Method Validation for Phenylalanine Analysis in Unconventional Food Plants

Dietary restriction of high-protein foods is the primary treatment strategy for phenylketonuria, a disease considered an inborn error of metabolism associated with phenylalanine. The diet of these patients is monotonous, consisting mainly of certain types of fruits and vegetables, and is often supplemented with the use of phenylalanine-free formulas. Considering that Brazil is one of the countries with the most incredible biodiversity in the world, Non-Conventional Food Plants (NCPPs) become food options that can be regularly introduced into the diet of phenylketonuric patients. In the present study, a method for quantifying phenylalanine in NCPPs was validated using high-performance liquid chromatography with an ultraviolet detector. The phenylalanine content was determined in 15 NCPPs samples from the Brazilian Cerrado. The validated method demonstrated selectivity for the amino acid phenylalanine, with linearity in the range of 1-10 nmol/mL, indicating no matrix effect, and provided proven recovery, repeatability, and precision. The detection and quantification limits were 0.0011 mg/100 g and 0.0035 mg/100 g, respectively. The phenylalanine content ranged from 20.28 to 235.58 mg/100 g. It was observed that leafy vegetables had a higher phenylalanine content than the taro stem (20.28 mg/100 g), the chayote fruit (32.67 mg/100 g), the sepal of the sorrel plant (38.21 mg/100 g), and the nasturtium flower (116.24 mg/100 g). These data suggest that these vegetables can be incorporated into the diet of phenylketonuric patients, thereby contributing to dietary diversity and making it less monotonous and more palatable.