can protect against the degenerative disorders. While possessing interesting properties, polyphenols suffer from low stability and a low bioavailability. Nano and microtechnologies can offer different solutions for enhancing the therapeutic efficiency of polyphenols1. It is well known that blueberries contain high level of anthocyanin (ATC) and phenolic compounds (PHC) with high in vitro antioxidant capacities compared with other fruits. In this work, gellan gum microspheres (G-MPs), containing blueberry extract (BEX) were prepared in order to preserve ATC and PHC antioxidant properties and to ensure a their efficient release. EXPERIMENTAL METHODS G-MPs were prepared through emulsion technique using phosphatidylcholine (PC) as emulsifier. The emulsion was stirred for 30 min at 50°C, then for 2h at room temperature and finally for 3h in ice at a lower stirring. G-MPs were washed in isopropyl alcohol to remove PC. A 4% w/w citric acid solution was added to the homogenized blueberries and stirred for 15 min. The obtained suspension was filtered to eliminate impurities. The obtained extract (BEX) was then freeze-dried and kept at -18°C. Total ATC concentration was determined using a spectrophotometer at 515 nm on samples of BEX diluted in aqueous solutions at pH 2.5 and 5.5. The content of phenolic compounds (PHC) was determined according to Folin-Ciocalteu method. The ATC and PHC content in dried BEX was 2.40 mg/g and 13.83 mg/g, respectively. BEX loading was performed by incubating the G-MPs in a citric acid solution at pH 2.5 containing 10% w/v BEX, until complete adsorption and finally dried. The G-MPs were characterized using SEM and FTIR. The degree of swelling of G-MPs was measured and release tests in aqueous solution at pH 2.5 were performed. The free radical scavenging activity of BEX, released from G-MPs, was assessed by DPPH assay. RESULTS AND DISCUSSION SEM analysis showed a spherical shape of G-MPs and a good porosity degree on their surface, before and after loading. The degree of swelling of loaded G-MPs (50%) showed a reduction if compared to unloaded G-MPs (109%) indicating the presence of interactions between gellan matrix and BEX. FTIR analysis confirmed the presence of all components in loaded G-MPs and the occurring of hydrogen bond interactions among components. The release curve of ATC and PHC (Fig. 1) showed a fast initial phase and a slower release until 120 min. The final amount of ATC and PHC released was about 35% respect to initial BEX content for both compounds. . Fig. 1 Trend of ATC and PHC release from G-MPs The DPPH free radical scavenging activity was calculated on ATC and PHC released from G-MPs and expressed as percentage of inhibition (I%). G-MPs have demonstrated to preserve ATC and PHC antioxidant properties also after 23 days from the loading (Fig 2). Fig. 2 Inhibition percentage of DPPH radicals after release from G-MPs loaded with BEX CONCLUSION In this work, G-MPs were capable of encapsulating, releasing and stabilizing antioxidant agents contained in BEX. Although the applications of free ATC and PHC are mainly used as functional foods or nutraceutical, the results obtained in this study suggest the utility of these microparticles as drug delivery systems with potential benefit in human health. REFERENCES 1. Klimaviciute R et al., Carbohydr Polym 129:70-78, 2015