Green extraction of phenolic compounds from plant matrices: a systematic review of yield, total phenolic content, and antioxidant activity (2019–2024)

Green extraction technologies are increasingly utilised to recover phenolic-rich bioactive compounds from plant matrices, aligning with sustainability and circular bioeconomy goals. This PRISMA-guided systematic literature review synthesises 69 peer-reviewed Q1/Q2 journal articles published between 2019 and 2024 that report extraction yield, total phenolic content (TPC), and antioxidant activity (AA) for green (UAE, MAE, PLE, SFE, SWE, and hybrid) and conventional methods applied to plant-based matrices. Across diverse leaves, peels, seeds, brans, and pulps, ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) emerged as the most frequently applied and highest-performing techniques, typically delivering higher yields, TPC, and AA than Soxhlet extraction or maceration when coupled with hydroalcoholic ethanol–water solvents. Matrix effects were evident: leaves and peels generally provided higher phenolic recovery than seeds, whereas cereal brans and seeds required pretreatments (e.g., alkaline hydrolysis or enzymatic treatment) or pressure-assisted methods to achieve comparable performance. A strong positive relationship between TPC and AA (often R² > 0.85) reinforced the role of phenolics as the primary contributors to antioxidant capacity. Key process drivers governing extraction yield, TPC, and AA across methods included solvent composition and polarity, solid-to-liquid ratio, temperature–time profiles, and the use of physical or chemical pretreatments. The review also shows that most studies remain at the bench scale, with limited reporting of energy consumption, solvent intensity, or CO₂-equivalent emissions, and almost no in vivo or clinical validation.