Anthocyanins and Total Phenolic Compounds from Pigment Extractions of Non-Native Species from the Umia River Basin: Eucalyptus globulus, Tradescantia fluminensis, and Arundo donax

Alien invasive species (AIS) and non-native species are a prominent and extended problem in a wide range of areas in Europe and around the world. Centered in the Umia’s riparian forest, in Galicia, we found at least three main AIS needing to be controlled and harvested to preserve the biodiversity of the area. Previous studies probed that leaves and bark of selected species—Tradescantia fluminensis, Arundo donax, and Eucalyptus globulus—have important antioxidant properties, suitable for use in pharmaceutical and industrial contexts. A comparison of four solid-liquid extraction methods—Soxhlet extraction, ultrasound assisted extraction, thermal agitator, and infusion—was conducted in order to define the most efficient method in correlation within antioxidant (anthocyanins and total phenols) extraction. Water was selected as solvent, providing a sustainable research background without implying any chemical additives. The best extraction yields were obtained with Soxhlet extraction for all raw matter, with best results for Tradescantia fluminensis (41.89%) and Eucalyptus globulus leaves (39.35%); followed by the ultrasonic assisted extraction method, with better yield performed with Eucalyptus leaves (27.07%). On the contrary, Tradescantia fluminensis showed better efficiency with thermal agitator (35.07% compared to 23.19% from ultrasound extraction). After extractions, identification and quantification of total phenolic compounds and anthocyanins were carried out using spectrophotometric determination and acid hydrolysis in butanol method. In general, the best extraction yield in correlation with higher antioxidant content was performed by thermal agitator method, and Eucalyptus globulus leaves were demonstrated to be the better anthocyanins (6.18 ± 0.82 mg CC/g) and total phenols containers (172.40 ± 44.53 mg GAE/g). Studies provided promising possibilities for the residues of the three non-native species analyzed, as a source of antioxidants, favoring circular economy systems, as well as taking care of biodiversity in affected environments.