Development and Validation of Spectrophotometric Techniques for the Determination of Total Flavonoids, Based on Quercetin, in the Leaves of Psidium guajava L.

Abstract

Pulverulent solids obtained from Psidium guajava L. (guava) leaves were analyzed. This was performed through a decoction extraction with acetone refluxing and an acid hydrolysis. Finally, a liquid–liquid extraction was performed using ethyl acetate. After being separated by a thin layer chromatography, flavonoids were identified by colorimetric reactions in total extracts. Ultraviolet-visible spectrophotometry was used for the quantification process as an analytical method for the determination of total flavonoids. It was developed as both a direct and an indirect method, in respect to the quercetin metabolite and both were validated on the basis of completion with the analytical performance parameters: linearity, precision, accuracy and sensitivity. The total flavonoid content in the sample of pulverulent solids from Psidium guajava L. leaves was 0.080 ± 1.01% through the direct method and 0.936 ± 0.090% for the indirect method. Both values were relatively close. The fact that the concentration obtained by the indirect method was slightly smaller was because, under the conditions of this analysis, the absorbance is less influenced of any interfering substances. The two spectrophotometric methods can be suitable to perform the quantification of flavonoids in Psidium guajava L. leaves.