Effect of Phenological Stage and Geographical Location on Antioxidant Activities of Tunisian Horehound: Marrubium vulgare L. (Lamiaceae)

Abstract Medicinal plants constitute an important source for a wide variety of natural antioxidants. Therefore, the aim of the present work was to compare the antioxidant activities, total phenolic and flavonoid contents of three wild populations of Marrubium vulgare L. The plant was collected from the South-East (Matmata and Thoujene) and the Central-Sahel (Melloulech) of Tunisia, at the vegetative and at the fruiting stages. The antioxidant activities were evaluated by the following methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity, reducing power and metal (Fe2+) chelating activity. Ethanolic extract of M. vulgare present the highest contents of phenolics (267–325 mg GAE/g extract) and flavonoids (212–245 mg QE/g extract) at the fruiting stage, regardless the geographical location. Furthermore, the highest antioxidant activities were also obtained at the fruiting stage of M. vulgare.