Development and Validation of Veratric Acid in Tabebuia avellanedae using Liquid Chromatography‑Electrospray Ionization‑Mass Spectrometry/Mass Spectrometry‑Multiple Reaction Monitoring‑Based Assay Coupled with 1,1‑Diphenyl‑2‑Picrylhydrazyl Method

Objective: The aim of the present study is to develop a new simple, precise, and accurate liquid chromatography‑tandem mass spectrometry (LC‑MS/MS) method for the quantification of veratric acid in Tabebuia avellanedae Linn. Materials and Methods: The quantification of veratric acid was done using collision‑induced dissociation multiple reaction monitoring scan of mass spectrometry technique. The developed method was validated according to the International Conference on Harmonization guidelines. The free radical scavenging activity was performed by 1,1‑diphenyl‑2‑picrylhydrazyl (DPPH) method. Results: The ion transitions of the precursor to the productions were principally protonated ion [M + H]+ at m/z 182.8 >139.20, 124.20, and 77.0 for veratric acid. The proposed method was validated for linearity with an excellent correlation coefficient of 0.9978. The intraday and intermediate precisions and repeatability showed the percentage relative standard deviation was <2%. The accuracy for the determination of veratric acid was within 82.20%–97.65%. The limit of detection and limit of quantitation were 0.66 and 2.21 ppm, respectively. The half‑maximal inhibitory concentration value for the DPPH radical scavenging activity of ascorbic acid and quality control sample (hydroalcoholic extract of T. avellanedae) was found to be 17.79 and 36.44 μg/ml, respectively. Conclusion: The developed LC‑MS/MS method is a simple, rapid, precise, accurate, and it is recommended for efficient assays in routine work. T. avellanedae exhibited strong DPPH radical scavenging activity.