Evaluation and identification of antioxidative components of Radix Rhodomyrti by DPPH–UPLC–PDA coupled with UPLC–QTOF-MS/MS

Radix Rhodomyrti is the dried root of Rhodomyrtus tomentosa (Aiton) Hassk., which is used as a herb in southeast Asian countries and regions. Its main active ingredients are phenols. To make efficient use of the active components in Radix Rhodomyrti, 2,2-diphenyl-1-picrylhydrazyl radical–ultra-high-performance liquid chromatography–photo diode array (DPPH–UPLC–PAD) analysis and UPLC–quadrupole time-of-flight tandem mass spectrometry (UPLC–QTOF-MS/MS) were applied to evaluate and identify the antioxidant phenolic components in Radix Rhodomyrti. Gallic acid and ellagic acid were identified as the major phenolic components in Radix Rhodomyrti. The levels of gallic acid and ellagic acid in Radix Rhodomyrti were 2.16 ± 0.27 mg/g and 0.17 ± 0.04 mg/g, respectively. Both compounds showed excellent free-radical scavenging activity in vitro. The known antioxidant capacity of ellagic acid is slightly higher than that of gallic acid, which is consistent with the results of the DPPH radical-scavenging assay. The results of this study indicate that the proposed method could be applied for rapid screening and identification of antioxidants from complex natural products.