Development and validation of analytical methodology for quantification of total flavonoids of Morus nigra by ultraviolet-visible absorption spectrophotometry

Morus nigra L. is known in the region of Brazilian Sao Francisco Valley as "amora-miura". It is widely used in traditional medicine, mainly in treatment of diabetes, hypercholesterolemia, cardiovascular problems, obesity and gout. This study proposed to develop and validate a fast, simple, efficient and low cost analytical method that could quantify total flavonoid content present in crude ethanolic extract of leaves of M. nigra (Mn EtOH). For this, ultraviolet-visible (UV-Vis) absorption spectrophotometry was used as the analytical tool and the complexation with aluminium chloride (AlCl3). The quantification of flavonoids by this method was based on the complexation of AlCl3 with the flavonoid nucleus as a selectivity tool made by two procedures: without complexation (NCP) and with complexation (WCP), in order to evaluate the effects of the complexing agent in quantification, proving the efficiency of this technique. In this way, it became necessary to validate the method used to ensure its efficiency. The validation of the method of quantification of total flavonoid content by UV-Vis demonstrated that the method was selective, linear, precise, accurate, and robust. Key words: Morus nigra, UV-Vis, Moraceae, total flavonoids, natural products.