Valorisation of Sunflower Crop Residue as a Potentially New Source of Bioactive Compounds

Reducing agricultural waste through reuse has become one of the most important strategies to minimise impact on the environment—an emerging global issue. Sunflower ranks fourth in the world in the production of vegetable oilseeds and therefore generates large amounts of agricultural waste. The aim of this study was to investigate the phytochemical composition and bioactivity of sunflower crop residues in order to open up new opportunities for waste management. TPC and TFC were determined spectrophotometrically, while the dominant compounds were identified by LC-DAD-ESI-MS as ent-kaur-16-en-19-oic acid (KA) and 6Ac-7OH-dimethylchromone (DMC). Both compounds were present in higher concentrations in the ethyl acetate fraction (245.5 and 16.8 mg/g, respectively) than in the ethanol extract. None of the tested samples showed antimicrobial effects in the microdilution test. DMC showed remarkable antioxidant activity by DPPH, ABTS, FRAP and TRC in vitro assays, while both compounds proved to be promising enzyme inhibitory agents, being particularly efficient in inhibiting anti-neurodegenerative enzymes (IC50 values of DMC and KA were 1.20/1.37 mg/mL and 1.44/1.63 mg/mL for AChE/BChE, respectively) and tyrosinase. The results presented indicate that sunflower crop residues are a good candidate for the extraction of bioactive compounds with potential application in the food, pharmaceutical and cosmetic industries.