Nutritional properties, identification of phenolic compounds, and enzyme inhibitory activities of Feijoa sellowiana leaves

The nutritional values, the identification of individual phenolic compounds as well as the functional properties (in vitro acetylcholinesterase (AChE) and pancreatic lipase inhibition) of Tunisian Feijoa sellowiana (O.Berg) leaves were determined by high-performance liquid chromatography coupled with diode array and mass spectrometry detector. Feijoa Sellowiana leaves Extract (FSLE) were evaluated in the present work. Macronutrient components (proteins, carbohydrates, dietary fiber, lipids, and ashes) of FSLE as well as their fatty acids and mineral content were determined. The individual phenolic composition was characterized by the presence of flavonols (mostly quercetin glycosides), flavan-3-ols (procyanidins and catechins), and phenolic acid derivatives. To understand the possible inhibition mechanism exerted by the extract components, enzyme kinetic studies using derived Lineweaver–Burk (LB) plots and Michaelis-Menten were performed. The obtained results evidenced that FSLE exhibited important AChE inhibitory effect, behaving as a noncompetitive inhibitor. Furthermore, the leaves' extract inhibited irreversibly the pancreatic lipase, with maximum inhibition (70%) achieved at 1 mg/ml. Practical applications In many countries of the world, Feijoa Sellowiana leaves are used as an alternative to tea drinks and as a folkloric medicine. Moreover, it is well known that the phytochemical compounds are a practical alternative for the prevention of many chronic diseases such as Alzheimer's and obesity. For this reason, the present study aimed to evaluate the nutritional, individual phenolic compounds, and functional properties of Feijoa Sellowiana leaves to valorize them as a food and pharmaceutical bioactive human source.