This study reports the phenolic profile screening of aromatic Lamiaceae species such as marjoram (Origanum majorana L.), lavender (Lavandula officinalis) and pennyroyal (Mentha pulegium L.) using a novel and validated ultra performance liquid chromatography method coupled with DAD diode array detector and tandem mass spectrometry (MS/MS) in negative mode of electrospray ionization. Identification and quantification of phenolics in these plant extracts has been realized within 12 min. This method showed good precision (percentage relative standard deviation; RSD% 0.54-2.72 for intra-day, 1.71-4.64 for inter-day), reproducibility (percentage recovery, REC% 92.0-109.0) and linearity (r = 0.9988-0.9999). Limits of detection ranged from 0.02 to 18.2 ng/mL. The extraction of plants was performed using microwave-assisted extraction technique and 60% (v/v) aqueous methanol solvent medium was selected as suitable solvent because of maximum extraction efficiency. Total antioxidant capacity, total phenolic content and free radical scavenging activity of these plant extracts were tested and the results correlated well among each other. According to the Folin assay, phenolic contents of Origanum majorana L., Mentha pulegium L. and Lavandula officinalis were calculated as 119 +/- 3.4, 85.1 +/- 2.8 and 57.8 +/- 2.1 mg GAE/g dry matter, respectively.