Phenolic compounds obtained from natural sources like Allium cepa and Allium sativum are of great interest due to their antioxidant capacity and the multiple benefits they represent for health. However, many factors interfere with the quantity and quality of these compounds in plant material, this implies the need for fast, economical, precise and effective analytical methods that can be used in the quality control of products based on plant extracts. In this work, we propose a fast and reliable method for identifying and quantifying antioxidant compounds from natural sources by RP-UHPLC. This RP-UHPLC method was developed and validated in terms of linearity (R