Chemical Composition, and Antioxidant and Antimicrobial Properties of Monarda didyma L.’s Essential Oils and Hydrosols

Aromatic medicinal plants are a constant focus of interest for scientists and producers. One example is Monarda didyma L., an aromatic perennial with proven health benefits. During the distillation process, hydrophobic (essential oils) and hydrophilic (hydrosols) fractions were obtained from the leaves, flowers and aerial parts (herb) of bee balm (M. didyma) in our study. The highest yield of essential oil (mL·100 g−1 DM) was obtained from the flowers, whilst the highest yield of hydrosol was obtained from the leaves (42.46 mL·100 g−1 DM). The dominant compound in both distillation products was thymol, with contents ranging from 51.55% to 68.63% (essential oils) and 90.31 to 100% (hydrosols). The essential oils that we analyzed were characterized by a higher polyphenol content than hydrolates. The highest polyphenol content among the essential oils was found in the flower essential oil (415.84 mg GAE·mL−1). All the essential oils tested were characterized by a high antioxidant activity (DPPH IC50 from 0.77 (leaf essential oil) to 0.92 μL (flower essential oil)). The essential oils tested also exhibited a broad spectrum of antimicrobial activity against Gram-positive and Gram-negative bacteria and yeasts, while hydrosols showed selective antifungal activity, without significant antibacterial activity.