Oil-in-water emulsion development for the encapsulation and sustained release of xanthone

In the present work, an oil-in-water emulsion was developed for the encapsulation of xanthone, a potent anti-inflammatory and antitumor molecule of natural source. The xanthone is insoluble in water so it was encapsulated for oral administration purposes. Then, nonionic surfactants and bovine serum albumin protein for interface stabilization were used, with a droplet size distribution around 0.2-1 mu m. Three initial concentrations of xanthone in the oil droplets were studied (0.142, 0.71 and 1.42 mg/ml), in all cases encapsulation was above 90%. Fourier transformed infrared spectroscopy (FTIR) results showed hydrophilic and hydrophobic interactions between xanthone and the oil droplets. There is a relationship between the initial concentration of xanthone inside the oil droplets and the controlled release. At 1.42 mg/ml, only 1 +/- 0.9% and 1.92 +/- 0.02% of xanthone was released after 2 hours of incubation in buffer solution pH = 7.1 and pH = 2.2 respectively. At high initial concentration, pi-stacking intermolecular interactions preclude the release of xanthone. While at 0.142 mg/ml, 14 +/- 1.25% and 10.33 +/- 0.1% of xanthone was released at pH = 7.1 and pH = 2.2 respectively. At low initial concentrations of xanthone and neutral pH conditions, the release seems to be mediated by ionic destabilization of the emulsion. In this sense, Na+ ions present in the buffer solution binds to ionized molecules of BSA (pH = 5.4) allocated at the interface of the emulsion. As a consequence, a faster release of xanthone is observed at low initial concentrations at neutral pH than at acidic pH.