Extraction and LC–MS characterization of bioactive compounds from spent coffee grounds

Spent coffee grounds (SCGs), an abundant byproduct of Coffea arabica L., hold significant potential as a renewable resource for bioactive compounds. This study explores ultrasound-assisted extraction (UAE) as a sustainable approach to enhance the recovery of phenolic-rich metabolites using seven solvents with varying polarity. The optimized glycerol/methanol co-solvent system achieved the highest extraction efficiency, with a total phenolic content (TPC) of 6.059 ± 0.089 mg GAE/g and a total flavonoid content (TFC) of 8.549 ± 0.010 mg QE/g. Comprehensive liquid chromatography − mass spectrometry (LC–MS) analysis identified key secondary metabolites, including caffeine, chlorogenic acids (CGAs), and phenolic compounds which contribute to diverse functional properties such as antioxidant, antimicrobial, UV-protective, anti-inflammatory, and anti-cellulite activities. These bioactive components have substantial applications in industrial crop-based pharmaceuticals, cosmetics, and bio-based materials. By integrating UAE with environmentally friendly co-solvents, this study presents a scalable and sustainable extraction strategy, reducing reliance on conventional solvents while maximizing yield and purity. Additionally, the findings support waste valorization and circular economy principles, positioning SCGs as a viable industrial crop resource with significant implications for biorefinery processes, bio-based product development, and sustainable cropping systems. This research provides a systematic framework for solvent selection in metabolite extraction, reinforcing its relevance to industrial crop management and sustainable bioactive compound production. The demonstrated efficiency of UAE highlights SCGs as a valuable and underutilized industrial by-product, supporting the development of sustainable extraction methods and their broader industrial applications.