Inhibition of Enzymatic Browning and Antioxidant Activities of Marrubium vulgare L Extracts: A Promising Natural Solution

In recent decades, medicinal plants have attracted significant interest due to their demonstrated therapeutic properties. This study analyzed different extracts of Marrubium vulgare L. (horehound) to assess their phytochemical composition and biological activities. Quantitative analysis revealed that methanolic leaf extracts were the richest in polyphenols, containing 23.48 to 35.36 mg EAG/g DM. These leaf extracts also had a particularly high flavonoid content, ranging from 12.55 ± 0.233 to 20.56 ± 0.54 mg EQ/g DM. In contrast, aqueous stem extracts were abundant in condensed tannins, with 72.82 ± 0.772 and 65.52 ± 1.216 mg EC/g DM in aqueous and methanolic extracts, respectively. The antioxidant potential of the extracts was evaluated through several in vitro assays. Leaf extracts demonstrated the highest antioxidant activity, with methanolic extracts exhibiting stronger antioxidant capacity than aqueous extracts. Furthermore, leaf extracts were capable of inhibiting peroxidase activity by up to 42.68%, although they showed weak inhibition of polyphenol oxidase. These findings suggest that Marrubium vulgare L is a promising source of natural antioxidants and enzyme inhibitors, with potential applications in the development of functional foods, cosmetics, and pharmaceuticals. The observed differences between extraction solvents highlight the importance of considering phytochemical profiles and bioactivities when selecting and optimizing plant-based ingredients.