Evaluation of the Enhanced Antioxidant Activity of Curcumin within Exosomes by Fluorescence Monitoring

In this study, we compared the antioxidant activities of curcumin (Cur) and a Cur formulation using a fluorescence analysis assay. The Cur formulation was prepared by a simple incorporation of Cur into exosomes (EXO) to produce Cur/EXOs. Free Cur had a low fluorescence intensity in aqueous solution because of its poor stability as a result of its autoxidation, whereas a significantly higher fluorescence intensity was observed for Cur/EXOs. Compared to free Cur, the increased level of intact Cur in EXOs allowed for enhanced antioxidant activity in H2O2 scavenging activity and DPPH assays. Compared to Cur at high concentration (200 mu M), Cur/ EXOs were significantly less cytotoxic. The antioxidant activity of Cur or Cur/EXOs in cells could be easily demonstrated by monitoring decreases in their fluorescence intensity. Following subcutaneous injection, the fluorescence intensities of Cur/EXOs were much higher than that of Cur, suggesting that Cur/EXOs improve Cur stability in vivo. Taken together, we have demonstrated the superiority of Cur/EXOs over free Cur in terms of aqueous stability and antioxidant activity using fluorescence monitoring both in vitro and in vivo.