Invasive Plants as a Source of Polyphenols with High Radical Scavenging Activity

The wide occurrence and expansive nature of invasive plant species are worldwide problems because these plants by their competitive character can lead to the loss of biodiversity. As a result, they significantly disrupt ecosystems, create economic damage and threats to human health, and diminish the quality of recreational resources. Therefore, sustainable, bio-based solutions are needed for their control, focusing on the utilization of their biomass after eradication. To better understand the potential application possibilities of invasive plants and their potential role in bioeconomy, species such as Lupinus polyphyllus—Lindl., Impatiens glandulifera Royle, Heracleum sosnowskyi Manden, Solidago canadensis L., Echinocystis lobata (Michx.), and Elodea canadensis Michx. were studied. These plants are not only widely spread but also form dense mono-stands and produce substantial amounts of biomass, which provides more options for their harvesting. In particular, their composition was analysed to assess the feasibility of their use for bioactive compound extraction. The amount of total polyphenols and flavonoids was determined in various parts of the studied invasive plants, and their corresponding radical scavenging activities were determined using DPPH, ABTS, FRAP and CUPRAC. The studied invasive plants are rich sources of polyphenols, and the highest concentrations were found in Impatiens glandulifera leaves, reaching a concentration of 7.78–11.75 g GAE/100 g DW, but in Lupinus polyphyllus, the highest concentrations of polyphenols were identified in the extracts of the flowers (12.77 g GAE/100 g DW) and leaves (11.88 g GAE/100 g DW) of the plant. Among the various plant parts studied, the leaves and flowers consistently showed the highest concentrations of polyphenols and flavonoids, as well as the greatest antioxidant and radical scavenging activities. These findings underscore the potential of invasive plant biomass as a source of valuable bioactive substances, particularly polyphenols, after the eradication of these invasive species.