Morphology and drug release of pH-sensitive microspheres containing flavonoids

In this work we developed pH‐sensitive microspherical dosage forms for poorly water soluble flavonoids (quercetin and naringenin) by using Eudragit L100 as enteric polymer. The systems were produced by water in oil (w/o) solvent evaporation method, optimizing the formulation and preparation conditions in order to obtain high encapsulation efficiency and production yield. The synthesized microspheres were characterized in terms of particle size distribution, drug loading, morphology and in vitro release properties. The performed analyses evidenced that the microspheres were free‐ flowing and spherical in shape, both quercetin and naringenin were microencapsulated in the amorphous state and the drug content was near to the theoretical one. Preliminary in vitro dissolution studies, carried out using a pH‐change method, showed that the samples exhibit a typical biphasic drug release trend, due to the pH dependent solubility of the enteric polymers used. In particular, the samples have a fairly gastroresistance followed by an about complete release in simulated intestinal fluid.