**2.1. Chemicals**

Chitosan and fluoxetine hydrochloride were purchased from Aldrich Chemical Co. (St. Louis, MO, USA), and vitamin B2 (riboflavin, 96%) and vitamin B12 (cyanocobalamin,, USP Grade) from Vetec Co. (Duque de Caxias, RJ, Brazil).and Merck Co. (Darmstadt, Hessen, Federal Republic of *German), respectively.* Other chemicals were ultraviolet/highperformance liquid chromatography grade and used without further purification; ultrapure water was supplied by a Milli-Q system.
