Evaluation of Marrubium vulgare Growing Wild in Tunisia for Its Potential as a Dietary Supplement

Marrubium vulgare L., known as horehound, is a widespread and widely known plant that is used in beer breweries and also as a traditional remedy in Tunisia. In this study, methanolic extracts of plants harvested from five different locations were investigated for their antioxidant activities using three assays (ferric reducing power, radical scavenging activity, and β-carotene-linoleic acid bleaching assay) as well as the total phenolic content. The mineral composition of the plant was also investigated concerning the following elements: Fe, Mg, Ca, Cu, Zn, Mn, K, and three heavy metals, Ni, Pb, and Cd. Marrubiin, the major bioactive diterpenoid lactone, was quantified by NMR in the samples. The essential oils were obtained by hydrodistillation, and their radical scavenging activity was investigated. The toxicity of essential oils was evaluated against Artemia salina (the brine shrimp larva). The essential oil showed a weak radical scavenging activity and low toxicity. Data obtained from the five different locations showed that the antioxidant activity, as well as the total phenolic and marrubiin content, were strongly affected by the harvest sites. The metal content in the samples showed differences with the harvest location, but there was always a great abundance of calcium, magnesium, and potassium.