Identification and quantification of phenolics in Australian native mint (Mentha australis R. Br.)

Australian native mints have traditionally been used by the aboriginal people for natural remedies; however, their bioactive components have not been studied. Antioxidant capacity and composition of phenolic compounds of Mentha australis R. Br., Lamiaceae were investigated for the first time. Phenolic compounds were analyzed by HPLC photodiode array detector, liquid chromatography high resolution mass spectrometry, tandem mass spectrometry and nuclear magnetic resonance spectroscopy. Aqueous methanolic extract of the mint exhibited comparable antioxidant capacity to the common spearmint. Major compounds identified in the extract were rosmarinic acid (160.4 ± 0.85 μg mg−1 purified extract), neoponcirin (145.0 ± 0.42 μg gallic acid equivalent (GAE) mg−1), narirutin (30.3 ± 0.02 μg GAE mg−1), chlorogenic acid (15.4 ± 0.05 μg mg−1) and biochanin A (9.6 ± 0.06 μg GAE mg−1), while minor compounds were caffeic acid, apigenin, hesperetin and naringenin. Neoponcirin and biochanin A were identified for the first time in the Mentha genus.