RP-UHPLC method development and validation for the rapid determination of phenolic antioxidants from Allium cepa and Allium sativum extracts.

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 > 0.99), precision (SD = < 3.41E), detection limit (LOD = 1.2-9 ppm), and quantification limit (LOQ = 9-27 ppm) based on standards of antioxidant phenols commonly found in vegetables and plants. An accurate and reproducible chromatographic method was developed to analyze eleven antioxidants in less than 14 min. With this method, compounds such as gallic acid (g = 39 ± 12 mg/kg and o = 231 ± 70 mg/kg), catechin (g = 53 ± 4 mg/kg), and epigallocatechin (o = 252 ± 54 mg/kg) were identified and quantified in garlic and onion extracts. Furthermore, we demonstrated the antioxidant capacity of the extracted compounds from garlic and onion using ABTS (g = 22 % and o = 47 %) and DPPH (g = 31 % and o = 15 %) assays. These results demonstrate that the proposed method can be widely used in the analysis and quality control of samples or products containing antioxidant phenolic compounds.